why do i receive distant sites instead of local sites

[tvengr]

i monitor and live in Richland county, however i regularly receive towers (sites) several counties away instead of my local towers(sites) why is this? i am using a wilson 6 element yagi. and monitor the ohio marcs radio system. Thank you.

Statewide systems reuse control channel frequencies on sites that are widely spaced and out of range from each other. Unfortunately, most scanners cannot differentiate between which site you are actually receiving. If a site at the other end of the state using the same control channel frequency as your local site is received first while scanning, the scanner will stop on that site. The scanner does not know the difference. The SDS100 and SDS200 scanners can use site NAC and are able to recognize which site you are receiving. Unless you are using a SDS scanner, the only way to eliminate false sites is to lockout, avoid, or delete out of range sites.

 

[mlc5eleven]

Statewide systems reuse control channel frequencies on sites that are widely spaced and out of range from each other. Unfortunately, most scanners cannot differentiate between which site you are actually receiving. If a site at the other end of the state using the same control channel frequency as your local site is received first while scanning, the scanner will stop on that site. The scanner does not know the difference. The SDS100 and SDS200 scanners can use site NAC and are able to recognize which site you are receiving. Unless you are using a SDS scanner, the only way to eliminate false sites is to lockout, avoid, or delete out of range sites.

I found this reply interesting, so I did a little research. The MARCS tower site I'm closest to uses 8 frequencies - 2 are control frequencies. I did a simple search for each of those frequencies to see what other towers are using those frequencies. 1 of the control frequencies is shared (but not as a control) with one other tower location. The other control frequency is shared with two other towers (also not as control frequencies). Of the remaining 6 non control frequencies , 2 are shared with 2 other sites, 2 are shared with 3 other sites and 2 are shared with 4 other sites. The most interesting fact is that one of the control site frequencies on my close tower is in fact showing on my display occasionally as one of the other sites. I'm scanning these on a Whistler TRX-1, so that makes more sense. Great input and point and you've now caused me to dig a little deeper.

 

[mlc5eleven]

So I think tvengr's reply is your answer. At least explains my TRX-1. When it's identifying sites, it must be doing it solely on a control frequency it's seeing and then identifying it as another frequency used at a diffrerent tower site. In fact, I'm fully convinced. One control channel on the Shelby tower shows up as Shelby, although it shares a frequency with Lake. The other will show up as New Lexington (Perry). A couple of days ago toward Lexington, I was showing I was hitting Rarden (Scioto) which is shared with Steam Corners (Morrow). Certainly I was hitting Steam Corners.

 

[Swipesy]

See Post #19 and there was your answer. You and TVengr are late to the party!

 

[wa8pyr]

I think it is because I have all 212 marcs sites enabled and my scanner is miss identifying them. Only thing I can come up with.

Yes, that's what I said in message #14.

 

[Swipesy]

Yes, that's what I said in message #14.

Yes Tom you did and to give credit where due you are the one who educated me to the OP's issue way back when MARCS came into existence about duplicate tower frequencies.

 

[mciupa]

Everyone must have missed my post in #6.

 

[mlc5eleven]

Yep, you're all right. I guess I glossed over and didn't catch them. I think I was just ticked at the discovery that is how the Whistler scanners identify tower sites. Garbage.

 

[wa8pyr]

Everyone must have missed my post in #6.

I did. Dopey me!

 

[wa8pyr]

Yes Tom you did and to give credit where due you are the one who educated me to the OP's issue way back when MARCS came into existence about duplicate tower frequencies.

Glad I could help! That issue bit me as well; same problem the OP is experiencing. I learned the hard way to set up different systems containing only the tower sites in the area I want to scan.

With Uniden's NAC feature it would almost be a non-issue, but the Whistler/GRE scanners don't have that feature.

 

[AA4BK]

Glad I could help! That issue bit me as well; same problem the OP is experiencing. I learned the hard way to set up different systems containing only the tower sites in the area I want to scan.

With Uniden's NAC feature it would almost be a non-issue, but the Whistler/GRE scanners don't have that feature.

Both Uniden and Whistler have advantages in different areas, but overall I do like my Unidens a lot and mostly prefer them because of most of their features. That NAC feature is really nice but it would be a lot more effective if sites would actually use it properly. I don't know about MARCS-IP but I know where I'm at (not Ohio) the NACs are not used very well. Sometimes even adjacent sites will have the same NAC, for example. So the NACs aren't always reliable depending on how the radio system you're monitoring is set up. But yeah it's a nice feature if you can use it!

I do like the Whistlers for the audio automatic gain control and so on though. They have some nice features too for sure.

 

[tvengr]

Sometimes even adjacent sites will have the same NAC, for example. So the NACs aren't always reliable depending on how the radio system you're monitoring is set up

Adjacent sites will not use the same control channel frequencies so having the same site NAC doesn't matter.

 

[AA4BK]

That may be so, but I have two sites within range of me that have the same NAC and they're in completely different counties and cover different agencies. So while they may not be "adjacent" they're both within receive range of my scanner using an omni.

 

[tvengr]

That may be so, but I have two sites within range of me that have the same NAC and they're in completely different counties and cover different agencies. So while they may not be "adjacent" they're both within receive range of my scanner using an omni.

Are those sites using the same control channel frequencies? If not, there is no problem.

 

[AA4BK]

Are those sites using the same control channel frequencies? If not, there is no problem.

Not all of the control frequencies are the same but they share at least one and maybe two, yes. That's what I mean, they're sharing the NAC but yes they have at least one common control frequency. I'm not trying to be argumentative but it's one of the first problems I ran into and had to figure out when I first got the scanner. I think it doesn't affect either agency though because I'm kind of in the middle of both and if you're in the area either agency covers, the other is probably out of range. It's just that I'm kind of in between and just in range of both. My whole point is this does happen. It's probably not really common because you need both common control frequencies and the same NAC though.

 

[wa8pyr]

Not all of the control frequencies are the same but they share at least one and maybe two, yes. That's what I mean, they're sharing the NAC but yes they have at least one common control frequency. I'm not trying to be argumentative but it's one of the first problems I ran into and had to figure out when I first got the scanner. I think it doesn't affect either agency though because I'm kind of in the middle of both and if you're in the area either agency covers, the other is probably out of range. It's just that I'm kind of in between and just in range of both. My whole point is this does happen. It's probably not really common because you need both common control frequencies and the same NAC though.

On Ohio MARCS, there are no adjacent sites using the same control channels, whether primary or alternate. That's by design.

There may be a site about 70 miles away (or more) sharing a control channel, but it will not be an adjacent site. In that case, the shared frequency will be the primary at one site, and an alternate at the other. This is to prevent interference as much as possible.

Both sites might be in range of whatever you're using to receive them (for example two sites separated by 70 miles with you right in the middle), but they will not be adjacent sites as far as the system is concerned.

If you're monitoring a system with adjacent sites that are sharing active control channels and the same NAC, somebody seriously screwed up in the design department.

 

[AA4BK]

I agree with you and Ohio MARCS-IP sounds very well designed!