At 04:35 PM 8/4/2008, w7lrd@comcast.net wrote:
Next question- which probably would be more aimed at a EME bb. I have a 12 foot TVRO I am building a patch feed for 1296, and feed it through 50 feet of LMR400 to my IC-1271A. I want to see if I am able to "hear" EME signals. Of course if I am able to, you can guess what my next effort will be. This will be a cheapie effort as I am only using stuff I already have. I do have a KJ6KO L band 70 watt amp. 73 Bob W7LRD Seattle
Bob,
Regarding 1296-eme: The 12-foot dish will do fine on eme and the 70w amp will do fine as a start, especially if you use JT65C.
Is your patch feed circular polar? EME on 1296 is RHCP in transmit and LHCP in receive. The switch of polarity sense is due to the fact that reflection at the moon reverses the sense of polarization. This might be difficult to achieve with a patch feed. Many eme stations are going to the septum feed since it produces both senses of circular polarization and eliminates the need for a high power coax relay. See http://www.ok1dfc.com/EME/emeweb.htm for septum designs.
50-feet of LMR-400 will lose a lot of power at 1296 (2.4dB loss); only 42w will reach the dish. You can solve this two ways: upgrade to 1-5/8-inch hardline (61w will reach the dish) or mount the amplifier at the dish (on the back side would work well). Then use a 10-12 foot 1/2-inch hardline to the feed so that 95% of the power reaches the feed. Typical stations on 1296 eme run a minimum of 150w and average 200-300w. I understand from talking with Gordy, WA6ZKY, that a 150w amp is being developed by KJ6KO. I probably let the cat out of the bag so my appology to Greg.
73 Ed - KL7UW