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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 | Microphone Wiring Microphone Pre-amplifier Ideas | Morse Code Practice Oscillator | Shortened Top Band Antenna | Balun and UnUn Ideas 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 beseen 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: 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 excelleint since I like analog S-Meters and 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. The menus of the FT-857 and FT-897 allow the radio to output indications of Signal Strength; Power; SWR; Modulation; Voltage and Discriminator. 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 above.  FT Meter schematic
circuit diagram
drawn by Frank OK2FJ
  FT-Meter - DIY Homebrew project by MØMTJ 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 reproducable for this homebrew 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 homebrew FT-Meter for a fraction of the cost of a commercial unit, but Frank has greater image editing and graphics skills 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. When printed, the image will need to be scaled quite accurately to suit the size of the particular meter movement being used, otherwise the needle will not line up properly with the scale and the indication will be inaccurate. This can be done by trial and error until the correct size is found - a bit of a fiddly and a rather wasteful method. Alternatively a bit of simple math's can be used. 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 reulting 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, becuase 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.  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 daw 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  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 transciever 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 transciever 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.      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 componets!  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 resemlence 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 germnium 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 deflecton (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!  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 relase 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 transciever (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"):
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
Directlvity .......................................................... Unidirectional Impedance ........................................................ 500 Ohms +/-30% (at 1,000 Hz) Sensitivity (at 1 kHz) ....................................... -75 dB +/-3 dB (0 dB = 1V/microbar) ** 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 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 -50dB sensitivity 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 Directlvity .......................................................... Cardioid - exhibiting nearly –35 dB of rear rejection Impedance ........................................................ 1000 ohm Sensitivity ................ ........................................ -55 dB 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. ‘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. 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 with this microphone and presumably other similar types, the proximity effect might 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! For spectrum efficiency - not to mention good manners and simple consideration to other users - for SSB transmitters to be ITU complient 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. We don't need to be WABC! 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. 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: Mic Gain 50 | Proc In 20 | Proc Out 80 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) 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-60 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. 2.2k Ohm + 100nF = 723Hz 2.2k Ohm + 220nF = 328Hz 2.2k Ohm + 470nF = 153Hz Rod Elliott explains "that a good mic preamp (for microphones of up to 600 Ohms) will have an input impedance of between 1.2k and 3k Ohms. This causes far less loading, and does not cause any problems for the microphone." Read much more detail on this important subject here.  Filtering with a
non-inverting operational amplifier arrangement - fc =
1/(2πRC)
First Order High Pass Filter Find more excellent information, designs and PCB's at 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 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 transciever. 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
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!! 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. 
Have you got one 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: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. http://www.shure.co.uk
 A Typical Inverting Operational Amplifier configuration The gain is set by R1 and R2. In this case 220,000 Ohms ÷ 2,200 Ohms = gain of 100 x C2 and R1 form a simple first order high pass input filter that would have a gentle filter slope from a cut off frequency of 72 Hertz  fc = 1/(2πRC) Where
fc is cut-off frequency in Hertz, R is resistance in Ohms and C
capacitance is
in Farads. (1µF = 0.000001F)
1 ÷ ( 2 x 3.14 x 2200 Ohms x 0.000001 Farads) = 72 Hertz A first order filter will reduce the amplitude of the signal by 6db (power reduces by half) every octave (halving or doubling of frequency) - that is -20dB per decade (factor of 10 of frequency). For SSB communications use a high pass filter with a cut-off frequency of somewhere around 300 Hz might be more appropriate. Changing the resistor R1 to a 5.6k Ohm device and the capacitor C2 to 0.1µF (0.0000001F) would produce an fc of 284 Hertz. Since most capacitors have a tolerance of +/- 20% the 0.1µF capacitor could, in reality, have a value of anywhere between 0.08 and 0.12 µF which would affect the fc quite significantly to between 355 Hertz and 236 Hertz. Switching C2 to 0.047µF (47nF) would change the fc to 606Hz Switching C2 to 0.22µF would change the fc to 129Hz and switching to 0.47µF would give an fc of 60Hz. Since R1 has been changed, the gain of the amplifier will have also changed. To retain a gain of 100x R2 will need to be adjusted accordingly to 560k Ohms. However a gain of somewhere between 10 and 20 might be more appropriate for connecting a microphone to a transceiver so a value of 100k Ohms could be used for R2 giving a gain of 17 x. The final output level being set by the 1k preset potentiometer being careful not to overdrive the microphone preamplifier in the transceiver. Alternatively, by retaining the 2.2 k Ohm resistor in the above circuit the gain could be set at 21 by changing R2 to 47k Ohms, for example, and the cut off point (fc) could be set to various other values by swapping the capacitor C2 according to fc = 1/(2πRC) : 2.2µF
-
fc
=
33Hz
1.0µF - fc = 72Hz 0.47µF - fc = 154Hz 0.22µF - fc = 329Hz 0.1 µF - fc = 723Hz + / - tolerances of capacitor and resistor 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 value of 220,000 Ohms for R2 would give a gain of around 18.
Non-Inverting Operational Amplifier example:  Non-Inverting
Operational
Amplifier
configuration
for
dynamic
and
electret
microphones
www.zen22142.zen.co.uk/Circuits/Audio/lf071_mic.htm Above, a
circuit
design by Andy Collinson for microphone preamplifier of high
quality. The circuit uses a single power supply and is particularly
suitable for dynamic microphones, although electret microphones can
also be used.
