[Lowfer] TH and HS

[Jay Rusgrove]

Bill

Here's what Paul and I have been using for a while now.

http://www.advancedreceiver.com/capture/3X365mdvc.jpg

Its a 3 X 365 pF variable mounted to a delrin base. The perpendicular piece of
delrin supports the 5 VDC "camera positioning"  gear motor and it connects to
the variable c through an adjustable clutch and large round delrin coupling.  No
breakage when you get lost and run the cap to the stops! The motor actually runs
well on 3 VDC (even at the end of 200 feet of CAT5!).  I use two C cells in a
small plastic Bud box with two pushbuttons - one for up and one for down. Just
diddle the switches back and forth until you're on resonance. The whole thing
fits inside a piece of pvc tubing with end caps just press fit on. Two brass
machine screws protrude through the pvc for connection points to the loop. The
unit hangs just below the frame of the loop.

Could probably have made it smaller but it's one of those things that worked so
well  I was reluctant to spend more time on it. I'm sure there are better ideas
out there - this is just one example of what we did with stuff on hand.

Jay

Bill Ashlock wrote:

> John,
>
> >No. I'm only using a 1 to 2 turns ratio right now. That has provided
> > >enough signal.
>
> And I wouldn't want you to gain an even bigger reception advantage over us
> mortals. <G>
>
> >I'm planning to add a motor driven variable cap to bridge the
> >gaps between the switched capacitor steps. This will allow me to raise >the
> >turns ratio and extract more of the available signal.
>
> This is where I'm confused. Wouldn't increasing the step-up ratio actually
> reduce the Q since the R seen by the loop would be lower? But this is a
> series circuit...... Hmmm. I'll have to work this out on paper.
>
> Looks like one of the biggest objectives to successful RX looping is to come
> up with a simple remote-tuned 1000pf(+) variable capacitor. I don't trust
> those tuning diodes in my high-noise environment. They seem to sensitive to
> out of band noise and modulate the desired signal. This new loop without
> diode tuning or pre-amp is the first loop I've used that is almost dead
> quiet when I tune the receiver off to the side of the loop resonant point.
> (And the Q is no higher than the others) I suppose one of my big compression
> mica timmers could be motor-driven with a compact gear reduction unit.
>
> Bill
>
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