Great discussion!
But personally, I think on CW your timing (call early, call late), keying
speed (call faster, call slower), and placement of your signal in the
receiver's passband (call high, call low) will all have a much bigger effect
on being noticed and answered than a 1dB increase in RF signal power.
On SSB your timing, mic equalization, enunciation, and inherent voice timbre
will similarly swamp a 1dB power increase.
73,
Steve
N6SJ
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of
dj7ww@t-online.de
Sent: Wednesday, April 29, 2020 8:47 AM
To: 'Brian Beezley' <k6sti@att.net>; towertalk@contesting.com
Subject: Re: [TowerTalk] 40m 4el KLM - replacing linear loading with coils
Physical bending of the tubing is not necessary.
By using mounting plates with isolating Stauff clamps at the needed angle as
element holders straight elements can be used.
73
Peter
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Brian
Beezley
Sent: Mittwoch, 29. April 2020 16:17
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 40m 4el KLM - replacing linear loading with coils
The forward gain difference between my single-coil and two-coil models is
0.02 dB. This is with no coil losses, whose difference might easily
overwhelm a small directivity difference. But I restored the coil losses and
got the same result.
Input resistance is in the mid-20s in ohms for the single coil model and in
the mid-40s for two coils. I had expected band-edge reactances to be about
the same for both models and thus SWR to significantly increase for the
single-coil model. Instead, the reactances are similar to the input
resistances, with only a small difference in band-edge SWR for the two
designs when each is matched at band center.
I neglected to say that the AWG 5 copper-clad aluminum wire weighs 37.42
lbs/1000' while pure copper is 100.2 lbs/1000'. 3/16" OD refrigeration
service soft copper (0.1875" instead of 0.1815") with a 0.03" wall weighs
57.5 lbs/1000'. 1/8" OD is 34.7 lbs/1000'. An optimized 7.7 uH coil using
1/8" copper is 5.6" by 3.3" with a Q of 985. (As wire diameter decreases,
the proximity effect that limits coil Q decreases, which enables coils that
are smaller, lighter, and cheaper.)
This describes an interesting trick for 40m Yagis:
http://ham-radio.com/k6sti/owa.htm
I had toyed with the idea of writing a little utility that generates wire
segments for an element bent using dacron lines that run from somewhere near
the half-element midpoints back to the boom. This would eliminate the need
for a custom bent-element mount. You could even run the lines between driven
element and reflector to bend both, which may improve gain even more. To do
this right you need the taper schedule and tubing bending parameters. Even
better would be to include the dacron line tension in the optimization
parameters and then optimize everything simultaneously. I'll leave this for
someone else.
If you think the 0.5 to 1 dB a conventional OWA costs in forward gain is
inconsequential, check this out:
http://ham-radio.com/k6sti/pileup.htm
The analysis isn't definitive. But the next time it takes forever to bust a
pileup with your OWA, you may not be able to get the probability curves out
of your head.
COIL 3.90 is here:
http://ham-radio.com/k6sti/coil.zip
Brian
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