Coax question

[jcmios]

For a 75ft radio to antenna which should I use RG-8/U or RG8-X? Whats the advantage or gain?

Thank you
Jim

 

[N_Jay]

For a 75ft radio to antenna which should I use RG-8/U or RG8-X? Whats the advantage or gain?

Thank you
Jim

Cable has loss not gain.

http://hamradio.arc.nasa.gov/coaxcableloss.html

Google is your friend.

Don't fear the Google.:lol:

(Google [Coax loss chart])

 

[jcmios]

I should have used the worf benifit not gain, sorry.
Jim

 

[N_Jay]

I should have used the worf benifit not gain, sorry.
Jim

Less loss is a benefit of better cable.

How much less loss you need to be noticeable is a guess.
I would not worry until you have over 3 dB.

 

[DPD1]

RG8/X is misleading... It's nothing like RG8. It's much smaller. It's a little bit bigger than RG58. It's not a bad cable, but not as good as normal RG8. Wireman #102 Flexi 4XL is a nice multi strand, fairly flexible RG8 type... A little easier to work with than single conductor RG8, but the same loss.

Dave
http://www.dpdproductions.com
- Custom Scanner, MURS, GMRS, Marine & Ham Antennas -

 

[LarrySC]

You failed to post what type of radio. What type of antenna. Some ant's are multi-band. This is another factor. Post more info and get better answers.

 

[Yokoshibu]

lmr-400 / 9913 ... I dont bother with rg-8 / 213 but as stated before post more info get a better answer ... I wouldnt dare use lmr-400 at 1.2+ ghz ... ldf time!

 

[jcmios]

I have one Motorola CM300 VHF and another in UHF, our frequecies are mostly clustered in the 147.0 to 152.0 and 456.0 to 472.0. As for the antennas I am still shopping and open to sugestions, they will be mast mounted on opposite ends of my roof. I am on a budget but then who isn't? Both radios are 45watts and I live on the highest ground in the county with nothing but corn and soybeans for obstructions and about 2 miles from the main repeater and base.

Jim

 

[N_Jay]

I have one Motorola CM300 VHF and another in UHF, our frequecies are mostly clustered in the 147.0 to 152.0 and 456.0 to 472.0. As for the antennas I am still shopping and open to sugestions, they will be mast mounted on opposite ends of my roof. I am on a budget but then who isn't? Both radios are 45watts and I live on the highest ground in the county with nothing but corn and soybeans for obstructions and about 2 miles from the main repeater and base.

Jim

2 miles from the repeater with 45 watts, any antenna is overkill.

 

[kf4lne]

2 miles from the repeater with 45 watts, any antenna is overkill.

Rubber duckie on the back of the radio should be fine

 

[flecom]

just dont put 45w into the rubber duckie unless you want it to melt

 

[kf4lne]

Dummy load with 10 feet of Radio Shack RG58 should work fine.

 

[jcmios]

Not all of the frequencies are run through the repeater and the radio can be switched to 25 watts power. I am looking for good reception and transmition of the non repeater frequencies, other wise I would just use a mobile mount antenna next to my window.

Thank you for all of the replies.

Jim

 

[kf4lne]

ok, here are a few questions:

The 75 FT cable run, is it mostly vertical up a tower or along the ground? how high is the antenna above ground?


Will there be any adapters, couplings, splitters or other lossy connections along this coax run?

What are you using for an antenna?

What kind of connectors will be used at the back of the radio and at the antenna feedpoint?

What kind of noise sources do you have near where the coax will be ran, things like motors, floresent and neon lights and computerized equipment?

What is your budget?

obviously you will want to use the best coax you can afford, but you also need to look at the costs of connectors to fit that type of coax and where it will be installed. i use 213 with my equipment, but its only a 40ft run to the antenna. You can get by just fine with the 213, but buy a good quality such as belden or times. Mini 8/RG8X is a bad choice, its nearly 3 times the loss of real RG8. Radio Shack coax is typically poorly shielded and lossy, avoid that too as well as RG58. Basically, look for a quality RG8/213 or something like the LMR400 or the Belden 9913. Compare the loss of the various cables and see what cable will provide the least loss within your price range. Also look at the costs of RF connectors for the various cables, PL259s are generally cheap, can be had for as little as $.99 each, but you will want to use a teflon insulated silver coated connector, so expect to pay ~$5 for each connector, and more for the "N" connectors that are commonly found on commercial band antennas. if your radios have mini-UHF or a small connector like that you will have to factor in the cost of adapters and other accessories to convert from the large diameter coax to the small diameter connectors. many commercial band mobile radios use the mini-UHF and TNC style connectors, a good quality coax will be larger in diameter than the connector on the back of the radio so in many cases an adapter has to be used. Hopes this helps.

 

[jcmios]

Most of the run is vertical to a height of 45 feet, the antenna will be direct to the radio with a lightining arrestor in-line. Pretty straight forward.