[ARC5] GRC-9 BFO

[robinson at tuberadio.com]

Hi Wayne,

Running the oscillator at 1/2 the frequency
eliminates pulling
by the received signal.

Regards
Ray vk2no

>
> The designers must have had stockpiles of 1R5's to use them as BFO and
> as crystal calibrator. I think I would have used that 1R5 BFO as product
> detector rather than feeding that diode, and driving the 3rd grid with
> IF instead of tying it to ground, and then take audio from the anode...
> Well the BFO does a good job if sigs are not too strong and lock HFO and
> BFO firmly to zero beat.
>
> Peter,
> PA0PJE
>
> Sorry Wayne, should have sent it to the list.
>
> Op 21-04-2020 om 19:01 schreef Robert Eleazer:
>> The GRC-9 receiver has a 456 KHZ IF and a BFO that runs at half the IF
>> frequency, 228 KHZ.  I've never seen this done before.
>>
>> Based on my own experience with adding a BFO to a SW receiver I can only
>> assume this design feature is to prevent the harmonics from the BFO from
>> overloading the receiver.  The receiver covers 2-12 MHZ so nothing below
>> the BFO 10th harmonic could get into the set, and I assume that by that
>> point the signal level is low enough to not be a problem/
>>
>> Wayne
>> WB5WSV
>>
>>
>>
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