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Author Topic: Advice on Building an EME Station  (Read 4183 times)
WA6MJE
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Posts: 71




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« on: November 23, 2010, 08:38:14 PM »

I have been a ham for about 50 years, with decades of inactivity from time to time.  I just returned to the hobby and am amazed, especially by digital modes.  PSK 31 led me to JT65 which then led me to reading about EME.  These days they tell me a single yagi 100w EME station can actually work.  I gotta give it a try.  I have thought out a basic station, and would appreciate feedback and critique.

1) I own an IC 7000 already which has 2m and 70 cm capability.
2) I have a HOA restricted home, so I will go for 70 cm hoping I can use a temporary Yagi that disappears after use. Thus far I am thinking about the M2 432-12EME Yagi Antenna for about $145. I get 12 elements and 14.4dbd gain with less than 10 feet of boom length.  I intend to mount it on a professional camera tripod that can put it up about 6 or 7 feet and aim it by hand.  A single Yagi does not have a narrow beamwidth, so I am told I need only re-adjust every 20 minutes. I do not know if the M2 can be easily disassembled into maybe two 5 foot segments for easy transport and storage. If anyone knows this it would be great.
3) I have not found a great selection of linear amps at a low price range.  There is a 100 watter "brick type" amp I am thinking about. Mirage D-3010-N  for under $400.  I would prefer something closer to 500 watts but have not found an economical one at this price point.
4) Some of the articles I read say you can get by without a low noise pre-amp. So I will omit this. BUT I will use high quality coax with a very short run out the door to the tripod a few feet away.

Other thoughts.  Two meters seems to be impractical because of antenna size. A 20 foot mast would be unwieldy for portable use. UHF or microwave would require a whole new rig.  440 seem like the easiest path.  If I can get this "single Yagi" EME station off the ground, I can then determine if it is worth the time, effort and money to get a more exotic solution. 

Any feedback on these ideas would be great.

Rene - WA6MJE
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WX7G
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Posts: 6041




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« Reply #1 on: November 25, 2010, 07:47:21 AM »

For EME a 432 MHz antenna will be no smaller than a 144 MHz antenna. For the same receiver antenna factor the 440 MHz antenna needs to have 5 dB more gain.

To work EME with 100 watts and a single Yagi means you will be working a "Super Station." As far as I know most if not all of the Super Stations are on 144 MHz.

You might look at purchasing a used amplifier. Give EME and try and when you're done sell the amp for what you paid for it.
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WA6MJE
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Posts: 71




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« Reply #2 on: November 27, 2010, 07:34:32 PM »

For the same receiver antenna factor the 440 MHz antenna needs to have 5 dB more gain.

To work EME with 100 watts and a single Yagi means you will be working a "Super Station." As far as I know most if not all of the Super Stations are on 144 MHz. 
David:  Thanks for the tip. I was not aware that the Super Stations hung out on 2m, nor did I know 2m would take less gain.  I am re-reading how EME works and did learn that there is more path losses on higher frequencies.  I am going to study this more.  Still, a 2m antenna for me is limited to about 7 elements (by boom length) so I am going to see if anyone has actually made contacts with a 2m yagi this small.  Thanks for the tip.

Rene - WA6MJE
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N0AZZ
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Posts: 241




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« Reply #3 on: November 28, 2010, 04:47:56 AM »

You might consider a Cushcraft 13B2 2m antenna and just take it into your garage and hang it from the ceiling is one option I started with one but it was tower mounted. I now have it mounted vertical for FM and a new VHF tower for 2 long boom 2/6m antennas. A used 2m brick about 160 w can be had used for around 150.00. Then you can work most all the big guns and there are quite few.
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WA6MJE
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Posts: 71




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« Reply #4 on: November 28, 2010, 07:12:06 AM »

You might consider a Cushcraft 13B2 2m antenna and just take it into your garage and hang it from the ceiling is one option I started with

That is another good tip, I will check out Cushcraft.  Meanwhile, I went back to the M2 site and looked over the 2M products. The 2MCP14 is circular polarized 7 element (each) on 10.6' boom with 10.2 db gain. At first I thought circular polarization would be an advantage to overcome Faraday polarization effects.  Then I looked deeper and learned that then I have to worry about right hand vs left hand circular polarization, one preferred for transmitting, the other for receiving. Then I got lost since I could not change the handedness so this antenna would not seem to work with just one. I would need two, one for receiving, the other for transmitting.

So, do I understand this correctly? For a single Yagi EME station, circular polarization does not seem to be an option because of the required left-right handedness between transmit and receive?  Or, am I over reacting?
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WA6NUT
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Posts: 8




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« Reply #5 on: December 02, 2010, 06:09:19 PM »

You might check out "The Bodger's Guide to Patio Moonbounce" by G4BAO at:

http://homepage.ntlworld.com/john.g4bao/Files/MRT2010.pdf

73, Rick, WA6NUT
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