Alan and Tim,
I built my helix dish feed using a short piece of approx. 1-inch diameter PVC with no discernable effect. I have a steel bolt running up the center inside the helix for support (not electrically connected to the helix). If well centered along the axis of the helix the bolt does not effect the pattern or impedance of the helix. http://www.kl7uw.com/sat.htm
A sure-fire way to test the PVC is to place it inside a microwave oven and heat it for about a minute. If it gets hot then do not use it. If only slightly warm its OK. CAUTION: DO place a cup of water in the oven with the plastic to act as a load for the oven...you should never run a microwave oven empty as there is no RF load for the magnetron (sort of like transmitting without an antenna). The water insures that there is a load.
73 Ed - KL7UW
At 12:05 PM 3/31/2008, Alan wrote:
Hi Tim and the group... Check AMSAT Journal May/June 2006 and Aug/July 2007 for articles by VE3NPC on helical design and boom materials.
Quoting from conclusion in the May/June 2006 Page 20 #3 "The use of aluminum for boom material has no affect on performance and the use of PVC also has minimal affect ( at least for antennas up to 3 wavelengths in length)."
Use a bias-tee to power the down converter. Depending on the power regulator inside, you may be able to power it with as little as 12VDC. You need a signal source to confirm it is working at whatever voltage you find will run on. A noisy computer, a WIFI router/access point etc will do it for a signal source. Otherwise, making a source such as http://ve2zaz.net/SigSourc/SigSourc.htm is very handy and inexpensive.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of CLAUDIA PIRKL Sent: March 31, 2008 12:51 PM To: [email protected] Subject: [amsat-bb] 2401/144 down conveter and antenna questions
Hello all. I found a 2401/144 down converter on the internet but when it came in the mail there was no info with it. It is a TranSystem Model AIDC-3733 and I think it came from K5GNA. I removed one cover (antenna on left/144 IF facing me) and found a wire with one end not connected. I realize it needs some DC volts to operate but how much and where it needs to be brought in. Does any one have any info to help me out?
On the internet there a few helix antenna designs for 2401. I found a piece of 1" PVC and some AL. ground wire. I wrapped the wire around the PVC and came up with the 4cm dia. the article talked about. But, in another article (435 Mhz) it was mentioned the PVC was very lossy. What do you think??
Thanks for any help!!
Tim N5KI EM65 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb