Why is my repeater's range Crap?

centuryvrproductions · Aug 23, 2011

I have a 25 Watt repeater running duplex on 440.

I have calculated the losses. duplexer is 1db and i am using rg-58u jumper cables duplexer to radios (About 2 feet total) and running about 3 feet of RG-58 to a colinear 9db antenna tuned to my 444.5MHz. I have also used a tuned coaxial dipole and a ground plane antenna at an elivation of about 30 feet, i drove around and after about 1/4 mile or so the siginal is almost gone on my HT. Flat ground for a few miles and i cannot hear the repeater. Running a calculated (with loss) 185Watts ERP...

Could this be because of bad antennas, loss in coax or somthing like that? please post any information you may have...

gewecke · Aug 23, 2011

centuryvrproductions said:
I have a 25 Watt repeater running duplex on 440.

I have calculated the losses. duplexer is 1db and i am using rg-58u jumper cables duplexer to radios (About 2 feet total) and running about 3 feet of RG-58 to a colinear 9db antenna tuned to my 444.5MHz. I have also used a tuned coaxial dipole and a ground plane antenna at an elivation of about 30 feet, i drove around and after about 1/4 mile or so the siginal is almost gone on my HT. Flat ground for a few miles and i cannot hear the repeater. Running a calculated (with loss) 185Watts ERP...

Could this be because of bad antennas, loss in coax or somthing like that? please post any information you may have...

All your answers and more are here,

repeaterbuilder.com

73,
n9zas

WA4VBC · Aug 23, 2011

For a repeater to function properly you need double shielded or hard line (such as Heliax) coax between the repeater and duplexer and to the antenna. Also duplexer tuning is critical. To properly test for desense will require a service monitor to do it right. Sid. .

centuryvrproductions · Aug 23, 2011

I have a properly tuned duplexer. Is RG-174 good for jumpers? and i am going to get LDF4-50A cable for the tower.

the antenna is a colinear made from RG-58 and is tuned to my frequency. it is suposed to be 9db

Citywide173 · Aug 23, 2011

WA4VBC said:
For a repeater to function properly you need double shielded or hard line (such as Heliax) coax between the repeater and duplexer and to the antenna. Also duplexer tuning is critical. To properly test for desense will require a service monitor to do it right. Sid. .

He's using a mobile duplexer....we're talking very short runs. In my experience, RG-58 works in these two-mobiles to form a repeater, but I'd recommend LMR-195. My money is on the tuning of the duplexer.....they claim to tune these things to your frequency in Hong Kong, but I have found that they usually need to be brought to a dealer and re-tuned once they get here.

gewecke · Aug 23, 2011

centuryvrproductions said:
I have a properly tuned duplexer. Is RG-174 good for jumpers? and i am going to get LDF4-50A cable for the tower.

the antenna is a colinear made from RG-58 and is tuned to my frequency. it is suposed to be 9db

No. rg-174 is even worse than rg58. Also buy a manufactured antenna designed for 450- 470 mhz. Homebrewing antennas is a talent that not everyone has. A good head for math, mechanical aptitude and radio theory is needed.

73,
n9zas

W2NJS · Aug 23, 2011

How about, as a first step, finding out how much wattage is actually coming out of the duplexer when transmitting? All the theory in the world counts for little or nothing if you've got a bad or poorly adjusted piece of equipment in the system. You find out why a system is in trouble by isolating and testing, and that's been the rule since the time of Marconi.

Citywide173 · Aug 23, 2011

W2NJS said:
How about, as a first step, finding out how much wattage is actually coming out of the duplexer when transmitting? All the theory in the world counts for little or nothing if you've got a bad or poorly adjusted piece of equipment in the system. You find out why a system is in trouble by isolating and testing, and that's been the rule since the time of Marconi.

What he said is very accurate and prophetic. Too many of us shoot out theories when we can't see the system....isolate and test is the way I'd approach it if it were one of my repeaters.

centuryvrproductions · Aug 23, 2011

Citywide173 said:
He's using a mobile duplexer....we're talking very short runs. In my experience, RG-58 works in these two-mobiles to form a repeater, but I'd recommend LMR-195. My money is on the tuning of the duplexer.....they claim to tune these things to your frequency in Hong Kong, but I have found that they usually need to be brought to a dealer and re-tuned once they get here.

awww. the transmitter is still feeding into the reciever sometimes. they wrote on it that it is tuned but i also believe that it was poorly tuned ... so i dont know where i would tune it...

mancow · Aug 23, 2011

I'm not trying to be mean if you are for real but if not it's getting kind of old.

GTR8000 · Aug 23, 2011

I think he's 100% for real, but it's still getting 100% old at this point. He has been advised countless times that he needs to develop a very basic understanding of how radios work before embarking on a project like this. Unfortunately he completely and willfully ignores those posts, and continues to plug away with his questions. Questions that are often very elementary in nature, and he could answer for himself if he took the time to learn the material in question the proper way. Asking individual questions that are all over the spectrum on a one-by-one basis on this board is not learning the proper way, it's trying to get all the quick answers to achieve the end result, without learning much along the way. In fact, the little bit of knowledge he has gleamed from his threads probably makes him even more dangerous, since he likely believes he knows a lot more than he actually does.

It's like trying to learn surgery by cutting a person open, then running over to the computer and posting on a message board frequented by surgeons "Okay so I've got the chest open, and I think I see the heart? but what do I do now?!? and is an 18 gauge IV needle big enough or should I use a 16 gauge?!??"

centuryvrproductions · Aug 23, 2011

I understand that you all hate that i ask so many questions. I am learning, doing research and reading up on antenna systems. I just cant figure this part out yet... im sorry if I am annoying.

But No.. its not the duplexer that is giving me no range... it may be contributing to the fact but i ran simplex with the repeater transmitter and various antennas and the range is the same with the duplexer. i think its the fact that i am running crap antennas and that i need comthing like better cable.. any suggestions or input?

mikewazowski · Aug 23, 2011

centuryvrproductions said:
awww. the transmitter is still feeding into the reciever sometimes. they wrote on it that it is tuned but i also believe that it was poorly tuned ... so i dont know where i would tune it...

You're using RG58 and wondering why you've got desense?

mancow · Aug 23, 2011

You asking questions is not annoying. It's just that it seems you aren't trying to listen. We have said countless times that you need fully shielded high grade interconnect cables but you come back and mention RG58. You then go and mention needle thin RG174 which is the worst thing in existence. That's our issue. It's like none of the advice is accumulating.

centuryvrproductions said:
I understand that you all hate that i ask so many questions. I am learning, doing research and reading up on antenna systems. I just cant figure this part out yet... im sorry if I am annoying.

But No.. its not the duplexer that is giving me no range... it may be contributing to the fact but i ran simplex with the repeater transmitter and various antennas and the range is the same with the duplexer. i think its the fact that i am running crap antennas and that i need comthing like better cable.. any suggestions or input?

KC4YIN · Aug 23, 2011

centuryvrproductions said:
I have a 25 Watt repeater running duplex on 440.

I have also used a tuned coaxial dipole and a ground plane antenna at an elivation of about 30 feet,

You also need height. Around here 400 ft. elevation yields county wide coverage easily with handheld.

zz0468 · Aug 23, 2011

centuryvrproductions said:
I have calculated the losses...

But have you MEASURED the losses?

centuryvrproductions said:
...Running a calculated (with loss) 185Watts ERP...

That seems pretty high, based on what you've previously told us. Show us the math. Where did this 9db gain antenna come from? Two days ago you were asking how you could build one.

centuryvrproductions said:
Could this be because of bad antennas, loss in coax or somthing like that?

Yes, yes, and yes. Obviously, the losses are higher than calculated. Or your calculations are way off. Probably both.

centuryvrproductions said:
I have a properly tuned duplexer.

How do you you know it's properly tuned?

centuryvrproductions said:
Is RG-174 good for jumpers? and i am going to get LDF4-50A cable for the tower.

Sure it is. It's good for 2" jumpers inside a radio.

centuryvrproductions said:
the antenna is a colinear made from RG-58 and is tuned to my frequency. it is suposed to be 9db

Ok, NOW we're getting somewhere. It's "supposed to be" 9db gain. Those collinear antenans can work quite well, but they have to be made with good quality coax - which RG-58 ISN'T, and they have to be VERY carefully made. If I was to venture a guess, I'd say it's 9db loss.

The numbers are starting to make sense now.

centuryvrproductions said:
awww. the transmitter is still feeding into the reciever sometimes. they wrote on it that it is tuned but i also believe that it was poorly tuned ... so i dont know where i would tune it...

Was the duplexer tuned on your exact frequency? Are you aware that in final installation, a duplexer frequently needs touch up tuning for optimization, because the load impedances it's seeing can be different than what it was seeing at the time it was tuned up.

mancow said:
I'm not trying to be mean if you are for real but if not it's getting kind of old.

Amen and hallelujah!

centuryvrproductions said:
I understand that you all hate that i ask so many questions.

It's not the questions that's annoying. It's the fact that you don't heed the advice. People want to help a new ham get started, but you have to actually listen to the advice in order to keep it coming.

centuryvrproductions said:
I am learning, doing research and reading up on antenna systems.

Part of the problem is, you're putting the horse before the cart. A repeater can be pretty finicky. Get some basic radio skills and knowledge under your belt first. Build antennas, get your simplex range out there. Start collecting bits of test gear, like a wattmeter and a service monitor. Get some experience, and THEN build a repeater... when you have the foggiest clue what you're doing.

centuryvrproductions said:
But No.. its not the duplexer that is giving me no range...

And you know this... how?

centuryvrproductions said:
...i think its the fact that i am running crap antennas and that i need comthing like better cable..

Bingo.

centuryvrproductions said:
any suggestions or input?

Yes. Sell the repeater and use the money for a nice two meter hand held.

mancow said:
It's like none of the advice is accumulating.

Nail. Head. Direct hit.

Farscan · Aug 23, 2011

Try a radio on your antenna and see what the range is without the repeater.

prcguy · Aug 23, 2011

A 9dBD gain UHF collinear made from coax is about 20ft tall, how tall is yours?

Testing the antenna for range with just a radio and no repeater is an excellent start, that will either eliminate the antenna or the repeater system as the major problem.

Even with a moderate antenna up 30ft, a 25w UHF repeater with a couple of feet of RG-174 jumpers and lousy coax should give a couple of miles of hand held coverage and probably 5 to 10 mile coverage to a mobile.

A wattmeter and load can verify jumper and feedline loss and tell you if the duplexer is connected backwards. To go deeper you really need a service monitor to test the system in full duplex and a spectrum analyzer with tracking generator or scaler network analyzer to test or tune the duplexer.

There is a good reason people who service repeaters have a shop full of expensive test equipment and charge $75 on up for simple bench work and at least double for service calls, that's what it takes to do the job.
prcguy

thomast77 · Aug 23, 2011

Isn't a forum for asking questions? Some people learn by experimentation. It's a good thing.

zz0468 · Aug 23, 2011

thomast77 said:
Isn't a forum for asking questions? Some people learn by experimentation. It's a good thing.

Read the entire series of questions posted over multiple threads. It's the asking of the same questions over and over, and paying no attention to the tons of good advice given that gets old.

Why is my repeater's range Crap?

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