I haven't looked to see if others organized large systems this way yet. I'm working toward having the MicroP25RX learn and store the network organization to flash memory (using LFS to prevent power glitch corruption of the file system). I think WACN-SYS_ID will work ok.
MicroP25RX
- Thread starter btt
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Thank you. I would probably ask for some IQ recordings if you were having issues with demod/decode with a BTT receiver. I think the P1 and P2 demod / decode is in pretty good shape now. I do wish I had more P2 activity around here. The state-wide Wa DOT system I mentioned a couple of posts back has some P2 subscribers, but they hardly use the system. Last winter it was pretty active when there was snow. Other than that, I might only hear 1 or 2 short transmissions per day.
I am just offering, only 2 P2 channels I have seen here. I want the micro2 so am offering my logs to help you out. I monitor the Palmetto 800 site with no simulcast problems in Pickens county, just a mile away from Greenville that I listen to. Just seeing if the logs from a simulcast system would help you.
BTT receivers love simulcast systems! I know if you read posts on RR, you will see a lot of people say that SDS-100 and SDS-200 are the only receivers that do a good job with simulcast. Not true. The P25RX, P25RX-II, and MicroP25RX work great with simulcast systems! Technically, the issue with other manufacturers and "simulcast distortion" is really an issue with traditional FM demodulation not doing a good job on the Pi/4 DQPSK (LSM) demod. If you watch the video I posted a few posts back, you will see why. FM is a constant amplitude and LSM is not.
I have been trying to find a portable solution for years. All my PC's and laptop work fine. They are to bulky for portable. I have a intel NUC running fine, but between the 5 inch screen a Power solution, aka a inverter it is not a solution Looking forward to the micro to come out. If you need a cash boost let me know, I am happy to pay 500 bucks to try one, if they come in at 200 bucks keep it toward research and development
Thank you sir, PC has been offering better reception for years. Same for satellite reception can't get this can't get 4.2.2, Use your damn PC solution.
Most people need hand fed now a day's. I for one do not, of coours I will have questions, but would never expect a solution just handed to me
I can if you also buy a $3k PC from me at the same time.Just to join the newbie crowd. could you build a scanner for 20 bucks that will receive every format on every band?
There is also a vendor-based limit to the number of sites per system.
Thank you!
I thought of another point to mention about the video. If you are looking at the span wondering why it is 24kHz, then you might be interested to know that is because it is a multiple of the symbol rate. For P1 this is 4800 sym/sec. After all the fir filtering, decimation, and rate-resampling, the final rate before demod/decode is 5 x 4800 or 24000 samples/sec. For P2, the span would be 30 kHz, or 5 x 6000 samples /sec.
The limit is in the standard. 8-bit site information, so 255 sites per control channel. That is probably why they broke it up like that.
150 sites (ASR and/or IP Simulcast) per ASTRO 25 zone (RFFS). That is the total number of Site ID's, obviously there can be more than 150 physical locations when you factor in IP Simulcast subsites.
It is a good question. I can't really say from my current location. I will record some IQ in one of the areas that sees multiple towers and post some images. Note in that last video I didn't have the reference frequency calibration done. I didn't catch that before making the video. When it is calibrated, the polar IQ plot has very well defined single-point peaks at symbol time (see attached image). I think as the delay spread increases, you will be able to see the effects of it, but I don't know how well you could identify it as such.
Attachments
I was going ask if you could sell the circuit board and we could install the parts from a list you supply. Then we could return it for final assembly?
The MicroP25RX analog boards have the passives installed and some of the semiconductors. I won't have as much work to do as the P25RX-II. Some of the parts are not common, but I have a large inventory of those. The digital board is a dev board that I am purchasing from a small business in Oregon. I don't know what his connections are in order to be able to buy MCU parts. Mouser, Digikey, Avenet, Newark do not have them in available. Chinese vendors are 10x to 100x higher for MCU parts right now.
The new LFS file system is working out nicely. It is fast, resistant to power-glitch corruption and is going to allow for some nice features. My current goal is to have the device be able to automatically self-configure for the most part. The rest of the configuration should be able to be easily done per site via the Wio buttons. The only thing that will require a PC is adding the talk group tags. That is the plan.
Another new development is the design of an enclosure that can be 3D printed by a regular in the forum here. There will be more information on that soon.
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