Getting traffic on distant trunk sites. How?

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KR7CQ

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Actually it's not nearly the same for VHF vs. 800 MHz just because of the physics:

~The higher the frequency the greater the path loss~

Path loss through 100 miles of free space, with 3 db gain transmitter and 0 db receiver gain @ 50 MHz = 107.6 db
Path loss through 100 miles of free space, with 3 db gain transmitter and 0 db receiver gain @ 155 MHz = 117.4 db
Path loss through 100 miles of free space, with 3 db gain transmitter and 0 db receiver gain @ 850 MHz = 132.2 db

Free space path loss calculator:

Free Space Path Loss Calculator

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Thank you.
 

KR7CQ

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i pick up a digital trunking system that is on 154.370c and it is 93 miles from me on a daily basis but i cant pick up some digital systems that are 50 miles from me

I've seen VHF do amazing things at times. UHF is much more predictable than VHF, though I've seen some magic there too. 800 MHz? Never seen it in any of the states I've played with radios in. But still I would be happy to hear examples that show otherwise.
 

nd5y

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~The higher the frequency the greater the path loss~
That means nothing if the signal you are receiving is stong enough to overcome path loss.
It's not unusual for me to be able to receive 700/800/900 MHz stuff from over 100 miles (relatively flat, no mountains, not heavily forested) with indoor yagi antennas.
 

slicerwizard

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Unfortunately, I don't check for DX in the 770 MHz band very often, so I can't say how often this happens here. Likely not that often. I'm sure the lakes helped a lot.

I've also picked up 770 MHz control channels from 180 km / 112 miles with an all land path a few times. Definitely not common though.
 

mortoma61

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there is a thing called radio propagation or skip. This is how the atmosphere handels radio signals during the day. living in the desert where you live you may very well be hearing something 100 miles away. There are so many other factors that come into play that its not funny, but if you do some basic homework you will learn a lot.

I would suggest reading up on radio propagation and see how signals work with atmospheric conditions during the day or over night even sometimes.
Nope, these distant sites can't skip consistently on such high frequencies over a long period of time. High UHF does not skip unless something really weird and sporadic is going on. So any such skip would not last long, and for sure not every day for weeks or months. Some of the other posts in here I think explain what's going on and it ain't skip. I used to be a ham radio operator (Advanced class, still licensed but not active) and forgot a lot but I do remember that high frequency skip would be very limited in duration and very rare.
 
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mortoma61

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It's probably more likely that it is a re-use of frequencies and a scanner can't differ between different sites in a SmartZone system and will display whatever are programmed to a sites frequency in the scanner.

/Ubbe
I think UBBE is onto something. It is not skip lasting for weeks. Just the way Motorola Smartzone systems work, which I still am learning about. Probably none of those signals actually came for those locations that far away. If I took the 'avoid' off of St. George Simulcast (the site that's over 300 miles from here) I'd probably start picking stuff up on it again but it would actually be from a more local site much closer on one of the same frequencies, the scanner would say 'St. George Simulcast" but it's sort of a lie I guess. It's a Smartzone trunking lie, courtesy of Motorola Corporation!!
 

mortoma61

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Some programming software imports all frequencies for all sites when only the primary and alternate control channels are needed. This creates a lot of potential for overlapping frequencies and false positives. Looking at the two sites you mentioned and the database reveals the "Howell" is probably Provo-BYU and "St. George Simulcast" is probably Utah County Simulcast.

Howell
851.175 - Provo-BYU Primary Control Channel
851.3125
851.9375c - Wasatch Simulcast Alternate Control Channel
857.7625a - Currant Creek Alternate Control Channel
859.5125

St. George Simulcast
851.1875 - Willow Peak Primary Control Channel
851.600
851.8375
852.0375 - South Mountain Alternate Control Channel
852.275
852.6625a - Utah County Simulcast Primary Control Channel
853.1875
853.6125c - Scotts Peak Primary Control Channel

You, UBBE and marksmith are the winners, (there is no prize, sorry) this is apparently what's happening. The skip posts are wrong in this case but I thank all for opinions and trying to sort it all out.
 

sparklehorse

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<snip> I'd probably start picking stuff up on it again but it would actually be from a more local site much closer on one of the same frequencies, the scanner would say 'St. George Simulcast" but it's sort of a lie I guess. It's a Smartzone trunking lie, courtesy of Motorola Corporation!!

