[FoxHunt] Attenuator

[Bob]

I've been trying to get Tony to part with one, but it is si
simple that he hasn't gotten to it. Contact Analog Devices
and get the application note for the AD-8307 and go from
there. I think there is a tuned circuit, a few stabilizing
caps and a resistor or two involved and thats it for the RF
thing. The chip inputs RF and outputs DC. The clicker is a
555 circuit set up for a voltage controlled VFO. The
attenuator is just resistors. The key to getting the thing
to work at close in is the shielding of the chip. I think
the chip costs about $12.00. Let me know what you find.

Bob, WB6JPI

Uwe DF7BL wrote:
> 
> Hi Bob, ist there a way to get the schematic of that sniffer. May be direkt.
> Sorry for the list but mailman does not accept attachments.
> 73 de uwe df7bl
> 
> Bob schrieb:
> >
> > My friend Tony has built a sniffer around the Analog Devices
> > Logrithmic amplifier chip. Here is his report...
> >
> >    "This week I finished my new sniffer with the AD 8307. It
> > is
> > the best I have ever used. I combined the 8307 and a ticker
> > that goes up
> > in tone with more RF. It starts to tick at -107 dbw and has
> > 70 db dynamic range to the high tone. I then can switch in
> > 30 and 35 db
> > attenuators to numb it  60 db. The lost 5 db is some kind of
> > leakage. (marginal shielding)   I think I did the
> > measurements correctly.    I can stand in my yard and key a
> > repeater 10 miles away and it
> > will start to tick when pointed in that direction. With the
> > switches in, -60db, I can DF my repeater, 80 watts at 25
> > feet."
> >
> > I suggested to Tony that he replace the toggle switches with
> > relays and use bypass feedthroughs for the wires to get
> > better shielding. He is working on numbing down the 8307 as
> > well. It is one hot chip It takes almost no support parts
> > and has a 90 dB dynamic range if you can figure out how to
> > get them all.
> >
> > cut cut....
> 
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