STATION ACCESSORIES

Antenna Tuning Unit

Or more correctly described as the Antenna Matching Unit - since an ATU cannot tune an antenna, it can only match the impedance presented by the antenna system to the 50 ohm impedance required by the transceiver or receiver.

Antenna Analyzer

I have found the antenna analyzer to be an invaluable piece of equipment.

It is extremely useful for checking and setting up external aerials since it save one having to keep running up and down stairs to the shack checking VSWR. With an antenna analyzer it is possible to remain by the antenna while making adjustments and checking.

The analyzer can also be used to diagnose faults and to assist in making many other extremely complex measurements and calculations.

Perhaps it is at its most valuable in everyday use when 'tuning up' before transmitting. Because an analyzer has an internal and adjustable oscillator, it can be used to check VSWR at and make ATU adjustments without having to press the PTT on the radio. This prevents any unnecessary interference to other radio operators. Essential!

To quote from MFJ Enterprises; "Read antenna SWR and Complex Impedance 1.8 to 170MHz. Read Complex Impedance as series resistance and reactance (R+jX) or as magnitude (Z) and phase (degrees). You can determine velocity factor, coax cable loss in dB, length of coax and distance to a short or open in feet. You can read SWR, return loss and reflection coefficient at any frequency simultaneously at a single glance. Also read inductance in UH and capacitance in pF at RF frequencies. Large easy-to-read two line LCD screen clearly displays your information. Built-in frequency counter, Ni-Cad charger circuit, battery saver, low battery warning and smooth re-duction drive tuning and much more. Super easy to use! Just set the bandswitch and tune the dial -- just like you transceiver. SWR and Complex Impedance are displayed instantly!"


Balun

One of the most useful devices for the shack is a balun, or more to use a more correct term, a 1:1 choke balun. This will match a balance 75 ohm twin feeder to the unbalanced 50 ohm input of the Antenna Matching Unit.  The Antenna Matching Unit (often referred to as an ATU) will then transform the impedance presented by the antenna feeder to the 50 ohms required by the transceiver.

Dummy Load

A dummy Load is an essential item of amateur radio equipment. It allows various tests to be carried out on the transmitter, such as checking modulation or deviation levels, without radiating an RF signal from the antenna. This avoids causing unnecessary interference to other users.


Power Supply Unit

Perhaps an obvious requirement! The PSU is needed for powering a transceiver that has no built in mains transformer and for powering other station accessories. The PSU needs to be able to provide a clean and stabilized 13.8 volt supply at the necessary current rating: A typical 100 watt transceiver would require around 20 Amps when running at full power.

I use a Palstar PS-30 PSU, it has short circuit protection and has an overcurrent warning indicator, a galvanised steel case, precision ammeter and voltmeter monitoring, thermostatically controlled fan, screw terminals and snap in terminals.


R.F. Filter - Low Pass Filter

An RF filter may not always be necessary, but if the transceiver suffers any spurious harmonic output when transmitting an external filter can filter such products out, thereby preventing or reducing any possible interference to receivers operating on higher frequencies, such as televisions and domestic radios etc.


External Loudspeaker

An external speaker is often better than the loudspeaker built into many radios. An external speaker also allows the use of external audio filters or digital signal processing units (DSP's) to be connected to the transceiver.

I have two external speakers -  a simple little CB speaker that I purchased from Knights. Although it is small it is very clear and because it cuts out a lot of low frequency sounds it can be very helpful in improving intelligibility in some circumstances. The other speaker is the large one that sits on top of the cabinet. This I made myself from a GL13 10 watt, 6 inch loudspeaker unit and grill that I purchased from Maplin. I find it very good in most circumstances. 


Headphones

Useful for personal listening so as not to disturb other people too much. Headphones may also be helpful when trying to hear weak signals. 'Closed-back' headphones cut out more external noise than 'open-back' headphones.



Alternative Microphone

The HM-103 hand mic that comes with my Icom IC706-mk2G seems very good, but I also have a Leson TW-232 Desk Mic available.



Morse Key for CW

This is my simple HK-705 Hi-Mound straight Morse key




Power Meter / SWR Bridge





Noise Reduction / Digital Signal Processor

I have a BHI NEIM 1031 Noise Eliminating Module that has adjustable DSP noise reduction. Even without using the DSP noise reduction the BHI unit has a built in 4.5 KHz low pass filter that can make harsh audio sound much more pleasant.

Personal Computer

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