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FT Meter | ALC Power Adjustment and Dummy Load for QRP op's | Field Strength Meter Using a Dynamic Microphone with the Kenwood TS-590 home-brew DIY Cable Adapter More About Microphones | Microphone Pre-amplifier Ideas | Icom HM-103 Microphone Mod's Microphone Wiring | Morse Code Practice Oscillator | Shortened Top Band Antenna | Balun and UnUn Ideas (External Link): Antenna project - Dual band vhf / uhf dipole antenna More pages: Speech Processor | Mic Preamps | Palstar PS-30 High Efficiency Extension Loudspeaker | Hands Free Mobile Microphone for FT-7900 etc “Anyone who has never made a mistake has never tried anything new.” - Albert Einstein RADIO PROJECTS & KITS One of the really fun aspects of amateur radio is making things for yourself and I like nothing better than making things, be they small circuits of kits or going outdoors with some antenna wire. Probably the best and most important DIY project for any amateur radio station is building an antenna of some kind. This is often a wire antenna for use on the HF bands such as an Inverted V, Inverted L, Dipole or Doublet Quad Loop or Windom etc. For the shorter wavelength VHF and UHF bands it's more practical to construct more complex antennas such as a single band Slim Jim or Yagis; I've had a go at a few such projects. Other projects will be an electronic unit of some kind: For the Intermediate Level licence it is necessary to make several practical electrical and electronic circuits and also build a complete and useful device related to the subject of amateur radio. I chose to make a Morse Code Practice Oscillator; this project can be seen a little bit further down this page here. I have also built a Field Strength Meter - "FSM" also shown further down this page here. In January 2012 I set about making a microphone adapter cable to connect a dynamic 'stick' microphone and a separate PTT hand or foot switch to the Kenwood TS-590s transceiver. This, of course, led to looking at the transmitted audio quality and the subsequent filtering and DSP adjustments which has all been very useful and interesting. Read more here. Due to being unable operate from March 2010 with all my equipment being packed away for a house move that had been constantly delayed and finally fell through, I began thinking about a few more ideas for homebrew (d.i.y.) projects. I have also put those ideas on this page: I built a a home-brew 'FT Meter' for the Yaesu FT-857D shown here and a QRP Dummy Load with power measurement and ALC adjustment for QRP operation of the FT-857D shown here. Previous to those projects I also did a little microphone re-wiring - to be seen here. I have also made some Baluns and Ununs and while I have not documented the whole projects I have noted down the ideas here. The other thing I have been doing is trying different types of antenna, my Compact Top Band Aerial can be seen here. Using a Dynamic Microphone with the TS-590s and Microphone Preamplifier ideas: I would like to be able to use a separate microphone on a boom or gooseneck, so I am bringing together some ideas for a dynamic mic' preamp and separate 'break-out' PTT switch here> The components required for the small electronic projects were ordered from Bowood Electronics and JAB Electronic Components. ESR supplied a couple of different uni-directional electret microphone elements which are quite difficult to find elsewhere. I just need to find some time to start - sometime after we've moved house! The necessary electrical conduit and aluminium round bar or tubes for the antenna projects will probably be obtained from B&Q. THE PROJECTS: EXTENSION SPEAKER With Low Pass Noise Filter  I have found that most of the small communications extension speakers that I have used have a harsh, resonant and 'tinny' sound that does assist in making speech especially intelligible. Another problem is that many speakers are also quite inefficient - that is to say that they need a good degree of audio power to drive which can mean that the audio amplifier in the transceiver may be run towards its power limitations resulting in undesirable harmonic distortion or even worse, clipping distortion. To overcome the harsh, tinny audio reproduction requires the use of a larger loudspeaker drive unit. To maximise the available audio output of the transceiver's audio amplifier requires the use of a highly efficient loudspeaker driver unit. To find out more click here > FT METER - An Analog Meter for Yaesu FT-857D and FT-897D - The Homebrew FT-Meter:  FT-Meter - DIY
Homebrew project by MØMTJ
Yaesu very thoughtfully added an external meter socket to the FT-857 and FT-897 which is excellent since I like analog S-Meters, so connecting a meter to these radios is child's play. There are no additional circuits required, merely a 100k preset potentiometer and a small microameter. A meter with a sensitivity of 100µA, 500µA or 1mA should be suitable, the final calibration being done with the small internal preset potentiometer, setting the meter for Full Scale Deflection using the calibration setting on the radio. Parts Required: Panel Meter with a rating of 100µA, 500µA or 1mA measuring 60mm x 50mm or larger A case of suitable size to house the chosen panel meter Small rubber feet for case Small rubber grommet to feed cable through rear of case 100 k Ohm preset potentiometer 3.5 mm jack plug Right Angled (I show a straight plug in the photographs, but a Right Angled plug is MUCH better!) A length of thin screened cable - an offcut of RG174 would be fine. I looked at the Bowood Electronics website and found a very nice little 100µA ammeter measuring about 60mm wide by 50mm high, so I ordered one along with some other components that were in my basket for the QRP power reducer and power measurement project mentioned below. The construction is very straightforward and should not need much explanation. The physical construction and the method by which the meter is fitted to the case will depend upon what type of meter and case is chosen and will be determined by individual ingenuity. The electronic construction is very simple indeed comprising a 3.5mm jack plug soldered onto a short length of cable, inner conductor to the tip of the plug and the screen to the ring. The cable is then fed through the rubber grommet that has been fitted into a small hole drilled in the rear of the case. Internally the screen of the cable is connected to the -ve terminal of the meter. One of the outer legs of the preset potentiometer is soldered on to the +ve terminal of the meter while the other outer leg of the preset is joined to the centre 'wiper' terminal to which is soldered the inner conductor of the screened cable. The menus of the FT-857 and FT-897 allow the radio to output indications of Signal Strength; Power; SWR; Modulation; Voltage and Discriminator etc. Menu 60 - I have set to 'SIG' to indicate signal strength in receive (RX) mode. Menu 61 - I have set to 'PWR' to indicate power output in transmit (TX) mode. The method for calibrating is described below.  FT Meter schematic
circuit diagram
drawn by Frank OK2FJ
 (I show a straight 3.5mm jack plug in the photographs, but a Right Angled plug is MUCH better!)
 FT-Meter - DIY Homebrew project by MØMTJ
(I show a straight 3.5mm jack plug in the photographs, but a Right Angled plug is MUCH better!)
