800 MHz D45 Maxtrac for 900 mobile use

wb1cmg · Post by **wb1cmg** » Thu Sep 18, 2003 8:16 pm

I have read the recent posts that indicate the Maxtrac receivers are usable on 900 even if it started out as an 800 model. Are the transmitters usable at all? Is it just a matter of scaling LC ratios in the various stages or is there another limitation? The unit is equipped with "Talkaround".

David, WB1CMG
Mont Vernon, NH

KF6HHS · Post by **KF6HHS** » Thu Sep 18, 2003 10:10 pm

David, seveal folks have modified the 800 MHz Maxtrac for use as a Rx unit for repeater service. And, only the "Talkaround" 800 model is capable of being able to Rx in the low part of the 900 amateur band. Don't believe anyone has used it as a user radio for 900 amateur - the Tx VCO and PA run out of steam for 900 use.

Regards, Hugh KF6HHS

PETNRDX · Post by **PETNRDX** » Sat Sep 20, 2003 8:14 am

What Hugh says is correct. They make good recievers for repeaters, but thats it.

wb1cmg · Post by **wb1cmg** » Tue Sep 23, 2003 7:11 pm

My modification of commercial equipment experiences are mainly in the VHF region. Also, the equipment I am used to working on was quite dated by comparison. Thanks for the advice. I guess I will hang on to it for receive duties anyway. I am just surprised that the Tx chain is that close. Of course, if this is contains a potted module hybrid then that makes sense.

David, WB1CMG

CTAMontrose · Post by **CTAMontrose** » Mon Sep 29, 2003 3:35 pm

keep in mind that its not just as simple as programming it at 902.. not only does the pin shift transistor have to be removed, but the murata filters in the front end have to be removed and replaced with the 915Mhz version.

chpalmer · Post by **chpalmer** » Sun Oct 19, 2003 1:57 pm

We've been playing with changing the origional 860 bandpass of the filters iin the 800's using paper and copper wire in the holes of the filters. Ive got one working as a commercial receiver right now. The loss is a tad higher but also more selective. Only real problem is that the 800 radios are not as stable as the 900 radios and converting to narrow band can give you a headache if the temperature changes to much where the radio resides.