Phased array (2) on MW project
Ron Hardin
active antennas on diagonal corners of the roof, and combine them in a
JPS ANC-4 interference eliminator, you have a neat-o antenna for MW.
The chief advantage over a MW loop is that they are broadband - the
quality of the audio is very noticeably improved; and they null
only in azimuth (= same null for all elevation angles of arrival).
Also, you can null out say the local 5000w WTVN on 610, and then hear
WSOM 600 in Salem OH, 1000w 125 miles away, and WKHB 620 1300w 175
miles away in Irwin PA, in the daytime, adjacent channels I've never heard before.
I don't know exactly why I haven't been able to do that with the big
Kiwa loop, but one thing is that you wind up aiming the loop at strange
angles in order to null out the local, and those angles aren't particularly
good for receiving the weak adjacents.
What I wanted a DA100-E for was for use as a good E-field whip against the Kiwa
loop main antenna, to put a good null west while keeping high gain east,
with the ANC-4, replacing a wind-up reel. The second one was on speculation,
just to see what could be done, or perhaps switch antennas depending on which
one was doing better.
But there's enough jacks on the back so you can (with an R8B) by flipping
switches (=no cable unplugging) hear:
1. The east DA100-E raw
2. The west DA100-E raw
3. The two DA100-E's combined in the ANC-4, which you can steer a null with.
4. The big Kiwa loop combined with the east DA100-E to steer a single null with.
5. Any single additional antenna replacing the east DA100-E (jack now has a Terk
loop) in its possibilities.
With cable unplugging, I guess you could swap the east and west antennas.
The output of the east DA100-E is split, full gain going to the R8B second antenna
jack, and reduced gain (see below) going to the ANC-4 noise input.
There's a few difficulties, after all this is RF and it does what it pleases:
1. The two DA100-E's don't match exactly, though I imagine changing the voltages would
change that favorably. The east one is less sensitive now, for most things but not all.
This may be an advantage or it may not; it adds variety to choose from, and that may be
good.
2. The east DA100-E, which feeds into the noise antenna input of the ANC-4, saturates
the ANC-4 and gives you harmonics (you hear 1460 on 2990); adding a 1000 ohm resistor
in series and then a 380 ohm resistor across the ANC-4 end and ground seems to fix that,
and also prevents the ANC-4 from feeding its settings back into the east DA-100E, where
it could be heard in the east DA-100E alone mode of listening. Higher resistance seems
to prevent the ANC-4 from having full phase control; lower resistance overloads it.
It still leaves you vulnerable to another RFI source if you use up your phasing
to kill off a station, and I will add another ANC-4 someday to take care of that too,
say with a noise antenna wrapped around the AC line, last thing before the receiver.
It's impossible to use well on SW at night because there are no stable azimuths, as far
as I can tell; or if there are, you can't find them. So far it works nicely on MW.
A single DA100-E isn't much good on MW because you can't null one of the stations
you wind up hearing at once, though it gives a very adequate signal, as good as a loop.
The key to the whole thing is the ANC-4.
--
Ron Hardin
rhha...@mindspring.com
On the internet, nobody knows you're a jerk.