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MarkInTampa

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Posts posted by MarkInTampa

  1. 6 minutes ago, SignallyCurious2 said:

    Here is the antenna on servicar building, they have antennas on all of their busses too, couldn’t find much online for them but didn’t dig too deep, either. 

    IMG_0075.png

    From ServiCar's website:

    RADIO COMMUNICATIONS - All of our School Buses are equipped with two-way radio communications with our dispatch center. Our system works off of three separate repeater stations on our private 900 MHz frequency through-out the Metro-Detroit area, providing us with communications through-out and beyond the tri-county area. They are also equipped with direct talk around for trips outside of the coverage area where communications between buses is needed.

  2. 5 minutes ago, SignallyCurious2 said:

    SOCWA with the water tower called back, it is not them but they’re also interested and going to help out. 
     

    That’s how the transmissions are for me too, most of them data, very very few actual calls more than 1.2 sec. Latest call so far was 4:45pm.

    If I had to guess they are running MotoTrbo GPS tracking on the radios. The GPS system can be programmed to poll the radios every 10 minutes or every 1 kilometer of movement. They are short bursts, around 600ms to 1 second. If a car is moving it sends a lot more traffic than if it doesn't. 

  3. 8 minutes ago, Lscott said:

    The oscillator in the repeater also could be off frequency a bit too. I have heard of some repeaters where they use an OCXO, Oven Controlled Crystal Oscillator, for very high frequency accuracy.

    I think the cheap SDR dongles use a simple TCXO, Temperature Compensated Crystal Oscillator, module. The usual specifications for those are +/- 0.5 PPM, Parts Per Million, frequency accuracy more or less.

    Usually portable or battery operated equipment use the TCXO module since the power requirements are way to much due to the electrically heated oven on an OCXO module.

    Understanding Ovenized Oscillators.pdf 126.47 kB · 0 downloads

    I have first hand experience with the SDR being slightly off frequency. I picked up a DMR HT awhile back and the strongest DMR repeater I could pickup showed as 443.188 on the SDR and couldn't find it listed anywhere to program the HT. Also searched a bit and above the frequency online and couldn't find it anywhere. I mentioned it to one of the area guys I talk to on D-Star also is really into DMR and he found that the frequency was actually 443.1875 and he got the ID. He ran the ID and got one single hit on it on the internet - on one of the area club's webpage that also showed all the programming information and talk groups. It's not listed anywhere else. I learned not to put a lot of faith with the SDR being spot on.

  4. 42 minutes ago, Lscott said:

     

    The closest to your frequency of 462.5325 is 462.5375. Given the tolerance of the oscillator in the SDR dongle this could be it. It's off by only 5.0KHz.

     

    The closest is actually 462.53125, same company (Deltacom) and licensed for trunk service. It's only .13 KHz down. Also 462.5325 isn't standard spacing, FCC only shows 2 experimental licenses in the the entire country and 100's licensed for 462.5312 I'd vote the oscillator is a bit off. With a SDR dongle using SDRSharp and Simple DMR decoder, I can decode DMR +/- 1KHz easy.

  5. 1 hour ago, SignallyCurious2 said:

    With my gain set all the way down, the strongest signal reading yet is behind AAM, next to the water tower. 
     

    it’s either on the water tower at 2725 Samoset Rd royal oak mi 48073

    inside AAM

    On the rail tracks proper, owned and operated by CN - maybe this is a Canadian system?

    Try running the address on https://www.antennasearch.com/ . It maps out both registered and unregistered towers that the FCC doesn't show, might give you a bit more to go on.

  6. 46 minutes ago, Lscott said:

    Flex-N-Gate is licensed for 462.5125MHz per FCC database. Emission is narrow band FM.

    Plant location in database is BATTLE CREEK, MI CALHOUN County.

    https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=3494581

    I wonder if somebody was miss programming radios for DMR and they ended up at the R.O. location.

     

     

    I spotted that as well but figured it was highly unlikely. 90 miles away from Oakland County (where the OP said he was) - also licensed for 2 watts.

  7. 3 minutes ago, SignallyCurious2 said:

    It is not, the gentlemen at delta com has confirmed this already. 

    It's so close that I don't know if most radios could tell the difference, especially in wide band. Not a lot of difference between 462.5325 and 462.53125. 

    Ether way, if it's its illegal good luck getting the FCC to do anything about it. There is a illegal encrypted DMR repeater near me that runs on 462.700 that has been reported countless times over the last year by lot's of folks. FCC hasn't done much about it. It's forced a local repeater to change frequencies and has rendered the frequency unusable.

  8. The strongest by far repeater in my area runs on 462.575 with the standard input of 467.575. It also has an alternate input on 467.725 with a dpl instead of ctcss tone on the same tower. It gets interference every now and then on the primary input from foreign ships in the port and the primary input gets shut down. The problem is some radios don't allow for anything other than a 5MHz split or split tones and it kinda locks them out until the primary input is turned back on.

     

  9. I ran a VGC VR-n7500 for a bit on the base station. It's basically a headless bluetooth app controlled mobile. With the app loaded and connected bluetooth using a cheapy tablet on WiFi you can use the radio anywhere on internet (or in on your home WiFi) using their app (kinda like Zellow) for free on any Android device. It actually worked great, got good reports on audio but hated the interface so it sits in a drawer...

