[Lowfer] RE: Worthwhile going to Shielded loop?

[Ed Phillips]

Alberto di Bene wrote:
> 
> Talking of tuned loops, are there any drawbacks in tuning the secondary
> side
> of the coupling toroid transformer, as opposed to tune directly the loop
> winding itself ?
> 
> This would have the advantage that, placing the, let's say,  1:6 (turn
> ratio)
> transformer directly at the loop location, then bringing its secondary
> into the
> shack via a length of coax, you could place the tuning variable
> capacitor in the
> shack, without the need of remote control.  The capacitance of the cable
> would
> of course be in parallel with the tuning capacitor, reducing the tuning
> range, but
> this could be accounted for.
> 
> Another advantage is that the loop would be balanced, if the only connection
> it does have is that to the primary of the transfomer.
> 
> I have to build a new receiving loop, so would like to hear opinions on the
> above before starting.  Thanks.
> 
> 73  Alberto  I2PHD

	I used exactly that configuration (tuning in secondary of coupling
transformer) in the one loop I built and it worked very well.  The
center tap of the loop was connected to ground and the primary of the
transformer was floating.  The transformer was a small ungapped Siemens
pot core and the turns ratio was adjusted so that the loop tuned from
about 140 kHz to 300+kHz with a pair of 365 uufd BC tuning capacitors in
parallel.  I didn't remote the loop but, considering its low impedance,
can't see why that wouldn't work OK.

Ed