The physical construction of putting a small meter movement into a case should be very straightforward, but there was the small problem of replacing the 0 - 100µA scale supplied with the standard ammeter with a suitably calibrated and printed scale. Producing a new scale for the meter's dial with a professional appearance was more of a challenge for my graphics / image editing skills! I searched Google for some helpful images. LDG market two commercially manufactured meters for this job - the FT-Meter and the much larger FTL-Meter; these retail at about £46.00 GBP and £66.00 GBP respectively - my FT-Meter should cost about £10.00, but I digress! The photographs of these products illustrated the layout of the graphics, but nothing that was reproducible for this' home-brew' project. I was beginning to think that I might have to draw something by hand - then I happened across the website of Frank OK2FJ. Frank has produced an excellent meter scale for his version of the Yaesu FT-Meter. Frank obviously had the same idea as me, to produce a home-brew FT-Meter for a fraction of the cost of a commercial unit, but Frank has greater image editing and graphics skills than mine. I saved Frank's image file and then made a few of my own simple modifications to the image file using a basic image editing program. The result is shown below and can be downloaded and saved, ready to be re-sized and printed to match the size of the particular meter being used:  Above: The image graphic for the Yaesu FT-857 and FT-897 meter scale. Save and print if required. Measure the horizontal width between the maximum and minimum point on the original (ammeter) scale. (Or with the original scale in the meter calibrate for Full Scale Deflection by entering menu 60 and set it to 'FS'. Then adjust the preset potentiometer so that the needle swings fully to the right and lines up with the maximum point on the scale and measure the distance between the two points.) Remove the original scale and print out the new scale as a test print and measure the distance between the minimum and maximum points on the new FT Meter scale. If it's too small, increase the size of the image on the page - using your word processor's functions - and print it again. If it's too big - make it smaller and try again until it's the correct size.  Here is an example document file to download and experiment with the size of the final printed image: FT-Meter.doc Alternatively a bit of simple math's can be used with an image editing program that allows accurate scaling: My image editing program allows scaling of the print-out using a sliding scale that shows the total width of the image when it's printed and the dpi (dots per inch) output to the printer. Knowing the total image width isn't especially helpful since what is needed in this case is the dimension that is the distance between the left and right end markers of the S scale - the top curve. My simple image editor does not allow an accurate measurement of a portion of the image, so I did a test print, estimating that the resultant image would need to be 50 mm wide, the output in this case was 920 dpi. I then measured the width of the top curve on the test print, from end marker to end marker - it was 40mm. The scale of the original microammeter is 34mm wide, so the print had to be scaled down in size. The magnitude of the size reduction can be found by dividing that measurement, 40mm, by the required measurement - in this case 34mm. 40mm ÷ 34mm = 1.176 (the scaling factor) The original test print produced an scale that, at 40mm, was too wide. It needed to be 34mm wide. The original image width of the test print was 50mm and therefore this needed to be divided by the scaling factor of 1.176 50mm ÷ 1.176 = 42.5mm The calculation suggests that 42.5 mm is the width required for the whole image. The image was printed again at that width and the resulting print measured. It was found that the width across the top curve from end marker to end marker was, indeed, the required 34mm. The other way of doing the scaling is to note the dpi output of the original test print, in this case 920 dpi, and multiply (not divide) that by the scaling factor. The original dpi figure is multiplied, rather than divided, because the dots per inch will increase as the original image size is shrunk. In this case the new, and correctly sized print, is 1082 dpi. Whichever method is used, the second print should produce a scale of the correct size. Reference: http://www.radio-foto.net/radio/ftmeter2.png This is the original meter scale image that was produced by Frank OK2FJ, I altered this to produce the meter image that is shown above. Calibration 1/ Enter menu 60 and set it to 'FS'. Now adjust the preset potentiometer so that the needle swings fully to the right and lines up with the maximum point on the scale - i.e. +60dB on the Signal scale or 15 Volts on the voltage scale. 2/ When the 'FS' has been adjusted accurately, set menu 60 back to 'SIG' and move to step 3. 3/ Enter menu 61. As an initial check set this to VLT. Exit the menus. Now press the PTT and transmit. The meter should now indicate the voltage - i.e. around 13.2 to 13.8 volts if running from a PSU. Once that is confirmed move to step 4. 4/ Enter menu 61 again and change the value back to SWR, PWR, MOD or ALC (i.e. whatever you want it to indicate when transmitting). 5/ Exit the menus. For reference the Yaesu manual provides this information about Menus 60 and 61: MENU MODE No•060 [MTR ARX SEL] Function: Selects the analog meter display configuration while the transceiver is receiving. Available Values: SIG, CTR, VLT, N/A, FS, OFF. The default is SIG. SIG: Indicates the incoming signal strength. CTR: Discriminator center meter. VLT: Indicates the battery voltage. N/A: Not available at this time. FS: Applies a calibration signal (1 mA for full scale) at the METER Jack on the transceiver bottom, for adjustment of an external meter’s calibration. This lets you adjust the external potentiometer in your metering system so that the external meter reading is full scale. OFF: Disables the meter MENU MODE No•061 [MTR ATX SEL] Function: Selects the analog meter display configuration while the transceiver is transmitting. Available Values: PWR, ALC, MOD, SWR, VLT, N/A, OFF. The default is PWR. PWR: Indicates the relative transmit power. ALC: Indicates the relative Automatic Level Control voltage. MOD: Indicates the deviation level. SWR: Indicates the Standing Wave Ratio (forward:reflected). VLT: Indicates the battery voltage. N/A: Not available at this time. OFF: Disables the meter.  Above: The image
graphic for a simple analog S Meter scale.
Save and print if required. John, G0TEV, emailed with a helpful suggestion for those who want to produce a custom made meter scale: Meter Basic is free and will produce a basic linear scale. Meter is a paid for program that will allow more complex designs such as dB, vu, VSWR and S-meter scales. Both programs are available here: http://www.tonnesoftware.com/index.html Felix, EC2ALV, writes: Hi, perhaps this may be of interest to you I use GALVA 1.85 to draw all kinds of scales: variables, pots, meters, etc. for my projects. Just follow the examples and you will learn to use it fast. Kind regards, Felix EC2ALV Stan, LT4TU, writes: Hello Mike, Please see my FT-meter scale. You can download the original Coreldraw file, designed by me: http://sites.google.com/site/lz4thankyou/projects/ft-meter There is no copyright, I am just happy to share and wanted to let you know. I made my Ft-Meter in 2006. 73 and GL Stan, LZ4TU (ex LZ2STO). FT-Meter by Helmut Rupprechter DJ0FP Hi Mike, As I promised here some photos from my “ brand new” FT Meter. I found an 40µA ammeter, the case is made by myself because I could not find the right size. I wanted to make it small as possible so now it is 5x5 cm and 8cm long. It is black!!! Normally I hate black because everthing today is black, black cars and TV`s ,black transceivers and so on. But here it was better because the scale is very small and when the case is black the eyes will focus the white scale. So thanks again for help and have a nice weekend. 73 DJ0FP Helmut Rupprechter.  FT-Meter by Helmut Rupprechter DJ0FP 
FT-Meter by Helmut Rupprechter DJ0FP
FT-Meter by Billy McFarland 2MØCSP  Hi Mike, I came across your website and tried your FT Meter Project. It works! I was very happy with it and wanted to share to you what I’ve done. I have incorporated it into my EMACS: Emcomm Modular Ammo Can System. See a photograph of Jesse's FT-Meter here. Jesse Francis, KJ4KPV. April 2013  Jesse Francis, KJ4KPV. April 2013
 6 watt QRP Dummy
Load with Power Measurement and ALC Adjustment
Many 100 watt rigs cannot
adjust RF power output to a low enough level
for QRP
operation. What is needed is a circuit to allow control of the ALC
circuits to reduce the power of a transceiver for QRP operation with
power levels below 5 watts.
