[AMRadio] Lots of AM on 7160 Right Now!


D. Chester k4kyv at charter.net
Tue Mar 31 13:24:39 EDT 2009


I have worked many AM  stations Sunday and Monday evenings and early the 
morning to follow.

This includes some Europeans.  The Euros have mostly been SSB, but one or 
two of them have switched over to AM to be perfectly readable, and they all 
gave me good signal reports.  I think two-way transatlantic AM QSO's should 
be easy, running only moderate power and antennas.

I have been running 450 watts input to a pair of 8005's modulated by 805's - 
the same rig I built when I was in Cambridge, MA and used when I was in 
Houston, TX.  The antenna is the 80m dipole, 110' high, fed with open wire 
line, broadside NE/SW.

I think for night time operation, this band is less useful for large 
roundtables like we are used to on 75 and 160.  Kind of like 20m, 
inevitably, someone in the group is skipping over someone else, and that 
person has to wait several minutes listening to background noise and dead 
air.  I  think it would be better, and make for more AM presence on the 
band, to break away from the original QSO once it begins to get large, and 
start new QSO's off to the side when a clear frequency can be found, and try 
to maintain small groups and one-on-one QSO's.

Some of the Europeans have indicated they still hear several broadcast 
stations occupying the usual channels on 7100-7200.  Evidently, as the major 
powerhouses have moved out of the band per the WARC agreement, lower power 
broadcasters from Africa and Asia are filling in the void to take advantage 
of the clear frequencies.  I  still hear broadcast activity from the Horn of 
Africa, Ethiopia and Eritrea on 7110, 7165 and 7175 to be specific.

Unfortunately, the whole region is in political turmoil right now, and armed 
conflict involving Eritrea, Ethiopia, Somalia and Djibouti could break out 
at any time.  Reportedly, there are troops from all sides amassed at the 
borders.  Ethiopians are already fighting inside Somalia, and Eritrean 
troops have reportedly crossed over into Djibouti territory.  Along with the 
armed tension, some of these broadcasts are being jammed with a transmitter 
that puts out white noise, sounding a lot like some kind of digital 
transmission, but I suspect it is only random noise.

Last night I listened in as the whole episode started up.  Radio Ethiopia 
has been  regularly signing on at 0300 GMT on 7110, and they are strong in 
here until fade-out, usually between 0600 and 0800 GMT, depending on band 
condx.  Starting about 0340 GMT, two strong unmodulated carriers appeared on 
7165 and 7175.  A few minutes before the hour, 7175 began broadcasting what 
sounded like Ethiopian or Eritrean music, with frequent announcements.  I 
don't understand the language, but I believe it was Tigrinya, and I could 
make out "Eritrea" in the announcements.  A ham in VK land  has identified 
this station as the Voice of the Broad Masses of Eritrea.  About the same 
time, similar music began to modulate the 7165 carrier.  Seconds before 0400 
GMT, the white noise opened up on top of the 7175 station.  It immediately 
moved to 7165, nearly exactly zero-beat with the station on there.  You 
could hear the simultaneous modulation of both signals and the carriers 
beating against each other.  Then the noise moved down to cover up both 
stations.  Occasionally the noise stops for 2-3 seconds, as if the operator 
is  listening to see if the stations are still transmitting.  Each pause, 
both signals were clearly audible.  This noise  can be very strong at times, 
and render useless an entire swath between 7155 and 7175.  A nearly 
identical sequence of events occurred Sunday evening.  I was able to sort 
out what was happening by the time Monday evening was over.

Here is my suggestion.  AM'ers should continue to use 7160 as a  gathering 
point, since this frequency has a long history of AM usage going back at 
least through the 70's.  But we should avoid huge roundtables and instead, 
spread out.  But we should avoid whenever possible, frequencies at even 5 
kHz intervals ending in 5 or 0 that have long been used as broadcast 
channels, for two reasons.  (1) A few broadcasters, as expected, continue to 
occupy these channels and cause QRM, particularly in Europe, VK/ZL and the 
Far East.  We will have a better chance of being heard by foreign DX if we 
operate in between the former broadcast channels. (2) Many US SSB stations 
are so used to hearing the foreign broadcast carriers at even 5-kHz 
intervals, that they are likely to mistake amateur AM carriers for broadcast 
signals without further listening, and fire up right on top of the AM QSO, 
even if they have no malicious intention of jamming amateur AM operation.

Don k4kyv
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This message was typed using the DVORAK keyboard layout.

http://www.mwbrooks.com/dvorak/
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