gr1225 conversion from repeater to simplex control station

[emtprt]

I am in the process of adding a control station and have a tight budget. I have a gr1225 UHF repeater that I would like to conevert to a simplex base for use as a control station a for 2 channels. The TX would be Channel 1 459.0/RX454.0 Channel 2 Tx 458.05/RX453.05. This unit would be intergrated into a console at our dispatch center for back communications.

Would this just alignment to the duplexer at the mid point between frequencies (TX 458.5/ Rx 453.5) or is there another device available which would connect theTX and RX coax together allowing a connection to the antenna and not have a dramatic impact on reception or TX power?

I realize using a duplexer will reduce the TX power and will limit the frequency range to operate. Use of the duplexer could help reduce noise from other transmiters at the site vs a mobile radio with a power supply.

Thanks
mark

[Bill_G]

One word - No.

Don't do it. Budget may be tight, but the GR does not lend itself to two freq simplex operation. It is designed as a reasonable quality lower tier single purpose repeater. Try to find another radio more suitable to do this with. You don't turn sedans into pickup trucks by taking the trunk lid off. You don't GR's into base stations. I'm just sayin, you know.

[emtprt]

Thanks for the input, I have a very limited budget and need to build a functional back up for our volunteer fire/ EMS/Hazmat agency.

[d119]

PTT based antenna relay will do the job, but I agree with Bill... I'd just get a GM300 or something you can steer the channels on and go that route. GR's are a PITA for things like that.

[PETNRDX]

It is very unlikely that you would be able to get the duplexer to handle freqs that far apart.
You might be able to re-configure separate cavities/tee's/coax jumpers to make a "window" filter for the freqs of interest.
Depends on the duplexer type.
Sell the GR and pick up a CDM or something similar that will do NB when the time comes.

[emtprt]

Original plan was to purchase a CDM1250 with power supply, UPS, Rack Mount, pre-selector. I was hoping using the r1225 would eliminating the purchase of everything except for the ups. I am trying to work within a budget that won't cover the project.

Unfortunately with the narrowanding I have a number of Maxtracs and GM300s that are collecting dust.

[Bill_G]

Are these channels in use as 12.5kc already? Are they specifically narrowband channels that cannot be programmed into the Maxtracs and GM300's? If not, you have time to make the changes. The drop dead date has moved out to 2013. You may be able to press these older radios into service for a bit longer while you accumulate money.

[emtprt]

One channel is 12.5KHz the channel has hadpaperwork submitted for the conversion. Our system is currently using CDM1250 radios for mobiles and HT 1000/750/1250/MT2000 and MTS2000 portables. The primary frequency has MTR2000 repeaters voted with 2 receivers and the low use channels (already 12.5) use r1225 repeaters.

There is an upgrade plan to replace the r1225 repeaters with continuous duty, higher power, radios but that is contingent on grants and budget restrictions.

[ifixmotorola]

Stupidly simple I know but if the budget is that tight just throw up an additional antenna and share Rx for the two on one antenna and find a small combiner for the Tx side.

[emtprt]

I just received a flyer from a vendor with some realistic 19" UPS and Power supply costs. This will take a good size dent from the oringial quote using a CDM1250. I was also given the name a a company the produces 19" rackmounts for the CDM Radio. Things are looking better for this project.