Shown below is a very simple circuit for this task - nothing more than a 9 volt battery, a switch, battery connector, 100k resistor and 100k preset potentiometer, a suitable connecting plug, some thin screened cable and a project case. When connected to the transceiver it allows a variable negative voltage to be applied to the transmitter's ALC line via the accessory socket. Increasing the applied negative voltage will reduce the transmitter's output power.  For QRP contest use
the power output will also need to be
measured accurately. The
second part of this project is to produce a meter that will allow
the measurement of voltage from the RF socket to determine an accurate
indication of power into a 50Ohm dummy load.
The dummy load shown below uses three 2 watt, 150 ohm resistors wired in parallel to produce the necessary 50 ohm load with a power rating of 6 watts. The resistors can be carbon or metal film, but must not be wire wound due to the undesirable inductive effects that these would cause. For 3 watt operation, the volt meter should read 16.7 volts with a loud whistle into the mic.      Note from Peter Alice I0YLI in Rome: Dear Mike, I am an Italian HAM living in Rome (I0YLI) and my name is Peter, you can have a look at my shack on QRZ.com. I bought the YAESU FT-897D few months ago and I enjoy it very much. Congrats for your very interesting web-site! Reading along the several articles I found exactly what I need ! Great - the power reduction by ALC plug of power out-put on FT-897D. Following given suggestions by your site, I realized the circuit works great in adjusting output power of the FT-897 even at very low level (Noting that the radio must initially be set to minimum power of 5 watts.) regardless modes; FM / AM / SSB and CW are all OK. (I was using 144MHz & 432MHz). I noted these important points: 1) Input NEGATIVE Voltage at ALC pin MUST-NOT exceed more than -6V ; If a voltage more negative than -6.1V is be injected to the ALC input, a "suspicious" High-SWR indication will be displayed. 2) I realized the "Power Reduction" (made via ALC) start to react at -4V up to -5.5V (Min. Power). Thus the Pot-meter has to scan voltages between -3.9V to -5.5V . The circuit has been changed: Voltage Regulator = µA-7905 with a Diode in series with its Common pin in order to achieve -5.5 V out. On the Ground side of Pot-meter a Resistor of 120K has been added in order the knob will cover a total range of about 1.5V (-4V ÷ -5.5V). Such a Pot-meter MUST be "Linear Type". 3) I tested the circuit at all different RF Power-setting in the User-Menu (5W to 50W) and it works fine. 4) Attached are circuit's schematics including component values. I hope these notes will help "experimenters" ! After a simulated verification I built the definitive box to give a good appearance (see attached diagram). Thanks a lot again ! 73 de Peter (I0YLI) - Rome.   ALC adjustment by Peter Alice I0YLI FIELD STRENGTH METER It is often said that one of the most useful pieces of test equipment in and around the shack is a Field Strength Meter. A Field Strength Meter can be used to quickly check the presence of RF energy, for example to check that a transmitter is transmitting, for use with antenna experiments such as judging the radiation pattern and efficiency of antenna and for checking RF oscillators etc. To buy a simple ready made FSM would cost around £30.00 and £50.00. Since such a device is simply a form of 'crystal set' without a tuned circuit I set about looking through the junk box to see what electronic components I had that I could use to make a suitable circuit. I found a nice aluminium case, a good telescopic aerial, a couple of germanium diodes, a potentiometer, some suitable ceramic capacitors, a nice 250µA signal meter (minus the scale which I had somehow lost) and some other useful bits and bobs. All I needed to assemble a simple yet perfectly effective Field Strength Meter that I am sure is as good as anything that could be purchased ready made - and all made from junk box components!  Photograph showing the simple construction of the Field Strength Meter  Circuit Diagram of the Field Strength Meter All the Field Strength Meter has to do is convert the radio frequency signal into a DC current that can drive a meter movement or digital multimeter (DMM). As can be seen from the above circuit diagram the field strength meter bears a great resemblance to a simple crystal set. The differences being that since the field strength meter needs to be sensitive to a wide range of frequencies the tuned circuit (inductor and variable capacitor usually found in a crystal set) is omitted, and rather than headphones or an earphone the output is fed as DC to a signal meter or to a digital multi-meter so that comparative (rather than absolute) measurements can be made. The telescopic aerial picks up the radio frequency signal and the germanium diode converts the signal to DC. It is important that germanium diodes are used as they exhibit a very small forward bias which is needed to make the meter sufficiently sensitive. |Silicon diodes have a substantially higher forward bias which would substantially reduce the sensitivity, so for this reason it is important to use germanium diodes. On the same theme it is important to use a sufficiently sensitive meter, so a microammeter will be required. I was lucky to have an old Maplin signal meter with a sensitivity of about 250µA for full scale deflection (FSD) in the junk box, although I would imagine that it would still be worth experimenting with any meter between 50µA to 1000µA. Alternatively a digital multi meter can be used to measure the output. The field strength meter that I built has both options selectable with the miniature DPDT switch. The meter is connected to the digital multimeter with a short fly-lead terminated with a red and black banana plug to identify the positive and negative wires. The 47K potentiometer allows for the adjustment of the overall sensitivity of the meter. The advantage of using a DMM is that it has a very high input impedance a therefore will not load the circuit to any great extent, it also enables the meter to be much more sensitive to weaker RF fields if required and also it will be easier to make more precise measurements from the digital readout, particularly small differences.I find that th e DMM is usually set to the 200mV range, or perhaps to 2000mV range if the RF field is especially strong. The value of the various components is not particularly critical, but as mentioned, the diodes must be germanium rather than silicon and any diodes such as OA90,OA91, OA80, OA81, OA47 could be used.
