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

[Mike Feher]

Hi Bob - 

In reality mixing is not non-linear. A mixer in theory is simply a multiplier, which is a linear process. Typically, in analog implementations, it does become non-linear, hence the other products. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
848-245-9115

-----Original Message-----
From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On Behalf Of Robert Nickels
Sent: Thursday, March 17, 2022 11:57 AM
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] HF Converter - feeding mixer with a square wave?

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


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