Motorola GR1225 REPEATER

[JD]

Are there still issues with these , PA's ?? NOt many favorable posts about this repeater .

Alternative manufacturesr, Kenwood or Vertex ?

Thanks.

[wavetar]

It's actually not a bad repeater...I've never had an issue with anything other than the P.A. on them, and some pre-planning helps a lot with those. Replace the solder on the P.A. transistor with silver solder, and run the unit 10 watts lower than they are spec'd for & you may never have an issue, assuming they aren't extended well beyond their 50% duty cycle. A good alternative, at a lower price, is the Kenwood TK750/850 repeaters. Similar in specs & size for the rack-mount versions. They require tuning if they are reprogrammed from their original frequency, but that makes them much more selective on RX than the GR1225.

Todd

[JD]

Thanks, what type of solder are they using currently ? Also, should I use Times LMR 200 for the cables rather than the supplied RG 58 ones? Or maybe another type than Times?
Also, I have heard good comments on the Vertex line .

[wavetar]

They use the standard tin/lead solder, which doesn't hold up well over time when the component generates significant heat. The supplied RG58 cables are well built, and you won't see any appreciable difference in performance at such small cable lengths. My only experience with Vertex repeaters wasn't a good one, so someone else will have to chime in on that. I wasn't impressed with the physical build of the various boards within the unit...looked like the boards I used to see in cheap cordless phones circa 1990.

Todd

[Vercomm]

I will agree with Todd, the Vertex are designed for Taxi Cab use at best. Unfortunately I took over a fire/rescue contract which has 7 wonderful VXR7000 repeaters, god they are a pain in the ass.

You get what you pay for, barely!!

[JD]

Thanks for the info. The GR's really took some bashing in previous posts. Sounds like M got something right.

I also have heard nothing but good reports on the Kenwoods.

I do like the audio on the GR's, Kenwoods have a strange sounding squelch tail. Can they be set for Squelch tail elimination?

[wavetar]

The new MotoTRBO repeater is promising. Same physical dimensions as the GR1225 rack-mount, and 100% duty cycle capable at 40-watts UHF & 50-watts VHF, all at a lower price than the GR1225 unit. Our two demo units have been working great for everyone we've demo'd them for. One drawback is that unlike the GR1225, there's no room internally for a small duplexer, it must be mounted external to the unit.

Todd

[JD]

They are less than a GR1225 ??

[escomm]

No, not by a long shot. The most expensive GR1225 is only about 2/3 of what an XPR8300 costs. Assembling it yourself also saves about $500...

Plus, keep in mind that you get to do monthly firmware updates to the XPR8300 to correct critical bugs whereas the GR1225 does not require any such nonsense

[Jay G.]

I've had a GR1225 on the air for 10 years or so, with no problems! (knock on wood!) Use it as my FD buff repeater. Works pretty well!

[jackhackett]

The GR1225 is a decent little repeater, IF you keep the duty cycle low. If you have a bunch of hams rag chewing on one, or something like a busy taxi service that's calling it's cabs all day and night, the PA is going to fail... silver solder or not. The upside is that they rarely actually have a part go bad, usually just the solder joints fail and a good resoldering puts them right back in service.

I have had a few fans go bad on them, both the chassis fan and the one in the power supply.

As for MotoTrbo, it's hard to say how well those will hold up, since they haven't been out all that long. I've seen inside one, looks like they took a CDM mobile, turned it upside down and stuck a CPU heatsink on it.

[MSS-Dave]

I built several LTR systems using RKR 1225 which is the same radio as the GR. For the most part... it worked OK. Most all of these used the 10 watt radio and I hung 100 Watt PA's on them, ran into TX and RX combining and it did good. Biggest problem was RX desense in high RF sites but that got cured either with RX filters in the multicoupler or in 1 case with a custom (read: thrown together at last minute due to dumb$#@ rental manager promising crap before checking ) transportable system that I used the individual RX preselectors on. The next problem is the PA fail thing on the 45 watt radio, just reduce the power. If it's a desktop cabinet and you are putting it somewhere other than a cool area, consider modifying the fan for hi speed continuous duty. If you have the RKR or the GR500 type wall cabinet, they vent a little better so the fan is more efficent at low speed.

Dave

[Rayjk110]

I have [2] GR1225's in service on UHF 462.x/463.x that have been up for about 3 years with no problems. One got it's antenna hit by lightning last year (thank god the lightning resistor was in line and grounded) and it's still working just fine. I think they actually use a GM300 variant mobile inside. It looks like a GM300, but with a longer, silver heatsink to compensate for repeater duty usage.

[JD]

If Motorola knows about the PA problem, why don't they fix it ? I keep hearing raves about the Kenwood and even the Vertex repeaters.

A friend of mine in the southwest , who is a Motorola dealer, will only now use Kenwoods for his uHF trunking system.

[MSS-Dave]

Well, Motorola knew about the problem. It's called "Duty Cycle". From the book, "25 watts continuous, 50% at 45 watts UHF, 50 watts VHF, 5 minutes on, 5 minutes standby." Most of the failures I fixed were repeaters running full power stuffed in a closet that was 90 degrees plus or worse. They could control the design but not the install situations.

I don't know about the duty cycle rating on the Kenwood or Vertex. I've run a GR1225 desktop cabinet at 45 watts keyed for days with the fan wired for full speed and it survived. Of course, that's not the way to run it. One of the other cures for the PA failure issue was to put a circulator between the PA output and the input to the duplexer but that still doesn't change the duty cycle rating. I'm just throwing the factory spec out there, there are lots of these things running full power keyed for long periods of time hanging in there.

Just thinking back, I don't remember ever replacing a PA in a station in the RKR rack or the GR500 wall mount box. It got so bad with the GR's, I had to check salesman orders for GR1225 repeaters before ordering them because they were selling these without regard for the install location. When the install happened, invariably the thing would get shoved in a air handler room or a closet.

Just my experiences, YMMV as they say..

Dave

[Bat2way]

Just had a 10 year-old GR500 repeater in for no Tx power and the PA was burnt up beyond recognition. Fortunately, having two GM300's in the box meant I could just swap, reprogram them, and reduce the power out to 30 Watts.

Cause of failure: TX programmed with no TOT, and a stuck mobile mic.