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Scanner / Receiver Antennas - For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

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Old 08-07-2018, 1:05 PM
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Default Which type of cable for Diamond Discone?

I just picked up a Diamond Discone antenna and will be installing on new home. I was wondering if anyone has advice on type of cable to use? I am thinking of going with LMR 240 Ultra Flex, 75 ft run. I was going to go with LMR 400, but I've used in the past and have found it to be very unflexible. Any other recommendations?
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Old 08-07-2018, 4:11 PM
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Try the ultraflex version of LMR 400 if you were happy with the performance but don't want the installation hassle for your new run. It's basically the same cable but uses a stranded center core and different plastic for the insulator between it and the shield to make it much more flexible. It costs just a bit more but will have lower loss than the LMR 240 will.
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Old 08-07-2018, 5:04 PM
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That is a long run for frequencies above 400 MHz and will suffer from heavy Db loss. If you cannot possibly make the length substantially shorter, I would go with the LMR-400 even if it is a pain to install - you only have to do it once.

Look up the loss charts for the different bands and coax cables, you will see what I mean.
Here is a link to one of them:

Coax Attenuation Chart
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Old 08-07-2018, 6:47 PM
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I agree, 75 feet is a lot.

You can try one of the online coaxial cable loss calculators to get an idea…

At 75 feet, 855MHz here are some numbers:
RG-6 6.8dB of loss, or almost 80% of your signal.
LMR-240 5.5dB of loss, or a bit over 70% of your signal.
LMR-400 2.83dB of loss, or just a bit less than 50% of your signal.
LMR-600 1.83dB of loss, or about 35% of your signal.
1/2" Heliax, 1.5dB of loss, or about 30% of your signal.

Any way you can move the radio and antenna closer together?
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Old 08-07-2018, 7:16 PM
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i love lmr 400..really improved my scanner listening
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Old 08-07-2018, 10:29 PM
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Quote:
Originally Posted by mmckenna View Post
I agree, 75 feet is a lot. <<snip>> Any way you can move the radio and antenna closer together?

As mmckenna advises, your best option is to move the antenna closer;

Failing that, I wouldn't use anything less than high-quality, LMR400-type cable.

By the way, be sure to order the correct coax connector for your Diamond discone... Some are UHF and some are N.
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Old 08-08-2018, 10:42 AM
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Use RG6, it's flexible enough, and add an amplifier at the antenna and you'll end up with gain instead of loss. Something that even the most expensive coax can't do on its own. Add a variable attenuator at the scanner and you can't go wrong. https://www.ebay.com/itm/Variable-At...Z/153096386799

If you get a low noise amp, 0.5-1.5dB NF, you will have a better signal than the scanners input amplifier can provide. It's a win-win situation. https://www.ebay.com/itm/Ultra-Low-N...A/283092038093

/Ubbe
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Old 08-08-2018, 10:46 AM
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If you use a preamp, ideally you want it at the antenna end of the coax, not at the radio end.
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Old 08-09-2018, 8:14 AM
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Thanks to all for the really helpful responses.
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Old 08-10-2018, 7:15 PM
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I used Bury-flex lmr 400 on my discone. Im running about 50ft of it. Got it online at one of the ham radio outlets at a good price all made up with the connectors. Cant think of the name of the site for the life me me lol. Was a good deal. I did alot of looking around for a deal on it.
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Thanks to all for the really helpful responses.
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Old 08-10-2018, 7:46 PM
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Plus One for nyair1

Davis RF Co. - Bury-FLEX Flexible Low-Loss Coax

Good stuff ...
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