Deciding on a Repeater

[WRTZ750]

I have a dream.  A dream that I can find a tower location and afford to rent a spot on it.  That's the first thing to address however I like to think ahead hence the following question.

What is a brand or model of continuous duty repeater that is tried and true that people like to use?

Is this a Chevy vs Ford type of question?

Motorola Quantar?  Vertex?  An old discontinued Motorola GRxxxx repeater?

This also leads to another question.  To minimize what I like to call riff-raff on the repeater, is there a way to keep people from scanning for the ctc tones when the repeater is auto-IDing and getting access to the repeater without first requesting?  Does that scenario occur?

If people are using the repeater inappropriately is there a way I can remotely shut it down, change ctc tones and bring it back online?

[BoxCar]

A couple points here. Duty cycle depends on how well the transmitter can dissipate the heat generated when in use. A 100% duty cycle unit would have a large enough area that the heat generated will not degrade or shut down the transmitter. The duty cycle of a repeater will be affected by the air temperature surrounding the unit. Most are rated when the ambient air temperature is closely regulated to be about 70 degrees F. As the air temp increases, the duty cycle decreases while the inverse is also true, lower the temp and duty cycle increases. I'm going back here almost 50 years, but I remember an axiom that stated lower the junction operating temperature of a transistor by 10 degrees C and you double its life.

Many of the commercial grade repeaters will incorporate the STUN/KILL mode where a specific code string can be sent to stop the transmitter until the restore code is sent. And, as to brands, there is a reason Motorola has the majority of the public safety business. It may be overpriced in comparison and incorporate proprietary software coding but, above all, its reliability is unquestioned. 

One of the agencies I worked with had a repeater that had been operating for close to 50 years with no failures. Around 2010 it was in an area that had a record flood and that old repeater was then stressed into operating at full capacity for a couple weeks during response and recovery. It came through with flying colors. The brand, Motorola.

[gortex2]

GR1225 is not a continuous duty repeater. The Motorola Quantar and MTR2000, GTR8000 are. 

I had created a post with some new out of box repeaters but only a few I would rely on for 100% continuous duty. I think you need to determine 100% continuous duty or q quality reliable repeater. A repeater than can stay keyed 24/7 is a step up from a good quality mid use repeater. Most repeaters sold are what I call mid duty. They may claim 100% but I've seen some keyed for a day and burn up a PA. Then there are home built ones out of mobiles that are not reliable to put at a tower site. Good for a garage home site.

 

 

 

[Sshannon]

9 hours ago, WRTZ750 said:

This also leads to another question.  To minimize what I like to call riff-raff on the repeater, is there a way to keep people from scanning for the ctc tones when the repeater is auto-IDing and getting access to the repeater without first requesting?  Does that scenario occur?

 

If CTCSS tones are used when transmitting, they can be scanned.  But, there’s nothing that says you have to use the same tone as the “input tone” on the receiver side. But, someone within range of a legitimate user can still scan for the input tone and use that to gain access.  I don’t know about scanning for DCS tones, but I assume it’s the same.  

In GMRS, there’s no foolproof way that I can think of to prevent unauthorized access and no radio is jam proof.  You can change tones frequently, but that will inconvenience your legitimate users.  There are a few forum posts by people who ended up taking their repeaters down because it just became too annoying.

[Sshannon]

9 hours ago, WRTZ750 said:

If people are using the repeater inappropriately is there a way I can remotely shut it down, change ctc tones and bring it back online?

My guess is that all professional repeaters have that ability, but I replied to this separately so someone with actual practical knowledge and experience can answer.  

[WRTZ750]

1 hour ago, gortex2 said:

GR1225 is not a continuous duty repeater. The Motorola Quantar and MTR2000, GTR8000 are. 

I had created a post with some new out of box repeaters but only a few I would rely on for 100% continuous duty. I think you need to determine 100% continuous duty or q quality reliable repeater. A repeater than can stay keyed 24/7 is a step up from a good quality mid use repeater. Most repeaters sold are what I call mid duty. They may claim 100% but I've seen some keyed for a day and burn up a PA. Then there are home built ones out of mobiles that are not reliable to put at a tower site. Good for a garage home site.

 

 

 

Thanks for that gortex.  Yeah, after reading that I'd say I'm a middle of the road kind of intent.  Not an $8000 GTR 8000 but definitely not 2 mobile radios connected together.  I did read that post you made but need to go back and read it again.  

[gortex2]

Many repeater support repeat enable and disable but many only support that via wireline connection. Some will support DTMF commands but most that require that will use an external controller for the enable disable. Use of a different input tone that output is a way some try to eliminate the use. DPL/DCS on input is a good way to do it with PL/CTCSS on output. Personally I find not advertising them on this site and other places keeps alot of the riff raff off the air. 

[WRKC935]

You are going to be looking for a MTR 2000/3000 or a Quantar.  There is the GTR8000 but those are hard to find and very expensive, so I would consider them outside the realm of a hobby GMRS / HAM repeater in all but the most well funded groups / clubs.

