Re: Useless questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

> >
> > The real problem will be that the inexpensive doppler radars (speed guns
> > and the like) are hideously sensitive to interference.  They work by
mixing
> > a bit of the outbound signal (around 0.5 mW, typically) with whatever
gets
> > reflected back, and then looking at the audio frequency on the mixer
diode.
> >  This is called homodyne operation, by the way.   The problem is that
the
> > selectivity of the receiver is pretty bad; as in non-existent.  Any RF
> > power that gets into the horn will be detected by the diode and its
> > envelope will show up.
>
> 1. Homodyne receivers are plenty sensitive.

That's what makes the interference issue so bad... but.. I think the WG
below cutoff will save you.. and, if need be, you could also stick a foot or
so of appropriate waveguide in there..
>
> 2. Think that the actual RF radiation from the streamers won't be a
> factor.  Would be easy enough to check by just using the schottky diode
> in the detector unit with the power removed from the transmitter.  I
> think the main problem would be with audio pickup in the detector
> output, and that could (probably) be minimized by careful shielding.
> I've taken pictures of streamers with my camcorder, and didn't have any
> noticeable audio pickup when I stuck my hand in front of the mikes.

Probably true... put the whole thing in a shielded box if needed, just the
WG port sticking out...

OK you L.A. area coilers.. TRW swapmeet tomorrow morning.. who's going to be
the first to snag a gunnplexer (or a DRO based unit) and make some
measurements... Brand new from shf electronics, they're $60 or so...


>
>
> Ed.
>
> I'm getting interested in the topic now, and wondering what I can do
> with my little TC in the basement where the rest of the RF stuff is.
> Maybe...................
>
>
>