Hi Tonno, very impressive results!
You may not be aware of the galactic noise arriving from various sources in
the heavens. The amplitude of these noise sources vary quite a bit from
day to day as the moon follows its' orbit around the earth. When the moon is
in the direction of the milky way, the noise level can be 10 or more dB
stronger, depending on the antenna beamwidth. Smaller beamwidths tend to show
higher noise levels. Typical hf antenna beamwidths are great enough that
the higher noise level is not noticeable.
Your antenna has a low enough beamwidth that the effect will be very
noticeable.
There is typically one or two days during each 27.3 day lunar cycle that
the moon is front of relatively low galactic noise. The next date for the
minimum noise is February 24 from 1430 to 1530z on your moon rise when
elevation falls between 1 and 5 degrees and again on your moonset February 25
0330
to 0430 when your elevation falls between 8 and 1 degrees.
Your ground gain peaks will be extremely important as they will provide
upwards of 5dB gain on both transmit and receive; as much as 10dB total.
There are other effects as well: one is Faraday rotation that rotates the
received echo return polarization which causes as much as 20 dB or more
signal loss for a few minutes at a time. The rotation speed on 6m is typically
5 minutes and much faster as frequency d=goes down. Another effect is
libration fading which is caused by echoes reflected from various parts of the
rough surface of the moon being received out of phase and partially
canceling. The nulls are typically 15 dB down. There are periods that the echo
reflections are more in phase and there will be signal peaks on the order of
5dB above average.
The libration effects are slowest near moon rise and moon set. There may be
periods of several minutes of signal enhancement or degradation at your
relatively low frequency.
When you add up all the plus and minuses the results at any given time will
vary from dismal to outstanding.
There is nothing you can do to change any of this but being aware will help
understand what is happening.
73,
Gerald K5GW
currently active on eme bands from 6m to 3cm
In a message dated 2/5/2013 5:49:45 A.M. Pacific Standard Time,
tonno.vahk@gmail.com writes:
Hi,
After two fruitless attempts at moonrise I got EME QSO with myself done
during moonset.
Here is the video of the best minute out of ca 10 minute period the signals
were audible with strong QSB on January 13th, from 1615 to 1625z ca 2 hours
after sunset:
<http://youtu.be/QCP0kisTbME> http://youtu.be/QCP0kisTbME
Moon was setting at ca 243 degrees azimuth and the signals were audible
while the moon was from 3.3 to 2.2 degrees of elevation peaking at 2.6
degrees. Antenna was pointing within 3 degrees of the correct direction.
Radio: FTDX5000 + ACOM2000A.
It is noteworhty that the band was not 100% closed as even some SA signals
were heard. Also the amazing strength of the signals at expecially the 3rd
time the signals come back is probably also attributable to some ground
gain
at this elevation.
I wish I had also tried SSB and maybe the 4 high tribander stack for
comparison but was too excited to remember. Should also try if changing the
radiation angle to say even 30 degrees would allow hearing moonbounce from
that elevation. Next timeJ
Now all I have to do is to find someone interested in attempting real 15m
EME QSO (anyone done that before?) who would have coinciding sunset/sunrise
and high gain antenna on 15m.
Can anyone recommend a good program that would picture moon grayline (like
DX Atlas for sun) that would enable to easily identify possible paths for
EME at any given time/day?
Here is also the high resolution video of the tower erection put together
by
ES5PC. It also includes the very first QSO with the new stack with Paul,
K8PO:
http://youtu.be/Z9fDlbIFhMs
I have also made tests regarding the use of different elevation angles (by
shifting the antenna pairs 180 degrees out of phase) and the first results
are very interesting. Proving that for DX normally the lowest 4 degrees is
best but even for DX sometimes 7 or 10 degrees is noticably better bringing
an otherwise not audible signal out from the noise. The same is true about
some EU signals that peaked at 15 degrees while almost not being audible on
low angles. So I will do more testing but I am more convinced now that even
in contest the switching of angles might be useful trying to get a weak
signal out from the noise and high angles are sometimes very necessary.
73
Tonno
ES5TV
From: Tõnno Vähk [mailto:tonno.vahk@gafm.ee]
Sent: Tuesday, September 25, 2012 9:48 PM
To: towertalk@contesting.com; cq-contest@contesting.com
Cc: es5tv@erau.ee
Subject: 15m monster finally up
I am happy to inform all friends that a project of last 4-5 years was
completed during the last weekend at ES5TV KO38CS central ES QTH and a
double H frame on 15m was finally erected what is probably one of the
biggest 15m setups in the world today.
See the full 2-day gallery at:
http://pontu.eenet.ee/es5tv/
Go to the last 16th page if you wish to see the final product right awayJ
70 meters high tower carries 8 5-element 15m yagis as pairs separated
horizontally by 12 meter distance and vertical stacking is 14 meters. The
heights of the antenna pairs are 64, 50, 36 and 22 meters.
Antennas are Optibeam OB5-15:
http://www.optibeam.info/index.php?article_id=76
<http://www.optibeam.info/index.php?article_id=76&clang=1> &clang=1
Tower is produced by 4O3A/YT3M:
http://www.4o3a.com/index.php?option=com_content
<http://www.4o3a.com/index.php?option=com_content&view=category&layout=blog&;
id=99&Itemid=499> &view=category&layout=blog&id=99&Itemid=499
Model shows ca 16 dbd free space gain and almost 24 dbi gain at 4 degrees
over real ground. Beamwidth is less than 30 degrees. Testing has been so
far
limited but the results confirm exactly the modelling results. Pattern
measured with signal generator and SDR was almost identical to what the
computer suggests and signal levels drop ca 12 db when antenna is 20
degrees
off and already 20 db when 25 degrees off the correct direction. There is
huge -50db+ null at 90 degrees confirmed with real measurements (!) and ca
-20-30 db signal drop on the other directions.
First comparisons with my best antenna so far (4 high tribander stack) show
ca 10 db advantage to US when pointed right. That is huge of course. At
the
same time east coast and west coast can’t be covered with one directionJ
The stack will have phase switching capability which allows any pair of the
4 to be switched out of phase to change the radiation angle. Pre-configured
steps are 4, 7, 10, 15, 30 degrees while maintaining most of the gain as
all
antennas are always connected. The phase switching is not yet connected but
will be very interesting to see the results and to get some real insights
into how the different angles play.
We briefly tried to hear the moonbounce when the moon was on horizon but
did
not succeed yet. But 15m was wide open and signals probably did not
penetrate the ionosphere. I still hope to be able to complete some EME QSOs
with the stackJ
CQWW RTTY on the coming weekend will be the first contest for the monster.
Let me know how ES9C will sound on 15 meters. As the rotating is still
manual will keep it either to US or JA.
73
Tonno
ES5TV
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