DYNAMIC MICROPHONE FOR THE KENWOOD TS-590s - or indeed many other rigs The February 2012 edition of Practical Wireless magazine included a competition to win a Heil HM-12 Genesis microphone, a new model from Heil, and adapter cable. I wasn't happy with the hand microphone supplied with the Kenwood TS-590s, so naturally I entered to competition hoping to win a prize worth over £100.00! - I didn't win however.  However it also made me think that, tucked away somewhere in my boxes of "junk", I had a dynamic microphone with cable, mic clip and a goose neck. After searching the shed I found the Radio Shack / Tandy Optimus 33-7058 unidirectional dynamic microphone and its accessories. I believe that the microphone was originally listed at about £30.00 or £40.00 but I purchased it for £10.00 in a sale. Noise Reduction: The bonus of using a Uni-Directional microphone mounted on a boom, stand, or goose-neck is that it will be isolated from noises caused my movement of hand and fingers and, being directional, will help reduce sounds from the rear, such as the whirring fans in radios, power supplies and computers. To use it I needed to make up a cable to connect between the microphone and transceiver and also provide a break out cable for a separate PTT switch - either a hand switch or a foot switch. A Heil cable would cost about £37.00, the Heil hand switch £39.00 and a Heil FS2 or FS3 footswitch also about £30.00. The Heil HM-12 microphone itself costing £70.00 with an HB-1 'anglepoise' desk mounted boom costing about £69.00 a complete mic system would cost around £216.00. With the things that I already had I thought that could put a separate microphone system together for under £20.00. Making A Microphone Adapter Cable: For microphone pin outs see this page: http://homepage.ntlworld.com/rg4wpw/date.html I had some suitable cables that could make a new microphone lead and the PTT lead, but if the cable had to be bought new it would probably have cost no more than £5.00. I had to buy an 8 pin mic plug (8 pin in-line socket) for £2.00 and a 6.3mm inline socket for £1.60 but I had a couple of 6.3mm jack plug for the hand switch, but that would cost about £1.60 if bought new. I also found something that could be used as a hand PTT switch in the junk box..... I retreived a 'panic button' from a bin that had been discarded from a PMR radio installation and saved it for some future use. I thought it could be used as a hand held PTT switch as it had a 'momentary' switching action required for push to talk applications and cost was zero. I had nothing for a foot switch, but I found a nice one of metal construction made by the Eagle brand for use with musical instruments such as keyboards. That cost only £7.00, so with having many components in the 'junk box' the total expenditure was around £11.00. Momentary Action switch:It's important that any switch considered for the PTT function has a momentary action - push for ON and release for OFF i.e. it is non latching and the contacts only connect and complete the circuit when pressed, disconnecting again when the button is released. Some foot switches are latching (which will not be suitable) and others may have the useful option to be wired for either push for on and release for off, OR push for off and release for on.  Preparing some of the parts for the homebrew microphone adapter cable
In-line XLR Socket (Plugged into microphone); 6.3mm in-line Socket for PTT switch; 6.3mm mono jack plug for PTT switch, 8 Pin in-line socket (plug) to connect to the radio; Shielded microphone cable. PARTS REQUIRED: (Approximate new prices 2012 - you may well find some of these items much cheaper) 2 or 3 metres of shielded microphone cable - 2 core for standard mic's or 4 core for Heil mic's with PTT switch. £5.00 2 metres of 2 core, or shielded single core cable for the break out PTT switch. £2.00 8 pin in-line socket ("microphone plug") for transceiver (or whatever connector is required for the particular rig check here: rg4wpw/date.html). £2.00 In-line, female, XLR socket to connect to microphone. 3 pin for many mic's or 4 pin for some Heil mic's. (Check heilsound.com). £2.00 6.3 mm (1/4") in-line jack socket to terminate the break out PTT cable. £1.60 6.3 mm (1/4") jack plug to fit to the PTT switch. £1.50 Momentary push-to-make switch or button for the hand held PTT switch. £2.00 Small plastic case to house the hand held PTT switch. £2.00 Eagle G028B Foot Switch or one of many similar available. £7.00 Goose-neck with base £11.00 to £14.00 - or Articulating Boom. £30.00 to £50.00 Dynamic Uni-Directional Vocal Microphone (Good quality e.g. AKG; Audio Technica; Beyerdynamic; Behringer; Heil; Sennheiser or Shure) from about £25.00 to £70.00 TOTAL WITHOUT MICROPHONE £36.00 to £76.00 (approximate) TOTAL WITH A MICROPHONE £61.00 to £107.00 (approximate) i.e. at the very worst, still half the price of a full Heil kit.  Microphone and the completed home-brew microphone adapter cable project with the
finished hand PTT switch below.
 Above: Kenwood TS-590s Microphone Socket Link: For microphone pin outs see this page: http://homepage.ntlworld.com/rg4wpw/date.html Diagrams for Microphone XLR Sockets
The 'plugs' that connect into the bottom of a microphone are actually in-line XLR sockets (famale), the 'socket' at the bottom of the microphone is actually the plug (male) part of the XLR system. Wiring for this and similar applications: Pin 1 of the radio's 8 Pin microphone socket is connected to Pin 2 of the microphone's XLR connector (MIC +ve) Pin 7 of the radio's 8 Pin microphone socket is connected to Pin 3 and 1 of the microphone's XLR connector (MIC -ve and SHIELD) Pin 2 of the radio's 8 Pin microphone socket is connected to the separate PTT breakout cable and 6.3mm In Line Jack Socket centre pin Pin 8 of the radio's 8 Pin microphone socket is connected to the separate PTT breakout cable and 6.3mm In Line Jack Socket body (SHIELD) Diagrams as viewed from the front of the in-line female XLR socket ("Mic Plug"):
*Microphones with a Balanced Output:
Professional quality microphones, such as the Shure models mentioned on
this page, have a Balanced Output where Pin 1 is Shield; PIN 2 is +ve
Mic Output and PIN 3 is -ve Mic Output. However if an unbalanced connection is required it should be possible to
simply connect Pin 3 to Pin 1 inside the inline XLR socket that plugs
into the base of the microphone to create an unbalanced connecting
cable. Ideally the balanced cable would be
preserved and suitably configured, i.e. balanced, microphone
amplifier circuit or an audio transformer used at the rig end. Balanced mic cables reduce noise hum and RF pick up.
Microphone Specifications - comparison between the Optimus 33-7058 and Heil HM-12
 Optimus 33-7058 Microphone Polar Diagram & Frequency Response Graph Optimus 33-7058 Microphone Specifications:
Type
..................................................................
