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

[Jesse Weideman]

Yep, there's a vibrant analog video synth community these days using that
same old tech from back when. Eurorack even.

LM6172 is a nice little dual opamp with something like 80mhz bandwidth
IIRC. Theyre easy to use because it's fine w +-12V rails. The DIP version
just went end of life a few weeks ago, SOIC package is still being
produced. Just mind the datasheet, it likes a 1k feedback resistor.

Here's a little summing mixer schematic maybe it'll be useful to you.

2mhz is nbd, I wouldn't sweat it too much.  We're a bunch of amateurs
monkeying w 60-80mhz for vertical rate stuff and seems like most people's
PCB's aren't laid out with any kind of understanding of signal integrity
whatsoever and it all works just fine.

Uninterrupted ground planes are your pal

You could probably ask on LZX Community Forum if you run into snags,
there's a handful of video DIYers there that kick schematics around and
tend to be helpful. There's a discord as well

Cheers,
Jesse


On Fri, Sep 29, 2023, 5:16 AM Roman Sowa <modular at go2.pl> 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
> >>
> >> _______________________________________________
> >> Synth-diy mailing list
> >> Synth-diy at synth-diy.org
> >> http://synth-diy.org/mailman/listinfo/synth-diy
> >> Selling or trading? Use marketplace at synth-diy.org
> >
> >
> > _______________________________________________
> > Synth-diy mailing list
> > Synth-diy at synth-diy.org
> > http://synth-diy.org/mailman/listinfo/synth-diy
> > Selling or trading? Use marketplace at synth-diy.org
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20231019/fbc7665a/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 719b02d8895541b1c2b4a89a63ec8d2a568dc626.png
Type: image/png
Size: 336180 bytes
Desc: not available
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20231019/fbc7665a/attachment.png>