To be clear, it’s not a Smartzone trunking lie, courtesy of Motorola. You would not have this issue on Motorola equipment. When designing radio systems, The Big /\/\ does not consider how well their systems will work on consumer grade scanners. The issue you’re having is due to the improvised ways consumer scanner makers have devised to handle big multi-site trunk systems without incorporating all of the proprietary Motorola hardware and software used in commercial radio equipment. It’s not really a “lie” per se, it’s just an undesirable byproduct of an imperfect solution.
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slicerwizard

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It's a Smartzone trunking lie, courtesy of Motorola Corporation!!
When designing radio systems, The Big /\/\ does not consider how well their systems will work on consumer grade scanners. The issue you’re having is due to the improvised ways consumer scanner makers have devised to handle big multi-site trunk systems without incorporating all of the proprietary Motorola hardware and software used in commercial radio equipment. It’s not really a “lie” per se, it’s just an undesirable byproduct of an imperfect solution.
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No to both. Trunk sites broadcast their site numbers and scanners can use those broadcasts to properly display site names and numbers. Any failure to do so comes down to dumb firmware coding by the scanner manufacturer. Trunking decoders like TRUNK88, Unitrunker, DSD+, SDRTrunk, OP25, etc. are always going to display the correct site name/number - go figure.
 

sparklehorse

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No to both. Trunk sites broadcast their site numbers and scanners can use those broadcasts to properly display site names and numbers. Any failure to do so comes down to dumb firmware coding by the scanner manufacturer. Trunking decoders like TRUNK88, Unitrunker, DSD+, SDRTrunk, OP25, etc. are always going to display the correct site name/number - go figure.

Which is why I said, “it’s an undesirable byproduct of an imperfect solution”, meaning an imperfect solution on the part of the scanner makers.
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slicerwizard

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No, you wrote "The Big /\/\ does not consider how well their systems will work on consumer grade scanners. The issue you’re having is due to the improvised ways consumer scanner makers have devised to handle big multi-site trunk systems without incorporating all of the proprietary Motorola hardware and software used in commercial radio equipment." which implies that an incorrect display is due to the quoted factors, which it is not. Motorola has made no concessions for the trunk decoding software I listed nor does said software use any proprietary anything, yet that software displays correct information.
 

GTR8000

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+1 to @slicerwizard's posts

There is nothing "proprietary" about the Site ID on either a Motorola SmartZone 3600 system, or a standard P25 9600 system; they are encoded in plain sight (no pun intended).

The fault lies entirely with the scanner manufacturers, who long ago made the conscious choice not to incorporate the Site ID in the programming. In fact, they don't even make use of the SysID or WACN-SysID, which are also in plain sight. Instead the scanner simply locks onto the very first control channel it finds in the list of programmed frequencies that matches the system type, and away it goes.

The laughable part is that if you put most of these scanners in any sort of control channel quick-tune or "analyze" mode, almost all of them readily display the SysID or WACN-SysID, as well as the Site ID. In other words, the scanner is perfectly able to decode those parameters, but still doesn't use them when you program the system.

The obvious side effect is that any co-channel usage by an undesired site that the scanner is able to receive may result in the scanner locking onto that site, not the one you're expecting (as the OP has discovered).

At least the Uniden SDS series can have the Site NAC programmed, which may convince the scanner that it's locked onto the wrong site. Of course this assumes that the system is setup with unique NACs for sites that share frequencies. Unfortunately, that is not always the case.
 

kayn1n32008

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Ok, those of you who have ducting and knife edge propogation with frequencies over 800 MHz please speak up and share that fact here. Lets see how many are seeing this.

Arizona has some pretty tall mountains too, but more than having the transmitter on that high mountain, you have to have nothing between you and that mountain that is 100 miles away unless we are saying that 800 MHz signals are being ducted or are following knife edge propogation. Think about it. How many mountains can most people see the top of from a hundred miles away?

800 MHz just does not propogate like VHF.

I have seen ducting where you can key UHF repeaters 100mi plus away with 5 watts and get 20 over S9 signals back.

Ducting can and does effect 800MHz. A good friend that hunts cellular interference in Alberta sees ducting, because he has tools that allow him to see 3G and LTE site data.

We also see ducting with our province wide 700Mhz P25 Network. Just because YOU don’t think it happens does not mean that it does not.


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KR7CQ

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I have seen ducting where you can key UHF repeaters 100mi plus away with 5 watts and get 20 over S9 signals back.

Ducting can and does effect 800MHz. A good friend that hunts cellular interference in Alberta sees ducting, because he has tools that allow him to see 3G and LTE site data.

We also see ducting with our province wide 700Mhz P25 Network. Just because YOU don’t think it happens does not mean that it does not.


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I said ducting would be rare and sporadic above 800 MHz and said that I haven't observed it personally, asked for examples, and thanked someone for providing their example. Still, as slicerwizard said, ducting is probably doubtful here.
 
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