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Tony Giacometti · November 22nd 07, 06:43 PM posted to rec.radio.amateur.antenna

wrote:

On Nov 21, 1:10 pm, Owen Duffy wrote:

I understand now, seeing your drawing clears it up for me.
No, I wasn't being difficult or silly, I kept thinking of how I have
the unit wired and I couldn't picture in my mind (senior moment?) the
changes. Anyway now I see what you are asking me to try and I will
give this a try. Hopefully tonite after work.

I will let you know the results. Thank You.

Tony,

Keep in mind this scheme improves the impedance match (ie reduces the
mismatch "losses", but it doesn't approach an MPT match unless the fixed
capacitor is very large, and in that case bandwidth would probably be too
narrow for your use. The trick is to improve the system gain enough to be
usable without making the system unusable because it is too narrow. The
suggested fixed capacitor of 1000pF should win you enough system gain, if
it doesn't try larger values (eg 4,700pF).

I will be offline for a few days, I look forward to hearing of the
outcome.

Owen

I guess it's worth a shot if the level is really that low.
But something seems strange that he would have that
problem. Using even my small 16 inch loop, fed using
the usual cap in parallel method, I have more signal level
than I actually need, even at the upper end of its range.
In general if the background noise level peaks, and there
is a definite difference between the antenna connected,
and unconnected, seems that should be enough
signal level.
On the recordings I made, I was comparing the 16 inch
loop vs full size wire antennas, and the drop in level
is really not that drastic.
IE: the stations still sound "loud" vs the large
wire antennas, and I have pretty decent S meter levels
on the loops.
I'm tuned to 740 kc AM-BC on my big loop right now and
the S meter is reading 40 over 9, and the radio preamp
is off.
I didn't really notice any level problems on the shielded
loops I've tried. But I'm starting to wonder if maybe
he might get a higher level just from using a regular
solenoid loop.

What is a solenoid loop?

It's also possible the radio could
use a tweak.. Which is easy to do on the drake
receivers. All the trimmers are on top of the chassis.
Don't even need any fancy gear. He can tune for the
middle of each band appx, and use the xtal calibrator
as the signal to tweak all the trimmers per each band.
Of course, you would peak each trimmer for max S
meter reading.
On the drakes, he should show a pretty healthy S
meter reading on the calibrator signal if it's working
right.
MK

I get 25 over 9 with the calibrator, but I will recheck
some things and make sure everything is ok.