R8600 ICOM IC-R8600 Not Decoding P25 Phase 1 Unencrypted Transmissions

[Floridasand]

Hi Everyone,

I did not see anything posted for my questions. I have a ICOM IC-R8600 receiver. I love this receiver however I have a problem that I need to figure out. I can see the waveform for a particular Phase 1 unencrypted signal with a good strong signal strength, but it will not decode or allow me to listen to the frequency. I also have the ICOM IC-R30 receiver and it decodes the NAC and channel information 100 percent of the time. I can listen to all unencrypted transmissions. Are there any special settings that I need to use to hear and decode the phase 1 signals??? The waveform shows it great. Signal strength is from -76 to -84 Dbm. I have switched antennas and tested both receivers with the different antennas. I am receiving in the 771 MHz band. I can post a Youtube video that shows exactly what is happening. I have the current firmware and like I said the R30 never missed one transmission. Thanks for any help or information.
Floridasand

 

[Citywide173]

Does it receive P25 on other frequencies? Also, the stupid question, is P25 set as the mode?

 

[Floridasand]

It is in the P25 mode and it is very random at decoding any P25. Sometimes the NAC information will come up for a second and the EMR code shows up for the encrypted transmissions but the R30 decodes all the same frequencies received by the R8600. They are both ICOM radio receivers and hi-end at that. Not sure why with such a strong signal the R8600 is not decoding P25. The R30 decodes 100% of the time. My AOR AR-DV1 decodes 100%, my SDS100 and SDS200 decode 100%. And my Uniden 536 decodes 100% so I know it is some kind of issue with the R8600.

 

[Citywide173]

One last idea before blaming the issue on a sketchy P25 module. Have you tried attenuation?

 

[Floridasand]

Yes. I have tried everything that I can think of. Changed attenuation, tuned off frequency, adjusted RF Gain nothing seems to work. I think the issue is something that I will need to talk to ICOM about. It does not make sense that all my other receivers decode it fine.

 

[KC1UA]

Have you tried doing a factory reset? And just for giggles, what is the firmware version you're using?

 

[kruser]

Yes. I have tried everything that I can think of. Changed attenuation, tuned off frequency, adjusted RF Gain nothing seems to work. I think the issue is something that I will need to talk to ICOM about. It does not make sense that all my other receivers decode it fine.

What are you using for an antenna on the 8600? Have you tried swapping it with the antenna the R30 is using if possible.

Also, the 8600 reference frequency did not get adjusted correct? That's a radio menu item with a warning about changing it as doing so can cause the issues such as you are describing. And no, I don't know the procedure to set the value correctly! I've never messed with that value on either 8600 I use.
Maybe someone else has some suggestions on checking and setting the REF Freq back on target correctly.

How about a Full Reset? Have you tried that? You can save your memories and all to an SD card in the radio first and then do the reset and load just the memories back after you determine if a reset helped.

 

[batdude]

i would try this!



IMHO - you have tried everything that I would do - so if the full reset doesn't fix the problem I think you are going to have to send it in to Icom - I would send a letter with the radio describing everything you have done above so that they understand exactly what your problem is.


doug

 

[prcguy]

What filter BW are you using for P25? I think the radio defaults to the correct BW but maybe not and if its too narrow it will wreak decode. Have you changed any filter BW profiles?

 

[escortz28]

I had similar issue when I first attempted to decode P25. Two issues - improper filter setting (pcrguy post), and I had the D Squelch set to an incorrect NAC. I set to FIlter 1 and D Squelch off, no issues in decoding.

 

[kruser]

I had similar issue when I first attempted to decode P25. Two issues - improper filter setting (pcrguy post), and I had the D Squelch set to an incorrect NAC. I set to FIlter 1 and D Squelch off, no issues in decoding.

All good advice for checking and troubleshooting!

On the 8600 set to P25 Mode, Filter 1 is 15 kHz wide, Filter 2 is 10 kHz wide and 3 is 7.0 kHz wide.

My 8600's will decode all P25 just fine with the Filter set on 3 (7.0 kHz). I'm usually dealing with clean and strong P25 signals though.
I have seen the wider 10 and 15 kHz filters help a bit with some weaker P25 signals or slightly off freq signals so all filters are worth trying if it's just one system like it seems to be for the OP.
I don't think the default filter widths can be changed in P25 or FM modes. Filter 1 is 50 kHz wide in FM mode but it drops to 15 kHz in P25 mode.

I usually program P25 signals with the filter set on medium or 2 (10 kHz) as long as I'm not dealing with adjacent channel issues, if so then I'll set the filter to its narrowest setting , filter 3 (7.0 kHz). I rarely need to open up the filter to 15 kHz width.
Either way, trying all three filter widths as troubleshooting steps should be done here as it only takes a second or so when you know you have clear chatter!
The NXDN-VN mode uses a slightly narrower set of filters but the narrowest cannot be selected when in P25 mode. NXDN-VN uses 10.0, 7.0 and 5.0 kHz widths. NXDN-N is the same as P25 widths.