  10. When conditions are good, I've checked into the Taylor County (Florida) repeater net from Brandon, FL - repeater is 170 miles north of me and talked with a guy in Quincy, FL that is 68 miles northwest of the repeater. 230 miles as the crow flies. 

    On the daily, 71 miles as the crow flies. 45 Miles to the Sarasota repeater south of me and 35 miles further south talking to folks in Port Charlotte.

  11. I scored around 300ft of hardline and had the same question. I watched Youtube videos on how to terminate the cable, tools required, etc. Since the connectors are around $25/each I didn't want to screw it up. I ended up just measuring how long I wanted the cables and took it to the local Motorola shop. The local shop is very active in the ham radio world and has a club station. I bought the connectors and they cut the cable to length and terminated them for free. Don't know if you have somebody around that has the tools and knowledge, it might be worth checking around.

  12. 42 minutes ago, PugetSounder said:

    Great idea. I'm going to check this out. I think I read somewhere that transmitting without an antenna would damage your radio? Is that untrue?

    Also, could you tell me how you got your screenshot? I fiddled with it for a bit and finally gave up and used a camera.

    FYI, found this YouTube video explaining how to set the ppm value...

     

  13. 22 minutes ago, PugetSounder said:

    Great idea. I'm going to check this out. I think I read somewhere that transmitting without an antenna would damage your radio? Is that untrue?

    Also, could you tell me how you got your screenshot? I fiddled with it for a bit and finally gave up and used a camera.

    On one watt for a few seconds at a time you aren't going to hurt the radio.

    Windows Clipboard is your friend ;)

  14. Sounds like you have not calibrated the SDR receiver/dongle from within SDR# software. Click on the gear icon within the software and adjust the frequency correction (ppm) to a known source. I use a HT set to a known frequency (in this case 462.625) on low power, no antenna and narrow FM to keep from overloading the front end of the SDR and keep the FM width as narrow as possible to adjust the ppm. Not lab perfect but close enough.

     

     

    tt.jpg

  15. I was a ham 30 years ago, just had a tech license but liked hanging around some of the VHF/UHF repeaters and made a few friends. The problem was we had two radio clubs that hated each other. If you got caught talking to the wrong person, you were shunned by one group or the other. It became a old wives club. I let my license expire, moved across 3 different states in those years and decided to give GMRS a try a bit over a year ago to see if I wanted to play with radios again.

    I got to be friends with a few guys on GMRS that went on to become ham's so I got went ahead on got my ham tech license back as well. For the most part I usually use simplex on ham and maybe one or two repeaters on occasion out of dozens available to me, just like the more more relaxed feeling of GMRS and the folk's I've met over the past year or two.

    The sad part is I was out riding my bike around 15 years ago through a park when it was field day. When I got back home I threw a few boxes of radio gear (a few radios, Astron power supply, SWR meters and the like that I had not used in since in the hobby) in the car, dropped them off at the club table and told them to do whatever they wanted with it. I wish I had it back. Oh well....

  16. Mixed thoughts. I used linked repeaters around me for a bit and it wasn't for me, just too much out of state traffic. If it gets a new user on GMRS excited about the radio hobby I guess that's a good thing. 

    The biggest issue I hear around here anyway if there is a bad user, repeater, kerchucker, radio, or whatever instead of affecting one repeater you are affecting many repeaters. The sad part is I was one of those bad users - I sit right between 2 repeaters on the same freq and tone, each around 35 miles from me and 70 miles from each other. One repeater is up 400ft and hits me full scale, the other is somewhat new that is networked at around 50ft hits me around S-2 on the meter. I can hear them if the 1st isn't in use but cant use it because the 1st repeater will bury it. I had no idea that I was hitting the 2nd repeater and causing a bit of chaos on the network. I have to drop my power down to 5 watts to avoid keying the 2nd repeater and have to monitor the 2nd repeaters network status page on the web to confirm I'm not keying it. It still happens even at 5 watts every now and then. Oh well, live and learn.

  17. I've got a couple of TYT MD-380's UHF DMR/Analog radios I've been pretty happy with. Not super cheap but not to bad, around $100 new. Part 90 certified and covers 400-480MHz, DMR, Analog (wide and narrow band), superhet receiver and aftermarket firmware if you want. They have been around for quite awhile and are pretty well known. I bought mine because a couple of guys were using them on a local GMRS repeater (analog of course) and the audio quality was outstanding and wanted something to play with on 70cm DMR. The biggest issue was figuring out the DMR code plug, nothing like a analog radio. That was a year or two ago, now for the same money you can get dual band DMR HT's but don't use a HT enough to try one out.

  18. 1 hour ago, Lscott said:

    Actually I was looking into dPMR radios, at one time. I still am occasionally. There are "license free" dPMR446 ones, for use on 446.0 to 446.2 band in the EU, but they are limited to 0.5 watts.  dPMR isn't used, or so minimally it doesn't exist as a practical mode here as far as I can tell. I was looking into it as a novelty. I have the radio programming software for Kenwood's TK-3701D dPMR446 radio, but no radio.

     

    TYT DP-290 DPMR HT perhaps?

  19. I've got a HT with a female SMA antenna connector and the center pin on the antenna broke in the connector somehow. The broken pin is buried deep enough that you can't really see it much less pull it out with tweezer's. I tried a kind of strong refrigerator magnet but that didn't work. Anybody know of a way to pull the pin without having to disassemble the radio?   

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