Strange Reception Issue on One Freq

[emsflyer84]

Hey all, I’m running a setup to supply a feed to Broadcastify in my county. It all works well with good reception. There is one analog vhf high frequency that has a funny issue. It’s also one of the closest regarding transmit sites, etc. This one frequency is dispatch for multiple fire departments. I’m not sure how it all works, but when different departments are dispatched they all sound different, some more clear then others, so I’d imagine they are using the same frequency but different towers depending on the department.

When the two departments closest to me are dispatched, the transmission goes from crystal clear to lots of static and actually cuts out, then back to clear again. It happens randomly. If I had to describe the effect, to me it’s like wind, or something like that, the way it swings from clear to unreadable back to clear again. It only happens on one frequency and only when one particular tower is being used (assuming based on the proximity of the departments dispatched when the issue happens), so I’m doubtful it’s my antenna that’s the issue, but I really have no idea.

Any thoughts about this? I’ll try to get a recording somehow, it’s just hard to predict. Thanks!

 

[letarotor]

Since you said that there are multiple users on that one frequency, it is possible that another user that is fairly close could also be broadcasting at the same time. That could make the frequency sound like there's interference or even staticky.

Are you using a PL tone on the frequency? I don't know if each agency or department using the frequency uses the same PL tone or different tones?

It might help if you told us what the frequency is and who the users are so we could look it up in the RadioReference database and see if we notice anything that might be causing it. Be sure to put in the CTCSS or DCS PL tone on the scanner and see if it helps. Back in the days before scanners had that capability, I would often hear something similar to what you're talking about when there were multiple users on one frequency. That's why I'm wondering if that's what's happening to you?

Brian
COMMSCAN

 

[slayer816]

Could be a number of reasons including different transmitters, tones, the different radios (the units) in use, etc..

Have you verified with a different scanner or antenna?

 

[emsflyer84]

Could be a number of reasons including different transmitters, tones, the different radios (the units) in use, etc..

Have you verified with a different scanner or antenna?

Yea, same happens with handheld scanner. The antenna on the roof is a Diamond dual band commercial antenna.

 

[Ubbe]

The antenna on the roof is a Diamond dual band commercial antenna.

I haven't heard of any dual band commercial antennas. It's always single band transmitters connected to single band antennas. But its' probably an amateur antenna shortened to cover higher frequencies in VHF and UHF. But what you could do are to monitor without any sub tones, to be able to receive all transmission on the frequency to tell if another transmitter blocks the transmissions.

It could also be an adjacent frequency that desense the receiver if it is of lower quality that can't handle that kind of signals. It depends of the scanner/receiver you are using.

/Ubbe

 

[trentbob]

I just skimmed over this so I might have missed it. What radio are you using? This is pertinent, an old analog radio? The word birdie comes to mind, again I may have missed something here, but in the old days in the back of the manual, would be a long list of frequencies that were birdies for that particular radio where the radio produced interference that interfered with its own reception LOL. What exact model radio are we talking about here?

 

[a417]

It might help if you told us what the frequency is and who the users are so we could look it up in the RadioReference database and see if we notice anything that might be causing it.

+1 to this.

if those two depts closest to you also cover a diverse graphical region, the dispatch entity could be doing the old "analog simulcast" where they multi-select two towers and send it out on both, and you're getting both signals - causing issues on reception.

 

[emsflyer84]

That makes sense to me. The Frequency is 154.175, it’s the Ossipee Valley Mutual Aid Assn dispatch frequency, for most departments in the county. It’s a pretty small operation, usually with one dispatcher so multiple transmissions at the same time on the frequency aren’t likely. I don’t see anything in the radio reference database on the county regarding different tones, etc:

Carroll County, New Hampshire (NH) Scanner Frequencies and Radio Frequency Reference

Scanner Frequencies and Radio Frequency Reference for Carroll County, New Hampshire (NH)

www.radioreference.com

Its interesting that this issue happens only when dispatching the 2-3 departments that are closest to my scanner. Departments 20+ miles farther away are a little weaker but the transmission is always consistent and readable.

Scanner is a Bearcat BCD325P2, antenna is a Diamond X50C2 dual band.

 

[ecps92]

as a417 indicated
Sounds like they are using Multiple TX sites and can manually select the needed sites, or let the computer do it, as each agency is toned out

Heard the same, with Lakes Region 159.9000 in the past, as they change to the best site or multiple sites [depending on the time of day - aka day shift/night shift] to get the best coverage for the Volunteer/Call Departments who likely work outside of town

Hey all, I’m running a setup to supply a feed to Broadcastify in my county. It all works well with good reception. There is one analog vhf high frequency that has a funny issue. It’s also one of the closest regarding transmit sites, etc. This one frequency is dispatch for multiple fire departments. I’m not sure how it all works, but when different departments are dispatched they all sound different, some more clear then others, so I’d imagine they are using the same frequency but different towers depending on the department.