For the NAC, I rarely use that feature so my D.SQL is usually turned off but it's worth checking if one system gives you nothing at all. With D.SQL on, a wrong NAC should not allow any P25 audio to pass but the OP claims some audio does pass sometimes. Possibly from not decoding the NAC if the filter width not correct.
That's definitely a good suggestion to check that D-SQL is off for troubleshooting the flaky system. That's an easy setting to enable by accident and not notice it!

All good suggestions for the OP to check if still around messing with this. I often overlook these things and take them for granted.

 

[toad99]

Our local site for the OKWIN state network just switched to P25 on Tuesday. Simulcast distortion is really bad in Oklahoma City, and my 8600 just about refuses to decode any of the P25 traffic. Another site in the system, about 30 miles away, not simulcast, decodes 100% with excellent audio. Watch your RSSI meter while trying to decode P25, if it fluctuates then simulcast may be the culprit.

 

[kruser]

Our local site for the OKWIN state network just switched to P25 on Tuesday. Simulcast distortion is really bad in Oklahoma City, and my 8600 just about refuses to decode any of the P25 traffic. Another site in the system, about 30 miles away, not simulcast, decodes 100% with excellent audio. Watch your RSSI meter while trying to decode P25, if it fluctuates then simulcast may be the culprit.

That's similar to what I see also.

While my 8600 definitely does better than the typical digital scanner with simulcast systems, it's still not perfect.
I also noticed the RSSI fluctuations being more pronounced when simulcast seems to be a problem.
My R30 works about the same as the R8600 for really bad LSM signals within my range.

Like said though, they both do better than the typical scanner. I test using the same antenna fed through a multicoupler to the radios.

 

[streetbob]

I had similar issue when I first attempted to decode P25. Two issues - improper filter setting (pcrguy post), and I had the D Squelch set to an incorrect NAC. I set to FIlter 1 and D Squelch off, no issues in decoding.

Hi, new guy to this forum and the 8600. I too had a problem decoding P25 transmissions with the D-squelch on and the NAC input . Thanks to your post problem solved. No more head banging. Thanks much. Streetbob.

 

[iMONITOR]

Hi Everyone,

I did not see anything posted for my questions. I have a ICOM IC-R8600 receiver. I love this receiver however I have a problem that I need to figure out. I can see the waveform for a particular Phase 1 unencrypted signal with a good strong signal strength, but it will not decode or allow me to listen to the frequency. I also have the ICOM IC-R30 receiver and it decodes the NAC and channel information 100 percent of the time. I can listen to all unencrypted transmissions. Are there any special settings that I need to use to hear and decode the phase 1 signals??? The waveform shows it great. Signal strength is from -76 to -84 Dbm. I have switched antennas and tested both receivers with the different antennas. I am receiving in the 771 MHz band. I can post a Youtube video that shows exactly what is happening. I have the current firmware and like I said the R30 never missed one transmission. Thanks for any help or information.
Floridasand

You probably already know this but if not, the R8600 does not trunk.

 

[Citywide173]

You probably already know this but if not, the R8600 does not trunk.

It does not, however if you scan the voice channels of a non-encrypted trunked system, it should decode. I occasionally use my R30 like this on the Metro site of RISCON

 

[iMONITOR]

It does not, however if you scan the voice channels of a non-encrypted trunked system, it should decode. I occasionally use my R30 like this on the Metro site of RISCON

Odd that it's not doing that. Probably something isn't configured properly. Maybe do a master re-set.

 

[kruser]

Odd that it's not doing that. Probably something isn't configured properly. Maybe do a master re-set.

The R8600 and R30 are both vulnerable to the good ole simulcast issues which could be a reason. I do find they both seem to handle simulcast signals a bit better than any of the scanners I use though except the SDS models.
The Icom's will also not decode a true Phase II P25 talkgroup either if your system is fully Phase II. Otherwise, it should do as @Citywide173 said.
I use my 8600 and R30 for monitoring the voice channels of the local electric utility here as it's a lightly used system. They both work very well for that but trying to monitor the voice channels on a busy public safety system is almost useless.
I wish they both had a feature where you could use a talkgroup number kind of like a tone squelch so they would stay quiet until your entered talkgroup was detected during a voice channel scan pass. That could be handy even on busy systems.
They can both detect and display the talkgroup as well as the UID on a P25 signal but the radios have no options to really do anything with that info other than display it for a second or so.

 

[n2pqq]

Can you tell us what frequency you are trying to listen to
that way we can look it up in the database and hopefully
help you

Also make sure NR is off

 

[R7000]

Mine does p25 just fine. I use filter 2