Re: [IRCA] New logbook started and new antennas tested

[Rick Kunath <k9ao@xxxxxxxxxxx>]

On 09/03/2011 12:32 PM, Tim Hills wrote:

> One is a dual spiral, 10 turns total and 30" diameter in 2 layers 1"
> apart with varactor tuning and a single turn pickup loop.
I'd be interested in seeing a photo of that loop, and a schematic as to 
your connections.
I've built a lot of loops over the years and have some ideas that you 
might find interesting.
I built a lot of spiral and solenoidal loops, as well as ferrite loops. 
The air-core loops always outperformed the ferrite loops. One of the 
things that I found important as far as loop pattern and null depth is 
symmetry, something yo cannot get right with a spiral loop because the 
windings are different diameters. Traditional split-stator air 
dielectric tuning capacitors always gave me a higher Q than varactors 
did. And this is important as you referred to off-channel rejection. 
With the frame of the split-stator capacitor connected to the loop 
center-tap I was able to get some good pattern symmetry and good null 
depth.
I either used a center-tapped secondary winding, or later on did away 
with the secondary winding entirely and used a high-impedance FET preamp 
across the primary that did the preamplification and conversion to 
unbalanced low-impedance output.
Rick Kunath
_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx