HT-1250 LTR decode problems

[RADIOMAN2002]

We have a large number of VHF HT-1250 LTR portables. Up until recently the radios were only used on conventional CSQ channels. The problem seems to be with the decode time for the LTR code. When trying to access a channel the radio will key up until busied out or will get in the first or second TX time. You can see in the display that the ANT bars are there, which means the radio is bringing up the channel, just the radio is not decoding the LTR code in time to recognize the channel. Now if you use another radio to bring up the channel, the radio with difficulty takes a good second to second and a half to decode the LTR signal. When it does decode there is a brief drop out once and then receives fine. All the problem radios have the same Tanapa of PMUD1481a. These radios are way past any warranty has anybody heard of or know of any problems of this type, and give me a direction to check.

[RADIOMAN2002]

Correction on the Tanapa 1816a and 1817a, the 1481 and 1482 are from the conventional only we have.

[com501]

Update to the newest firmware, first.

Second, what is the system deviation on the LTR system? If wideband, the radio is happy with LTR deviation around 1kHz to decode adequately.

[MSS-Dave]

I echo com 501 on the firmware check. I found decode problems a lot on 1250's especially on narrow band UHF systems with mis-aligned TX on the repeater. Check the level but you also need to check the symmetry of the wave form on a service monitor. It should be reasonably square. If there is any "slope" to the waveform, you could have RX problems. Motorola MTR, MSF 5K, Quantar and RKR1225 had modulation compensation (well...it's been a long time, the 1225 radio may NOT have mod comp..) where you can adjust the waveform if needed.

If all this checks out, there can still be issues. What kind of repeaters are being used and what brand are the trunking panels?

Dave

[chartofmaryland]

Make sure to check the Data deviation, LS Trunking, Site, LS Trunking Site.

Medium was okay but went to High when the noise at the site went up same issue and was easy to resolve, jacked all users up to high and things ran great.

I was having many problems when a 3rd harmonic near one of the LTR 450 mhz sites I serviced went from -108dbm to
-89dbm due to an FM station right on the 3rd harmonic was loosing their filtering in one part of the station's transmitter. Noise floor went up and data was not making the haul.

Real problem still needs to be resolved though as more noise will just keep the users pissed when it happens again. The boss did not want to hear it when I mentioned we needed 2 10" bandpass cans at minimum to resolve the adjacent noise problems, I left it up to them to resolve the issues with the FM station as that was only going to get worse.

1.2 kc was what I was told was the standard for the Trident Raider LTR panels FYI.

CoM

[RADIOMAN2002]

The system operates in narrow band mode, the station works fine with newer radios. Just the older ones are problematic. The station is on channel with LTR deviation of about 650hz, any higher, and we had problems with the radios that do work. The is very much a portable radio decode issue, the firmware upgrade was going to be my next step. Whats interesting is some of these Tanapa's, with the same firmware level work fine. No rhyme or reason. I guess I'll get my firmware upgrade setup warmed up. Thanks for the reply.