SDR Help

[pathamilton1501]

Hey all.

I have just received my first SDR and I am trying to access P25 PII RMR (Regional Mobile Radio) systems here in Victoria, Australia.

I have downloaded the channels from Radio Reference and successfully imported those.
I am in-between 2 transmitters (16km~ from each) and I am sometimes seeing packets flowing in with the TSBK figure increasing but it seems to not be consistent. I can see site details, as well as extensive details on the 'neighbour sites' as well as the 'patches' tabs. I am however not hearing any transmissions whatsoever and nothing is updating on the scanner screen.
I just wanted to check if the SDR dongle I have obtained is potentially missing a crucial component or whether it's the current P25 PII issue with the app that may be at play. Another possibility is the antenna I am using. Please see links below for what I have purchased.
I am happy to purchase a RTL SDR V4 adaptor if I am sure that it will help to fix the problem.

As a backstory, I am trying to piece together a cheap DIY system for myself and my local fire brigade members as the official units by Uniden are approx $680 AUD to purchase and I just can't justify that!

Happy to help however possible to get this project off the ground and app store ready

dongle: https://www.aliexpress.com/item/100....order_list.order_list_main.35.32d21802u9kU4B
antenna: https://www.aliexpress.com/item/100....order_list.order_list_main.23.32d21802u9kU4B

Cheers,
Pat

 

[pathamilton1501]

Please see video attached regarding above:
screen-20260205-233111.mp4

 

[rgchristy]

I'm no expert, but just a few things I've learned the hard way:

I would be suspect of any SDR that is not genuine RTL-SDR Blog or Nooelectric.

This post was on Facebook:



The last comment got me...

Your antenna should work, but it's not designed for your VHF Hi system that's in your video. I had an antenna just like that and instead of throwing it out, I removed the mast and replaced it with a quarter-wave straight mast. I use it for POCSAG decoding in VHF Hi and I consistently decodes at 100%.



I have it mounted on a ground plane. I just moved the antenna to take the picture. It works great!

For my SDR, I use an external antenna.

Hope this helps some. Maybe someone that has that specific SDR could chime in.

Good luck Brother!

 

[pathamilton1501]

Thanks!
And apologies for not thinking of posting in a more specific section.

I’ve just ordered a genuine dongle from the official AliExpress store, and I’m also ordering a sturdy quarter wave antenna for the front of the car from a local seller that’ll stand the elements a bit more then the magnetic base ones. Will update on my progress

 

[rgchristy]

Thanks!
And apologies for not thinking of posting in a more specific section.

I’ve just ordered a genuine dongle from the official AliExpress store, and I’m also ordering a sturdy quarter wave antenna for the front of the car from a local seller that’ll stand the elements a bit more then the magnetic base ones. Will update on my progress

You should never feel the need to apologize on here. For most of us, this is a hobby and we're all here to learn and share. I don't know where else you would have posted your message.

This is a great forum for anything antenna related:

Antennas and Associated Hardware

Sub-forums for discussing various hardware for scanners and receivers such as antennas, filters, splitter/multicouplers and towers.

forums.radioreference.com

@mmckenna is a professional and a huge proponent or 1/4 wave antennas and rightfully so. There are many people that are excellent resources over there.

It's nice to see more brother and sister FF/EMTs involved, especially active duty. It give us retired old farts someone to talk shop with.

You can't go wrong with a genuine SDR dongle. It eliminates a possible variable out of the puzzle. That was one of the things that I didn't understand about the NEW GEN SDR that you posted. It had a strange antenna connection. I believe it's a push-type connector instead of a threaded one. I've never seen one on a SDR before.

Anyway, please keep us posted.

Oh, and welcome to RR!

 

[pathamilton1501]

It was originally on the Pocket25 thread as I didn't know whether it was app or hardware related, but now appears to be confirmed hardware.

Genuine adapter on the way which I believe will make a huge difference but have to wait for it to come across the ocean unfortunately.
I also have an antenna coming locally from Oz which will help to get me the best coverage while I am mobile.
I would still like to establish that everything works with a smaller antenna regardless as I would like to be able to help the other volunteers to setup their own systems (but ill probably try and source the hardware for them once I've nailed down what works).

In positive news following some advice sent via PM I have been able to get the adapter working on PC and there is a considerable PPM adjustment required in order to get it working even remotely correctly. The figure I ended up with was -80 which according to Google is extreme and not in the usual spec for those dongles. I did manage to get some P2 transmissions through although they were garbled and not able to be understood, but still a good start. Attempts to reproduce this result the following day failed - so I think the hardware I am using is just way too unpredictable for the purpose.

I will update as soon as the genuine adapter arrives and any differences noticed between the portable antenna and car mounted antenna, and hopefully I can start contributing some valid data to the Pocket25 threads soon!

Thanks for your support,

Cheers,
Pat