[KL7AA] Fwd: Re: [QRP-L] qrp moonbounce?

[Jim Larsen - AL7FS]

This may be of interest to a few of you.

73, Jim

Jim Larsen, AL7FS
http://www.AL7FS.us/
Section Manager - Alaska

ARRL, the national association for Amateur Radio™
http://www.ARRL.org/
907-345-3190
AL7FS at ARRL.org




-------- Original Message --------
Subject: Re: [QRP-L] qrp moonbounce?
Date: Wed, 7 Apr 2010 22:14:16 -0600

To: qrp-l at mailman.qth.net


KP4AO will be active on EME from Puerto Rico using the Arecibo dish 
April 16, 17 and 18:

< http://www.arrl.org/news/stories/2010/04/07/11420/?nc=1 >

If you are at all interested in VHF weak signal work, this is worth 
participating in. Large institutional antennas are seldom made available 
to hams, so it is best to take advantage of these opportunities when 
they arise.

At 432 MHz, the Arecibo disk has about 60 dBi antenna gain. They will be 
using 400 W.

You should be able to hear them on CW with modest equipment, say an 
FT817 and an 11 element WA5VJB Yagi:

< http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf >

You can make the WA5VJB Yagi pretty simply with materials at hand or 
easily purchased. Use a short feeline, say 10 ft of RG213 or better.

A preamplifier will help a lot if you have one.

You will need 100 W to the above setup to make a CW contact. You could 
make up the difference in antenna, but that is a pretty big array, say 
16 of the above antennas.

There will be lots of stations who want to make QSOs. You will probably 
need around 3kW EIRP to make a CW contact. That is 100W to a 15 dBi 
antenna. This is a modest setup. For a SSB contact you will need about 
10X that amount. The big issue is that you will be fighting with other 
stations for a contact and as these are fairly modest requirements for 
EME, you will be fighting in a pileup with lots of other stations for a 
contact.

Modern digital signal processing, coding, decoding, and error correction 
can significantly reduce signal to noise ration required for a contact 
over SSB or CW. Using JT65b, a digital mode in the WSJT suite of weak 
signal modes, you may be able to make a contact with 10W as long as you 
have a decent length Yagi. But KP4AO won't be running JT65b until they 
have worked out the available CW and SSB contacts. Still it is worth trying.

So you can make a QRP EME contact, but it will be hard. You can make one 
without the big station usually required though and many people already 
have adequate equipment or it is within reach. It is certainly worth 
trying. And just listening to signals off the moon is a big kick. - 
Duffey KK6MC/5