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Friday
Mar102017

Antenna System Upgrades

Since my last post which was way too long ago I've had to make a few changes.

In getting things ready for the installation of my tower I've installed a new length of coaxial cable. In doing this I found a little issue. I've been having issues with range on 2m (VHF). I used to be able to talk about 30 to 40km away but this dropped back to about 15kms away. I first thought it was my radio but I then connected my handheld radio with a little 35 watt linear amp and the problem was still there, in fact a little worse. So this cleared my radio. So I asked a broadcast tech I know if he could help and he got me to do a couple of tests. I don't have much test equipment and I can only really check the VSWR and power from the radio. He got me to measure the power at my antenna connection box (this is where I or anyone else (with a key) can quickly disconnect my antennas if there is thunderstorm coming), the power at the this point was 50 watts just what the radio was giving out. The next test was to measure the power at my antenna switch (this is a relay box I built to enable me to switch antenna from inside the house without having to go outside and do it) and I measured 32 watts. WHAT? almost 20 watts lost within the coax? I was told the losses in 22 metres of RG213 can be a lot at the frequency I'm using. Wow what do I do? I put this issue onto Facebook and a fellow amateur said they could help me. They were doing work on a few communication towers and they could get me a length of LDF450 coaxial cable (hard line). So off to Barham I had to go, as this is where they were working at the time. I ended up getting two big rolls of LDF450 plus a few N type connectors for that type of coax.

So last week I installed a length of this new coax between my antenna connected box and the antenna switch and once completed I redone the test and now I have 49 watts at that point. The 20 watt loss was gone and the next lot of work is now to replace the length of RG213 between the antenna switch and the antenna itself. Hopefully this will give me a lot more power at the antenna. I'm expecting some losses but it's going to be nothing like it was or would be with when I was using the RG213 coax. I have ordered a few connectors so I can compelte this part of the job. The parts are coming via Express Post so I'm hoping they will be here on Monday or Tuesday. I then need to work out how I'm going to do the work as I have to pull down an antenna to replace the coax.

I'm also hoping to start, sometime this month, the upgrades to my mast. I have to replace an antenna that was damaged a while back and I'm also thinking of replacing a length of RG213 that is being used for my UHF CB antenna and replacing it with a length of LDF450. This will liek with the VHF antenna system remove the losses I have in that coax and give me the full 5 watts to the antenna instead of about 2 to 3 watts now. I'm also going to extend that mast up a little higher so I can fit a coupe of antennas on it. To do this job I will need to have a friend bring a forklift around so I can access the top of the mast and do the works safely. I will have to work in with my mate for this as I'm guessing this job will take a few hours to complete to the point I can do the rest via a ladder safely.

I have a bit of works in the planning and hopefully some day down the track I will be able to get my tower up and get a couple of 2m yagi's up. I currently have one of my 2m yagi's up which is mounted vertically so I so can access some of the local, well Swan Hill or Robinvale repeaters when the conidiotns are good.