[sdiy] 4 channel mixer of signals with frequencies between 2Mhz and lower.. any circuits available.. ??

[Magnus Danielson]

Roman,

Agree. You can build essentially the same mixer as we use for audio with 
modern op-amps.

Having said that, one need to be careful about de-coupling caps, etc. 
Still, 2 MHz is pretty close DC these days. :)

Cheers,
Magnus

On 2023-09-29 12:14, Roman Sowa wrote:
> Come on, this is basicaly almost a DC signal, let's not overkill this!
> I especially liked as someone joked about doing it digitally in FPGA.
>
> In the old days of analog television, this was called "video 
> bandwidth" and what comes wit it - huge variety of video opamps, with 
> enough power, bandwidth and low distortion to use in such scenario. My 
> prefered all-purpose models were AD818 and AD817, but that was 25 
> years ago. Nowadays there should be hundreds of better and cheaper 
> opamps. Just build resistive adder like you would do for CV in modular 
> synth, the only difference being resistor values to provide matched 
> load impedance for individual transmitters. The opamp will provide 
> enough gain and output power to drive antenna directly with those few 
> miliwatts.
>
> Roman
>
>
> W dniu 2023-09-28 o 23:02, Jean-Pierre Desrochers pisze:
>> Here is what I'm trying to do as an experiment.
>>
>> I have 4 small AM transmitters transmitting at 600, 900, 1200 and 
>> 1600Khz.
>> At about 10mW of power each.
>> I was thinking about mixing the 4 frequencies as a single unit
>> that I could adjust the final output transmitted on a small antenna.
>> That's my idea so far..
>>
>>
>>> -----Message d'origine-----
>>> De : Synth-diy <synth-diy-bounces at synth-diy.org> De la part de 
>>> Gordonjcp
>>> Envoyé : 28 septembre 2023 16:46
>>> À : synth-diy at synth-diy.org
>>> Objet : Re: [sdiy] 4 channel mixer of signals with frequencies between
>> 2Mhz
>>> and lower.. any circuits available.. ??
>>>
>>> On Thu, Sep 28, 2023 at 03:17:56PM -0400, Jean-Pierre Desrochers wrote:
>>>> Hi all,
>>>>
>>>>
>>>>
>>>> This is an out off topics question but I will ask you anyway..
>>>>
>>>>
>>>>
>>>> I want to build a 4 channel mixer that would receive signal
>>>> frequencies between 2Mhz and lower one channel..
>>>> These 4 frequencies won't change. They will be fixed.
>>>>
>>>> Google would give me lots of Radio/Ham solutions that imply the use of
>>>> tuning coils and such things I don't want to get into.
>>>>
>>>> The idea would be to use ready available opamps with high bandwidth
>>>> with the use of resistors and caps only. Gain would be of one.
>>>
>>> For the avoidance of the XY Problem, what exactly are you trying to do?
>>>
>>> -- 
>>> Gordonjcp
>>>
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>>
>>
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