hardline vs. catv hardline

[firefighter14_22]

Coax/Hardline VS. CATV Hardline?
can you use CATV Hardline for a UHF repeater?
i know coax/hardline is 50ohm and CATV hardline is 75ohm does it matter?
what would happen if you use 75ohm CATV hardline on a uhf repeater?

 

[prcguy]

If you use 75ohm hardline on your repeater you will only be able to communicate with others using 75ohm cable.





Just kidding.

A repeater is usually a finely tuned, high performance system with everything aligned to 50ohm cables and loads. I have seen duplexer and filter response skewed when subjected to an impedance mismatch and using 75 ohm cable could cause degradation beyond the simple impedance mismatch.
In my opinion, if your going to assemble a repeater do it first class or don't bother.
prcguy

Coax/Hardline VS. CATV Hardline?
can you use CATV Hardline for a UHF repeater?
i know coax/hardline is 50ohm and CATV hardline is 75ohm does it matter?
what would happen if you use 75ohm CATV hardline on a uhf repeater?

 

[burner50]

In my opinion, if your going to assemble a repeater do it first class or don't bother.
prcguy

I'll second that...

Using 75ohm hardline is an exercise in futility. What you would gain by using hardline, you would lose because of the impedance mismatch... and then some.

If you're going up a tower proper hardline is a must... Shorter applications, you could get away with some good LMR400 since distance isnt the objective.

 

[AK9R]

If you use 75 ohm CATV hardline in a system designed for 50 ohm impedances, the best SWR you will see is 1.5:1. I know of amateur radio repeaters that have been put up with 75 ohm CATV hardline and they do work. But doing so is a cost-cutting move that can degrade performance.

 

[ka5lqj]

75 CATV hardline vs 50 ohm hardline, LOL!

Well,

There are other factors involved as well. Depending on WHOM you get the CATV cable from Time-Warner or others) there is a good chance, your repeater will be plagued with Über-Leftist News media "talk" from CNN, M$NBC, ABC, CBS, or NBC, constantly. This will cause a "Bravo Sierra overload" in all the input circuits, stopping up normal radio "traffic" about radios and all you will have is an B$ repeater. I would suggest cutting a large, 4" drain hole in the bottom of the repeater cabinet and adding a one horse suction pump to evacuate any B$ that collects and pipe it BACK to Congress where it belongs, LOL!

(No political "junkies" were harmed in this message) ;-)

Respectfully submitted,
73,

Don/KA5LQJ

 

[IdaScan]

First of all...

Look here:
Building 75 to 50 ohm CATV matching stubs

Secondly...

Please stay _far_ away from LMR400 in repeater station use... The vast majority of the commercial radio sites here in Southwest Idaho (amongst others throughout the country) explicitly prohibit the use of any LMR/9913/9914 dual shield (braid & foil, not double shielded like RG214 braid over braid) cable anywhere in the installation due to the poor PIM performance. If USFS and BLM won't allow it, why on earth would you have it at your installation?

Getting the most from your repeater system

Finally...

Check out the Repeater Builder site... A lot less "bravo-sierra" than this thread has generated...

 

[stevelton]

I own a UHF repeater.

Not all repeaters have to be at the 2000 foot mark on a big hill pushing 300 watts.
YES, it IS ok to have a small "low cost" repeater for some local use.

My repeater is sitting at 45' AGL, fed with LMR400 transmitting 6 watts into a cheap fiberglass antenna.
Im paying for it, I have put all the money into I can, and it works fine for what I want it to.
There are 4-5 other hams here in the county that also use it, and it does what they want it to.
There are no other repeaters in my county, or any that cover the county very well, so this cheap set up is better than nothing. If I didnt spend the little money I did, then there would be no repeater, and that wont do anyone any good.

So whos to say that the guy that started this thread doesnt want to do the same?

All I know is my system works well, even though it doesnt use 1 5/8 hardline and a DB408 at 300'. My money my way, and it works well.

Steven, KC9GMX
442.625 PL123.0

WHERE Amateur Radio Club

 

[gcgrotz]

CATV stuff works great for feeding that 4 square vertical array that you have down in the back 40 about 300 feet from your house. Not my house you understand, but theoretically.

 

[lmrtek]

MANY hams use 75 ohm feedline for repeaters and it's not a problem.

I ran a UHF repeater on 75 ohm RG-11 for many years since I had several thousand feet laying around and had absolutely no problems

And it has lower loss than it's 50 ohm cousins.

W3KKC has several repeaters on Pennsylvania mountain tops using 75 ohm hardline

Pictures of the Hay's Mill Fire Tower

 

[code3cowboy]

W3KKC has several repeaters on Pennsylvania mountain tops using 75 ohm hardline

Pictures of the Hay's Mill Fire Tower

There are no mountains in Pennsylvania.