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Found 3 results

  1. Hello, all. I have a unique situation for my base station setup and wondered if anyone could offer some advice. In the past I ran a Sirio CX 455 antenna. It works really well for GMRS and I believe it's based on a JPole design (not requiring a ground plane). But, it's limited to higher frequency UHF. Again, perfect for GMRS and the SWR is 1.01 on 467 and 1.02 on 462. I'm also running 35' of LMR 400 with N connectors and the antenna is about 19' high. Here's the interesting part: my roof is made of metal tiles. Coated, galvanized steal to be exact and they are not bonded or grounded. I know, weird, and this is what makes things a bit complicated. Since buying the Sirio antenna, I got my technicians license and wanted to upgrade to a dual band antenna. Many local radio nerds rave about the Diamond X50 so I purchased an X50NA at HRO. I understand it's not ideal for GMRS, but I think the SWR compromise is worth it. So, I mounted the X50 on my mast, which is metal and grounded, standing about 2' off the roof, almost at the peak of the roof. I climbed down the latter and went into my office to check the SWR. It was about 3.5 on the GMRS bands. I was expecting something like 1.6 or 1.8 which is typical of this antenna. Rechecked my connections, tested and re-tested. Still, the SWR was very high. That's when it dawned on me that the metal roof is probably causing my problem and acting as a ground plane. I went back on the roof, removed the ground radials from the X50 and checked the SWR. It was much better, about 2.1 for GMRS. So I moved the antenna down (closer to the roof) and the SWR dropped to 1.02 on GMRS. This made the 70cm SWR high though. Eventually I found the sweet spot where 70cm was where it should be and 467 was at 1.6 SWR. VHF SWR is near perfect BTW. The one thing I noticed and thought was strange: the X50 doesn't hear as well as the Sirio did. The X50 measures lower on the S meter for repeaters that would normally be higher (actually, all of them). All transmit reports are good. Is it possible that removing the ground radials effects the receive signal? Is there some way I could better use the metal roof as a counterpoise? is the reduced receive signal just a result of this antenna not being tuned specifically for 462/467? Below is a picture of the roof. The antenna in the picture is not the X50, but the Sirio.
  2. I don't know how many will care about this but I built a box and thought I'd post it. For the woodworkers here, please ignore the joints. I used the miter corner "tape trick" instead of clamping and the thing blew up on me during glue up and I had to scramble for clamps. Didn't get my usual, clean corners. I was also too lazy to route the edges.
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