2 Meter Reepater Help

[K9TSU]

I posted this on QRZ earlier and already I'm being told I'm too young/stupid to have a repeater and I should bascially go dig a hole and die.

I'm posting here because I've been told this is a much friendlier forum.. so..


Hi all,

I run a repeater on 147.345 + made from two mobile radios that are isolated (sorta) from each other and a Sinclair 4 cavity duplexer tuned to my frequency, as of one day ago, so it shouldn't be out of tune. We are running double shielded coax for the jumpers to the radio, and a 17 foot UVS300 by Workman for a temporary antenna, which is sitting at 6 feet (again, just to find any issues before we put it up at the site.)

My problem is..

I got literally 1 mile from my house in the mobile (5/8 wave antenna) and it went to S-0!! It is running 75 watts. Even if the thing was "cutting down" for SWR, I should still hear it more than S 0. (I can even see the antenna) I'm kind of concerned. Any ideas, anyone on what to check into?

Thanks!

[NQ6U]

I'm shooting from the hip here since I've never set up a repeater myself but the first thing I would suspect is the antenna system. Have you put an antenna analyzer on it yet?

BTW, Welcome to the Island, where you're never too young or too stupid to do anything in ham radio. I'm living proof of the latter.

[W2NAP]

Not sure what mobiles you are running. but this is what I can say.

Find a GE Mastr exec II mobile and do the full duplex conversion (you can find at repeater-builder) ( I see them on crapbay for as little as $20 sometimes.) for tone (PL control) TS64.
Or bite the bullet and buy an actual repeater GE Mastr II or Motorola MSR-2000 or Quantar (if you are rich) ect.

Antenna get a good antenna. 4 bay dipole or grab a hustler G7-144 or diamond F23H. (if its going to be low to the ground Id roll with a Hustler or Diamond. the 4 bays are 20ft long itself)

Feedline - HARDLINE HARDLINE HARDLINE

using junk radios for the repeater or a junk antenna or junk feedline will make the repeater useless. So bite the bullet and just get the good stuff right off. and you will be much happier believe me.

[XE1/N5AL]

Welcome to the Island!!!

Is it possible that you have accidentally reversed the connections to the transmitter and receiver ports of your duplexer, so that the signals at both frequencies are being attenuated inside the duplexer?

I've never worked on repeaters and know very little about them, but would recommend testing piece-by-piece to determine where your problem is. For example:

1. With everything else disconnected, connect the transmitter unit directly to the antenna and verify that the signal is getting out. This tests the transmitter and the antenna.

2. With everything else disconnected, connect the receiver directly to the antenna and verify that you are receiving a strong signal. This tests the receiver and the antenna.

3. Now, connect the transmitter to the duplexer transmit port and the duplexer to the antenna, while terminating the duplexer receive port with a 50 ohm load.
How is the signal getting out? This tests that the duplexer isn't attenuating the transmit signal.

4. Connect the receiver to the duplexer receive port and the duplexer to the antenna, while terminating the duplexer transmit port with a 50 ohm load.
How are you receiving the signal? This tests that the duplexer isn't attenuating the received signal.

Good Luck!

[WX7P]

Welcome to the Island!!!

Is it possible that you have accidentally reversed the the transmitting and receiving ports to your duplexer, so that the signals at both frequencies are being attenuated inside the duplexer?

I've never worked on repeaters and know very little about them, but would recommend testing piece-by-piece to determine where your problem is. For example:

1. With everything else disconnected, connect the transmitter unit directly to the antenna and verify that the signal is getting out. This tests the transmitter and the antenna.

2. With everything else disconnected, connect the receiver directly to the antenna and verify that you are receiving a strong signal. This tests the receiver and the antenna.

3. Now, connect the transmitter to the duplexer transmit port and the duplexer to the antenna, while terminating the duplexer receive port with a 50 ohm load.
How is the signal getting out? This tests that the duplexer isn't attenuating the transmit signal.

4. Connect the receiver to the duplexer receive port and the duplexer to the antenna, while terminating the duplexer transmit port with a 50 ohm load.
How are you recieving the signal? This tests that the duplexer isn't attenuating the received signal.

Good Luck!

Not bad for an ex-pat.

Good show!

[XE1/N5AL]

Not bad for an ex-pat.

Good show!
Thanks, I wish I knew more about repeaters!

If the combination of the pieces work (per my last post), yet the fully-connected configuration of transmitter/receiver/duplexer/antenna still has a problem: I might suspect that the duplexer is allowng enough of the transmitted signal to feed back into the receiver to overload/desensitize the receiver. That is, the duplexer isn't isolating the transmitted signal from the receiver enough. I don't know the easiest way to check this: maybe reducing the transmitter power to see it the problem disappears? Or, temporarily connecting the receiver to a physically seperate receive antenna, located at a distance from the transmit antenna, while terminating the duplexer receive port in a 50 Ohm load (to keep it happy). Or, temporarily removing the duplexer and running the repeater with separate transmitter and receiver antennas that are located at a distance from each other.

