Batboard

Is there anyone here with a nice explanation of what happens with PL & DPL on the same frequency? We are PL (@ this time) and have a co-channel user who is about 80 miles away (and all of us are within our emissions envelope & specification) who is using DPL on the same frequency. We are getting some pretty bad reciever falsing on our end, and we need to find a way to get more separation from these guys. How does PL & DPL play on the same frequency? Are there any benefits to using matching or separate squelching types on a common frequency? Are there PLs which are more likely to false on DPL data? (Blendermike you are a god, i read that whole page on your DPL information - i can honestly say i now understand Golay (23,12) numbers and the basics of DPL determination, error correction and encoding). If they are currently using DPL 205 & we are using PL 218.1, where do we go from here? Going thru the blendermike pages and finding the ENTIRE DCS list and the multi-codes that are out there, what should i do for a DPL? I've found some hammies who say that higher PLs might sneak thru a poor RX audio filter and show up as a "low hum" on the RX audio, pages that say that low PLs "take longer to decode", lower DPLs have more innocouous "non returning zero bits" & that "higher DPLs are more reliably decoded, however have more "false positive" codes or "100 signature matches" that create mutiple accurate codes.

I'm stuck, need a guding hand here.

AND/OR.. need to look for this setting in your repeater receiver. .. and set it for.

Also, be advised that we have observed falsing if one of two co-channel users is using DPL (any code) and other is using PL 3B (131., particularly when a mobile on the DPL system sends a disconnect code. Solution is to change your PL tone.

For what it is worth, there was a pretty intense study done a couple of years ago by some of the folks on this board that disproved the notion that lower PLs take longer to decode than higher ones. Turned out that about 175 ms was required for all tones. It is true that higher tones may show up as a hum that leaks through the hi-pass audio filter.

AND/OR was set correctly, there was an "Audio path" setting, when combined with an AUX/IO card & Aux IN which was allowing undiscriminated audio to be piped into a link radio, so it was a setup problem.

Anyone have any of that study information about timings & durations as was mentioned?

I believe "the study" is documented in a series of posts on this forum. Perhaps Alex remembers and can locate it.

One note for anyone who chooses to follow through the posts in the original thread down to the point where I posted the results of several bench tests - the method of procedure used was apparently suggested by Nand in one of his posts.

Unfortunately, Nand left the board for a period of time and edited out all of the contend of his posts when he left.

Basically, the procedure used would be similar to the "Receiver Audio Attack Time" test outlined in TIA-603-C 2.4.2. wherein the test is conducted under certain specified conditions of audio modulation, subaudible signaling moduation, and RF carrier level.

The TIA test calls for test tone at 'standard' modulation level [60% of system deviation], subaudible signaling at 'standard' level and carrier level 12 dB above reference sensitivity.

RKG wrote:For what it is worth, there was a pretty intense study done a couple of years ago . . . .

I was surprised to see that that was six years ago!

One of the first replys in the link was from Monty, still miss his posts. He was always willing to help.

I have not done any real testing but in our system (Mt-2000 and CDM with Quantar repeaters on UHF) I have not noticed any change since we converted to DPL 10 years ago. We do have MDC with 250ms pre time so that would likely cover any decode delay, users wait for the MDC side tone to end before they speak.