new 900Mhz Repeater in the Raleigh N.C. area...

10-95 · Post by **10-95** » Fri Jun 10, 2005 9:24 am

Well, after working for about 6 hours last night on this with Danny Kd4raa we have the transmitter and receiver ready to go. The repeater should be operational in the next week or so, it will be located on the D.H. Hill library building in Raleigh. The input is 902.5125Mhz and the output is 927.5125 Mhz, PL 100.0 Hz. Danny should be getting the the radios, antenna and duplexer up on the building in the next few days so if any of you are in Raleigh be sure to check it out.

Frank
AD4XE

bellersley · Post by **bellersley** » Fri Jun 10, 2005 9:28 am

For curiosity sake, what are you running equipment wise, and can you post pics?

10-95 · Post by **10-95** » Fri Jun 10, 2005 9:39 am

bellersley wrote:For curiosity sake, what are you running equipment wise, and can you post pics?

We are running an 800Mhz maxtrac for the receiver on 902.5125Mhz and
a 900 Mhz Maxtrac as the transmitter on 927.5125Mhz at about 16 watts.

We did the filter change in the receiver and got it working in about 30 minutes total. We had the ransmitter working in about an hour, we had to put a new PA on the radio and replace the firmware chip with one out of a conventional vhf and we were in business. We spent an hour or two fine tuning everything . I'll get some pictures once the controller is wired up, I believe Danny is doing that as I write this. The radios are pretty ugly, just some stuff we had laying around . One of the radios is surplus from the policve service and the other is one from a local two way shop, it had the blown PA we had to replace. The duplexers are from a now defunct paging system.

Frank

bellersley · Post by **bellersley** » Fri Jun 10, 2005 10:41 am

Sounds like quite the setup!
I've toyed with the idea of using a few of the 900MHz radios I have kicking around at home for a simple 900MHz repeater. I've never really put any serious work into it, and it'd most likely end up sitting on the bench for the rest of time, but it'd still be a nifty project.

How do you find the coverage with 900? I did some testing by setting up a 900 GTX and putting a simple 555 timer on the PTT line that'd key up the radio every minute for about 10 seconds. I had the radio on a simple 1/4 wave Sinclabs antenna at about 700 feet, using a GTX for receive in a car with a 1/4 wave magmount, I found coverage to be very spotty once you were even 10km away from the transmitter.

My guess is because I never bothered to retune the radios for the specific frequency I was using.

10-95 · Post by **10-95** » Fri Jun 10, 2005 11:22 am

bellersley wrote:Sounds like quite the setup!
I've toyed with the idea of using a few of the 900MHz radios I have kicking around at home for a simple 900MHz repeater. I've never really put any serious work into it, and it'd most likely end up sitting on the bench for the rest of time, but it'd still be a nifty project.

How do you find the coverage with 900? I did some testing by setting up a 900 GTX and putting a simple 555 timer on the PTT line that'd key up the radio every minute for about 10 seconds. I had the radio on a simple 1/4 wave Sinclabs antenna at about 700 feet, using a GTX for receive in a car with a 1/4 wave magmount, I found coverage to be very spotty once you were even 10km away from the transmitter.

My guess is because I never bothered to retune the radios for the specific frequency I was using.

I'll give a report on coverage once we get it up on the site. We are hoping for coverage at least within the county.

frank

kd6kml · Post by **kd6kml** » Fri Jun 10, 2005 9:15 pm

Other then the filter, what did you do to the 800 radio to make it play. I made one take the freqs, but had VCO problems.

Thanks,
Josh

kcbooboo · Post by **kcbooboo** » Sat Jun 11, 2005 2:22 am

The conversion from 800 to 900 has been written up and is posted on repeater-builder.com in the MaxTrac section of the Motorola area. Besides the filters and a small change on the RF board, you need to have a conventional firmware chip in the logic board and be able to blank the board and reinitialize it.

Also on the same web site is an article about manual power control of a 900 MHz MaxTrac transmitter. They're only rated for 12 watts but they tend to run wide open when used in the 927 MHz range, which will slowly destroy the PA.