Dynamic (Balanced output via XLR
connector)
Directvity .......................................................... Unidirectional Impedance ........................................................ 500 Ohms +/-30% (at 1,000 Hz) Sensitivity (at 1 kHz) ....................................... -75 dB +/-3 dB (0 dB = 1V/microbar) i.e -55db re 1V/Pa or 1.78 mV/Pa Frequency Response ......................................... 60 - 15,000 Hz Cable Dimensions (Length x Diameter) .............. 5 meters x 5.5 mm Microphone Dimensions (Length x Diameter) ..... 161.5 x 51 mm Plug ........ .. ................ . ..................................... 6.35 mm (1/4 inch) Jack Plug Included Accessory ............................................. Microphone Stand Adapter & Zippered Carrying Bag 5 Meter Microphone Cable with XLR Connector and 6.35 mm Phono Plug (cable supplied with unbalanced configuration) Weight . ............................................................... 198 g (Excluding Cable) The output will not be enough for many Icom rigs, particularly older ones that have insufficient microphone pre-amplification. In this case an electret microphone with around a -42 to -45dB sensitivity (7.0 to 5.6mV/Pa/1kHz) may be more suitable, or an add-on home-brew pre-amplifier could be constructed - perhaps like this > Heil HM-12 Microphone Specifications: Type .................................................................. Dynamic, moving coil, copper wound, mylar with internal shock mount Directvity .......................................................... Cardioid - exhibiting nearly –35 dB of rear rejection Impedance ........................................................ 1000 ohm Sensitivity ................ ........................................ -55 dB (no reference specified by Heil but presumably dB re 1 V/Pa ) Frequency Response ......................................... 80 Hz - 14 kHz @ -55 dB +4 dB peak centered at 2 kHz Connection......................................................... 4 pin XLR Included Accessory ............................................. Microphone Stand Adapter Weight . .............................................................. 250 grams (8.8 oz) (Excluding Cable) Cable required...................................................... HEIL CC-1 Connecting Cables. (cable with unbalanced configuration) ‘Soft touch’ PTT switch is wired to pins 3 and 4 for transmitter control with the microphone signal fed to pins 1 and 2 of the 4 pin XLR. Link: Microphone Sensitivity Calculations: http://www.sengpielaudio.com/calculator-transferfactor.htm AUDIO TAILORING - Filtering / Carrier Point / DSP: Microphones of this type are very good for sound recording and hi-fi applications as they have a good wide frequency response of 60 Hz to 15,000 Hz. However as with all cardioid / unidirectional microphones, this mic' exhibits the "proximity effect" which can make the low frequency bass response rather too full for efficient communications audio. For best intelligibility good communications audio should have a range of around 400 Hz to 2600 Hz - this is particularly important for spectrum efficiency so as not to hog a wide bandwidth and cause unnecessary QRM to other users desperately trying to find a bit of clear space on the bands!  http://www.shure.co.uk Above: A graphic representation of the 'Proximity Effect' - an effect of directional microphones whereby the bass output rises as the distance to the microphone decreases. Different makes and models of microphone will vary significantly. Some models are designed to minimise the proximity effect to some extent, e.g. the Shure SM-48. Large amounts of bass output are undesirable for clear, intelligible, communications speech. Spectrum and Power Efficiency: For spectrum efficiency and best use of transmitter power - not to mention good manners and simple consideration to other users - for SSB transmitters to be ITU compliant the audio bandwidth should be no wider than 300 Hz to 2700 Hz. After all SSB communications do not need to be "Hi Fi" - just clear and spectrum efficient - I don't need to be WABC! A wide transmission can cause great annoyance to adjacent channel operators who are trying to find a little bit of clear space, only to be splattered! Narrow Filter: Appropriate audio bandwidth may be achieved by the use of a narrow filter within the radio, either a mechanical or DSP IF filter. Carrier Point: In the Icom IC-706, for example, by using Menu Q4 the bass response can be rolled off by setting the Carrier Point to Carrier Point +100. Adjusting the Carrier Point for TX is equivalent to I.F. Shift in RX. (The Icom IC706 and other older Icom rigs, has comparatively low microphone gain and will need a microphone pre-amplifier if using most standard dynamic microphones. Dynamic mic's have lower electrical output than the electret microphones for which the radio is designed.) DSP: TS-590s: With the Kenwood TS-590s I found that, as a minimum, it was necessary to set DSP TX filter for SSB/AM low cut to 400 Hz [Menu 25], leaving the DSP TX filter for SSB/AM high cut at the default 2,700 Hz [Menu 26]. Matters could be further improved by use of the DSP audio equalizer: Whereas I found the DSP TX equalizer [Menu 30] was best set to C (Conventional) or HB2 (High Boost 2) best with the supplied Kenwood hand microphone, I found that the HB1 (High Boost 1) setting was better with the Optimus dynamic microphone. HB1 reduces the low frequency response slightly more than HB2. The best results were obtained by using Kenwood's ARCP-590 computer software to custom tailor the U (User) setting with a little more high boost and a little more low cut than with the HB1 setting using the on screen graphic equalizer. Mic Gain and Processor: Initial starting points with Optimus dynamic mic were: Mic Gain 50 - 60 | Proc In 40 - 50 | Proc Out 50 - 60 Designing and constructing some input filtering: For radios without adjustable filtering or comprehensive DSP control a simple high pass filter using a capacitor an resistor arrangement similar to that shown below might usefully reduce low, bass, response and not only make the audio clearer but also reduce bandwidth and unnecessary splatter affecting other users on a crowded band. Use the formula fc = 1/(2πRC) to find the -3dB cut off frequency. Where R is resistance in Ohms and C is Capacitance in Farads (note 1µF = 0.000001F) Note: For proper loading of a typical dynamic microphone with an impedance up to 600 Ohms, a microphone preamp for should ideally have an input impedance of between 1200 Ohms and 3000 Ohms. Read much more detail on this important subject on this external link. Some examples: In the example below if the resistor was 1.2k Ohms and the capacitor was 0.47µF the cut off frequency (fc) would be 282 Hertz. If the capacitor was 0.22µF then the cut off frequency would be 603 Hertz. (Incidentally these are the values used in the Kenwood MC-90 desk microphone). If the capacitor was 0.33µF then the cut off frequency would be 402 Hertz. Using a 12k Ohm resistor the capacitor value would be 0.047µF (47nF) to provide a cut off frequency of 282 Hertz, a capacitor value of 0.033µF (33nF) would provide an cut off frequency of 402 Hertz or a capacitor value of 0.022µF (22nF) for a cut off frequency of 603 Hz. Using a 2.2 k resistor may possibly be more appropriate, so here are some recalculations that include some capacitor values that are achieved by using capacitors connected in parallel. e.g: 2.2k Ohm + 220nF + 22nF = fc 299 Hertz or 2.2k Ohm + 100nF + 47nF = fc 492 Hertz. This is done because using standard value capacitors would produce some inappropriate & widely spaced cut-off frequencies.  Filtering with a
non-inverting operational amplifier arrangement - fc =
1/(2πRC)
First Order High Pass Filter ESP Elliott Sound Products  Another idea for a homebrew (DIY) PTT hand switch and the parts required - M0MTJ Momentary Contact Button for PTT switching; A length of shielded cable; A 6.3mm jack plug; A small plastic enclosure. Cost? £5.00 to £7.00 ?
