MicroP25RX

[maus92]

Those of us who need to monitor 700 MHz systems and have adjacent Band 14 are very interested in your solution, and what you might recommend in terms of filtering.

 

[KevinC]

Those of us who need to monitor 700 MHz systems and have adjacent Band 14 are very interested in your solution, and what you might recommend in terms of filtering.

I’ll be very honest, I was very disappointed in this product. I don’t own any other BTT products so this was my first exposure.

Maybe my composite power was too much, I don’t know. But filtering 700 LTE has brought this little device to life. Now I can start really playing with it.

And I’m not exaggerating at all when I say it’s a night and day difference.

 

[KevinC]

No need to let it run for a day or so, this has made a day and night difference. I may mess with gains to see if I can get it better, but right now I'm very satisfied with the results.

But Todd was very receptive to getting this going and as I posted even offer me a refund. I’m glad I didn’t take him up on this offer.

Thinking about composite power. I do have almost all TV stations in my area about 12 miles from me (probably about a dozen or so) with many ERP’s in the million watt range. So….????

 

[KevinC]

I have gains at “auto” and everything seems to be cruising along. I’ll try the 700 only sites more in-depth tomorrow, but the quick test has very good results.

 

[KevinC]

More thinking. I think I’ll try to filter out some of the blowtorch UHF TV stations and see if that makes a difference (leaving 700 LTE unfiltered). Unless Todd thinks this will be useless.

 

[btt]

More thinking. I think I’ll try to filter out some of the blowtorch UHF TV stations and see if that makes a difference (leaving 700 LTE unfiltered). Unless Todd thinks this will be useless.

I look forward to the results. Either way, I will setup here to make the ACRR measurements again. Your results so far seem to indicate the filters that I had on the rev1 design would have taken care of the issues you are seeing. Once the decision was made to remove them, I decided to match wide band to allow VHF systems with the lower-cost design. If there is enough interest, I could add another 700-800-only design with both filters / front-end switch. This would reduce sensitivity further. ~3-4 dB.

 

[maus92]

In urban / suburban areas where it is likely to have both 7/800 systems and Band 14 density, this would be useful if not required. In our area, VHF has almost disappeared (or regulated to FTO and legacy systems) wrt public safety, and UHF is now only used in mountainous areas. It's all 7/800 in Northern Virginia, Maryland and Southeastern PA, NJ, etc.

 

[KevinC]

After some some more open-stub filter tests I’m guessing the receiver was just getting saturated by all the UHF TV in my area. As I said I have about a dozen stations 12 miles from me on 2,000’ towers with ERP’s of a million watts on a lot of them. This also kills UHF on my Uniden scanners which is why I use the diplexer (the port for UHF and below has a band pass filter of 0-470 MHz).

I doubt most people would be in this situation so this should affect a small number of buyers.

 

[brndnstffrd]

It sounds like it didn't save the system information to flash for the site / sites before it disabled the LEARN MODE. You can enable the learn mode with the top-left button when in CONFIG mode. After entering a new frequency, the learn mode is enabled for a period of time. While in learn mode, system, site, frequency plan information is written to flash. It does keep track of hashes for this information so that it doesn't keep writing the information to flash continuously. It won't be able to import talk groups, alias information if the system/site information hasn't already been written to flash. This needs to be clarified better in the user manual. Another thing that needs to be added to the user manual is how to save the global configuration. You can save the global configuration information (including preferred startup frequency) by pressing and holding the top middle button for > 3 seconds when in monitor mode.

About how long would it need to stay in Learn Mode, because I am still having the same issue after retrying.

 

[btt]

About how long would it need to stay in Learn Mode, because I am still having the same issue after retrying.

Most of the time, it only takes a few seconds. On some systems, it may take 30 seconds. If the system has constant traffic, it may not get a chance to learn the system information. Try disabling TG Zone 1 while in learn mode to prevent voice traffic. Does that help? I can make some firmware changes to prevent voice traffic during learn mode.

 

[brndnstffrd]

Most of the time, it only takes a few seconds. On some systems, it may take 30 seconds. If the system has constant traffic, it may not get a chance to learn the system information. Try disabling TG Zone 1 while in learn mode to prevent voice traffic. Does that help? I can make some firmware changes to prevent voice traffic during learn mode.

Yea thats definately not happening for me. It shows that its learning some things in green, but even after leaving for a few minutes and repeating the learn process its still not working.

 

[btt]

Yea thats definately not happening for me. It shows that its learning some things in green, but even after leaving for a few minutes and repeating the learn process its still not working.

Please make a backup. CONFIG->SD CARD->BACKUP. email the microp25rx_backup.ini file or post here if you prefer.

 

[btt]

I made a few fw changes related to the "learn mode". This is available on the web site as the TESTING version.
2022-11-25-01

• Learn mode timeout is 30 seconds after enabling learn mode. Enabling learn mode will force re-learning CC information. During the learn mode timeout period, voice-traffic grants will be ignored. Learn mode is automatically enabled after manually entering a new frequency.

 

[maus92]

After some some more open-stub filter tests I’m guessing the receiver was just getting saturated by all the UHF TV in my area. As I said I have about a dozen stations 12 miles from me on 2,000’ towers with ERP’s of a million watts on a lot of them. This also kills UHF on my Uniden scanners which is why I use the diplexer (the port for UHF and below has a band pass filter of 0-470 MHz).

I doubt most people would be in this situation so this should affect a small number of buyers.

Luckily, there is only one TV transmitter near me, lol - conveniently located in the same antenna farm as one of the subsites of our state 700 system about 4.6 miles away. 521 MHz / channel 22 - it's the only OTA television that we can receive without an outdoor antenna. I don't think that it's an issue for me. However, there is a cell monopole about 700' away that I can see out my office window that has three carrier's equipment on it, ahem. My FirstNet phone works well here, lol.

There is a regular-ish pulsing of energy at 765.5 to 766.0 and 762.5 to 763.775 in Band 14 that *seems* to correlate with changes in the noise floor in the PS 769-775 band. Looking at this with non-calibrated Airspy stuff.

 

[KevinC]

Luckily, there is only one TV transmitter near me, lol - conveniently located in the same antenna farm as one of the subsites of our state 700 system about 4.6 miles away. 521 MHz / channel 22 - it's the only OTA television that we can receive without an outdoor antenna. I don't think that it's an issue for me. However, there is a cell monopole about 700' away that I can see out my office window that has three carrier's equipment on it, ahem. My FirstNet phone works well here, lol.

There is a regular-ish pulsing of energy at 765.5 to 766.0 and 762.5 to 763.775 in Band 14 that *seems* to correlate with changes in the noise floor in the PS 769-775 band. Looking at this with non-calibrated Airspy stuff.

I can’t guarantee anything, but I’d bet as long as your Band 14 isn’t smokin (-50 or better) you’ll probably be fine. I’m quite sure my issue was all the 1 megawatt TV stations.

 

[KMG54]

Yes I got mine today! Of course it came with two other packages that are not mine. Up and running and so far sounding good. Thank you Todd for all the work.

 

[KevinC]

I did the "hole in the case" for the reset button. For some reason I'm extremely good at eyeballing stuff like this (from my years of doing mobile installs I guess) so I nailed it. Whew!

 

[KMG54]

I am waiting for cases to be in stock, running naked right now.

 

[btt]

I am waiting for cases to be in stock, running naked right now.

I have both the original white and also the high-temp black available. The white enclosure is available as an option on the product page. If you want the high-temp/black version, email me.

 

[KMG54]

Email sent.