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

[Tom Lee]

Hi Dave,

Yes, those authors are guilty of making this common error. It’s the result of over-generalizing. Just because nonlinearity has been exploited for decades to make mixers, many people come to believe that nonlinearity is essential. In fact the opposite is true.

An ideal mixer is linear, but time varying. The gain varies at the LO rate (a multiplier can be viewed this way).

So, some mixers are nonlinear but not all. and by production volume linear mixers overwhelmingly dominate. Every cellphone uses linear mixers.

Mixers based on nonlinearity make sense when that’s all you’ve got (as in millimeter wave work), or if that’s all you are willing to pay for.

Beef is meat, but not all meat is beef. :)

Cheers
Tom

Sent from my iThing; please forgive the typos and brevity

> On Mar 17, 2022, at 12:51, DaveJ <cjack93907 at charter.net> wrote:
> 
> FWIW only.
> 
> Paper on  mixers:
> 
> 
> https://ijirt.org/master/publishedpaper/IJIRT100873_PAPER.pdf
> 
> 
> sincerely,
> 
> 
> Dave WA4OBJ
> 
> -----Original Message-----
> From: arc5-bounces at mailman.qth.net On Behalf Of Tom Lee
> Sent: Thursday, March 17, 2022 12:16 PM
> To: MICHAEL ST ANGELO <mstangelo at comcast.net>
> Cc: ARC-5 List <ARC5 at mailman.qth.net>
> Subject: Re: [ARC5] HF Converter - feeding mixer with a square wave?
> 
> I wish people would stop repeating the claim that mixers are inherently nonlinear. That’s completely false. It is true that nonlinear things can produce mixing, but that’s a side effect, not an inherent property!
> 
> Good mixers have to be linear. You want the IF output to be proportional to the RF input.
> 
> We treat mixer nonlinearity in much the same way as we treat amplifier nonlinearity. It is an undesirable property and considerable effort is expended to minimize it.
> 
> Tom
> 
> Sent from my iThing; please forgive the typos and brevity
> 
>> On Mar 17, 2022, at 11:39, MICHAEL ST ANGELO <mstangelo at comcast.net> wrote:
>> 
>> Bob,
>> 
>> Enjoyed that article and the one about the Si5351 Quadrature oscillator. Have the tried feeding the Si5351 to the SA612 instead of an Epson? It gives the the ability of easily changing frequency. 
>> 
>> The SA612 and Si5351, what a pair for experimenters.
>> 
>> Mike N2MS
>> 
>>>> On 03/17/2022 1:05 PM Robert Nickels <ranickels at gmail.com> wrote:
>>> 
>>> 
>>>> On 3/17/2022 11:10 AM, Phillip Carpenter wrote:
>>>> Can you please share the circuit diagram of your universal converter board that you used with the BC-453 receiver?
>>> 
>>> I've added an article about it to my website: 
>>> https://tinyurl.com/mrj7rndd
>>> 
>>> The 4.7uH/100pF values shown work for 40 meters, or calculate your 
>>> own - I use a 10uH fixed inductor and 150-180pf capacitor for 75-80 meters.
>>> 
>>> 73, Bob W9RAN
>>> 
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