[K9TSU]

Thanks for the help, everyone! I'm sixteen and found a good spot for the repeater at 75 feet, however, the site is at 1134' above sealevel, while the surrounding area is around 900-1000 feet. I have connected the TX radio to the antenna direct and got out good... last night. Last night It was making the trip to my "testing guy" who is about 25 miles away, on a base, so I'm guessing something drastic happened over night. Maybe a connector came loose or something stupid. I'll have to disconnect everything and re-connect everything and go from there. Will report back once I've played with it a bit more.

[kb2vxa]

Apparently the controller is working and probably stating the obvious, I hope you're planning on a telco interface (radio isn't the most reliable in the world nor is it secure) for DTMF control. It looks to me like the Islanders as usual have things well in hand, the bottom line is diagnosis by process of elimination. I agree, two radios really aren't the way to go, a commercial transceiver modified for full duplex or better still a repeater will do you justice. Do I have to tell you two of everything is the goal? Complete redundancy cuts down time to the bone and users will drift away from an unreliable repeater.

That having been said, sounds to me like typical QRZ snobbery. They're treating you like a new tech and frankly I have the same (although with courtesy) discouragement policy when it comes to them, I can't say with any degree of accuracy of how many want ego boxes. That's all it is where they're concerned, they think owning and operating is easy when it entails a sizable money investment and a helluva lot of WORK all the way around. You are just beginning to see the complications in the testing phase alone and it's not even at the site yet. That's why I tell them repeaters are best left to clubs with financial and physical resources beyond those of the average ham let alone some kid who doesn't know what he's doing. We know this which is why we help as much as we can rather than flat out discourage, you'll find plenty of help in all phases, some of us are hands on with repeaters and not just users.

"Thanks, I wish I knew more about repeaters!"
Yeah, I do too. (;->)

"I might suspect that the duplexer is allowng enough of the transmitted signal to feed back into the receiver to overload/desensitize the receiver."
Er, he didn't mention a receiver problem, the signal falling flat at a distance of one mile indicates a transmitter problem and a BAD one at that. Even crap coax won't cause that severe a problem but like the man said when it gets to the site hard line throughout is a must. That leaves a bad antenna or a problem with the cans and that's where it gets sticky. If they're not set up right the fix is fairly easy, make the proper connections. Other problems get way too complicated to go into here, right now the problem is getting the beast to radiate more than a few milliwatts.

[K7SGJ]

Welcome to the Island.

All the above are very good suggestions. One thing I'd be inclined to do is put a power/swr meter in line right after the transmitter and see if everything is okay, and then put it after the duplexer and see whats going to the antenna. If you do have a funky connector or coax, or the duplexer went TU, it should show up pretty quickly. Good luck and let us know what you find.

Oh, and Pope Carlo I is correct. He is indeed living proof of whatever he claims he is living proof of. He is a holy man and won't ever get caught telling a lie. It isn't that he doesn't lie, he just won't get caught at it.

[kb2vxa]

Of course he won't get caught, the Pope is infallible.

[K7SGJ]

You mean inflatable?

[K9TSU]

Well, I'll report back my findings. When the reciever is unhooked from the duplexers, there is zero S units of desense, so it isn't RF jumping from the TX radio to the RX radio (which is what I thought it would be.) It must be the duplexers, correct? Because there is only desense when the rx radio is hooked up. The problem is there's no one around here to tune them.

[W2NAP]

Well, I'll report back my findings. When the reciever is unhooked from the duplexers, there is zero S units of desense, so it isn't RF jumping from the TX radio to the RX radio (which is what I thought it would be.) It must be the duplexers, correct? Because there is only desense when the rx radio is hooked up. The problem is there's no one around here to tune them.

I asked earlier what exactly were you using. I want to know every peice in line make/model from the antenna to the TX/RX

I have a GE. with the cans it works (well till the rx died but thats another story). system works no desense. now if I take the Maxtrac I have and hook it inline for the RX what happens? moble is desensed even though the cans. Now i take my IC-2100. its desensed even worse.

[N2CHX]

N connectors frequently develop problems with the braid/shield tearing and becoming disconnected, which would cause issues with duplex operation, I'm certain. I've seen countless bad N connector installs in 20+ years. Things like this are almost always something simple & stupid, but can be frustrating as hell.

16 isn't too young BTW. Some people just have issues. Rock on.

[K7SGJ]

N connectors frequently develop problems with the braid/shield tearing and becoming disconnected, which would cause issues with duplex operation, I'm certain. I've seen countless bad N connector installs in 20+ years. Things like this are almost always something simple & stupid, but can be frustrating as hell.

16 isn't too young BTW. Some people just have issues. Rock on.


This is a true statement. I was 14 when I was licensed, and I didn't know a rock from a diode. But I learned, and made a career out of it. 30 years in a rock quarry really sucks.

[kb2vxa]

"You mean inflatable?"

http://www.youtube.com/watch?v=Nd1B_sYunAE