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

[Robert Nickels]

On 3/17/2022 10:13 AM, Bob kb8tq wrote:
> driving with a square wave vs driving with a sine wave is not a big deal.

That's been my experience too.   Mixing is inherently a non-linear 
process and whatever unwanted mixing products are created will mostly be 
suppressed by the tuned circuits ahead of and after the mixer.     It's 
not a technique for perfectionists but I found myself wanting to convert 
from one frequency to another often enough I designed a little universal 
converter board that uses an NE-602 mixer and an Epson programmable 
oscillator that's 2" square.    There's only one tuned circuit on the 
input but the result is good enough for my purposes, which has included 
putting the highly selective BC-453 on the ham bands (my modern version 
of Don Stoner's "Novice Q5er" and "Single Sideband Q5er") and for 
converting numerous AM boat and oddball commercial radios for ham band 
use.   Using the converter allows me to leave the original receiver 
unmolested and take advantage of it's filtering.

Here's a video I made showing it used to convert the 455 kHz IF of a 
low-end shortwave receiver up to 3395 kHz for display on a Heathkit 
SB-620 panadaptor:

https://youtu.be/iFT2atgLogo

I didn't go hunting for spurs but the resulting display shows that the 
technique works well.   A double-tuned preselector would be easy to add 
for more serious work.

73,  Bob W9RAN