Von: BueschelW@web.de im Auftrag von Wolfgang Bueschel ...

about broadcast engineering. He told me they are going to be doing some
work on their main mediumwave antenna soon which they hope will improve
the signal.
In a follow up email, we were discussing ground conductivity here in
Afghanistan and the merits of a 120/50 radial system. He also asked if I
knew anyone who was using a CFA MF antenna system. I have written back to
determine if they are looking to go to that system, or are using it now,
but no answer as of yet. His email is
(Al Muick-AFG, dxld Aug 5)
Hasn't the CFA [crossed field antenna] been pretty well debunked by now?
Or useful in certain applications (gh to Al, ibid.)
The CFA hasn't exactly been debunked, but it has fallen into disfavor.
Jean-Paul sent me this email, excerpted below:
"My MF antenna is located at the sea front in mud water, excellent
conductivity but Ant impedance changes with the tides. It goes from no
water above the radial (low tide) to almost 1.7m at times. 50R to
something like 60+j24 at worst.
"Was thinking of a raised counterpoise GND system to sort out this problem
but now we have to relocate as too much interference to phones and other
equipment. New site is located in a small valley next to a water
reservoir.
"Was looking at CFA some time back. Had a rf specialist in Australia who
was going to build one to do some test but then dropped the idea. Could
not at that time find parts to build it. A colleague who went to Egypt
says Radio Cairo has one on top of their Radio house.
"I think will stick to series fed tower 90 degrees, although I read that
folded mono pole(shunt feed) works better than series fed over poor gnd
system and can be set to 50R and no ATU required."
His current antenna was all over the j-omega scale because of the tides.
That tells me they didn't put the antenna far enough out to where the
tides would not affect it. All of the "sea antennas" I have ever seen are
in places where the tide does not remove all the water. This is the reason
they are killing all the phones and other things in the area.
The raised counterpoise is good if they have the real estate to put it on
or it is out of the way. There is always someone who will come along and
hurt themselves on it. The Government of South Sudan was trying to get me
to assist them to install one for their 100 kW transmitters in Goomba
(when I was with the UN), but they did not want to spend the money to
fence it off and the place was crawling with children. I respectfully
declined.
The folded monopole he is looking at would be good for him commercially,
but would probably screw DX'ers because it greatly reduces the skywave
content and converts it to groundwave, plus it has the added benefit of
easy matching.
(Al Muick-AFG, dxld Aug 8)
file:///E|/datentransfer/wwdfxc_2010/BCDX976.TXT[06.01.2011 12:40:14]