vhf hi band maratrac radios

smokey705 · Post by **smokey705** » Thu Jan 24, 2002 5:43 am

I have some questions about the ability to put 12.5 khz spaced frequencies in a maratrac radio. I have put one freq in one of our radios and I am going to do some testing with it. The reason I am asking this
question is that we are in process of trying to set up a repeater system and the company that is supplying the equipment is telling us that 12.5 khz freqs wont work in these radios. are there any upgrades that can be done to make this work. all of our radios our 1993 or newer. thanks for your help.

Post by **/\/\y 2 cents** » Fri Jan 25, 2002 9:52 am

what the guy is telling you is partially correct. On a per channel basis there is no way to put only a few channels 25khz and 12.5Khz...............the radio has to be either or. The Maratrac can be modified to do 12.5 khz...but it will be radio wide, not selectable by mode. If you have no need to listen to 25 KHz channels and only 12.5 you will be ok with a little bit of modification. but it will cut out when listening to 25Khz channels. You can't mix and match or it will sound bad plus operate wrong.

Post by **vcaruso** » Fri Jan 25, 2002 10:01 am

What kind of Mods, Software or Hardware?

April · Post by **April** » Fri Jan 25, 2002 7:11 pm

The receiver needs to have the crystal filters changed to the narrower band and a resistor in the audio amp stage needs to be incresed to make up for the lower deviation of 2.5khz. The transmitter needs to be set to 2.5khz deviation total max. If you are using the newer HT750 series radios with companding the Maratrac will not work well as it does not have compression or expansion "companding" capabilities.

Crystal filter kits are available at CommSpec in Orange CA.