How to find RSSI/1st limiter test point?

[kl7hny]

Hiya, all. So, I've never been an "early adopter;" indeed, I probably qualify as a "really, really late adopter." My newest scanners are a pair of GRE PSR-200s. I use an XTS2500 for scanning P25 stuff around NC.

As further evidence of "hams keeping stuff running forever" I still have one each Bearcat 210, 20/20, 250, 760XLT, AND 800XLT (did I mention I'm old?) Having been a commercial tech for 50 years has helped.

What I'd like to do is add an RSSI ("S-meter') to each of these receivers. I don't need them to be calibrated; I have a spectrum analyzer for that. Having an indication of relative received signal strength would make me happy.

Anyone here know where to find the output of the 1st Limiter circuits in any of these units? An ideal answer would include something like "Pin 6 of IC-3" or "Where the blue wire attaches to trim pot #2." I'm adept & equipped to handle SMD manipulation.

All (printable) responses are welcome.

tnx es 73 de KL7HNY
diddly dahdidah
dit dit
-- Barney --

 

[merlin]

For that, you need the service manuals for any radio you wish to do this with.
Some PC board often have a pad labeled RSSI, gotta hunt for it. Usually near the discriminator AGC.
Your XTS with FCC menu enabled, can display RSSI, in Dbm

 

[kl7hny]

For that, you need the service manuals for any radio you wish to do this with.
Some PC board often have a pad labeled RSSI, gotta hunt for it. Usually near the discriminator AGC.
Your XTS with FCC menu enabled, can display RSSI, in Dbm

Great idea, Merlin -- thanks for the suggestion. I was able to d/l manuals for just a couple of the Electras from Elektrotanya.com. Uniden, however, has long refused to turn loose any of the service docs for their CB line.
It's been awhile since I've actually taken a look at the PCBs. I'll take another look this weekend.
73 de KL7HNY

 

[kl7hny]

Great idea, Merlin -- thanks for the suggestion. I was able to d/l manuals for just a couple of the Electras from Elektrotanya.com. Uniden, however, has long refused to turn loose any of the service docs for their CB line.
It's been awhile since I've actually taken a look at the PCBs. I'll take another look this weekend.
73 de KL7HNY

BTW, I found the instructions for RSSI Mode on one of the newer /\/\ handhelds -- maybe an APX? It consisted of "left x3, right x3." Would you please advise me of the command for the XTS?

 

[merlin]

Try the same commands as the APX. If that doesn't work, consult the Astro XTS user manual.
Given RSSI is a test state, you may need the service manual.
Getting technical documents for Uniden has often been unotanium.

 

[kl7hny]

Try the same commands as the APX. If that doesn't work, consult the Astro XTS user manual.
Given RSSI is a test state, you may need the service manual.
Getting technical documents for Uniden has often been unotanium.

Great idea, I'll try to find that manual. The APX command didn't work. Thanks for the pointer! 🙂

 

[kl7hny]

OK, I got the Complete Service Manual for the XTS series. But, naturally enough, the feature can only be enabled in CPS, and apparently require that I reprogram some of the button functions..
Ay, there's the rub. I received this '2500 programmed by the ham who picked it up at Dayton a few years ago. That lad has moved away, and I no longer get have easy access to anyone with the CPS.
Oh well, I can live without it. If money were not an object, I'd see if /\/\ still has subscriptions for this CPS.
Many thanks for your insights.
73 de KL7HNY
diddly dahdidah
dit dit

 

[KG4INW]

XTSs will only display RSSI on trunked radio systems and not in dBm (some 3 digit number scale). Has to be enabled in the programming software as you’ve found. Then it’s just a matter of pressing whichever button you assign that function to.

TRBO radios will display RSSI in dBm with the left/right arrow key sequence though, on any signal, as well as having a nice s-meter (again, XTS radios only display an s-meter on wide area trunked systems).

APX radios with recent firmware are finally able to display proper RSSI in dBm on conventional or trunked systems but that also needs to be enabled in CPS and a button assigned.

I don’t believe they sell Astro25 CPS anymore but it’s out there (is all I’m going to say about that!).

 

[merlin]

OP is using the XTS for P25 system, same as me. Astro 25 CPS is no longer supported, But I think programming is beyon the OPs skills.
As I recall from the manuals, that 3 digit number is the DbMv. (wrong?)

 

[kl7hny]

XTSs will only display RSSI on trunked radio systems and not in dBm (some 3 digit number scale). Has to be enabled in the programming software as you’ve found. Then it’s just a matter of pressing whichever button you assign that function to.

TRBO radios will display RSSI in dBm with the left/right arrow key sequence though, on any signal, as well as having a nice s-meter (again, XTS radios only display an s-meter on wide area trunked systems).

APX radios with recent firmware are finally able to display proper RSSI in dBm on conventional or trunked systems but that also needs to be enabled in CPS and a button assigned.

I don’t believe they sell Astro25 CPS anymore but it’s out there (is all I’m going to say about that!).

Excellent info! Helps me narrow down some of the Model vs. Feature buggaboos (that's an EMS technical term, but it likely has Comms parallels.
I spent a couple of years helping to maintain gear at a couple of the agencies on the NC Viper system. I'm familiar with subscriber equipment programming and P25 site optimization. But the agency who employed me (quite naturally) took back their laptop(s) and CPSs when we amicably parted company.
It's only now that I've acquired a couple of personal P25 rigs that I find myself pining for the tools to modify the stuff I now have. And yes, I know that it's "out there in the wild." I just haven't looked very hard (yet.) I'll see what the Autumnal Equinox Fairy brings to my shack.
Thanks for all the great info.
73 de Barney
KL7HNY/4

 

[KG4INW]

OP is using the XTS for P25 system, same as me. Astro 25 CPS is no longer supported, But I think programming is beyon the OPs skills.
As I recall from the manuals, that 3 digit number is the DbMv. (wrong?)

I seem to recall it was something proprietary they came up with. Folks determined what the equivalent dBm values were and had to reference a chart or use converters until Motorola finally changed it (they still use their scale but thankfully with dBm beside it now).

Excellent info! Helps me narrow down some of the Model vs. Feature buggaboos (that's an EMS technical term, but it likely has Comms parallels.
I spent a couple of years helping to maintain gear at a couple of the agencies on the NC Viper system. I'm familiar with subscriber equipment programming and P25 site optimization. But the agency who employed me (quite naturally) took back their laptop(s) and CPSs when we amicably parted company.
It's only now that I've acquired a couple of personal P25 rigs that I find myself pining for the tools to modify the stuff I now have. And yes, I know that it's "out there in the wild." I just haven't looked very hard (yet.) I'll see what the Autumnal Equinox Fairy brings to my shack.
Thanks for all the great info.
73 de Barney
KL7HNY/4

Happy to help! I've been working on these radios (TRBO and Astro) professionally for more than a dozen years now so naturally, I enjoy using them for my hobby as well. Once you get the CPS and cables, you should be good to go!

 

[kl7hny]

I seem to recall it was something proprietary they came up with. Folks determined what the equivalent dBm values were and had to reference a chart or use converters until Motorola finally changed it (they still use their scale but thankfully with dBm beside it now).

Happy to help! I've been working on these radios (TRBO and Astro) professionally for more than a dozen years now so naturally, I enjoy using them for my hobby as well. Once you get the CPS and cables, you should be good to go!

KG4INW de KL7HNY
R R
Yea, verily, I shall look forward to that happy juxtaposition of hardware & software with great anticipation.
tnx agn es 73 de KL7HNY
diddly dahdidah
dit dit
-- Barney --