Re: [IRCA] ALA 100

["Chris Knight" <chris@xxxxxxxxxxxxxxx>]

Just as a follow-up, a cardioid pattern can be broken into parts. It is
equal to the combination of a vertical and a loop antenna. Adding another
loop antenna to mix would probably just make the main lobe of the original
cardioid even wider with slightly less pickup in the center of the main
lobe. Oh well, it was a thought...

73, Chris

-----Original Message-----
From: irca-bounces@xxxxxxxxxxxxxxxx
[mailto:irca-bounces@xxxxxxxxxxxxxxxx]On Behalf Of Chris Knight
Sent: Wednesday, January 28, 2009 10:49 AM
To: Mailing list for the International Radio Club of America
Subject: Re: [IRCA] ALA 100


Hi Steve, Nick, et. al,

The ALA100 sounds like a great antenna!

Some observations/thoughts...

Each antenna has its (dis)advantages. The 17'x37' corner-fed loop here is
very quiet, but has a broad lobe (= more splatter). Signals aren't as strong
as a bi-directional loop, but they are quiet. The corner-fed allows almost
nightly reception of Spain-639. A bi-directional loop (i.e.: ALA100) would
not, since pest KFI on 640 is smack in the opposite lobe. The corner-fed
also has a narrow, but very effective null that will entirely null any one
of my locals. And, it does a great job nulling KFI's sky wave signal.

The cogs are turning (WD-40 may be needed)...

Guy Atkins posted a couple of small loop configurations, rotatable with a TV
rotor such as a Channel Master or similar (I've gotten these on ebay for
cheap). It would be possible to build a generic, 10'x10' loop (or smaller),
match it with a 1:1 transformer and rotate that setup on one end of the yard
(or house). At the other end, rotate a slightly larger,  rectangular,
corner-fed loop (~16:1 transformer). Broadband amplification would be needed
for both antennas (especially the corner-fed) and could possibly be handled
with a Quantum Phaser (or similar), either alone or in combo.

Next, to hear Spain on 639, one could aim these antennas Southwest/Northeast
(from Colorado). The corner-fed loop lobe would point SW toward the pest
station (KFI), its null positioned toward Spain. Both antennas would produce
lobes in the SW direction. The Quantum Phaser would come to the rescue and
phase-cancel the nearly equal SW lobes (little adjustment required -
important!) leaving Spain on 639 stronger than what it normally would be on
just a NE corner-fed. The remaining phase-cancelled pickup would be almost
entirely from the NE lobe of the bi-directional loop - at least in my mind
it would be or am I assuming too much?

Supposing this works, would it approximate the pickup from a phased BoG
system? Or (and I think this matters) is the spacing of the 2 above antennas
critical? If so, the BoG remains the winner since, as a traveling-wave
antenna spacing isn't too critical.

Speaking of BoGs, they take up less space than a Beverage antenna and when
phased they either equal or beat a Beverage in terms of DX performance. Neil
Kazaross' stellar loggings attest to that. No room here for one,
unfortunately. :-(

I would love to stumble upon/design an antenna setup that would emulate a
BoG system, that could easily fit in my 50'x60' backyard. Having the ability
to control direction and angle of signal pickup would be a plus...hi. (like
a mini Wullenweber antenna)

Cogs still turning (squeak, kah-thump), the next thought is a sloper toward
the pest station phased against an ALA-100, for example. Would that work
better as a phased combo? (think patterns and signal strengths)

Another thought: How about a phasing unit with independent antenna
amplification and linear gain control? This could be the key to making
steer-able backyard BoG emulation work and should be easy enough to design
if it hasn't been already.

Comments, critiques, alternative suggestions, etc. are appreciated!

73.

Chris Knight
Fort Lupton, Colorado


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