Link: Microphone Sensitivity Calculations: http://www.sengpielaudio.com/calculator-transferfactor.htm MORE ABOUT MICROPHONES
Is there one of these lurking in a cupboard somewhere? A typical dynamic microphone - Shure model SM48 - http://www.shure.co.uk
Basic Microphone preamplifier
using simple inverting op-amp arrangement - Needs Development Work! :Unlike the Optimus 33-7058 the Shure microphone has higher output which could be useful, see spec's below:
Shure also produce the famous SM58 vocal
microphone which has a flatter wider frequency response than the SM48
& PG48 which, perhaps, may be a disadvantage for amateur radio use;
the mid-range lift and more rolled off bass response of the SM48 and
PG48 might be more desirable for clearer speech. Having said that, the SM58 minimizes proximity effect which could be useful. http://www.shure.co.uk
Link: Microphone Sensitivity Calculations: http://www.sengpielaudio.com/calculator-transferfactor.htm Microphones with a Balanced Output: Professional quality microphones, such as the Shure models mentioned on this page, have a Balanced Output where Pin 1 is Shield; PIN 2 is +ve Mic Output and PIN 3 is -ve Mic Output. However if an unbalanced connection is required it should be possible to simply connect Pin 3 to Pin 1 inside the inline XLR socket that plugs into the base of the microphone to create an unbalanced connecting cable. Ideally the balanced cable would be preserved and suitably configured, i.e. balanced, microphone amplifier circuit or an audio transformer used at the rig end. Balanced mic cables reduce noise hum and RF pick up. See balanced microphone preamplifiers here and also here. Dynamic Microphones designed specifically for amateur radio use: Heil HM-12 Genesis microphone The Heil HM-12 Genesis dynamic microphone I am told, uses Heil's new HC-6 dynamic element and therefore has a higher output than some typical dynamic mic's. The frequency response is 80 Hz to 14 kHz together with the hallmark Heil +4dB lift at 2kHz to enhance the clarity of the audio and unlike a standard dynamic hand microphone, the HM-12 also has a built in PTT switch. Too Expensive? - The HM-12 might seem rather expensive at £70.00 when you consider that a microphone such as the t.bone MB 95, which as very crisp clear vocal audio, can be bought for £20.00 from www.thomann.de , even a high quality vocal microphone such as Beyerdynamic TGV 35d s can be bought for about £45.00 from many authorized dealers such as www.soundexposure.com Heil HC-6 & the new Gold Elite microphone Heil Press Release for the HC-6 dynamic element: "Heil Sound Introduces New HC-6 Dynamic Microphone Element: Official Introduction at the Dayton Hamvention May 14, 2010. Heil Sound revolutionized amateur radio audio with their tailored response HC Series elements in 1982, which allowed the non-DSP transmitters of that era to produce different transmit responses by selecting the right microphone element. Fast-forward 30 years. Bob Heil has designed the new Heil HC-6 that, by adjusting the DSP EQ of the modern transceivers, will produce Beautiful, full range broadcast audio as well as narrow response contest/DX audio of the Heil HC-4 all from this one specially designed dynamic microphone element. The many 'voices' of the HC-6 are truly amazing. Using a .82 inch diameter Mylar diaphragm, the - 3dB points of the wide frequency range is set at 100Hz and 12.5 kHz. With sensitivity of - 57dB at 600 Ohms nominal output impedance centered at 1 kHz. The HC -6 Audio response can be equalized to match just about any requirements." The HC-6 element is used in the Gold Elite microphone "The new Gold Elite microphone is designed and crafted specifically for amateur radio communications. It contains two distinctly different high performance dynamic elements that are available at the flip of a switch to meet the different types of communications. The WIDE position has the HEIL Elite full range element producing smooth articulate 60Hz – 16 kHz audio with the traditional Heil +4 dB peak centered at 2 kHz. This gives the new Gold Elite excellent voice articulation". "The NARROW position features the new HC-5.1 dynamic element. In 1982, Heil Sound revolutionized amateur radio audio with their tailored response HC-4 and HC-5 elements for radios that had NO tone adjustments". "The HC-6 is designed to respond to those older rigs as well as today’s transceivers with on-board DSP EQ. The HC-6 produces full range broadcast audio as well as the tailored DX/Contest audio by simply adjusting your DSP EQ". http://www.heilsound.com/amateur Spec's
HC-6 wide.............................: 60 Hz - 16 kHz @ -55 dB at 600 Ohms HC-6 wide -6dB points.....: 100Hz - 12.5 kHz @ - 57dB at 600 Ohms HC-5.1 narrow..................... 200 Hz - 8 kHz @-58 dB at 1000 Ohms  Heil HC-6 Frequency Response Graph
 Heil HC-4 Narrow, HC-5 and GM Wide (not Gold Elite) Comparison Frequency Response Graph  Above graph from VK1OD - http://vk1od.net Other graphs and information from Heil Sound - http://www.heilsound.com/amateur
Interesting Reference : Sound System Interconnections incl. balanced audio at Rane.com
Link: Microphone Sensitivity Calculations: http://www.sengpielaudio.com/calculator-transferfactor.htm MICROPHONE PRE-AMPLIFIER IDEAS
Is there a hand held dynamic 'stick' microphone lurking in a drawer or cupboard somewhere? Rather than always using a hand held microphone I have experimented with a different microphone that can be suspended from a boom or goose-neck. I have a good quality Optimus dynamic microphone that I have found works well the the Kenwood TS-590s - see above. However the Icom IC-706MK2G is not best suited to dynamic microphones due to their low output and the 706, like many Icom radios, not having sufficient microphone amplifier gain. One route to take would be to use an electret condenser microphone or microphone element which have higher output than many dynamic microphones. I also have a couple of different unidirectional electret condenser elements to experiment with. To use a typical low impedance, lower output dynamic microphone would require some additional amplification with the Icom and would likely also require some additional filtering to roll off undesirable bass response that would make the transmitted audio less intelligible at RX. I therefore had a look at what might be required to build a simple external microphone preamplifier to compensate. Building an external amplifier would also allow experiments with some simple audio filtering, particularly concentrating on a low pass filter to roll off audio frequencies below a certain point, say below 300 Hz or below 400 hertz, for example.  