The design is a typical non-inverting configuration with input impedance is 23.5k Ohms. The op-amp should be of high quality for best performance with high signal o noise ratio. e.g.TL071, NE5534 or OPA 371 Voltage gain is set by R2 and R1 - use the formula: Vo = ( R2 / R1) + 1 It could also be possible to power the electret element remotely by the addition of a resistor of 1k or 2k from the power supply line to the audio input, but this arrangement needs a DC blocking capacitor at the input - as shown in the above diagram the capacitor is of the incorrect polarity for this function so this would need to be slightly redesigned - a second electret capacitor before the 10µF shown but with reversed polarity should do the job. Care should be taken with values as this will affect the input filtering - a non polarised capacitor might also be considered for this position. Audio Filtering: Rod Elliott of ESP (Elliott Sound Products) provides information in the diagram below for a simple first order input filter when using an operational amplifier in a non inverting configuration. As with the previous example, the cut off frequency, fc, is determined by the formula fc = 1/(2πRC)  Filtering with a
non-inverting operational amplifier arrangement - fc =
1/(2πRC)
http://sound.westhost.com/dwopa2.htm ESP articles index here
2.2k Ohm + 100nF = 723Hz 2.2k Ohm + 220nF = 328Hz 2.2k Ohm + 470nF = 153Hz Just a thought: Perhaps using a fixed 100nF capacitor with a fixed 2.2k Ohm resistor in series with a 4.7k Ohm potentiometer might allow the cut off frequency to be continually varied between 723Hz and 230Hz. With a 10k Ohm potentiometer the range could be 723Hz down to 130Hz. However: Rod Elliott explains "that a good mic preamp (for microphones of up to 600 Ohms) will have an input impedance of between 1.2k and 3k Ohms. This causes far less loading, and does not cause any problems for the microphone." Read much more detail on this important subject here. Microphone Preamplifier with compressor using the Analog Devices SSM2165-1 integrated circuit:  SSM2165-1 Microphone Preamplifier and Compressor A building block idea that can be modified as explained below Perhaps the most interesting mic preamp, and one that I intend to construct, is based around the Analog
Devices SSM2165-1 integrated
circuit along the lines of the circuit diagram shown above which is
based on the DYC817 implementation.
The BC549 transistor is a simple input preamplifier stage. The input level to the SSM2165 integrated circuit being adjusted by the 1k Ohm preset potentiometer. Some designs omit the transistor stage when using electret condenser microphones since these have higher output, however if connecting a dynamic microphone directly to the SSM2165 the internal noise gate may not be successfully opened - causing obvious operational problems! The BC549 stage is therefore included in this design for use with lower output dynamic microphones so that the noise gate within the SSM2165-1 will be opened successfully. The 1k preset potentiometer can be carefully adjusted for proper noise gate operation with both dynamic and electret microphones. The capacitor across pins 3 and 2 couples the internal buffer amplifier to the internal output VCA. The value of this capacitor determines the low frequency response of the unit because it forms a simple high pass filter in conjunction with two 500 Ohm internal resistors - a total of 1000 Ohms; so fc = 1/(2πRC) so; fc = 1 ÷ 6.28 x 1000 x 0.0000033F = 48 Hertz. For voice communications a value of 1µF would provide a roll off below 160 Hertz. A 0.47µF capacitor would produce an fc of 339 Hertz. The compression ratio can be adjusted from 1:1 up to 15:1. The resistor or variable preset potentiometer between pin 6 and ground sets the compression level. The diagram above allows the resistance to be varied between 47k and 147k which adjusts the compression ratio between 4:1 and 9:1. A value of 5k Ohm or less will produce a compression ratio of 1:1 while using a 200k Ohm variable potentiometer will allow the compression ratio to be adjusted up to 15:1 The capacitors at the input pin 4 and output pin 7 should be non polarised, this helps prevent a 'pop' as the noise gate opens and closes. The capacitor from pin 5 to ground controls the time constant of the internal level detector, values of between 2.2µF and 22µF can be used and will change the response to low frequency sounds. According to the data sheet 'Capacitor values from 18µF to 22µF have been found to be more appropriate in voice band applications, where capacitors on the low end of the range seem more appropriate for music program material. For optimal low frequency operation of the level detector down to 10 Hz, the value of the capacitor should be around 22µF. Some experimentation with larger values for this AVG CAP may be necessary to reduce the effects of excessive low frequency ambient background noise. The value of the averaging capacitor affects sound quality: too small a value for this capacitor may cause a “pumping effect” for some signals, while too large a value can result in slow response times to signal dynamics'. Adding a 47k Ohm resistor in parallel with a 22µF capacitor from pin 5 to ground will also help to eliminate the 'pop' from the noise gate as it opens and closes by smoothing the attack and release curve, reducing the attack and release time constant. The SSM2165 datasheet suggests that a 22µF would be suitable for music use, but during speech communications one would always hear a noticeable rise in audio level during a pause in speech for an additional one or two seconds before the noise gate closes - a very annoying effect for the receiving station. The use of a 22µF in conjunction with a parallel 47k Ohm resistor will cause the noise gate to close immediately after the speech stops of during a short break in speech. (Tip by DG2IAQ ) Analog Devices SSM2165 datasheet SSM2167 datasheet
Some more information about the DYC-817 speech processor / compressor here Link: Microphone Sensitivity Calculations: http://www.sengpielaudio.com/calculator-transferfactor.htm Dynamic Microphones designed specifically for amateur radio use Heil HM-12 Genesis microphone The Heil HM-12 Genesis dynamic microphone 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. The HM-12 might be all you need with many rigs that have sufficient microphone pre-amplification and the necessary audio tailoring and filtering. Unlike any other standard dynamic hand microphone, the HM-12 also has a built in PTT switch. 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". 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 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  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 PROJECTS 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! The soldering iron could be busy!
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Mike Smith - MDS975.co.uk © 2003 - 2012
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;