When the two departments closest to me are dispatched, the transmission goes from crystal clear to lots of static and actually cuts out, then back to clear again. It happens randomly. If I had to describe the effect, to me it’s like wind, or something like that, the way it swings from clear to unreadable back to clear again. It only happens on one frequency and only when one particular tower is being used (assuming based on the proximity of the departments dispatched when the issue happens), so I’m doubtful it’s my antenna that’s the issue, but I really have no idea.

Any thoughts about this? I’ll try to get a recording somehow, it’s just hard to predict. Thanks!

 

[emsflyer84]

as a417 indicated
Sounds like they are using Multiple TX sites and can manually select the needed sites, or let the computer do it, as each agency is toned out

Heard the same, with Lakes Region 159.9000 in the past, as they change to the best site or multiple sites [depending on the time of day - aka day shift/night shift] to get the best coverage for the Volunteer/Call Departments who likely work outside of town

This seems like the most plausible explanation to me. It’s very possible there are 2+ transmit sites being used at the same time when certain departments are dispatched.

Are there scanners that deal well with this simulcast issue? How do the radios used by the FD’s deal with it? Thanks.

 

[a417]

This seems like the most plausible explanation to me. It’s very possible there are 2+ transmit sites being used at the same time when certain departments are dispatched.

Are there scanners that deal well with this simulcast issue? How do the radios used by the FD’s deal with it? Thanks.

you can try attenuating the signal on that channel, to see if it affects the reception.

 

[buddrousa]

It could also be this is a SIMPLEX SYSTEM or this could also be caused by DESENSE.

 

[ecps92]

Don't confuse this with the Digital Simulcast issues.

From past knowledge [may have changed, but....] they actively select each of the transmit sites, not Simulcasting...

ie: Lakes Region, altho Belknap [main TX site is great] it does not penetrate into the Newfound area or Waterville Valley
so they have [again - may have changed] to Page from both Belknap, then Waterville, but then select one site to Dispatch from [usually the main]

I'm sure some of our other members [who dispatch from other agencies] will chime in, but since this question is more a LOCAL vs general scanning, you may want to ask the moderators to move to the NH Forums [Select the "REPORT"] below your original post #1

This seems like the most plausible explanation to me. It’s very possible there are 2+ transmit sites being used at the same time when certain departments are dispatched.

Are there scanners that deal well with this simulcast issue? How do the radios used by the FD’s deal with it? Thanks.

 

[ecps92]

Ossipee Valley Mutual Aid - Scan New England Wiki

www.snewiki.com

No this Dispatch is on a Repeater, but they actively can select each TX site and page, then the next site and page

It could also be this is a SIMPLEX SYSTEM or this could also be caused by DESENSE.

 

[jmarcel66]

Local Answer:
As you guessed, Ossipee Valley operates from at least three separate repeaters (maybe four) on 154.175 called 1A, 1B, etc. None are simulcast. They will tone on the closest two sites to the community typically, which is why one sounds better than the other. They do not transmit from two sites at the same time, but in sequence (one after the other), repeating the dispatch. They will then communicate on the primary site for the duration unless a different repeater is receiving the field units better.

The repeater input frequency uses different tones to access each repeater, but 136.5 is the output tone on all sites.

Diamond makes the X50C2 Commercial Antenna, although the splits are kind of weird (146-155 & 450-465).

Lakes Region is essentially full time Simulcast on 159.900 with a few exceptions for a couple towns that both have reception issues and aren't on the simulcast.

Hope that helps,
John

 

[emsflyer84]

Local Answer:
As you guessed, Ossipee Valley operates from at least three separate repeaters (maybe four) on 154.175 called 1A, 1B, etc. None are simulcast. They will tone on the closest two sites to the community typically, which is why one sounds better than the other. They do not transmit from two sites at the same time, but in sequence (one after the other), repeating the dispatch. They will then communicate on the primary site for the duration unless a different repeater is receiving the field units better.

The repeater input frequency uses different tones to access each repeater, but 136.5 is the output tone on all sites.

Diamond makes the X50C2 Commercial Antenna, although the splits are kind of weird (146-155 & 450-465).

Lakes Region is essentially full time Simulcast on 159.900 with a few exceptions for a couple towns that both have reception issues and aren't on the simulcast.

Hope that helps,
John

Thanks, so it seems like I’m back to square one in trying to figure this issue out...

 

[emsflyer84]

Not to revive an old thread but... I think I solved my issue. I was re-programming my scanner last night using ProScan and I realized that the ATT function was selected on this frequency, along with a few others. I have no idea what this does, but I un-checked it and frequency seems to come in clear now...

 

[ecps92]

Good to hear/know

What is ATT, read here from the Famous RR Wiki

Attenuator - The RadioReference Wiki

wiki.radioreference.com

Not to revive an old thread but... I think I solved my issue. I was re-programming my scanner last night using ProScan and I realized that the ATT function was selected on this frequency, along with a few others. I have no idea what this does, but I un-checked it and frequency seems to come in clear now...