Bob M.

(Toot Toot - that's me blowing my own horn!)

kd6kml · Post by **kd6kml** » Sat Jun 11, 2005 5:39 am

Bob,

Thanks!

I already dealt with the power issue on the 900 Maxtracs.

Josh

10-95 · Post by **10-95** » Sat Jun 11, 2005 9:48 am

kcbooboo wrote:The conversion from 800 to 900 has been written up and is posted on repeater-builder.com in the MaxTrac section of the Motorola area. Besides the filters and a small change on the RF board, you need to have a conventional firmware chip in the logic board and be able to blank the board and reinitialize it.

Also on the same web site is an article about manual power control of a 900 MHz MaxTrac transmitter. They're only rated for 12 watts but they tend to run wide open when used in the 927 MHz range, which will slowly destroy the PA.

Bob M.

(Toot Toot - that's me blowing my own horn!)

Yep! Changed the filters and put in a conventional firmware chip, and a little tweaking and we had it playing. We are looking at having it in place and operational tomorrow afternoon. And you are right about the PA, we had it running for a shot tme last night at 16 watts and after talking on it for a while the heat sink got "HOT", we knocked it back to 10 watts for now.

Frank

kcbooboo · Post by **kcbooboo** » Sat Jun 11, 2005 11:17 am

Every MaxTrac/Radius gets hot when transmitting, regardless of the power setting. Just make sure you have plenty of forced air cooling on it, and it should survive at 10-12 watts.

Bob M.

10-95 · Post by **10-95** » Sat Jun 11, 2005 11:20 am

kcbooboo wrote:Every MaxTrac/Radius gets hot when transmitting, regardless of the power setting. Just make sure you have plenty of forced air cooling on it, and it should survive at 10-12 watts.

Bob M.

I understand that but the 16 watts was certainly not healthy, and when i say "HOT", I'm not talking normal usage hot, I mean burn the skin on your finger hot . We are mounting two fans on the fins. Interestingly enough when we first checked out the transmitter we were running 15 volts off the power supply and the thing was blowing out 26 watts

kcbooboo · Post by **kcbooboo** » Sat Jun 11, 2005 11:37 am

I guess my comment came across the wrong way. I meant no disrespect nor was I criticizing your decision.

I was trying to emphasize the point that EVERY MaxTrac or Radius radio gets ridiculously hot while transmitting at any power setting, even those that are running at their designed frequency and power setting. It doesn't really matter if you are getting 80 watts or 2 watts out of one - they get hot almost if you just stare at them long enough. Very inefficient and a pain to keep cool. Plus, the microprocessor inside will think the radio is getting so hot that it should be shut down if you try to transmit long enough, even with adequate cooling. Luckily some of the newer radios actually sense the PA temperature and act accordingly, rather than just assuming it's getting hot.

Sounds like you have matters well under control.

Bob M.

10-95 · Post by **10-95** » Sat Jun 11, 2005 11:57 am

kcbooboo wrote:I guess my comment came across the wrong way. I meant no disrespect nor was I criticizing your decision.

I was trying to emphasize the point that EVERY MaxTrac or Radius radio gets ridiculously hot while transmitting at any power setting, even those that are running at their designed frequency and power setting. It doesn't really matter if you are getting 80 watts or 2 watts out of one - they get hot almost if you just stare at them long enough. Very inefficient and a pain to keep cool. Plus, the microprocessor inside will think the radio is getting so hot that it should be shut down if you try to transmit long enough, even with adequate cooling. Luckily some of the newer radios actually sense the PA temperature and act accordingly, rather than just assuming it's getting hot.

Sounds like you have matters well under control.

Bob M.

No problem, mine may have came across the wrong way, that's why I hate written communication. Anyway I am worried now, the repeater group runs a lot of GM300's on UHF and VHF but this is the first experience with the 900 stuff . I have felt the heat sinks on the warm UHF/VHF units but this was really hot so I hope we don't see the PA failing in a week or so. We probably need to find something rated for continuous duty. I'll give an update on this in the few days after we get it up on the site, I hope I'm not reporting that the PA died, I have my fingers crossed.

