[Lowfer] New Loop NG

[Peter Barick]

Tim Brannon writes:

>>> timbmd@swbell.net 04/15/02 09:26PM >>>
Peter,
I also read John Andrews' reply.  Two more questions...

1.  Is your pick-up loop electrically isolated from the tuned loop?; 
i.e.
is there any wire connection between say, the coax shield and the main
loop?
As I understand it, you want to ensure that there is only inductive
coupling
to the pickup loop--the tuned loop should be "floating" electrically
with no
DC connection to the pickup loop.

*PB: Oh yes. It was but an afterthought and something I considered a
fallback at the time. There was no conn. to the main. However, I noted
the greater sig on the s-meter, when used. I'm thinking now that this
may indicate a better match for the rx.

2.  What kind of capacitors are you using in your switching bank?  I
would
suggest using silver-mica caps for the best Q.  Ceramic disk caps may
limit
the Q of the tuned circuit and cause the broad tuning.  You might try
connecting an old air-dielectric variable capacitor ala the BCB variety
for
comparison--if its clean and in good condition it should have excellent
Q,
and might give you some insight into what's going on.

*PB: Yep, silver micas, albeit of the older "box" type having black
dots for silver. And I also had a port to inject a variable cap of the
rx variety. To use it I switched out the fixed caps (3 on slide
switches) and stuck in the handheald variable. Rotating it produced the
sought for rise on the s-meter. Estimating that value, I removed the
variable and switched in approximate C.

Tim Brannon
Dallas
----------------------------

Thanks for the input, Peter, Northern Illinois

<<klip orig msg>>