At 06:29 PM 4/8/2007, Steve Attfield wrote:
I have a few questions for the group about a portale setup I'm orking on. I intend to use it for both linear transponder and FM satellites. the setup will consist of yagis for V and U mounted on a camera tripod with a short run 5-6 feet of coax to the radios. the first thing i'd like to know is: is it worth it to put something like lmr 400 ultraflex or will rg 213 work well. also would it be benificial to have a preamp to mount on the feedpoint of the downlink antenna? -Steve VA3SAX
Steve,
Good that you posted the second message. Running very short coax lines probably will be fine with RG-213. I would switch to LMR-400 at over 25-feet. Somewhere between 50 and 75 feet one should upgrade to at least 1/2-inch hardline for the Transmitter. For example I have a 170-foot run from my shack to the tower-top of my eme array. Using 150-feet 7/8-inch hardline and remainder LMR-400, I still have 1.7 dB loss on 2m getting only 67% of my transmit power to the antennas.
As far as preamps, it will depend some on what radio you are using. The newer mobile/base radios probably will work fine without a preamp on the Leos. I do favor using them, though. For the Heos I think you should plan on using preamps on the down link whatever band that is in use.
This weekend I had some problems with running my 2m SSB Net and thinking I lost my tower-top preamp I switched to the transmit feed line to bypass it. It was an eye opener how much weaker stations were. Typical S9+ signals were down to S3-S5. Fortunately, I discovered I had lifted a control line disabling a coax relay (thus disconnecting the preamp input) so I avoided a tower climb.
73, Ed - KL7UW ====================================== BP40IQ 50-MHz - 10-GHz www.kl7uw.com 144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w DUBUS Magazine USA Rep [email protected] ======================================