Pro-96 off frequency

[902]

Hi all,

I searched the archives and the wiki (and I don't think I've asked before), and haven't seen anything with respect to my problem, so... I have a Pro-96 that I've had for 12 years. It's beat up and held together with gaffer's tape, but it still powers up and receives. I used to live in a VHF area and moved a while ago to an area served by a ubiquitous analog 800 MHz trunked system. A few years ago, I noticed the 800 audio sounded distorted (not a simulcast overlap). After hooking the Pro-96 to a service monitor, I found that the reference oscillator had gone off frequency. I programmed it 6.25 kHz offset from the real frequencies and it worked okay, but I want to set it up and pass it down to one of my kids, as I'm planning to get myself something more recent. Does anyone know of the alignment point to set this back on freq (I have a full shop/bench setup)? I know about the VR-2, 3, and 4 adjustments, and those help but have not put the scanner "on frequency." There is a coil potted in waxy goo under a shield cover that does affect frequency very coarsely (gosh I'm hoping that's not the way those things were netted in). Is that it? Is it the yet to be turned inductor next to the crystal (which, if my luck follows, probably has nothing to do with it)? Or is there something else I haven't yet ventured into?

I had a service manual CD years ago that was copied onto maybe 5 generations of computer ago. The CD got cracked and is "no esta" anymore (no, I'm not asking for a copy of the CD, although I'm surprised it's not "out there" since GRE is gone and RS is "something else" now), and I'm more or less winging it. Anybody definitively know how to net this thing in?

Thank you!

 

[ecps92]

My GRE 600 did the same thing for 700-900 Only and is quite DEAF anyway up there.
Gave up and it's my FED Radio instead

Hi all,

I searched the archives and the wiki (and I don't think I've asked before), and haven't seen anything with respect to my problem, so... I have a Pro-96 that I've had for 12 years. It's beat up and held together with gaffer's tape, but it still powers up and receives. I used to live in a VHF area and moved a while ago to an area served by a ubiquitous analog 800 MHz trunked system. A few years ago, I noticed the 800 audio sounded distorted (not a simulcast overlap). After hooking the Pro-96 to a service monitor, I found that the reference oscillator had gone off frequency. I programmed it 6.25 kHz offset from the real frequencies and it worked okay, but I want to set it up and pass it down to one of my kids, as I'm planning to get myself something more recent. Does anyone know of the alignment point to set this back on freq (I have a full shop/bench setup)? I know about the VR-2, 3, and 4 adjustments, and those help but have not put the scanner "on frequency." There is a coil potted in waxy goo under a shield cover that does affect frequency very coarsely (gosh I'm hoping that's not the way those things were netted in). Is that it? Is it the yet to be turned inductor next to the crystal (which, if my luck follows, probably has nothing to do with it)? Or is there something else I haven't yet ventured into?

I had a service manual CD years ago that was copied onto maybe 5 generations of computer ago. The CD got cracked and is "no esta" anymore (no, I'm not asking for a copy of the CD, although I'm surprised it's not "out there" since GRE is gone and RS is "something else" now), and I'm more or less winging it. Anybody definitively know how to net this thing in?

Thank you!

 

[Voyager]

I know about the VR-2, 3, and 4 adjustments, and those help but have not put the scanner "on frequency."

Those are what you want to use. It's possible the drift is so far off they don't have the adjustment range, but there are no other frequency controls.

 

[902]

Those are what you want to use. It's possible the drift is so far off they don't have the adjustment range, but there are no other frequency controls.

Thank you very much, Voyager. I was afraid of that. Since I'm not going to really "break" anything (more than what it is), I'm probably going to mess around and see if I can warp the reference oscillator. Got a box of small value chip caps, so why not?

Thanks again!

 

[902]

My GRE 600 did the same thing for 700-900 Only and is quite DEAF anyway up there.
Gave up and it's my FED Radio instead

This isn't so bad in terms of receive. I have about 0.5 uV/12 dB SINAD for 800. That's not two-way radio quality, but I'm not far from a simulcast site and there's pretty strong signal saturation where I'm at. That deafness also helps me reject some of the cellphone interference I come across if I'm too close to a cell site. I don't have a lot of fed activity by me. That's probably a good thing.

 

[Joseph11]

Bump. I'm having the same issue with a PRO-96 I bought used recently. Everything under 800 MHz seems fine, but 800 MHz is off frequency slightly. I had a PRO-164 before that was entirely off frequency that I resolved by adjusting a POT inside the scanner, but how would I handle fixing this problem with only 800 MHz on the PRO-96? Thanks.

 

[INDY72]

Open it up.. Adjust the VR4 pot very slightly.
PRO-96 Internal Adjustments - The RadioReference Wiki
http://forums.radioreference.com/radio-shack-scanners/178696-modifying-rs-pro96.html

 

[Joseph11]

Thank you! That did help quite a bit, but it still is slightly off. Would adjusting VR2 and/or VR3 potentially help more?

 

[INDY72]

Not without freq generator etc. Those are for Vhf and uh etc

Sent from my LG-K330 using Tapatalk

 

[Joseph11]

So, the only thing relevant to 800 MHz reception is VR4?

 

[INDY72]

The VR4 is primarily 800 MHz, as it effects the 440 MHz oscillator stage, as well as a couple of other things thereof. But the VR2 and VR3 seem to more effect the other frequency stages etc. The only way to do correct full realignment is to follow the steps listed using an frequency generator etc... The slight adjustment to the VR4 has been found to directly effect 800 MHz reception, and 800 MHz P25 especially, and improves performance on LSM systems dramatically. Also, make sure you have upgraded the DSP to 1.4.

 

[Joseph11]

Adjusting VR4 put UHF in the 406-512 MHz range off. After a couple of hours of tweaking VR2 and VR3, I finally got it almost perfect.