I would advise the MTR over the Quantar as they are a bit less expensive but are mostly the same electronically.  Gonna see similar performance from either.

I will say this, the MTR software will not run natively on Windows 7 or above.  This creates a small issue that needs to be addressed.  But finding a Windows XP laptop isn't a bad thing regardless as there are numerous other radios that you will need an XP or even a DOS machine for.  An old laptop set to dual boot between DOS and XP is a very handy thing to have as a radio hobbyist. 

There are two versions of the MTR platform.  One is 40 watt and the other is 100 watt.  DO NOT get it in your head that the 40 watt units should be avoided since they will not TX 50 watts.  The difference in performance between 40 and 50 watts is NOTHING.  NO one will know the difference and it's not going to add any measurable distance to the coverage.  If you don't believe me, go download Radio Mobile and run a coverage map from a tower site, run one with a 40 watt transmitter and then run the same map with a 50 watt transmitter.

 

The second thing you need to be looking at is a GOOD duplexer.  The little 'mobile' duplexer's work ok for a small setup  that's not got much antenna height or is NOT in a high RF environment.  Those will cost you coverage on receive due to allowing out of band RF into the receiver. That OOB RF will cause the first RF stage AGC to lower the gain of the first RF stage and make the repeater less sensitive to incoming signals.  So you need to be looking for a pass / notch duplexer for a tower site install.

I would advise against jumping into this with both feet straight away and instead setting up a repeater at your house or some spot you have access to.  Get a feel for what it takes to do it and how much effort it takes.  The other thing it will do is get you familiar with the money it takes to put together a system and get it on the air.

EXPECTED COSTS for a large repeater system.  I am looking this stuff up on eBay as I am writing this.  So these are the expected costs for USED gear.

MTR2000 UHF 100 watt repeater $1000

CELWAVE DUPLEXER  $600

7/8 cable   around 3.00 per foot used if you can find it.

7/8 cable connectors   $30 each

DB-408 antenna     $100 - $200

another  300 in misc stuff

Then a tower crew to install the  antenna and line on a tower.  Looking between 2000 and 5000 for that, at bargain doing yo a favor prices.

Not Cheap.

 

 

[WRTZ750]

Thanks WRKC, I wasn't aware of the need for older software for programming so that in itself just saved some headaches.

Also I see Celwave and Sinclair as a couple of options for duplexers and if I'm understanding correctly, if I'm going to set this up for testing at my home the mobile duplexer is likely good enough but for a tower site the more expensive pass/notch duplexer is needed.

There's another Motorola Repeater I'm curious about.  I'll try to find it and edit the model in here but I think it's 2 mobiles in a case.   It's the XPR 8300 and 8400 models.

Edited February 20, 2023 by WRTZ750
Add repeater model

[gortex2]

The XPR series is two mobiles in a box. Many of them online used have a blown PA on one of the radios and most likely swapped between RX and TX. If your going to go mobile just get CDM. If you want a true repeater stay away from the XPR.

If you can get a better duplexer do so. No sense in getting mobile flat pack if you goal is to move it to a tower site. Sinclair, DB and others make good UHF repeaters. Keep an eye out on ebay and you will find a decent one, normally cheaper then a new flat pack. I've picked up UHF LMR DB spectra duplexers for $75.00

[WRTZ750]

Thahxks.  I'll skip the mobile radio configuration.  Hopefully a duplexer on ebay will not be defective.

[MarkInTampa]

FYI - I've had a page on how to program the Maxtrac using the DOS software under Windows 10 using DosBox in my bookmarks for awhile. More or less a step by step guide on setting up DosBox to use old Motorola software for the Maxtrac but should be applicable to most of the other old Motorola DOS software as well. 

https://www.nv9p.com/blog/program-maxtrac-with-dosbox

[WRTZ750]

Using DOS makes me nervous and I don't have any XP laptops around.  I looked at repeater builder and read about the Quantar repeater but wasn't clear on programming.  Can it be done with Windows 10 or is it similar to the MTR 2000 and requires an older software to program?

[gortex2]

Quantar can be programmed in W10. I have a cheap DOS only computer for some stuff as awell as a old 98 laptop for stuff. You can get them at garage sales for pennies. 

[WRKC935]

Yeah, if you are going to be messing with radios to any great extent and your not going to be buying radios and repeaters that are new.  You need to look at an old XP laptop being as necessary as a screwdriver or a Cresent wrench. 

Yes, they are old and not supported.  But while you can do work around's with DOSBOX, and other things on the newer operating systems, then you are getting into needing to understand PC's at a higher level as well to get things done.  And that adds complication to getting things done.

I have a couple old ToughBook laptops that are XP and Windows 7 that I use for programming.  They are rugged and well suited to be taken out and worked with.  Batteries are still available for them so that's the route I went.  As others have said, that stuff is cheap to get and is a good investment.