UHF Repeater question

[motofan44705]

We currently have a GM300 repeater programmed on 463.575 and it is starting to fail so we are looking for a new repeater but only have around $400-$450 to play with and would like to get something like a CDM1250 or a newer more serviceable type unit. Can we convert a CDM1250 into a repeater with the plug kit? If anybody has any suggestion or any offers on a GOOD at least 50 watt preferably 100 watt repeater please PM me we have about 3-4 weeks before we need to make a buy but we want to start getting ideas and offers now.

Jim

[Grog]

In what way is your current repeater failing? Are you interested in fixing what you already have? Using any mobile as a repeater transmitter can always lead to issues sooner or later depending on the duty cycle you are trying to do.

[motofan44705]

We are not really interested in fixing it really we need to just replace if we can find a good deal on a repeater but would like to replace it with a more up to date easier to service unit.

Jim

[motofan44705]

Correction the Frequency it is on is 464.375 and 468.375 is the TX and RX freqs

[Rayjk110]

The CDM-Based repeater is the CDR series. The most common one I've seen is the CDR700, although I'm not sure how much they cost. I'll look in my price book when I get home. I would assume it shouldn't be much more than the GR1225 when it came out.

They look like the GR300 cabinet, but retrofitted to accept the CDM body style.

[tvsjr]

Correction the Frequency it is on is 464.375 and 468.375 is the TX and RX freqs

Incorrect. UHF uses a 5MHz split.

You need to slow down, take a deep breath, and analyze the situation. Repeaters don't "wear out". If the repeater isn't performing up to your expectations, who's to say that replacing the repeater will do you any good? The issue could lie in a poorly-tuned duplexer or one damaged by lighting, a lightning protector that's taken one strike too many, a bad piece of feedline, a bad antenna, or any number of other issues.

You aren't going to find a new repeater for $400-$450, especially not one capable of 100 watts. A 100-watt PA from Crescend costs significantly more than that. Hell, old used MSF5000s and Exec 2s are still going for $500 at hamfests. And, the GR300 is still a very serviceable platform... arguably more so than a CDM/CDR platform.

Finally, you can't just buy a new repeater and throw it on the air. Installation requires the same equipment that testing out your current repeater would... since you apparently haven't done any testing of your current repeater, I doubt you possess the equipment or experience to bring a new repeater on the air either.

You need to find someone who knows RF and is good at repeater installations and have them check out what you have now before you make ANY decisions.

[motofan44705]

tvsjr Thanks for slamming me but I have had it checked out by a guy who has been in the radio business for 25 years and he says it's time for a new repeater the one we have is 20 years old and not working up to it's full potential and $400-$450 was just a starting price I figured we would end up somewhere around 7 or $800 when it was said and done. Usually I check thing ou.t thoroughly before speaking on them so that should tell you where I have already been with this.

Jim

[Bat2way]

We currently have a GM300 repeater programmed on 463.575 and it is starting to fail. I have had it checked out by a guy who has been in the radio business for 25 years and he says it's time for a new repeater the one we have is 20 years old and not working up to it's full potential...Jim

Thanks. That gave me a laugh. I get new business from other area techs who say "it's time to get a new one". Guess I'm from the "old school" of Service, not Sales.

What make and model is the failing 20 year old repeater? Never saw any GM300-type repeaters in '87. Seriously, these repeaters are fine as long as you DON'T run them at full power. I've previously posted an easy PA repair for these units. One of the other bad things are the crappy RG-58 cables supplied with these units. Just throw them away and put in the yellow looking double-shielded type. Cures the intermittent desense problems.

[escomm]

Correction the Frequency it is on is 464.375 and 468.375 is the TX and RX freqs

Incorrect. UHF uses a 5MHz split.

Incorrect. UHF uses whatever split was authorized by the FCC on the recommendation of the frequency coordinator. I've seen 4.9 MHz split and 5.2 MHz splits quite commonly here in LA. 5 MHz is not written in stone.

[tvsjr]

tvsjr Thanks for slamming me but I have had it checked out by a guy who has been in the radio business for 25 years and he says it's time for a new repeater the one we have is 20 years old and not working up to it's full potential and $400-$450 was just a starting price I figured we would end up somewhere around 7 or $800 when it was said and done. Usually I check thing ou.t thoroughly before speaking on them so that should tell you where I have already been with this.

Jim

Not slamming you. What you want is unrealistic and a foolish waste of money.

We have an amateur system that covers most of the state of Texas. The vast majority of the radios in use are either GE Mastr 2s, Mastr Exec 2s, or MVPs... to the tune of 55 repeaters and a couple hundred link radios. The last of these units rolled off the assembly line in the early 1990s... they went into production in the mid to late 70s. They work just fine. They require care and feeding, just like any repeater does (ask someone who maintains a few dozen Quantars about care and feeding...) but that doesn't mean they're junk. They continue to work just fine for us. Other large-scale networks are using even older Motracs and Mitreks with no problems. Hell, many of the local trunking systems are using MSF5000s, which aren't any newer than your GR300 - and they're trusted to handle public safety communications every day.

Contrary to your "guy" and his opinion... it's not like the transistors have a fixed, exhaustible quantity of electrons that, once used up, render the repeater useless. Unless the repeater has been damaged (lightning strike, power surge, overheating, etc.) there's a very good chance your issue isn't with the repeater itself.

