If you are seeing dB increases like this based on cable lengths, you have an impedance mismatch issue and the cable is performing the function of a transmission line transformer. So, you could have internal damage to the antenna, or a bad connection or fitting etc etc.
From: Glen Waldrop Sent: Wednesday, April 08, 2015 10:12 PM To: [email protected] Subject: Re: [AFMUG] Quick antenna question I don't know if you guys saw the update, but I swapped the coax and antenna. Still didn't gain the 15-20dB I'm missing on rx, but I did gain about 6dB. Odd thing is I went with a longer cable and got better signal. I used a 20ft that I made years ago, got a 6dB better signal than a 10ft purchased cable. Really odd thing is I've used two different radios, two different coax and two different antennas, they all have the rx signal lower than it should be. ----- Original Message ----- From: Jaime Solorza To: Animal Farm Sent: Wednesday, April 08, 2015 9:30 PM Subject: Re: [AFMUG] Quick antenna question Yep...protect your fade margin Jaime Solorza On Apr 8, 2015 7:56 PM, "Mike Hammett" <[email protected]> wrote: Every db counts... ----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com ---------------------------------------------------------------------------- From: "Josh Luthman" <[email protected]> To: [email protected] Sent: Tuesday, April 7, 2015 1:20:03 PM Subject: Re: [AFMUG] Quick antenna question 6db??? Omg!!! Use the 400! Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Apr 7, 2015 2:18 PM, "Mathew Howard" <[email protected]> wrote: It looks like there'd be about 6db of loss on 20' of LMR195 vs. 2.2db on LMR400... that's actually not as bad as I thought. Personally, I'd go with at least LMR240 for that long of a run. On Tue, Apr 7, 2015 at 1:06 PM, Josh Luthman <[email protected]> wrote: For the AN50s I always did LMR400 because that's what was there. It was never more than 3 meters (9 feet). For every other radio it's generally what's included. The biggest I can think of is the brand we can't say here - might be heavy duty LMR195, though. Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Tue, Apr 7, 2015 at 2:01 PM, Glen Waldrop <[email protected]> wrote: I might do that. Is that what you use for less than 20ft? LMR400 has less loss, but I think at that length all the loss is going to be the connectors anyway. 400 is a bit stiff. ----- Original Message ----- From: Josh Luthman To: [email protected] Sent: Tuesday, April 07, 2015 12:58 PM Subject: Re: [AFMUG] Quick antenna question For <20 feet you could just use 195, I don't think you get any much difference at 5 GHz. Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Tue, Apr 7, 2015 at 1:56 PM, Glen Waldrop <[email protected]> wrote: We seal ours as well. I recrimped most of the premade cables I purchased after I got a batch where the ends just came off. Assemble the equipment on the ground for testing, go to line the antenna up for a test shot, notice no signal, the coax is laying on the ground. I didn't take the end off, just hit it again with the crimpers from each direction. That has made me a bit gun shy about LMR400, especially after it happened on a tower. ----- Original Message ----- From: Josh Luthman To: [email protected] Sent: Tuesday, April 07, 2015 12:49 PM Subject: Re: [AFMUG] Quick antenna question Nearly all of my coax is preterminated. It's all a) Streakwave or b) included with the antenna. I can't recall if we've ever had a problem with any of it, but we always use coax seal. Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Tue, Apr 7, 2015 at 1:34 PM, Glen Waldrop <[email protected]> wrote: 15dBi omni and ~15 to 20ft LMR400. Lightning blew the door off the power box on the ground, fried the mini PCI cards, but the RB600 still worked, just no data across the ethernet port. The unit was hit in 09, was replaced and the antenna and coax have been in service the whole time. I never replaced it as I thought the hinky rx signal was just misreported, a 24Mbps link @ -88 shouldn't happen. Rx signal quality has finally gone down to match the actual numbers now, so I think something in the antenna was damaged. The problem I have here is quality cables. I've gone through around 50 that were replaced by Streakwave. They had a bad batch. Made me quite shy to replace what appears to be a good cable with one that might just quit like some others have. I made this one in late 08. ----- Original Message ----- From: Jaime Solorza To: Animal Farm Sent: Tuesday, April 07, 2015 12:12 PM Subject: Re: [AFMUG] Quick antenna question more info ...what kind of antenna? how much RF cable and what kind is it? what do connectors look like ? Jaime Solorza Wireless Systems Architect 915-861-1390 On Tue, Apr 7, 2015 at 11:09 AM, Glen Waldrop <[email protected]> wrote: I had a tower hit by lightning. The antenna appeared to survive, so I replaced electronics and let it go. The system reports low rx signal, 20dB worse than expected, but got the speeds I expected, so originally I thought the signal was just being misreported by the new equipment. It has degraded now, so we're working on it this afternoon. I'm replacing the antenna, but what are the odds that the coax is damaged as well? I've got spare, probably going to send it up with the climber anyway.
