[Milsurplus] Chinese 102/139 set

[Richard]

Well, I can't find my documentation, but from  memory:

The Chinese sets came a bit later than the GRC-9, and are very similar, 
but with interesting differences.  The set came with phones, key, 
microphone, spare tubes in nice boxes, antennas, and a nice Chinese copy 
of the Triplett 666 multi-meter.  Also a soldering iron to be heated in 
a fire, which would be fine in the field.

The main transmitting antenna is a 200 foot (?) dipole fed with open 
wire feeder, and the transmitter output tuning is designed to feed it. 
There was also a 60 foot hank of insulated wire, perhaps for use on 
higher frequencies, or maybe as a separate antenna for the receiver.  
The transmitter VFO has direct calibration, rather than a chart as on 
the GRC-9.  There is provision for maybe 10 crystals.

The receiver is closer to the GRC-9, but with design differences.  One 
feature of the dual-diode detector first audio stage in one tube is 
"play through," wherein when the audio gain control is completely down 
there is some audio "play through," due to uncontrolled electron flows 
in the tube.  The GRC-9 overcomes this by using a dual pot, with one 
section to the 1'st audio, and one section feeding the audio output 
stage.  The Chinese receiver changes screen grid voltage to the RF and 
IF stages to vary set gain.  It uses a resistor in the B- lead to 
provide bias to the audio output stage rather than use a bias battery as 
in the GRC-9.

Construction is first class, as good as to better than ours.  For 
example, capacitors are inside solder-sealed ceramic tubes, and I think 
it would survive longer in a humid jungle environment than ours.  
However, I slightly prefer the GRC-9 because it's easier to use.  Good 
luck on finding the hand-crank generator.  My guess is they were held 
back due to the weight.  There was also a mythical dynamotor for mobile use.

Richard, AA1P



On 10/03/2018 02:38 PM, Kenneth G. Gordon wrote:
> OK, Guys, tell us some details about this thing. I thought it was a Chinese version of the
> GRC-9.
>
> Obviously it isn't.
>
> Ken W7EKB
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