[amsat-bb] Re: Arrow and EME?

Idle-Tyme nss at mwt.net
Thu Apr 1 10:52:46 PDT 2010

Another very important thing is polarity.
the ability to change polarity can easily me a completed QSO or one 
where not a peep was heard.

In the late 80's early 90's I had a small station of 4  eight element 2 
meter yagis.  I think they were a W1JR design?

anyway I mounted them in a way that i could rotate them in polarity also.

It was amazing I never thought i could do moonbounce with them  but just 
for kicks was listening down at the bottom of the band one day and heard 
someone CQing and wortking someone off he moon. of course it was W5UN.  
but a random call when he finished and we had a complete QSO in the log 
with no repeats solid exchange both ways!

what make this amazing was I was using a kenwood TS700 rig into a old 
KLM (remember KLM amps?) a 70 watt one that was tired and only putting 
out about 35 watts, into a run of rg 213 50 feet to the antenna,  no pre 
amps at all. and on CW by ear! no filters either just the standard 2.XX 
whatever wide filter.
But the polarity made all the difference!  In horizontal mode i heard 
NOTHING. but somewhere inbetween H and V he wa solid copy and he had no 
problem hearing me too.

I eventually went on to work about 30 other stations as small as other 4 
yagi stations.  The ability to make polarity changes is a GIANT advantage!


The Original Rolling Ball Clock
Idle Tyme

On 4/1/2010 12:11 PM, Mark Lunday wrote:
> I have been doing some reading on this also.  Although I have not yet made
> any EME contacts, I have been uncovered the following:
> 1. Moonrise/moonset will enhance signals because of ground reflections,
> something like 6 dB.  Many folks intentionally use moonrise and moonset
> attempts for this reason.
> 2. Mast mounted pre-amp is essential
> 3. Higher frequencies need more gain (so I have been told).  But the 440 MHz
> part of the arrow antenna should have a LOT more gain than the 2 meter part.
> 4. Low loss coax is very important, esp at VHF.  Keep the runs short and use
> something equiv to LMR 400 (50 foot of the good stuff is probably under
> $100, and worth it.
> 5. Definitely try to set up a sked with W5UN.  If you can hear him, then you
> are halfway there!
> 6. Monitor websites like http://www.chris.org/cgi-bin/jt65emeA
> 7. 2010 appears to be a promising year for EME, here is a good calendar:
> http://www.vhfdx.net/w5luu.html
> Mark Lunday
> Greensboro, NC - FM06be
> wd4elg at arrl.net
> http://wd4elg.net
> http://wd4elg.blogspot.com
> -----Original Message-----
> From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
> Behalf Of MM
> Sent: Thursday, April 01, 2010 8:37 AM
> To: AMSAT-BB at amsat.org
> Subject: [amsat-bb] Arrow and EME?
> Arrow Antenna and EME:
> It is possible to work Earth Moon Earth with an Arrow Antenna.
> Of course, it is.  You just need to make a schedule with someone on the
> other side of the link with enough Antenna Gain.  You also need to be
> running the new digital text messaging mode called JT65B
> Link for JT65
> http://www.physics.princeton.edu/pulsar/K1JT/
> Definitions:
> In this document I will refer to all antenna gain values based on the number
> of elements.
> Example: A Single half-wave Dipole = 0 dBd
> Elements 2 = 3 dBd
> Elements 4 = 6 dBd
> Elements 8 = 9 dBd
> Elements 16 = 12 dBd
> The Arrow antenna (Model 146/436-10) has 3 elements on the 2-meter band, so
> its maximum theoretical "Element Gain" is 4.5 dBd.
> With the invention of the JT65 protocols, thousands of Amateur Radio
> stations running a Single Yagi 2-meter antennas, now have access to the Moon
> and EME contacts.
> To make a contact on Moon bounce, the "Total Antenna Gain" from both
> stations is added up  and will need to be in the approximate range of 25-30
> dBd.  With this gain and the average transmitter power of (100-400 watts)
> you will have a 10-20+ percent chance of completing a 2-way EME JT65B link,
> with another station.
> Note: There are many other factures used in EME gain calculations.  For
> simplicity, we will just focus on the antenna Gain.
> The amount of Total Antenna Gain required depends on the mode you wish to
> use.  The wider the mode, the more gain that is required.  The mode JT65B is
> a very narrow mode and requires less gain.  I am not going to go over all of
> the details of JT65 in this article, look it up.
> Gain required by mode: (All values are approximate)
> JT65	28-30 dBd (1-Yagi + 4-Yagi)
> CW	30-40 dBd (4-Yagi + 4-Yagi)
> SSB	40-50 dBd (8-Yagi + 8-Yagi)
> FM	60-70 dBd (16 + 24) Guess
> The Mode JT65B requires approximately 30 dB of Total Antenna Gain for an EME
> contact.
> If we assume the average 12-element 2-Meter Yagi has 10.5 dBd (round to 11
> for easy math) of  "Element Gain", then the more Yagi's you stack, the more
> gain you will have.  In EME lingo, 1x12 means, you have One Yagi, with 12
> elements,  4x12 means you have a stack of 4 yagis with 12 elements each (48
> elements total) and an approximate gain of 17 dBd.
> 1-Yagi = 11 dBd
> 2-Yagi = 14 dBd
> 4-Yagi = 17 dBd
> 8-Yagi = 20 dBd
> 16-Yagi = 23 dBd
> 32-Yagi = 26 dBd
> 64-Yagi = 29 dBd  (W5UN)
> A Single-Yagi station  (11 dBd) calling a 4-Yagi (17 dBd) station will have
> approximately 28 dBd Total Antenna Gain.  The 4xYagi stations are very
> common on JT56B EME.
> Let's go back to the Arrow Antenna:
> We need 30 dBd of total antenna gain.
> The Arrow antenna has 4.5 dBd.
> The Arrow also has a Maximum power limitation of 150 watts (10 watts if hand
> held).
> If you are running the maximum 150 watts  on your Arrow antenna, you should
> be able to work stations with 32 to 64 Yagi's.  There are not very many 64
> Yagi stations out there, however Dave W5UN has been active on JT65 EME
> recently.
> If you want more of a challenge, you can try QRP at 5 watts and your Arrow
> antenna.
> Reducing you power from 150 watts to 5-10 watts, will reduce your
> performance by 12 db.
> To compensate for the reduce power, you will just need to find a station
> with a bigger antenna.
> There is another big gun on EME.  Two weeks ago, Arecibo was on EME, running
> CW, working EME stations on the 440 band.  The antenna used at Arecibo is a
> simple 1,000 foot dish.  The actual gain for 2-meters is not known, however
> I will assume it is more than 64-Yagi's.
> http://www.naic.edu/
> So here is your chance.  Make a schedule with Arecibo and go for QRP, EME,
> with a held Arrow antenna, or if you know of any good contacts at Arecibo,
> send me the data and I'll try to arrange a schedule and try it from my
> station.
> Other Hardware:
> A good Receiver Preamp (similar to ARR)
> http://www.advancedreceiver.com/
> A good SSB 2-meter Transceiver (the best ever made Yaesu FT-736R)
> http://www.xs4all.nl/~ketel/ham/ft736.htm
> Good Coax (RG-8 coax is 11 Millimeter coax.  That is ok for 50' EME runs,
> for longer runs use 12+ Millimeter coax)
> 73
> WF1F
> www.marexmg.org
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