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| | |-+  Radio Shack RG-58 - good or bad.....
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Author Topic: Radio Shack RG-58 - good or bad.....  (Read 1371 times)
Muggle
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« on: September 10, 2012, 01:53:11 AM »

Guys,

I have a very simple scanner setup...a BC350A with RS RG-58 to my  homemade 3-element Yagi tuned to 119.4. If the other channels at the airport come in, fine...but the only freq I'm concerned with at this time is 119.4.

My questions is: should I be using a better coax ? My run is less than 50'.

I also read in another post here that TV antenna wire would work also Huh

I'm VERY new to this scanning thing, so any assistance would be great. Ultimately, I want to pull in that freq the best I can. BTW - as the crow flies, I'm 4 miles from the airport.

Thanks for any help !!
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dave
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« Reply #1 on: September 10, 2012, 07:06:33 AM »

For a 50-foot run of RG-58 you're losing on the order of half the signal power in the coax.  That's less than ideal. 

Here is a table showing loss for various types of commercial coax cable:
http://www.w4rp.com/ref/coax.html

RG-6 is quite a bit better (in terms of loss) than RG-58 but its impedance is 75 ohms vs. 50 ohms.  That impedance mismatch in an application like this is around 0.2dB (small).  So, bottom line...it's perfectly fine to use it in this application.  It's widely available, very cheap, and easy to work with.  I use tons of it in a number of feed setups.  For best immunity to local noise sources try to use RG-6 with good shielding...either good double-shielded cable with 95% or greater shield coverage or quad-shielded cable.

There are lower loss 50-ohm cables as well...some of them more suited to transmitting applications...the cables will be thicker and harder to work with.  Stay away from Belden 9913 - it will get water in it eventually and become useless.  Some people like LMR400 - it will have only 1.4dB of loss per 100' at airband (under 1dB for 50 feet).  But again, thicker and harder to work with...but if you have an easy way to bring it into the house then you might look at that.  But even with the impedance mismatch, the RG-6 solution won't be much more than 1dB loss at a length of 50'.  And lots cheaper and easier to work with.  You will need RF adapters at at least one end of the cable, though, since it's hard to find connectors other than BNC and F connectors for RG-6.

Hope this helps,
Dave


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