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Need diagnosis for an outdoor scanner antenna problem

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petbytes

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Last year I installed a Diamond wideband discone antenna on the outside of my house by mounting it on the non-used chimney. I ran RG-8X coax from the antenna, under the eaves of the roof and into the wall, and routed it a Uniden BCT15 scanner. The length the of the cable run is 90 feet.

I wasn’t impressed with the reception I thought I should get since the antenna is at least roof height, but I know the 90 foot coax run is pretty far. My hand-held Uniden BCD 396T receives radio traffic very well indoors with the included rubber whip.

Recently for some reason, I’m not picking up radio traffic like I had in the past. I’m only hearing close strong traffic, about 5% of what my handheld gets.

These are some possible causes I came up with:

The RG-8X coax runs next to TV cable under the eaves for about 40 feet, but nowhere do they touch. The TV cable is shielded RG 6. Could this be an issue?

Is the RG-8X is too long of a run and I’m suffering attenuation loss?

I had to add the BCN connectors on the cable ends. Could they have come loose from the cable?

Anything else I might look at or do to diagnose?
 

Highpockets

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petbytes said:
Last year I installed a Diamond wideband discone antenna on the outside of my house by mounting it on the non-used chimney. I ran RG-8X coax from the antenna, under the eaves of the roof and into the wall, and routed it a Uniden BCT15 scanner. The length the of the cable run is 90 feet.

I wasn’t impressed with the reception I thought I should get since the antenna is at least roof height, but I know the 90 foot coax run is pretty far. My hand-held Uniden BCD 396T receives radio traffic very well indoors with the included rubber whip.

Recently for some reason, I’m not picking up radio traffic like I had in the past. I’m only hearing close strong traffic, about 5% of what my handheld gets.

These are some possible causes I came up with:

The RG-8X coax runs next to TV cable under the eaves for about 40 feet, but nowhere do they touch. The TV cable is shielded RG 6. Could this be an issue?

Is the RG-8X is too long of a run and I’m suffering attenuation loss?

I had to add the BCN connectors on the cable ends. Could they have come loose from the cable?

Anything else I might look at or do to diagnose?
Maybe water got into the cable near the connector up at the antenna.
 

N1BHH

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Jackson Square, East Weymouth, MA.
You may have water in the feedline. You should check the connections to be sure they are secure. The connection you made to the discone may also need attention. If the jacket is nicked in anyway, you will get contamination, thus you'll need replacement with something along the line of RG8U or LMR 400 or something similar, something with lower loss than your RG8X. I use it here for short runs and it works great, long runs are okay at HF, but not good for VHF and up.

Funny thing though, I had some RG8U that got water in it, despite being heavily gunked on the antenna feedpoint, but I would drain it out and in a few hours could connect it back to the radio and all was well. That was the strangest thing I had ever seen.
 

zz0468

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RG8X is crappy cable to start with for VHF/UHF service. Quadruple that statement if you're trying to listen to 800 MHz. If performance is deteriorating from where it was a year ago, water or corrosion are a good possibility. Replacement of the coax is the only good option if it has water in it. Even if you manage to get it dried out, it'll never be the same.

In regard to N1BHH's comment about getting water even though it was 'gunked' at the antenna, I've seen plenty of antennas where the feedpoint itself is the source of water into the connector, so that if the connector and cable are sealed, it gets in through the exposed portion of the feedpoint itself. Not much you can do there beyond weather proofing the feed (which may degrade performance) and getting a higher quality antenna that offers more protection. This is one reason why I will only use real commercial grade antennas.
 

DPD1

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Check the connectors... You may have only had one side of the line (center or shield) making contact to begin with, and now both sides have lost contact, so you're basically just getting whatever the coax itself is picking up. RG8X isn't the best, but it should still be better than an indoor antenna.

Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
 

kb2vxa

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Since you installed the worst possible coax forget all the gyrations, just replace it with "the good stuff" (don't ask, we've been down that road so many times the Chinese complain about wheel ruts), do a careful job on the connectors and wrap them tightly with black vinyl tape for waterproofing.
 

gmclam

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Fair Oaks, CA
petbytes said:
Last year I installed a Diamond wideband discone antenna on the outside of my house
Keep in mind the discone antenna has no gain. So other than increased signal you pick up from the elevation of the antenna, the signal is typically no better than a duckie.

The length the of the cable run is 90 feet... My hand-held Uniden BCD 396T receives radio traffic very well indoors with the included rubber whip.
Comapring the two depends your location. If your indoor antenna is next to a window on the side of your home facing the transmitting location, it will do good. That 90 foot run of coax is going to attenuate your signal, which had to gain to start with. In many cases, you'll actually get less signal from the roof antenna than from the duckie.

The RG-8X coax runs next to TV cable under the eaves for about 40 feet, but nowhere do they touch. The TV cable is shielded RG 6. Could this be an issue?
No.

Is the RG-8X is too long of a run and I’m suffering attenuation loss?
Yes, but it should not have changed from when you installed it. Certainly you want the shortest run using the best coax.

I had to add the BCN connectors on the cable ends. Could they have come loose from the cable?
Yes. Very likely depending on the exact BNCs you used. RG-8 is often too large for BNCs I've seen. I've had better luck putting PL-259s on my RG-8 an using a SO-239 to BNC adapter.

Anything else I might look at or do to diagnose?
All the things people have already suggested. Certainly CONNECTIONS are the first place I'd check. Many come loose over time. That includes the connections at the antenna, especially if you've had high winds in your area.
 

hoser147

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Grand Lake St. Marys Ohio
Since you mentioned the bnc connectors and everyone one else has covered the bases, If you used those crimp on bnc pins do yourself a favor and solder them. Ive had much better luck with soldering them than with the crimp, besides when you solder them you can usually reuse them over crimpin them.........Hoser
 

N1BHH

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I thought I answered that in my previous post. Let's start again. Anything like RG8U and better, such as LMR400 will be very good for any antenna installation. RG8X should be used for relatively short runs. RG8U is okay to use, but LMR400 makes a very good feeder for your antenna. There are plenty of outlets for it, just use your favorite search engine and you'll get plenty of hits.
 
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