About the cheapest repeater you're going to find is the TKR-850, and that will run you around $1K. An outboard amp to bring power up to 100 watts will run another $1K-$1.5K. Have you checked your license for the amount of power you're authorized? You can't simply run whatever power you feel like... and I suspect you don't know what the license says, as you asked for 50-100 watts.

Until you have someone out who possesses the knowledge AND the test equipment (good service monitor, spectrum analyzer, antenna analyzer, etc.) to thoroughly test what you have now, you are throwing money into a hole. If you do throw something up and try to crank the power up above what your license specifies, you're likely to end up explaining yourself to the FCC.

[J.Sanor]

Jim,
License is for 45 watts output power with a 75 watt ERP.
Look for a 45 watt repeater.
I know for a fact the GM300 has had PA problems,over heating, dead cooling fan for an extended period of time.
The reciever has had issues too, that flashy stuff that comes out of the sky, lightning .

[motofan44705]

Ok there we go the verdict is in J. Sanor knows alot about this unit he is very familiar with the workings and licensing of it so I guess we need a 45 watt repeater if anybody has one please let me know.

Jim

[jackhackett]

So when all is said and done, what you're looking for is a used 45W UHF repeater, in which case you might want to ask in the For Sale/Wanted section.

One thing you could also look at... according to J. your current repeater has a PA problem and a receive problem. The GR300 has 2 radios in it with only the RX used on one and only the TX on the other, if the unused parts of each radio are still good you may be able to just swap the radios around... put the one with the bad PA in the receive position where the PA isn't needed, and the one with the RX problem in the transmit position, then just reprogram.
Where you might run into a problem with this is when the repeater was originally built with a low power radio in the receive position (often done to save a bit of money).

[werdnuts]

Jim,

Just a suggestion, but if your duplexor, powersupply, and RICK are all in good order, then maybe you guys can just replace the radios in the unit. First try switching the TX and the RX radio (obviously reprogram them). If the PA is shot on the TX, then it wont be an issue if used as the RX radio. This wont cost you guys anythin but time.

Another suggestion would be to locate replacement radios (maxtracs, gm300 or even cdm750). Slap those babies right into the same GR housing. That way you aren't dumping a ton of money into replacing the whole unit with another outdated unit. ($500 for a great condition repeater is a tough find... especially if the cans are good.)

I know the repeater case is a pain, but they dont get much better with the newer lines. Similar design, different sized holes and still difficult to get into. Kinda like girls... (Sorry, couldn't help it.)

The GR300 is a rock-solid repeater setup. With the radios being in good supply, it's hard to justify replacing it just because of the housing. Don't be afraid to replace the parts to keep it running. Kinda like a classic car... as long as the chassis is good...

A new duplexor (and preselector - if you use one) is gonna run you $400+ (each). I have a UHF duplexor and preselector that was used for about 2 hours. I am asking about that price for each. Anything you find on eBay is buyer beware... you cant tell if its good or bad until you put it on a monitor.

If servicing is really a concern, build your own case. You dont have to use the GR housing. Slap that stuff up on a piece of plywood and hang it on the wall. Space it out for cooling. Ditch the fan and PS, use a couple of good power supplies. Use your imagination. Save your money for the time when you have a catastrophic failure.

Good luck!

[Jim202]

Since when have the UHF channels not been a 5 MHz split? Been in this field for better than 40 years and
have always seen the UHF set as a 5 MHz split with the input high.

If there is a change, please provide the FCC rule that has allowed this drift from the 5 MHz split that has
been in place since day one.

Jim

Correction the Frequency it is on is 464.375 and 468.375 is the TX and RX freqs

Incorrect. UHF uses a 5MHz split.

Incorrect. UHF uses whatever split was authorized by the FCC on the recommendation of the frequency coordinator. I've seen 4.9 MHz split and 5.2 MHz splits quite commonly here in LA. 5 MHz is not written in stone.

[Rayjk110]

In my personal travels around I've only seen a couple repeaters that had those wierd splits (But they were in really highly-populated areas were UHF frequencies were already hard to get - I have never seen this in an urban/rural area).

I've also seen some repeaters where aka 464.100 was the input and 469.100 was the output. Just wierd little things.

[escomm]

Since frequency coordinators started assigning frequencies way back when? I don't know.

A news station in LA is on a 4.9MHz split, and has been for at least 30 years. A security company I do business with has a 4 MHz split. I have seen the licenses and confirmed them in the FCC database.

You evidently have never been to California. We are on a low input scheme here, by the way. Amateur and commercial.

So, like I said, nothing is written in stone. There is no rule that says all UHF frequencies shall be on a 5 MHz split, and besides we haven't even delved into 470-520MHz channels that are commonly on a 3 MHz split (but not always). Of course, there are only a few TV band cities in the US, perhaps you're nowhere near one and didn't know about that either.

Chief point being that the only thing written in stone is that nothing is written in stone.

Since when have the UHF channels not been a 5 MHz split? Been in this field for better than 40 years and
have always seen the UHF set as a 5 MHz split with the input high.

If there is a change, please provide the FCC rule that has allowed this drift from the 5 MHz split that has
been in place since day one.

Jim

[J.Sanor]

freqs are 464.375 and 469.375 = 5mHz split.

[RKG]

I don't want to get too deeply into this debate, but note that press channels ("Relay Press") are not licensed under Part 90; the 5 MHz for UHF repeater channel pairs between 450 and 470 MHz has always been a Part 90 rule.