Pl vs DPL

[kens]

A friend just reporgrammed some portables (vhf not Mototola) for a school. He thought they might be experiencing some interference from some local kids so he changed them from pl to dpl. The school then complained about poor range of the radios. Is this possible? I have never used a dpl simplex system so I have no experience in this.
Thanks to all.
Ken

[Motoman]

Yeah i've found the same problem, this is usually cause over range the DPL sometimes isn't strong enough to unlock the squelch in the recivers radio even though the transmission may make it, just the DPL code sometimes is too weak. What type of radios are these? If u want these kind of secuirites for the radio communications, upgrade to some good quality radios. Any of the Commerical radio versions of Kenwood, Motorola, Yaesu, Icom, GME Electrophone, Tait..etc most will have not have range compromissed by comms securities.
For me i use Motorola MTS-2000 with MDC-1200 enabled to give some secuirty over interferance makers on other radios.

[raymond345]

When we come across this problem
we putan added channel with cs on
the same frequency and they try the call
from the same location with tone and without tone.
Then you get the answer without any other testing.
We always try both systems.

Keep us informed.

[RKG]

We have been using DPL inputs for repeater pairs for years without detecting any effect on range. Be sure your alignments are correct.

In theory, DPL should be easier to detect (i.e., result in increased effective receiver sensitivity) because decoding analog PL requires assessment of the envelope shape of the audio, which can be affected by marginal-range-noise, whereas decoding DPL requires only evaluation of the audio 0-V crossing points. Frankly, I think that is more theory than reality, and that the effective sensitivity of a properly aligned system is the same for PL and DPL.

[nmfire10]

I'm a big fan of DPL because the turn-off code is universal... unlike PL where Mother M uses a different reverse burst than everyone else. I have not seen any decreased range either.

[n9upc]

My question would be what portables you are using???

I tried making a post on this before but it did not go through.

If it is a Kenwood I would have it checked out as sometimes get of of tune and boom it causes a problem with PL/DPL.

[Wowbagger]

Depending upon the DCS encoder in the radios, it is possible that you did not get all the bits set correctly, and that is causing your problem.

DCS uses an error correction algorithm that can detect and correct a one bit error, but cannot correct a two bit error. The idea is that when the signal is marginal, you may mis-detect one bit of the code word, but if you can correct it you can still function - all the way down until you start mis-detecting 2 bits per code word.

However, if the DCS encoder is stupid, and requires you to program the full code word rather than just the last 9 bits and computing the correction code from there, you can have a case where you have a built-in one bit error, which will greatly reduce your range.

The other thing to be sure of is that the code used is a valid code - not all of the 512 possible values of the code are valid, and I have seen people pull a DCS code out of their .... well, it was not a valid code. The reason some DCS codes are valid and some are not is that the valid codes have a special property that makes them always detect correctly no matter where in the data stream you start looking, while the invalid codes can cause you to mis-detect the code word if you start at the wrong place.

[kens]

The radios are Icom F-30's. We reloaded the program to the radios and they seem to be working well. We tried them over a variety of typical ranges in the school and all worked.
Yes they are gradually converting to Motorola. We had to reprogram these for them to use until the next budget when they replace them.
Thanks again for the assistance.
Ken

[n0wmh]

some DCS codes are valid and some are not is that the valid codes have a special property that makes them always detect correctly no matter where in the data stream you start looking

What are the valid DCS codes?

[kcbooboo]

Here's the DPL table from the GTX RSS help screen. I believe the DCS table would be similar:

Valid DPL Codes:
023 071 134 223 306 411 503 631 734
025 072 143 226 311 412 506 632 743
026 073 152 243 315 413 516 654 754
031 074 155 244 331 423 532 662
032 114 156 245 343 431 546 664
043 115 162 251 346 432 565 703
047 116 165 261 351 445 606 712
051 125 172 263 364 464 612 723
054 131 174 265 365 465 624 731
065 132 205 271 371 466 627 732

Note that this is a 9-bit value, allowing for 512 possibilities, and these numbers are OCTAL (i.e. 0..7). The invalid codes would be things like all zeroes, all ones, or strings of four or more bits turned on, like 00x or 77x.

Bob M.

[Bat2way]

Never had any problems with range or sensitivity using DPL vs PL on Motorola radios other then TX rumble caused by DPL level setting too high. There was an old sheet floating around which specifically noted what DPL codes to avoid due to falsing or improper decoding abnormalities, if anyone may have it to share.

[Glen W Christen]

The only problem that I ever had with DPL was early Maxars which would take as much as three seconds to open. The factory fix was to adjust the detector idle level so that it was the same level as when the Tx was keyed. Problem solved.

[abrasowski]

This thread is a few years old but it is the first search result to pop up on google so I thought I'd contribute.

Recently had a similar issue with a garden center using Motorola radios. They had no PL/DPL code at all so we added a DPL code for them, no problems there. They ran into issues when they started adding Icom radios to the mix. Apparently Icom radios are not as good as decoding DPL (DCS) codes as Motorola (according to a good freind/Motorola buff). We received numerous complaints after they added the Icom radios about missed messages, radios can't hear each other, etc. Had to get rid of all of the Icom radios and keep them with Motorola. Since then have not heard any trouble from them other than the usual repairs.

No doubt in my mind that if we left them on carrier squelch with no DPL the Icom radios would mx fine with the Motorolas. Was not able to test the radios with PL to see if there was a difference PL vs. DPL.

[Stage 2]

Sorry to resurrect an ancient thread like this but, it has the topic I am interested in.

To the point, I am about to have one of the repeaters at work moved from a 450 MHz frequency pair to a 460 MHz pair. My part of this fun is I get to add the new 460MHz frequency pair to the 100 plus Motorola portables that are in service so, I want to get this right with the first try. My facility is a combination manufacturing operation with packaging machinery along with a sizeable warehouse that is a regional distribution operation.

A friend who is a radio tech prefers using PL tones as he tells me he doesn't care for some sort of "flutter" there is in DPL codes while the senior tech from my local Motorola dealer tells me he believes that using DPL codes would be beneficial in an operation such as ours. Full disclosure is we currently have 3 repeaters in service, all with pl tones and it seems one of them appears to sound noticeably crisp but at the same time it is used strictly by our warehouse personnel. The repeater being moved will be used plant wide. Both the warehouse and the repeater to be moved to the new frequencies are both Motorola SLR500's that were purchased at the same time and are only a few years old.

Can anyone help with settling the stalemate between my friend tech and our local service tech as to whether PL or DPL would be better? Both guys are nice but, I would appreciate not having to reprogram all those portables more than once.

Thanks in advance to all who reply.