Thanks Bob Reducing power was no measured help till I got to minimal watts and unfortunately there are no extra VHF band antennas to try (unless I borrow one from the GOV or the TX highway patrol or state park folks) I guess I won't try "those" feed lines/antennas. J
73 Don W5DK From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, June 01, 2008 4:03 PM To: [email protected] Subject: RE: [Repeater-Builder] Re: noise on exposed folded dipole arrays and fiberglass encased antennas - YES At 6/1/2008 14:58, you wrote: >Bob, > >How much noise? I have a current situation at 580 ft. I m diagnosing. Enough to get into another antenna ~30 ft. away. After the lightning strike we had severe desense (over 30 dB) so we tried to run split antennas with the 4-pole on TX & GP9 on RX. Still had several dB of desense until we reversed the antenna connections. >Station works fine into a dummy load tested with a sampler slug and no >desense. Add the feedline and antenna and I get 15db degradation. I have >looked at the freqs the ant is hearing and don t see an IMD issue. >Spectrum looks normal. The problem is a steady 15 db. I think it s the db >antenna. We re 20ft from the top of the tower. > > >Any suggestions before we pay a climber? Try reducing the TX power & see if there's some "threshold" power level where the desense suddenly appears. That would likely indicate something arcing somewhere. The problem could be in the feedline, your antenna or an antenna mounted close to yours. In situations like this a spare antenna of some sort really comes in handy, even if it's relatively low on the tower. You could then continue to RX off the "defective" antenna & TX on the low spare antenna. Bob NO6B
