Discriminator Tap on maxtrax800

firemedic4 · Post by **firemedic4** » Mon Dec 27, 2004 8:46 am

I just got a used 800 mhz maxtrac, Has anyone every put a Discriminator Tap on one ? any help or pics would be great... Thanks Bob

Post by **xmo** » Mon Dec 27, 2004 9:45 am

http://www.batlabs.com/maxrad.html

redbeard · Post by **redbeard** » Mon Dec 27, 2004 2:54 pm

Is it 5 pin or 16 pin? Trunking or conventional? I've been hacking these for some neat uses lately and I have one that I use exclusively for running trunker on my local TRS. I took the logic board out and put in a limited 5 pin board and used the good 16 pin board to upgrade a VHF radio with, after a firmware change. I used the old logic board and 2ch face to make a conventional 800 radio and then tapped it for Discr. out and feed it into my Trunker computer. Works real nice, even mounted a female RCA jack on the side of the PA. Works like a champ too.

Depending on what your radio does and what you intend to do with it will make a big difference. If it's a 16 pin and capable of conventional modes then just make a cable. Otherwise I can go more in depth to what I did and how.

Will · Post by **Will** » Tue Dec 28, 2004 3:56 pm

There is a convenit place on the logic board at JU601 B side. That is Disc audio filtered by the 3KHz low-pass filter. Another point is pin 3 on the logic board to RF board connector, raw detected audio.

redbeard · Post by **redbeard** » Tue Dec 28, 2004 11:32 pm

Ok what I did was all done on the RF board, mine is a HLF9122A. Looking at the front of the radio there is an IC in the front left corner marked '79G05'. I followed pin 6 to a set of three test points right between the Sq pot and an ajustable inductor with a yellow top. The point you want is the one on the left side. I used a piece of shielded cable cut from a computer cd-rom audio cable. I soldered the center to the test point, and the ground to one of the ground pads near to the right of the 3 test points. I ran the cable back into the PA through the same hole the grey coax goes through. I then drilled a hole and mounted a female RCA connector to the left side of the PA housing. It is a very neat install and my only wish is that there was a spot with enough room I could have mounted it on the rear of the radio and not the side.

Here's some pics of it to get an idea. Sorry the pics suck so bad, but there's no focus on my camera and it takes lousy close ups.

http://unwired.ovscan.com/images/maxtrac_tap/

Notice the salvaged 800MHz bag phone antenna. It works like a champ and I was lucky to find one with the right connector, most are TNC instead of mini-UHF.