Tuesday, 22 September 2015

Chinese Airband Receiver

Well, this finally arrived today! And it rather distracted me from my principle task of checking and adjusting the PRC-351's deviation, which is what I was meant to be doing since ive yet to manage a QSO with it, however I do think that might just be down to low power and low activity.

First impressions are good. It was all shipped in resealable plastic bags, all the parts are present (and as usual, a few extra!), and the PCB is high quality, through hole plated, with, as seems normal for Chinese kits, the groundplane on the solder side. The band pass filter components were already installed. Im not entirely sure why, but as the coils are the most tricky part for a less seasoned constructor, perhaps its actually for the best.

Ive installed the resistors, a couple of ferrite chokes, the molded coil, and the IC sockets. I'll do the capacitors and maybe a few more bits over the next few days.

Ive also had the PRC-320 open for its first inspection since coming into my ownership. Partly this was to allow inspection of the PSU module and the dreaded tantalum capacitors. I found that the case bolts were rather easy to unfasten, so thats something I need to ensure when im finished - that the case is up to correct torque. Some of the internal modules could also do with their screws nipping up a bit.

I was quite impressed by the build quality, especially the antenna tuner, which uses a permeability tuning technique. The module to the top left in the above picture is the synthesiser. This is where my attentions will be, along with the decade switches, when planning the VFO control system.
The picture below shows the underside, and the main board. The turret tuner is the big cylindrical block in the middle.

Taking the lid off the PSU module revealed that im too late! 

Instead of the MoD issue module with its dodgy tantalums, I found instead three modern DC-DC converter modules and a nixie type high voltage PSU module. So the PSU has already been thoroughly converted.
I have only one slight worry, and that is that this bit fell out -

and ive no idea where from! The radio works perfectly without it! I suspect its a locating stud from a module thats come loose.

Incidentally, if anyone who reads this blog is located either close to Selby or close to Emley Moor, and has 70MHz FM equipment, I really would appreciate a sked to get a check on my deviation level!

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