Using a High Power Spectra as a Base Station

[jchapman]

I just acquired a Motorola Spectra UHF (450-482 MHz) radio (110 watts) with a Spectra Systems 9000 remote head, and I would like to use it as a base station for GMRS. I have tried my best to make sense of the information on Batlabs and Repeater Builder, but I still don't understand because I've only dealt with Jedi and Waris portable radios in the past.

I would appreciate it if anyone could help me answer some of the following questions:

• What type of power supply, fuses, etc. should I use?
• What considerations, if any, should I make in regards to cooling?
• Are there any desktop mounts available for this type of configuration?
• What type of programming cable should I order? (I already have the software.)

I've tried to locate the answers to these and other questions myself, which has lead to nothing but confusion so far.

Thanks,
John

[Jim202]

I just acquired a Motorola Spectra UHF (450-482 MHz) radio (110 watts) with a Spectra Systems 9000 remote head, and I would like to use it as a base station for GMRS. I have tried my best to make sense of the information on Batlabs and Repeater Builder, but I still don't understand because I've only dealt with Jedi and Waris portable radios in the past.

I would appreciate it if anyone could help me answer some of the following questions:

• What type of power supply, fuses, etc. should I use?
• What considerations, if any, should I make in regards to cooling?
• Are there any desktop mounts available for this type of configuration?
• What type of programming cable should I order? (I already have the software.)

I've tried to locate the answers to these and other questions myself, which has lead to nothing but confusion so far.

Thanks,
John

You should check the FCC rules on the GMRS service and make sure your operating per the requirements and power levels that your authorized. A 100 watt radio just can't be turned way down and expected to operate normally. The PA stage in the transmitter gets unstable at low power levels. You could safely go down to about 70 or 80 watts, but lower than that, you could turn the transmitter into a comb generator and cause all sorts of interference to other users and services around you.

You will need a power supply with the ability to supply about 22 to 25 amps to the transmitter. I would get at least a 30 amp rated supply.

In repeater use, the heat sink will get hot in just a few minutes of transmitting. These radios are not designed to to be in constant transmit. they were designed to be in TX only 5 % of the time.

You can make your own programming cable with a couple of DB25 connectors, one male and the other female. Wiring info for it can be found on the batlabs.com site. However you will need a slow computer and run it in a true DOS mode, not inside a windows dos mode. You will also need a RIB to convert the computer voltage levels to the voltage levels that the radio is looking for. Again the plans for the RIB are on the batlabs site. You could go out and buy (I hate that word) a RIB from several sources.

I don't know why your so confused. Some simple reading and searches on the Internet should produce all sorts of information on the Spectra radio. Another site that should have some good information on the Motorola Spectra is the repeater builder site. You indicated that you have already been there. If you don't understand what your reading, then maybe it is time to find someone in your area to help and act as a mentor to help you along.

If your not willing to do your homework on the subject first, don't expect a free ride from the guys here. There are some very talented people on here, but like I have stated, they do expect you to learn most of the information yourself. Then when you start to stumble, come back and ask for help. Don't just start messing with a radio transmitter and try putting it on an antenna without knowing what your doing. That is like asking the FCC to come knocking on your front door.

Just learning your way around the Spectra software can be a real chore. I have been doing it since the radios came out and have to stop and think for a while just what I am trying to do to change something in the radio software. Each radio family has it's own different software package. So it takes a few moments to regain your direction path each time you go into it.

Jim

[jchapman]

Jim,

Thank you for your response. I don't intend to transmit higher than the maximum allowable output of 50 watts, but I was under the impression that the high power model could be operated at a lower power if desired. Also, I just wanted to be sure that I build the correct programming cable, since I noticed that there is a distinction between cables for the low/mid power and high power models.

I don't know why your so confused. Some simple reading and searches on the Internet should produce all sorts of information on the Spectra radio. Another site that should have some good information on the Motorola Spectra is the repeater builder site. You indicated that you have already been there. If you don't understand what your reading, then maybe it is time to find someone in your area to help and act as a mentor to help you along.

If your not willing to do your homework on the subject first, don't expect a free ride from the guys here. There are some very talented people on here, but like I have stated, they do expect you to learn most of the information yourself. Then when you start to stumble, come back and ask for help. Don't just start messing with a radio transmitter and try putting it on an antenna without knowing what your doing. That is like asking the FCC to come knocking on your front door.

It's not that I don't understand what I'm reading. I browsed through the information available at Batlabs and Repeater Builder and did not find any information specific to my intended configuration, which is the reason I decided to ask for help from the Batlabs community. I'm only a little confused because I have never taken on an endeavor such as this before. I have a lot of experience with Motorola portable radios and knowledge of radio communications in general, but I have never had any experience with Motorola mobile radios. I don't expect a free ride, just some assistance from those whom have done this before.

Thanks,
John

[kb2crk]

for gmrs a dash mount spectra or even a maxtrac would work quite well. there are only a few gmrs frequencies and a 32 channel maxtrac would do that easily at 40 watts. a 15 amp power supply would handle that easily.

[MT2000 man]

for gmrs a dash mount spectra or even a maxtrac would work quite well. there are only a few gmrs frequencies and a 32 channel maxtrac would do that easily at 40 watts. a 15 amp power supply would handle that easily.

X2

A few years back I had a 16 channel GM300 set up on GMRS. Worked just dandy. You really don't need a 110watt High Power Spectra for that.

I used the GM300, Astron Power Supply, "base microphone", and a short UHF antenna that I stuck out the window, and called it a day. Talking from the "base station" to my mobile rig (on Simplex) I was able to reach about 4 miles away (in hilly terrain with trees / homes all over the place to boot).

Edit : I forgot to mention, the GM300 I used as a base station was putting out about 25 Watts, and the unit in my truck was also putting out about 25 Watts of power.

[Will]

jchapman You may use a high power Spectra at 50 watts output on GMRS as a base station or mobile.

You will have to realign the transmitter to 50 watts, and yes it will do that ok for mobile or base usage.

To be on the safe side have a licensed comm tech certify, in writing, that the transmitter is 50 watts and the radio only contains the GMRS frequencies. NOT the interstitial freqs.

[jchapman]

Thank you for your responses. The high power Spectra wouldn't have been my first choice, but it just sort of fell into my lap. I suppose I could sell it and get a 45 watt CDM1250 instead...I like the Astron CDM power supply.

[N4KVE]

Also consider if the caps haven't been changed yet, it's time. The Spectra is a great radio, but the hi power version isn't a great choice for a base. If you could swap it for a medium power front mount Spectra, that would be great. GARY N4KVE