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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.  Front panel of my MFJ Antenna Matching Unit  Rear panel
of my MFJ Antenna Matching Unit
BalunOne 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.  MFJ 260C 300 Watt Dummy Load Filter - Low Pass Filter A 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.  My useful little CRT mobile extension speaker  My larger speaker, made using a Maplin GL13 6 inch 10 watt drive unit plus grill 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  Standard type power and SWR meter  Cross Needle type power meter 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.  BHI NEIM 1031 dsp module Personal Computer A personal computer might not be regarded as an accessory as such, but it an essential tool. I use the PC for all the usual things such as researching amateur radio subjects on the internet, but it can also be used for decoding and sending data modes, e.g. CW (Morse), Packet, PSK31, RTTY, SSTV and keeping a station log book. Data modes> Antenna Analyser I haven't got one of these, but an antenna analyser would be an extremely useful in setting up antenna systems. Even the simplest hand held SWR Analyser would save a lot of time running back and forth to the 'shack' to check the SWR at the radio end when making adjustments to an aerial. The more complex Antenna Analysers can do a lot more than take simple measurements. 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!" Power Supply 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. 
If you have got any specific Amateur Radio questions try visiting a specialist forum on the net :-  http://www.transmission1.co.uk |
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Mike Smith - MDS975.co.uk © 2003 - 2008
Subjects covered on this page:
Amateur Radio; Ham Radio; Radio; Transceivers; HF; VHF; UHF; Data Modes; Morse Code; RTTY; PSK31; SSTV; FSTV; Amtor; Sitor
Antennas; Aerials; Cable; Coaxial Cable; Twin Lead; Masts; Poles; Propagation; Computer; PC; USB Computer Interface; Microphone
Loudspeaker; Filters; Noise Reuction; DSP; Digital Signal Processing; Morse Key; SWR ; Inverted L; Inverted V; Dipole; Doublet;