DPL Major Interference Issue

CHEFA2001 · Post by **CHEFA2001** » Sat Apr 06, 2002 10:46 pm

I'll try to make this brief.
I have a UHF repeater system running at quite a good elevation point,and line of sight wise, I can for quite many miles.

I originally had a DPL of 423 for the system, then due to interference being received on portables in the field, I changed the DPL to another one.

Here comes the problem:
Portable radio(s) have:
Rx=464.XXX
Tx into repeater is 469.XXX

The first DPL which was in place was letting a decent bit of chatter through on the 464 freq, and after changing the dpl to the 364, I got rid of that party's radio chatter, but now I have an occasional interference coming through the repeater, Actually talking through it! Not loud, and actually barely audible, but still very frustrating......

I have heard somewhere, Maybe here? That when using DPL, Strong signals with TPL can "bleed" through the DPL.... Any truth to this??? Am I better off using inverted DPL, if so, are there any cons or pros to it?

Or am I better off just trying another DPL, or go to TPL al together??

Any opinions are very much appreciated, as I know when a comment or two start, then everyone on here chips in their help....

Thanks guys

Monty · Post by **Monty** » Sun Apr 07, 2002 12:46 am

Hi:

I believe you may have a controller
problem. There should be NO Audio Bleed
through at all ! Even with / without a
strong signal.

Sounds like your Repeater Receiver is hearing
a very Strong Signal, and even if the interfering signal ( had no tone ) you
should not hear anything.

Depending on the Controller being used, and
how its set up plays a very important role
as to Quality.

None of our repeaters have " any " bleed-through, but they are also all Motorola Factory stock radios.

In other words, unless the proper tone is detected, the Audio path to the transmitter
is cut off.

Inverting / changing / PL - DPL tones will
only Rid the Repeater of offending signals
far away

Monty

Ray D. O'Mann #2 · Post by **Ray D. O'Mann #2** » Sun Apr 07, 2002 6:38 am

You should also keep in mind that even if your controller does prevent an invalid tone from accessing the repeater, if the signal is stronger than the "valid" user's signal, you will have poor range and intermittent performance as a result...Freq change needed???? You may want to put a logging recorder on your receiver just to hear how much activity is coming in.

Nand · Post by **Nand** » Sun Apr 07, 2002 7:06 am

Will · Post by **Will** » Sun Apr 07, 2002 5:18 pm

Is there a RICK in this setup?

CHEFA2001 · Post by **CHEFA2001** » Sun Apr 07, 2002 6:35 pm

hi Will, Originally there was an I750r and now there is a rick.
This is one out of two systems that are running.

I swapped entire setups to verify that it was not the equipment, and I was right in my thinking that there was simply another user which has the same DPL tone on TX on my repeater's input freq.

Thats the reason the crap was coming through the system.

But anyway Will, Did you have a comment about the rick setup which might possibly apply.

Will · Post by **Will** » Tue Apr 09, 2002 12:19 am

It is hard for me to tell just where the problem lies for sure. It could be co-channel or someone on the repeater input with a DPL with some simular bits in the code, falsing the DPL decoder. The DPL decoder checks fewer bits of the code at first to speed up the decode process then switching to a higher bit checking to hold the code decode. The decoder starts to decode then switches off, and during the dropout delay in the rick some audio may "leak thru" the RICK into the keyed transmitter.
In the RICK there is some coupling in the audio which causes cross talk on the transmit mic line.
Also the RICK can be falsed to keyup the tx for the dropout delay period and that is when you can get weak distorted audio in the tx during the dropout. All the 16 pins from the accessory jacks on the radios out to the RICK are in the same shield and pickup noise and crosstalk. I had one with data noise getting into the receiver RF thru the two connecting cables going out to the RICK. I chopped out all the wires not used in each cable and it was still there somewhat. I put one of my repeater modules in, no changes to the radios and the problem went away.

MicorRT · Post by **MicorRT** » Tue Apr 09, 2002 5:06 am

You could do a split DPL using 423 inbound to the repeater since you haven't had any problem on that end and use your current DPL outbound from your repeater to your subscriber units... May have to spend a day up at your machine and see what DPLs and PLs are getting hits and which ones aren't.