HT1000 and DPL

dgruver911 · #1 (**permalink**) 01-23-2013, 3:37 PM

We have about 50 HT1000's in our system (in addition to 500+ others). We are in the process of testing all radios on a service monitor. We have discovered that the HT1000's universally have very poor/no receive on the 3 channels that use DPL (1 repeater, 2 simplex, different tones). The radios appear to be receiving the signal as the LED flashes as we generate signal, but the squelch never opens. On CTCSS they work fine, and other model radios work fine on both DPL/CTCSS. Has anyone run into this, and is there a solution? Thanks.

cabletech · #2 (**permalink**) 01-23-2013, 7:42 PM

The only time I have run into a similar problem, the radio(s) were A) off frequency more then 200hz
B) the tone level senitivity was also way off.

If you have the service monitor, first to do is a complete alignment of the radio.

Read your programing, save it, then go into the 'read' and remove any PL/DPL, just a open frequency, with the squelch full open.

After you have the radio realigned, then enter your PL/DPL and see were the radio opens up.

For that radio should be .25-.28microvolts for 12db sinad.

RKG · #3 (**permalink**) 01-23-2013, 9:46 PM

Another issue you should investigate is DPL polarity. DPL is a digital form of continuous coded squelch (or audio gating), but there is no convention for which way voltage departs from zero at the start of a code. Sometimes you will find that a transmitter and a receiver appear not to work together, but if you change the polarity of the receiver from "normal" to "inverted" they will work fine.

Offhand, I don't recall this problem with HT1000s, but I seem to recall it was an issue with Sabers -- either originals or Systems Sabers, I can't recall which -- which was odd because the other radios were also Motorola (but different models).

I should add: we have run HT1000s using DPLs for a long time without any issues, so it is not a model-specific issue.

com501 · #4 (**permalink**) 01-23-2013, 10:24 PM

There was an issue with some A and B versions which involved replacing a BGA. We scrapped them. Are these units narrowband? If they are, its a different issue. Do the alignment and make sure the transmitted tones are within specs also.

cmdrwill · #5 (**permalink**) 01-24-2013, 3:19 PM

One of the reasons we do not use DPL......

com501 · #6 (**permalink**) 01-24-2013, 6:54 PM

Seriously? Welcome to the 80's....

dgruver911 · #7 (**permalink**) 01-25-2013, 6:44 AM

Quote:

Originally Posted by com501

There was an issue with some A and B versions which involved replacing a BGA. We scrapped them. Are these units narrowband? If they are, its a different issue. Do the alignment and make sure the transmitted tones are within specs also.

These are all D models and they are narrowband. dg

com501 · #8 (**permalink**) 01-25-2013, 10:06 AM

Report back when you have done your due diligence. They are not worth repairing, as they are relatively inexpensive on eBay and they are outside support at Motorola. If the issue persists, you will have to replace them.

dgruver911 · #9 (**permalink**) 01-25-2013, 7:38 PM

Well, thanks to clues given here, we found the answer. All the Ht1000's are off-freq by 200-400hz. This doesn't affect CTCSS but negates DPL. When we match the service monitor signal generator to the off frequency, DPL works. In practical use, they appear to work, but it's obvious we can't rely on them for officer safety. I agree that they are not worth repairing. Will suggest they be phased out. Thanks for the help.