SURF (Selector Unit Radio Frequency)
Heres what to do if you think you need a SURF - Forget it!
The Selector Unit Radio Frequency is one of those devices which, particularly the 4W SURF for the PRC-351, you will be offered. You dont need one! In fact, it can even make your signal worse! The purpose of a SURF is to prevent adjacent channel interference or receiver blocking when two or more radios are used very close together physically - for example in a command post bunker. It is simply a preselector. If your going for the 'CES' look (Complete Equipment Specification) for a collection or re-enactment, or to equip your newly restored FFR Landrover (Fitted For Radio, not to be confused with most MoD hardware acquisitions of the last two decades - FFBNW - Fitted For But Not With) then by all means put a 4W SURF on the top of your PRC-351 (I have!) but dont use it for actual on the air operation.
|PRC-350 with SURF|
SURFs are also available for the PRC-320 (only ever seen one and that was on a table at the Finningley Rally today!) and the PRC-350.
While we are on RF accessories, i'll mention the 20W amp that turns a 4W PRC-351 into ...
The PRC-351 when used with the clip on 20W amplifier becomes designated the PRC-352. At this point, you must start using proper antennas not the battle whips. If you do use the amp, make sure you physically remove the whip, otherwise the resulting dual radiation and poor impedance match causes poor performance.
|20W amplifier block|
So, if you have got yourself a Clansman radio, be it a 320 for HF, or a 350 or 351, even a 352, for VHF, your almost ready to go. But not quite. You now need a power source - a battery. But, unlike modern amateur equipment, you still cant then just turn it on and go. You need audio ancillaries!
I wont put pictures of batteries up, as you can easily find these on the blog, and besides you have hopefully got the seller to throw one in!
Both the PRC-320 and PRC-351/2, and the PRC-319, use the standard 24V NiCd packs. These come in two current flavours - 1Ahr and 4Ahr (some variations do exist) and either plastic or alloy cases. The alloy cased batteries are easiest to strip to build modern batteries into. The 1Ahr is about half the size of the 4Ahr. There is even a primary lithium version available.
These batteries of course need a charger. The standard charger is the DCCU, but 12V fed DCCUs are hard to find and expensive. Most are 24V for vehicle use. It is much easier to charge them using a modern intelligent charger that can do all your batteries, such as the Turnigy Accucel-8 I use.
The PRC-350 uses a special and unique 15V battery. Most likely you will get a battery cassette, to take D cells. Invest in some NiMH cells for this, as using alkalines will cost a fortune. Likewise the PRC-349s use an odd 12V 600mAh pack, and if you did get one of these radios you'd most likely get a cassette with it. Incidentally ive got hundreds of these...
I'll talk about audio ancillaries in the next entry. This is quite a wide subject.
Over the past few days ive had my EKGSA antenna rigged on one of my 5.4m masts. This had to come down today, and did so shortly after the heavy showers. Luckily the showers held of for the duration of the Finningley clubs radio rally.
It was great wandering around in the sunshine deciding what junk I could get away with taking home! In the end though, I bought very little - a surface mount relay, and a Clansman Remote Handset.
You might notice that the handset has no cable... find out why in the next thrilling installment!