> >> --www.wescottdesign.com-Hide quoted text -
>
> >> - Show quoted text -
>
> > Yeah, I wanted to make one that works below 100kHz. So I ordered some
> > Audio transformers. 600 ohm impedance.. so the 1 k ohm is not too far
> > off.
>
> > The audio transformers only claim to work up to 15kHz. But here's a
> > 'scope shot of the DBM at 100kHz LO and 1 kHz RF
>
> >
http://imageshack.us/photo/my-images/850/tek0032.png/Things get a bit
> > 'squirrelly' above 300kHz.
>
> > The same drives but 10kHz on the LO.
>
> >
http://imageshack.us/photo/my-images/838/tek0033.png/
>
> > It's great fun, I've got this SRS spectrum analyzer so I can play with
> > the drive levels and watch all the harmonics move around.
>
> Have you checked the MiniCircuits catalog? I seem to recall that they
> have mixers that work down to 50kHz or even lower. They're on the web,
> at the obvious address.
Yup not only the catalog but I've got an SBL-3+ from minicircuits
lashed up in front of me.
Good for 25 kHz to 200 MHz. (well my some what sloppy soldering job
may not get to 200 Meg.)
>
> Things will work at your 600 ohm impedance level, but the distortion-free
> power levels will suck. If I recall what you're trying to do that
> shouldn't be a big deal -- just don't try to use them for receiving LORAN.
>
> Also check the amateur radio literature. Winding a pair of balanced
> transformers for 100kHz service shouldn't be too tedious if you start
> with the right core material -- audio transformers need all the windings
> so they'll work down at 300Hz (or 30Hz, or whatever); those windings (and
> core losses) just get in the way at higher frequencies.
Well, for like $3 I bought a few from digikey. I'l have to measure
it's freqeucny response.
>
> On most of those mixers there's at least one port that works all the way
> down to DC, and if there's no bells and whistles there's nothing to keep
> the mixer from operating in "reverse". So you do need to inject your
> high-level drive into the LO at the rated frequency, and you do need to
> deal with signals above the rated frequency at the "RF" port, but there's
> nothing to say that the "IF" port (the one that goes down to DC, usually)
> has to be an outie -- you can inject your low-level low frequency signal
> there and extract your high-frequency signal at the "RF" port.
Yeah I saw that on some audio site. (they call 'em diode ring
modulators) Putting the one signal into the 'IF' port and taking the
output from the RF. I'll try that with the mini-circuits DBM. It
would be nice if I could run the LO at ~50kHz and then modulate at
~1kHz.
Well it works... but the output is not so clean. I'll play around
with spice at home tonight.
George H.