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Antenna
phasing makes a difference
After waiting for the second Alpha Delta DX-SWL Sloper for two weeks
and one day...it finally arrived.
The first sloper is installed off the tower at 50' and I hung the
second sloper at 40' up the tower at 40 degrees from each other.
I'm sure most of you know what a Quantum Phaser from Radio Plus
Electronics is but for those who don't... it simply combines signals
from two different antennas in such a way that a null or peak of
a target station is obtained. In other words, you null one station
out to hear another station on the same frequency.
The Quantum Phaser is a standard broadcast device only, so for those
of you who enjoy listening to your favorite talk radio, such as
myself, or AM music or sports you might want to play with one.
Over the winter months I'm going to try and log as many frequencies
as possible to see what lurks in the crowded channels and to see
what modifications I need to do with the antennas, such as spacing.
After a quick scan on the higher AM frequencies I was able to listen
to two different stations on the same frequency on a few frequencies.
Without the phaser I couldn't hear anything but garble, so it seems
to work as advertised. So far, I'm pleased with it.
Here's a link to their web site for anyone who hasn't read about
it:
http://www.dx-tools.com/PRODUCTS.htm
Harry, W5HC, rec.radio.shortwave,
November 2002
I am one
of those that know what the Quantum Phaser is. Of the three
commercially available Phasers (Quantum, ANC-4, MFJ) this one is
by far the easiest to operate and to to get a null. I have used
all three.
Note - the MFJ needs
to be modified to work on MW/AM.
I have several products from Radio Plus. They are all top notch.
Gerry Thomas is a genius and great to work with.
Russ,
K3Pi, rec.radio.shortwave, November 2002
Two phased
antennas produce a "V'' null that you can sweep from one
endfire to the other. It's actually a cone, but the trace on the
ground is a V, opening up to a plane at exact broadside.
[Even that differs from a loop, which always has point (not plane)
nulls in opposite directions.]
A difficult station to null is best placed at endfire, so there
are two nulls in its vicinity.
Increased separation gives you an advantage up to a quarter wavelength.
Any separation (no matter how close) gives you nulls but costs you
gain in directions not nulled. That cost in gain becomes zero at
a quarter wavelength separation.
At zero separation, you null all directions at once, the ultimate
cost in gain. But you don't need full gain on MW, where the point
is eliminating competing signals, not so much pulling up weak isolated
ones.
If the antennas themselves have patterns, they multiply the phased
array pattern.
A loop as one antenna lets you actually use zero separation,
giving you in effect a free quarter wave through responding to the
magnetic field rather than the electric field. As with two similar
antennas, you get a V pattern which you can sweep from one endfire
to the other. Endfire in the case of a co-located loop and whip
is in the plane of the loop, that is, at the maximum of the loop
alone.
The loop has to be broadband to successfully null a station across
its entire bandwidth, otherwise there's no single gain that exactly
cancels the whole station. So a tuned loop won't work as well as
an untuned one.
The loop plus whip is a great option though if you have zero real
estate to work with.
Phasing two loops is much harder than phasing two whips because
except at the native maximum of the loops, the signals they give
have much less stable phase and gain (at the native nulls, broadside
to the loops, the signals are completely unstable and no
setting of the phasing unit will work very long).
So to null a station with two loops, paradoxically you should aim
the loops to maximize that station, unless it's daytime and the
signals are very stable. Two loops have to be separated like two
whips do, up to a quarter wave, with the same benefits.
Electrically combining two close loops or whips essentially gives
you a single loop or whip. Only the combination of one loop and
one whip works usefully at zero separation.
Ron
Hardin, rec.radio.shortwave, November 2002
One of my
reasons for buying the Phaser was to see if I could listen to
a couple of local stations on 1180 kHz and 1280 kHz at night.
WGAB, 1180 kHz, reduces it's power from 670 watts in the daytime
to 1 watt at night. I wonder what the coverage of 1 watt is? 1180kHz
on the Drake R8B at night is covered by stations and none is dominate
except a Spanish station from God only knows where.
With the Phaser I'm able to null the Spanish station out and WHAM
in Rochester, NY comes in perfectly clear. I never heard it before
tonight. Ummm, Michael Savage is on now. I like him because he doesn't
like anyone.
On 1280 kHz WGBF is a 5000 watt daytime station and a 1000 watt
night time station. I'm about, ohh, maybe 20 miles as the crow flies
from both WGAB and WGBF and there's a pretty good hill between us.
WGBF at night time is mixed with other stations and never Q5 copy
until tonight. Another notch for the Quantum Phaser.
The phaser also did clean up 1510 kHz, WLAC in Nashville, TN. Although,
if I want to listen to Art Bell, I usually tune in 1100 kHz, WTAM
in Cleveland, OH and never bother with WLAC.
This phaser is an interesting little gadget!
Harry, W5HC, rec.radio.shortwave,
November 2002
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antennX