[TowerTalk] 15m monster finally up - EME and Video

Tue Feb 5 12:09:51 EST 2013

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 at 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 at gafm.ee] 
Sent: Tuesday, September 25, 2012  9:48 PM
To: towertalk at contesting.com; cq-contest at contesting.com
Cc:  es5tv at 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

_______________________________________________

_______________________________________________
TowerTalk  mailing  list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk