Lscott
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Posts posted by Lscott
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25 minutes ago, WRYS709 said:
NOTE: How did such a discussion of ham radio dmr get into the GMRS subtopic?
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28 minutes ago, Guest larry said:
i know i am very late to this party.
but the yaesu VX6 is your radio,
they say good to 30 min under water down to 3 meters. unit is sealed up, has extras.
is a try band radio fits in your shirt pocket.
2meter, 1.25 cm, 70cm.
the battery is not so great do to the size of the radio so must have a second, but can be charged in your car or off any 12 V dc source. no cradle needed.
can be mars adjusted.
but the cost…. 3 - 4 US bills in 2024 new. and still in production.
Also NOT certified for GMRS.
For new users to GMRS the recommendation is to get a radio with Part 95A, under old rules, or Part 95E under the new rules certification. Some of the older commercial radios are certified under Part 95A and perfectly legal to use on GMRS. Plus, with some effort, they can be used outside of their official band split to allow operation into the upper half of the Ham 70cm band where the repeaters are typically located. Not all commercial radios allow this.
This is just one such example:
https://forums.mygmrs.com/gallery/image/263-tk-3170jpg/?context=new
The difference between a 4 watt verses a 5 watt radio isn't very significant. Some may recommend a higher power handheld radio. What you'll get is a much shorter battery life and a great hand warmer, burner, if the radios is used at high power for more than very brief transmissions. I've read where some people have destroyed their radio from heat, even at the 4 to 5 watt level, when used at high duty cycles.
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I've been monitoring 462.5325MHz here at the office. I'm only a few miles directly due east of that water tower. I am getting something on the CCR triband radio I use as a scanner. It's not real strong and just short transmissions, about a second or two at a time.
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20 minutes ago, WSBB368 said:
So I received my radio on Saturday and yes it’s a lot took me the whole day to figure it out but I have it set up now and have a somewhat good understanding of how to program it. You definitely need a hotspot to connect to the internet to use talk groups. I am just barely close enough to a repeater but the socal and California talk groups are pretty much dead. Someone will chime in every now and then but that’s about it. Gonna play with it some more today and see if maybe I’m doing something wrong
Sent from my iPhone using TapatalkMy biggest problem with DMR is the ever changing repeater settings. Identifying new talkgroups, deleting old talkgroups, changes in which network the repeater belongs to etc. I think I have a radio setup then a few weeks/months later it's all in the crapper and I have to update the zone for that repeater. PIA. DMR is nice, but the frequent changes aren't, and trying to find the current info is a crap-shoot.
This repeater example is one of the more messy and busy systems I've seen.
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5 minutes ago, SignallyCurious2 said:
Yes, that is too far away. You lose signal completely by 13 and greenfield
That's really poor coverage for a repeater system if it dies there.
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3 minutes ago, SignallyCurious2 said:
at this point my focus is gathering calls and extrapolating who it is, which will lead us to the result. I understand what you’re saying in theory, but it doesn’t add up to the real world results.
Stranger things have happened.
Had a thought. If it's a trunking system then there is an input and output frequency. You should see at least two pips on the spectrum display during each transmission. The lower power signal is likely the input. That one might be easier to zero in on since the area will be smaller and help localize the source.
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I looked up the address. Surprise, It's not where I thought it was. The address listed in the FCC's database shows its across the street from the golf course on Evergreen. It's looks like it's almost across the street from the Southfield City offices, library, court house and jail on the east side. They just recently built a couple of round-abouts there I believe.
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Well then it wasn't DMR after all.
The FCC database shows Delta Com is licensed for 462.53125, which is a standard frequency. The location shown is in Southfield, another is in Novi. NX48 is the very narrow mode of NXDN. This was the result of doing a search on digitalfrequencysearch.com under NXDN. Then looked up the license on the FCC's ULS license database.
https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseLocDetail.jsp?licKey=1925372&keyLoc=15068559
The building in Southfield I think is the huge gold coated glass building near Evergreen and 10 Mile in Southfield. Right across the expressway from Lawrence Technological University, LTU, and down the street from Channel 7 TV.
The signal might be a strong reflection off the water tower by the AAM plant in Royal Oak.
I can't monitor an NXDN trunked system using my Kenwood NXDN radios. The firmware will refuse to open the audio on the radio. It detects the packets are coming from a trunked system and as a security measure won't produce audio unless the radio is registered on the system. Entering the frequencies as simplex won't work either. I've been told that Icom NXDN radios would likely work, they don't have that quirk builtin to their firmware, however I can't confirm that.
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I’ve attached one of the DMR standards documents I have on file. Starting in section 10 the RF specifications start. That covers permissible frequency errors, slot timing etc.
Elsewhere the various types and headers are covered. The are about 7 documents for the base DMR protocol.
When reading the document “BS” is read as Base Station and “MS” as Mobile Station.
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Apparently there are some of the VHF NOAA transmitters connected to the studio/control site through a UHF link. See attached file. So far I haven’t had any luck with the UHF link frequencies but others might.
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This looks like it’s going off the rails.
I would quit looking at what’s coming out of the packet decoders until with 100 percent certainly the mode is positively identified. For the various modes the RF has some very characteristic features. For example DMR, P25 Phase-2 and Tetra are all TDMA based with particular bandwidths of the signal and slot timing. P25 Phase-1 is like NXDN, both are ONLY FDMA based. But, NXDN has two bandwidths, narrow and very narrow that are used.
Once there is zero doubt about the mode then worry what’s coming out of the decoders. For now it looks like garbage mostly. Even if the voice payload is encrypted the headers are not. It’s has to be this way for the state machine in the radio’s firmware to figure out what type of packet it is and what to do with it. If you’re getting good decodes then at least the packet type should be identifiable even if the payload is encrypted.
Assuming it’s a Motorola system then the encryption is likely one of several types, basic - enhanced - AES/DES.
The basic mode used on Motorola radios is a low bit count scrambler type proprietary to Motorola. It’s available on many of their digital radios.
The enhanced encryption is usually RC4, a 40 bit stream encryption, available on many radios besides Motorola. I have it on several of my Kenwood NX-1300DUK5’s.
https://forums.mygmrs.com/gallery/image/290-nx-1300duk5/?context=new
The AES/DES encryption is available on the higher end Motorola radios only, I believe, and on other manufacturers as well. It’s also on my Anytone D878 and D578 too at no extra cost.
Currently you’re not likely to find much in the way of decryption software since the FCC rules now make it clear it’s against the law to decode encrypted transmissions you’re not authorized to receive. The guys doing the SDR software have said they won’t touch it for that reason.
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3 hours ago, SignallyCurious2 said:
The frequency I’m measuring is the transmitter as I have confirmed multiple times through this process by adjusting the PPM of the oscillator via software used against stable, confirmed signals in the same band. The SDR is not part of the equation as I’ve done multiple controlled tests to rule it out.
Not to mention it’s a RSP1A, not some cheapo China boy.
What we are left with is a transmitter that is inbetween those channels. That’s what I’m here to figure out.
Microprocessor crystals are not that accurate compared to communication grade TCXO’s.
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1 hour ago, SignallyCurious2 said:
I have a HT but again, the freq they’re on isn’t centered so using anything it will sort of pick it up but it’s just interference between multiple channels unless you can tune inbetween channels.
If it’s really a transmitter you can only program in fixed step sizes unless it has a “true” VFO. The common usual step sizes I’m aware of by are 2.5, 3.125, 6.25, 12.5, 20 and 25 KHz. The frequency you’re measuring is likely a combination of the frequency error of both the SDR dongle and the transmitter’s reference oscillator.
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3 hours ago, SignallyCurious2 said:
another thing to note is there is a channel marker that aligns with a NXDN48 trunked system, it’s there all day / all night.
That’s the very narrow mode of NXDN. The bandwidth is only 6.25KHz.
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1 hour ago, SignallyCurious2 said:
It’s is a moto trbo NXDN trunking system operating in dual capacity direct mode, and contrary to what I thought, there is activity today.
NXDN is FDMA only. There is no TDMA mode, so it can’t be DCDM. The later is for DMR only. Motorola doesn’t sell any NXDN equipment I’m aware of.
Now if it’s really TDMA it could be a P25 Phase 2 trunking system. So far TDMA mode is only used with P25 on trunking systems, not used for simplex as far as I know.
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3 hours ago, SignallyCurious2 said:
This is the next step - readily available
That’s a Doppler direction finding setup. You see about the same thing on cop cars, Lojack system I believe it’s called.
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The mystery continues.
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1 minute ago, SignallyCurious2 said:
He said whatever this is, is not on their tower. He was very nice and knowledgeable, they only have 900mhz systems.
It looks like there are some cell phone slot antennas up there in the photo. I doubt those are 900MHz. I wouldn't trust their response just yet.
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Yeah, there is specific software for that sort of thing, CAD-AVL, Computer Aided Dispatch - Automatic Vehicle Location, applications.
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3 minutes ago, markskjerve said:
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.
Now that would start to make a lot more sense.
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10 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.
They have no idea whose antennas are on THEIR tower!
The repeater is likely in the small block house at ground level. Maybe if you could gain access to the inside you might find some contact info on the equipment. That would save you a lot of research.
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1 hour ago, WRYZ926 said:
@Lscott That's good information for those considering the BTech amp. 20 or 30 watts is still better than 5 watts when using a decent base or mobile antenna.
Yup, just don't expect to get the full boogie out of it.
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Still getting basically sporadic noise bursts.
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5 minutes ago, SignallyCurious2 said:
I had the best luck at 462.53188 as a “center”
Closest I can tune my radio is 462.53125MHz.
Would like to know what radio you are using
in General Discussion
Posted
OK, you asked.
https://forums.mygmrs.com/gallery/image/249-934916052_radiocollectionjpg/?context=new
https://forums.mygmrs.com/gallery/image/259-ca-2x4mb-jeepjpg/?context=new