Frank

kcbooboo · Post by **kcbooboo** » Sat Jun 11, 2005 1:11 pm

The GM300s have a temp sensor on the PA, so they keep themselves cool, sort of. They're not as plentiful as MaxTracs, unfortunately.

None of the mobile radios are rated for continuous repeater use, but we hams have a way of making them work somehow. Even when used in a vehicle to talk ON a repeater, they get hot.

I'm using a pair of MaxTracs myself on 902/927, and had used a pair on 444/449, but after 45 minutes or so of transmitting, even at 6 watts out, the UHF ones throttle their output power down to zero - most annoying. Now I use an MSF5000 which IS rated for continuous duty, if the power level is set appropriately.

Bob M.

10-95 · Post by **10-95** » Sun Jul 10, 2005 12:29 pm

Update: We installed the permanent antenna last night at about 700 Ft on top of the building in downtown Raleigh. So far we have determined we have mobile coverage throughout Wake county and into parts of Durham county. Nice portable coverage throughout Wake county as well with just a few spotty areas. So far the Maxtracs are performing well, we are keeping them cooled off pretty well and we have not experienced any PA shutdowns as of yet. If anyone gets in the Raleigh area give it a try we have about four people monitoring most of the time.

Frank
AD4XE

Oh, the darn antenna would not fit in the elevator so I ended up taking it up 9 floors of stairs!! I think it was worth it!

mike m · Post by **mike m** » Sun Jul 24, 2005 7:38 pm

Frank,

What model antenna are you using and what are the spec's on it ? I've had my Maxtrac 900 rptr with a Azden 6 FM meter remote on for several months now running at 22 watts out and no PA problems yet.

I'm using a pair of Cushcraft 13 element phased yagis to cover more area but its still nothing close to omni( about 100 degrees at the 3 dB points) and I'm in the market for a medium to high gain omni antenna.

Mike

10-95 · Post by **10-95** » Mon Jul 25, 2005 5:18 am

mike m wrote:Frank,

What model antenna are you using and what are the spec's on it ? I've had my Maxtrac 900 rptr with a Azden 6 FM meter remote on for several months now running at 22 watts out and no PA problems yet.

I'm using a pair of Cushcraft 13 element phased yagis to cover more area but its still nothing close to omni( about 100 degrees at the 3 dB points) and I'm in the market for a medium to high gain omni antenna.

Mike

Mike , we are using a Decibel 890-960 vertical with 16 Db gain. The only real minor problem we are running into is the VCO on the transmitter making some harmonic noises from time to time. We are going to replace the Maxtrac on the transmitter side with a Kenwood .

Frank

10-95 · Post by **10-95** » Mon Jul 25, 2005 6:46 am

10-95 wrote:
mike m wrote:Frank,

What model antenna are you using and what are the spec's on it ? I've had my Maxtrac 900 rptr with a Azden 6 FM meter remote on for several months now running at 22 watts out and no PA problems yet.

I'm using a pair of Cushcraft 13 element phased yagis to cover more area but its still nothing close to omni( about 100 degrees at the 3 dB points) and I'm in the market for a medium to high gain omni antenna.

Mike
Mike , we are using a Decibel 890-960 vertical with 16 Db gain, the model number escapes me right now. The antenna was formerly usied on a paging system. The only real minor problem we are running into is the VCO on the transmitter making some harmonic noises from time to time. We are going to replace the Maxtrac on the transmitter side with a Kenwood .

Frank

Big BOB · Post by **Big BOB** » Mon Jul 25, 2005 5:23 pm

Here in Prescott, AZ just this weekend we put up a new Celwave (RFS) Super StationMaster antenna with 1-5/8" Heliax on our 900 repeater. It works great.

We are using a pair of 900 GTX mobiles. The transmit GTX has the PA removed and using it as an exciter to drive a commercial TPL amplifier. Get 55 watts out of the duplexer.

In about a month we will be replacing it with a 150 watt MSF 5000 900 Mhz repeater.

Big BOB
927.3875/902.3875 PL 151.4