[ARC5] HF Converter - feeding mixer with a square wave?

[Tim]

Hi Les et al - As a "hack" I used the Epson programmable oscillator chips
(5V p-p square wave output) to revive an AN/TRC-88 transceiver.  Receiver
Mixer/LO circuit unknown as there is no documentation available for this
set; I cannot reverse engineer it due to tight construction.  Anyway, I
have not measured, noticed or even looked for any unwanted spurious
responses in the receiver while operating this way on 80, 60 or 40 meters.
I just AC coupled the square wave into the LO crystal sockets.  I see no
performance difference between the square wave or crystal-generated LO....
It works fine for my purposes..
Cheers!  Tim
N6CC

On Thu, Mar 17, 2022 at 6:43 AM Leslie Smith <lnsmith99 at gmail.com> wrote:

> Good-day Tom & others:
>
> A suggestion has been made: Harmonics found in the LO signal will mix with
> 'out of band signals' to create spurs.  An obvious example would be:
>    Signal - 3x LO -> IF frequency.
>     10.000 - 3x 3.2 -> 400kHz
>
> Since the BC-453 has an accurate dial and a 10MHz signal is easily found a
> test rig can easily demonstrate the proposal above.  The desired 80m signal
> would be at 3600 kHz.
>
> I propose to build this circuit using a 2n3819 + some sort of binary
> divider.  I'm thinking a 4027 JK FF.  Alternately, other frequencies might
> be tested:
>     1512(kHz) - 3x 400 -> 312(kHz)
> This is a conveniently done here at my QTH.  ABC Radio National broadcasts
> on 1512 locally.  Other nearby stations (both weak and strong) will provide
> more test signals.
>
> Once this has been done, I can test Wayne's suggestion of feeding a
> sine-wave to the mixer at the frequencies listed above.
>
> Leslie
>
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