Well no contest is ever dull when it starts out like this. We have been experiencing some problems on 1296. Our 1296 DEMI 120watt amplifier was cutting out due to High SWR.
So the first order of business was to lower the antennas back down to the roof so I could work on it. We unfortunately waited until the holiday weekend before the contest to do this. We went to lower the mast and nothing happened. The winch would not work. We ended up uninstalling the wench and taking it apart. Upon unspection beyond finding lots of rust on the terminal bolts, we found that the insulator on one of the terminals was gone. This was causing the winch to short to the chasis which eventually connected it back to ground through the long path (mast->to bumper mount->to bumper->to vehicle frame). What was really interesting was when i plugged just the positive lead to the WATTS UP meter (This is a neat little volt/amp meter that has powerpoles on it) it would shut off. Couldn’t understand why until we found the short. So we searched high and Lowes (lol) for some sort of insulator piece that would fit over a 1/4″ bolt and the best we could come up with was a rubber end cap for 1/4″ bolt and a nylon washer. So we cutoff the end of the rubber end cap and slid it down the bolt and slightly into the hole, placed the rubber washer on and then tightened the bolt together. Since we were worried about the terminals turning we decided to attach the two leads to the terminal with it still open. After doing that we reassembled the winch and presto chango it was functional again. This was Saturday. At the end of all that we were tired so we decided to pick that up on Sunday morning to reinstall it. Meanwhile Dad took a look at the winch controller which has been broken since the last outing. Turns out it was designed very well to be weatherproofed except at one part, where the wires entered it. Well it was full of water and the switches inside were completely rusted out. So for now we will just connect the power poles together manually to turn on the winch unless we come up with something better before the contest.
So Sunday morning, the first order of business was we decided to make an cut to something that is getting in the way of working on the mast. We use a Rohn-25 house bracket to support the mast on the back of the RV. It’s two metal arms are getting in the way and poking you in the gut when you are on the ladder trying to work on things so we decided to cutoff the unnecessary bits. We don’t plan on reusing this anytime soon anyhow. After that I reinstalled the winch and we were able to lower the mast back down to the roof. We took some measurements and attempted to adjust the antenna to eliminate the SWR problems. While I could minimize it by .10 watt it still was high taking readings from the radio bypassing the amp. We then decided to place a dummy load on the end of the coax up on the roof of the RV. Sure enough there was still SWR there. So we start to think we have a bad piece of coax. We then unplug the input and outputs from the amp and connect them together with a barrel connector and the SWR goes away completely. So now we believe we have something going awry in the amplifier. It may be a bad relay or dirty contacts or something else. Hopefully we will figure it out before the contest. In the meantime, we are limited to 10 watts for the contest.
Today, we will be installing a 900 mhz amplifier that is a modified cellular amp. It’s estimated to put out about 250 watts with 4 watts drive. We shall see. We’ll just be happy to see it work and put out more than our 30 watts we get out lol.