Typical Inverting Operational Amplifier configuration [ Read about experiments with a microphone preamplifier circuit HERE > > ] ICOM HM-103 MICROPHONE MODIFICATION for the IC-706mk2g When I first got my Icom IC-706mk2g I had several reports of quiet audio that could not be fully corrected by using mic gain or compressor controls. It was suggested by a couple of fellow radio amateurs that I modify the HM-103 microphone that is supplied with the IC-706 radio. The modification was done in this way: The microphone casing is opened by removing the three screws on the rear panel. It is very important to hold the PTT switch in place while doing this otherwise it will come adrift and the spring could fly out and be lost! Next remove the three screws that hold the circular metal plate in place. Then remove the two very tiny screws that hold the small PCB in place. Behind this PCB is located the electret microphone element. Remove the electret element and also the rubber gasket. After discarding the rubber gasket the microphone could be fully reassembled and tested for audio improvements - it should be noticeably better, but if it's still not satisfactory the modification could be taken one stage further: Remove the circular metal plate and electret capsule again. Then, using a sharp modelling knife or scalpel, scrape away some of the plastic from the molding that holds the electret capsule in place to enlarge the aperture between the capsule and the larger circular area under the metal plate - where the sound enters from the exterior of the microphone's casing - as shown in the photograph below. This should allow more volume to reach the electret capsule and provide greater drive and punch to the rig. I have had no complaints about low audio since doing these modifications.  Icom HM-103 Microphone modification for IC-706mk2g by M0MTJ  WIRING A CABLE FOR A DIFFERENT MICROPHONE I decided to use my existing Leson (Altai) TW-232 Desk Microphone as an alternative to the Icom HM-103 hand mic that is supplied with the Icom IC-706MK2G transceiver. The TW-232 desk mic is fitted with a standard type 6 pin mic plug wired for my Midland 48 Excel CB radio. The Icom 706 has a completely different RJ45 type mic socket. I needed to make a 'cross-over cable' to fit between the mic plug on the TW-232 and the Icom 706 transceiver. Looking at the circuit diagram for the Icom IC706, the basic wiring only needs four wires: PTT (Push To Talk transmit switch), PTT Ground, Microphone Audio and Microphone Audio Ground. This is slightly different to CB wiring which does not have separate grounds for PTT and Mic, inside the plug on the TW-232 microphone these two ground wires were connected together. I therefore I separated the MIC Ground and PTT Ground within that plug. This would require two Cross-over cables; one for the CB that re-combined the two grounds together to match the wiring scheme required for CB and the second cross-over cable for the connection to the IC706Mk2G. Here is the wiring scheme for the TW-232 mic and the Icom transceiver: The Leson (Altai) TW-232 desk microphone wiring is as follows: White = PTT Black = PTT / Receive Ground Blue = Receive Red = Mic audio Shield = Shield (mic audio shield) Icom IC706Mk2G microphone plug wiring for RJ45 plug: 1 = +8 volts d.c. *** Do not connect & be careful NOT to short out otherwise the radio will be damaged *** 2 = Frequency up/down buttons 3 = Audio output 4 = PTT >>>>>>>>>>>>>>>>>>>> Connects to the White wire of the TW-232 Mic 5 = GND - Microphone Ground >>>>>> Connects to the Shield wire of the TW-232 Mic 6 = Microphone audio input >>>>>>>> Connects to the Red wire of the TW-232 Mic 7 = GND - PTT Ground >>>>>>>>>> Connects to the Black wire of the TW-232 Mic 8 = Squelch control
Above:
Leson
/
Altai
TW-232
wiring
diagram
*Important: Please check that the colour coding of the wiring of your TW-232 microphone is the same as that shown above - if not note the differences and proceed accordingly
Wiring
diagram
for
Icom
HM-103
microphone
shows
the
microphone
socket
as
seen
from
the
front
of
the
radio
(Icom Corporation) Icom IC-7000 The wiring for the IC-7000 would be similar for the TW-232 microphone (see TW-232 diagram above)
1 = +8 volts d.c. *** Do not connect & be careful NOT to short out otherwise the radio will be damaged *** 2 = Frequency up/down buttons 3 = HM-151 connection 4 = PTT >>>>>>>>>>>>>>>>>>>> Connects to the White wire of the TW-232 Mic 5 = GND - Microphone Ground >>>>>> Connects to the Shield wire of the TW-232 Mic 6 = Microphone audio input >>>>>>>> Connects to the Red wire of the TW-232 Mic 7 = GND - PTT Ground >>>>>>>>>> Connects to the Black wire of the TW-232 Mic 8 = Squelch control (HM-103) or Data in (HM-151)  Above - Microphone wiring for HM-103 and HM-151
pertaining to the Icom IC-7000 transceiver (Icom Corporation) The
Up / Down frequency buttons are not wired in my cross-over cable, but
could be used if required if additional switches were fitted into the
desk mic. The basic wiring only requires four wires to pins
4,5,6
& 7 in the RJ45 plug - as seen below:
 The RJ45 plug fitted to a short piece of mic cable  Fitting
the
RJ45
plug
to
the
mic
cable
 Fitting the mic socket on the other end of the cable  The completed cross-over cable Thanks to Alex and Dave at the Charlie Delta ARC for the necessary plugs that enabled me to make this cross-over lead. Cheers guys!! MORSE CODE PRACTICE OSCILLATOR  Internal view showing PCB and other components 
The
completed
CW
Practice
Oscillator
with
Morse
Key
 Morse Code practice oscillator using 4047B CMOS integrated circuit Parts Required: 4047B CMOS Integrated Circuit BFY51 Transistor 1M Ohm Preset Potentiometer - skeletal or enclosed, horizontal or vertical depending on physical layout 22k Ohm linear Standard Potentiometer Small Knob for 22k potentiometer 100k Ohm carbon or metal film resistor, 0.25 or 0.6 watt 150 Ohm carbon or metal film resistor, 0.25 or 0.6 watt 1nF ceramic or monolithic ceramic capacitor 6.3 mm (1/4 inch) Jack Socket for connecting morse key 15 Ohm miniature loudspeaker PP3 9 volt battery PP3 battery clip Vero Board Project Case Kit Available Here SHORT LOADED TOP BAND ANTENNA FOR 160 Metres / 1.810 to 2.0 MHz My experimental project during 2009 was trying to accommodate a small top band antenna in the restricted space at my QTH. A full size aerial for Top Band is going to be far too big for most back gardens, but the basic requirement really is to get as much aerial wire in the air as possible - the longer the better - and then load the antenna to bring it to resonance on the band. I used a small inductor wound on a 50mm diameter plastic tube. A top band aerial like this also needs the very best earth possible - i.e. as many ground wires as can be accommodated. I gradually refined my ideas and have now put the results on the antennas page here BALUN and UNUN CONSTRUCTION I needed a 4:1 Balun for my Delta Loop antenna, so I built one inside a 100mm x 100mm IP54 weatherproof box. It is wound on a T200-2 toroid core using 1.2mm diameter / 18 s.w.g. enamelled copped wire and so should handle about 400 watts:  The Feed Point of the Delta Loop Antenna is fed via this 'home brew' 4:1 balun by M0MTJ Previously
I had constructed a smaller 4:1 balun in a non weatherproof enclosure.
This is wound on a T157-2 toroid core which should handle about 200
watts.
