A possible solution to P25 simulcast reception

[SCPD]

I live 4.5 miles from the closest node and the 2nd closest node is 6.5 miles away and am just off center of the two. i built a 5 element beam and it was great for analog systems in the next county but no help locally. I could null the data channel some but not even to stop the multipath problem.

With a portable GRE PSR-500 I was getting frustrated as 50 to 70% packet loss on a 800 quarterwave and the elevated quarter wave and stock antennawas worse. The best antenna was larsen yellow tip 150mhz 10 inch koolduck it worked vhf and 800 adequately but was still 30 to 40% packet loss on P25.

THE BEST SOLUTION (for me)

If the pringles can works on 2.4 GHZ then a 6 to 7 inch coffee can should work on 800 MHZ. Separate a RG-58 for 3.5 inches... drill a hole in the can 3.5 inches from the bottom along the side. I used the seam insert the 3.5 inch center of the coax with the clear insulation still on it take the braided side and SOLDER a 1 inch piece of it to the can (2.5 inches can be discarded. This is a super corner reflector directional antenna or a quasi wave guide that will HELP shield any signals coming in from the side. ITS NOT PERFECT But Im in the 95% copy mode right now and actually able to hear completed messages on my PSR-500. As a bonus I can still copy the analog statewide system. Not perfect but a near free compromises that is working.............Have to use a 2nd conventional scanner for the 450 and below stuff..

 

[SCPD]

Added a second plated type can in front of the other can. It makes it more directional but its not 100%..I did not mention I lived in a HOLE !! Sorta like dealing with an HF sideband signal from time to time..

 

[SCPD]

Now what I'm finding out is I live in a hole. the 2 cans sharpen the signal but I only have 70 to 88 percent data channel strength with the 6 inch diameter can I may not be passing signal like I should with the smaller diameter waveguide. It may be a directional negative gain antenna... This is experimentation right ?

 

[MTS2000des]

I've found the best solution...

is to use a receiver with a proper I/Q demodulator and superb performance. I get perfect reception of many simulcast systems with stock rubber duck antennas anywhere I go, no fancy tricks needed using these widely available commercial radios and the well documented "no affiliate" scan method.



Maybe someday soon the scanner manufacturers will get with the program too.

 

[6520tkp]

P/25 Reception

Can u provide a picture of your antenna.

P/25 reception is terrible here also, I have a yagi ordered and is on it's way.

Thanks.

 

[cmdrwill]

Here is what a friend in Michigan had to do to get 800 P25 Trunking clearly. He is in the middle of four simulcast sites.

 

[MTS2000des]

That is pretty sad cmdrwill. Not real fun to have to haul all a huge piece of foil lined cardboard with a handheld scanner just get it to work.

I have a BC-996T with a Radio Shack 800MHz whip attached through a small right angle elbow BNC adapter, and it is pathetically horrible on my county DTRS. No matter what I do it won't even come close to the super clean performance of my 11 year old well worn XTS5000.

Maybe I should try what people used to do by putting balls of aluminum foil on the tip of their TV antennas? Seems to have worked miracles back in the 1950's!

One day the scanner manufacturers will get it right. I hear SDR users with OP25 are getting perfect decode of LSM on their $15 dongles with free software. But not real practical to carry that around under your coat.

 

[SCPD]

That is pretty sad cmdrwill. Not real fun to have to haul all a huge piece of foil lined cardboard with a handheld scanner just get it to work.

Look at it this way... he can always bust a quick move and put that foil on his head when things take a turn for the worse.

 

[MTS2000des]

yeah you got a point there. That makes it more utilitarian!

 

[cmdrwill]

Sorry the photo got tilted on it's side. Maybe the RR did that so it would fit..

That corner reflector does shade out the three other 'towers' so he does get better reception. But as you point out it is not practical for mobile use.

The shorter 1/4 wave antenna did help. The poor old scanner was getting swamped...

 

[RFI-EMI-GUY]

That is like only 10.8 uS time differential. Are you sure you are not getting signals from another site much further away?

I live 4.5 miles from the closest node and the 2nd closest node is 6.5 miles away and am just off center of the two. i built a 5 element beam and it was great for analog systems in the next county but no help locally. I could null the data channel some but not even to stop the multipath problem..