DPS (NEW) Band Plan

[mass-man]

Touche!!!

Mam1081...thanks for the correction! It is an interesting system the DPS has used for years...

I am dreading the move to P25...while I try to keep up with what is going on, I am lacking in my knowledge of P25!!! Guess it is a bit of laziness. Until Dallas moves PD and FD to something else, the old Pro2006 just scans away!!! I even found a BC101 and plugged the DPS freq. into it. Good to hear an oldie and goodie still working.

 

[VintageJon]

"Unless things change under a P25 scenario, the 155.46 is only the base transmit freq...the mobiles transmit on 154.68!!! A DUPLEX system. They can patch it to sound like a repeater, but most of the time it is duplex. The 159.21 system, is a true repeater. The DPS has used a duplex system for as many years as I can remember. Many years ago it was 42.90 for base and 42.74 for mobile"

This explains why I'm not hearing the mobiles. THANKS.

I hope to put 155.460 and 155.680 in a channel all to themselves so that the 91 scans between the two.
I reckon I'll stick 159.21 in there too.

Will post results...

73's
Jon

 

[mass-man]

Remember, the mobiles are going to have to be pretty close to you for you to hear them...I usually only hear the mobiles when I am mobile and see the trooper on his microphone asking for a 28/29!!!

73's...cleve

 

[VintageJon]

Somehow I double-posted. I've deleted this second, SORRY!
73's,
Jon

 

[DPS8504]

"Unless things change under a P25 scenario, the 155.46 is only the base transmit freq...the mobiles transmit on 154.68!!! A DUPLEX system."

Your scanner is not narrow band capable. There are going to be seveal frequencies that when the digital system gets going good that will splinter off the 155.460 and the other base station frequency of 155.445. Plus several other 159.210 splits. Since the scanners do not have the filters for the narrow band, they will pickup on what ever you have programmed in the scanner that is close.

 

[rattlerbb01]

My Pro 96 and BC785D pick up 155.4675, 155.4525, and 159.2175. Also, my Pro-96 goes even narrower, with 700 and 800 MHZ splitting with 6.25 khz steps. The only VHF supernarrow frequencies it can pick up are the 154.46375 and such that are used for telemetry. It would take a huge reworking of VHF to split further than 7.5 khz steps in the current band plan. Most narowband two way radios go off of 2.5 khz steps though, so I guess if the FCC allots 2.5 khz licenses for VHF, they would have to be digital to cut down on interference from close stations. Interesting topic for future discussion.

 

[nd5y]

You are confusing channels steps with emission bandwidth. You could receive all of those even if you only had 5 KHz steps. The signals you are trying to receive are 11 kHz wide or less if they are digital and 11 to 20 kHz wide if they are FM. According to the PRO-96 manual its selectivity is +/- 18 kHz @ -50 dB. That is a window up to 36 kHz wide. If you programmed 155.460, for example, you would also probably receive 155.4525 and 155.4675 as well.

 

[DPS8504]

Tom hit the nail on the head. The scanners may be able to program the narrow band frequencies, but they have not had the necessary filters and such built into them. You will get a lot of bleed over on close frequencies. I have Pro96 and have experimented with it and the motorola astro in my dps unit. The Pro96 does a good job of decoding the digital and you can program the narrow band frequencies, but the split frequencies will bled over into the scanner if they are in the 36 kHz range.

 

[VintageJon]

Hummmm, perhaps it would be better to use the Pro96 here as I could vary the bandwidth to some extent.
Perhaps this is the "off-freq" reception I mentioned in an earlier post in this thread...

This has given me some focus for my monitoring efforts, though time will be short for the next few days. The 3 freq experiment with the Pro91 has yeilded dismal results and I fear the this old girl may just be good for Aircraft and Ham. If so, so be it as it was a good scanner before APCO 25 and I sure got my money's-worth out of the 91 over the years.


73's
Jon

 

[nd5y]

From looking at the owners manual I don't think it is possible to manually change the bandwidth on a PRO-96.
It has a narrow filter for 25 - 28 MHz AM only and a wide filter for everything else.

 

[VintageJon]

Having read the whole page of posts here, I believe you are correct.

73's
Jon

 

[rattlerbb01]

OK, I catch you. I thought he was just referring to the steps. I have had experiences before with bandwidth bleedovers on adjacent channels. When I was living in Riverside and driving to Navasota on my days off, I used to have an old bearcat scanner without PL. I would get close to Anderson and pick up Grimes County SO bleedover on the Trinity SO channel 154.815 since I had both programmed. Being young to the scanner world at the time, I thought I had stumbled on a back channel!!! Noticed the same occurence on 154.800 when I travelled to Groveton.