Simple 4:1 Balun by M0MTJ A Small Combined Balun / Unun for Portable Use:
Small compact antenna tuning units such as the LDG Z11 Pro or MFJ 945E, for example, do not have a built in 4:1 balun so, depending on the type of aerial being used a balun (or unun) may well be needed and so should be added to the equipment list. A resonant dipole or doublet fed with twin lead for lightness will need a 4:1 balun at the ATU. Alternatively a simple vertical (random length) wire up the 7 metre tall fishing pole with a counterpoise run along the ground could be used. Such an aerial would use an Unun as a more appropriate matching device. To save having to carry both a 4:1 balun and a 4:1 unun, I decided to make a combined Balun / UnUn unit housed in a small plastics case. Since an Unun is merely a balun with the PL259 socket wired in reverse (see diagrams below) it seemed logical to make an impedance transformer with two SO239 sockets; one wired as a Balun for doublet antennas and the other wired as an UnUn configuration for unbalanced antenna wires. As a quick test I fixed a 7.2 metre length of wire to my fishing pole, supported vertically, and ran out a similar length of counterpoise wire. Connected to the Baln/Unun unit with the coaxial feeder connected to the UnUn socket, I could obtain an easy match using my MFJ-945E on 40m; 17m; 15m; 12m and 10 metres. Surprisingly 20 metres was a more tricky band, the best SWR that could be obtained using the ATU was about 1.5 on this band. No doubt with a bit more experimentation I will find a more suitable length for the radiator wire for the, admittedly compromised, but easy to erect antenna. If using a twin lead fed doublet antenna then the coaxial cable is plugged in to the other socket so that the Balun configuration is used. 
Combined 4:1 Balun and 4:1 Unun
The Balun/Unun unit is housed in a small plastics case measuring a mere 76mm x 50mm x 28mm. A standard T130-2 toroid core is used with 18 bifilar turns of 18 SWG enamelled copper wire make up the windings in a standard 4:1 balun configuration (see diagram below) wired to the top S0239 socket and the red and green binding posts. The top socket is used when using the unit as a Balun. A second socket is mounted on the side of the case and is wired for using the unit as an Unun - this is simply connected to the top SO239 socket in 'reverse' - i.e. the centre pin of the top (balun) socket is connected by a short wire link (brown) to the body of the side (unun) socket while the body of the top (balun) socket is connected by a short wire (blue) to the centre pin of the side (unun) socket. When used with a balanced antenna the twin feeder connects to the two binding posts (red and green) either way around; When used with an unbalanced antenna, such as described above, the radiating wire connects to the red terminal post while the counterpoise or earth wire connects to the green terminal.
Power Handling? I would guess that by using a T130-2 toroid and 18 SWG wire should be adequate for up to about 100 watts power handling, but it is only intended for portable low power use of, perhaps, around 10 watts to 50 watts and so it should handle those levels easily. * * * Below is some more information from 2E0KGV, M0UKD, and W4ED which was helpful when working on these little projects: http://www.sdarc.net/wp-content/uploads/pdfs/Making_Baluns.pdf  4:1 BALUN  4:1 UNUN  9:1 UNUN 1:1 Balun :
1:1 Balun details by M0UKD     http://www.m0ukd.com/1to1_HF_Balun_for_dipole/index.php http://warga11mc.blogspot.com/2010/07/balun-11-14.html 4:1 Current Balun Design by W4ED :
  W4ED 4:1 Current Balun Design OTHER PROJECT IDEAS There are many other useful devices that can be made, such as an ATU for portable QRP use, various types of receivers, pocket sized QRP CW transmitters, complex transceivers - the list is endless. Some projects have to be built from scratch which involves making the necessary PCB, other designs provide a pre-etched PCB while many are available in complete kit form. Moxon Antennas: I quite fancy having a go at building a Moxon antenna for the SSB portions of 70cm and perhaps another for 2 metres. Other good projects would be a Noise Bridge or Crystal Calibrator - and more experimental antennas! Noise Bridge - a much lower cost alternative to an expensive antenna analyser
Antenna analysers now tend to be extremely expensive, but a good noise bridge could be used as a much lower cost alternative. A noise bridge can be used for measuring the impedance of antennas and traps at various frequencies. Your H.F receiver is used as the bridge null detector. A number a circuits are available on the internet and kits are also available, such as the high quality RX2 from VK3AQZ Kits. Here are some useful links: http://www.vk3aqzkits.com RX2 Information sheet
http://jandek.co.uk/Assets/JD031.PDF http://newenglandqrp.org/files/noise-bridge-instructions.pdf http://www.spirat.com.au/vk5zvs/pic21.htm http://www.qsl.net/m/m0pmb/m0pmb/noisebridge.html http://forums.qrz.com/archive/index.php/t-266081.html  High quality RX2 Noise Bridge Kit from VK3AQZ your H.F receiver is used as the bridge null detector. LED VU Meter - LM3915 provides 3dB steps
Posted by Jeroen Vreuls This
simple LED VU meter has only a few parts but is useful as an indication
of the noise. The circuit is built around a LM3915, the brother of the
logarithmic LM3914. The input
signal of the VU meter on pin 5 of IC1 put. By pin 9 of IC1 is the
display mode sets (bar or dot display). In the situation shown works IC1
in the dot-mode (point). When pin 9 to pin 3 is connected, the IC
operates in bar-mode (beam) - the circuit will consume less power in dot
mode.
 http://www.circuitsonline.net
http://www.next.gr free online electronic circuits (External Link) Here's a nice little dual band vhf / uhf antenna project !
(External Link) Ham Radio 2m / 70cm Vertical Dipole Antenna Sleeve dipole type for 144 MHz and 430 MHz VHF / UHF top of page ^   "One person's junk is another person's treasure" Links to Electronic Component Suppliers DISCLAIMER: If you attempt any of these projects proceed with due caution with regard your own safety and the safety of the equipment that you are working with! I cannot be held responsible for any accidents, injuries or damage caused to any equipment that may result. |
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Mike Smith - MDS975.co.uk © 2003 - 2013
M0MTJ
Subjects covered on this page:
Heil HM-12 Gold Elite Goldline HC-4 HC-5 HC5.1 Handi-Mic
Shure PG48 PG58 SM48 SM58; Behringer Ultrvoice XM8500; AKG D5; Audio-Technica VC5; PRO41; ATR1300
Beyerdynamic; Sennheiser.
Using a dynamic stick microphone with the Kenwood TS-590s
Amateur Radio; Ham Radio; Radio; Transceivers; HF; VHF; UHF; Data Modes; Morse Code; RTTY; PSK31; SSTV; FSTV; Amtor; Sitor;
Morse Code; CW; Microphone Adapters; Field Strength; Meter; Yaesu LDG FT Meter; ALC Power Adjustment; Dummy Load;
Antennas; Aerials; Top Band; 160 metres; Cable; Coaxial Cable; Twin Lead; Propagation; Computer; PC; USB Computer Interface; Microphone
Loudspeaker; Filters; Noise Reduction; DSP; Digital Signal Processing.