- Dec 3, 2007I have the one with the external jack on it. I opened it up to
examine it, by cutting a hole in the back of the case. And found that
the Select-A-Tenna consists of a round case with about #28 magnet wire
wound around the circumference, the ends soldered to a single gang
365pf capacitor mounted in the middle of the front panel. No trimming
is provided. The External jack model varies from the origional by the
addition of an extra turn wound around the circumfrence and connected
to a cheap 1/8" (3.5mm) phone jack. This results in very tight
coupling, which if hooked to a low-impedance load, will 'short out'
the floating tank circuit Q.
What I did was to first try a looser coupling by taping a single turn
to the back of the case, and it worked a bit better for all the
receivers except the R-392. I then modeled the Select-a-tenna using
RJELOOP3. It gives me a 100-400 ohm impedance for the pick-up loop.
To get more impedance for the pick-up loop, I decided to try a ferite
loop pick-up instead. I wired the promary coil to a BNC connector and
connected the BNC connector to my R-392. The result was much better.
I then moved the ferite loop around inside, looking for a sweet-spot,
which was near the center, about three inches from the edge. Finally,
I mounted the BNC connector to the front panel where the phone jack
used to be, and epoxied the ferite core to the inside of the back
panel, orentated with the core going back to front. Finally, a few
pieces of Duck-Tape to cover the hole, and glued the Select-A-Tenna
base to a plastic condement turntable to allow me to turn the loop.
--- In email@example.com, Richards <jruing@...> wrote:
> Great story --- I will have to rent a copy of that flick. I like
> You put the ferrite loop antenna from the little radio into the
> S-a-Tenna? Or did you use that as the coupler for outside?
> Sorry if I am a little dense and did not quite get the picture...
> I am getting the notion you put the ferrite bar inside as the
> pickup loop and then hard wired the thing to the antenna jack
> on the receiver. Or is it the other way around...?
> /////////////// Richards ///////////////
> mhatlau wrote:
> and pulled the one inch ferite
> > antenna out of it. Then ripped out the useless miniature audio jack
> > and hooked a BNC connector up to the ferite loop. Cut a hole in the
> > back of the Select-A-Tenna so I could put it inside, about three
> > inches from the loop and at right angles to it with Epoxy.
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