Sudden Loss of Reception

[emsflyer84]

Hey all, I've got my BCD996P2 hooked to a Diamond XC50C2 antenna on my roof. It's worked great for couple years. Recently I've noticed a drop off in reception of a particular frequency that I monitor. It's on the edge of my reception area, so I can't say I'm surprised. But I stopped picking them up suddenly which was strange. It's a conventional VHF digital frequency for a police dispatch center. I still get the analog VHF FD frequency in the same town. It's scratchy but it's always been. To try and eliminate any potential issues on my end, I shorted up my coax run, bought all new LMR-400 and now have a 50' run from the antenna on the roof, down the side of the house and into a window right to the scanner. Previously it went into my basement and tapped into the network of coax already run in my walls for cable tv so I could access it at my desk (not ideal, but it worked). After shortening up the run, I got that frequency back, but still broken and choppy, not as clear as it used to be.

Another observation, I actually pick this frequency up in my car with a handheld scanner and a mobile antenna when I drive from my house AWAY from the dispatch center. Even quite a distance further from it then my house is.

Here are my thoughts:

- The dispatch center changed something (antenna / tower site, output power, etc...)
- I have interference at my house somewhere (all other frequencies I'm scanning come in great with no noise)

It's confusing to me because I used to pick this frequency up and I haven't changed anything until I improved my coax and shortened my coax run, which helped a little but it's still not back to where it used to be for reception on this frequency. It also seems like reception in all other aspects is as good, or better then it was before since I improved my coax situation. All of this leads me to believe that something changed on their end, not mine. The only problem with that is, why am I able to pick them up on a smaller antenna on my car when I leave my house? Am I driving into line of site? I know no one here would know that, these are just the things I'm thinking about. Is there anything else I can check for? Could it be a setting on the scanner? Any thoughts are appreciated. Thanks!

 

[a417]

You made significant changes, but you made them after the department changed - and your changes haven't improved things for you.

But I stopped picking them up suddenly which was strange. It's a conventional VHF digital frequency for a police dispatch center. I still get the analog VHF FD frequency in the same town. It's scratchy but it's always been

This makes me think that they lost a primary transmitter (and are happy running on their backup), made infrastructure changes, had their site damaged in any of the recent storms, etc...

Does the sudden loss of reception date correlate to the storms?

The only problem with that is, why am I able to pick them up on a smaller antenna on my car when I leave my house?

The (possibly) new transmitter emissions envelope may not cover your house?

Am I driving into line of site?

Could be? Have you played with any of the available LOS tools online to see if you have disadvantageous landmasses between you and them?

 

[tvengr]

What is the frequency and agency giving you the problem. There could be new construction between you and the transmitter site. Any new tall buildings? It is possible that they are using a simulcast site now.

 

[emsflyer84]

You made significant changes, but you made them after the department changed - and your changes haven't improved things for you.


This makes me think that they lost a primary transmitter (and are happy running on their backup), made infrastructure changes, had their site damaged in any of the recent storms, etc...

Does the sudden loss of reception date correlate to the storms?


The (possibly) new transmitter emissions envelope may not cover your house?


Could be? Have you played with any of the available LOS tools online to see if you have disadvantageous landmasses between you and them?

Thanks for the reply. I haven't played with LOS tools, I'll do that. I don't believe there is any correlation with a storm, etc. I just now completed a small experiment, I sat in my car only 1/2 mile from my house at a slightly lower elevation then my house and received this frequency BETTER then my scanner at home picked it up. Since I have a broadcastify feed I'm able to listen to my home setup on my phone. I heard one specific transmission ok in my car. A minute later the same transmission came over my broadcastify feed and it was so broken I couldn't understand it. Now this is making me think there is an issue at my house, or with my setup. More experimenting to do...

 

[emsflyer84]

What is the frequency and agency giving you the problem. There could be new construction between you and the transmitter site. Any new tall buildings? It is possible that they are using a simulcast site now.

The following is what I'm trying to get:

155.640

KRC763

RM

817 NAC

Conway PD

Police Operations

No new construction I don't believe. Looking at the RR database, it looks like there are 6 antenna sights registered to that frequency / callsign. I don't know if they simulcast, or if dispatchers pick which site they want to use, etc. In the past the reception was always consistent, so I don't believe they were switching sites all the time....

 

[Swipesy]

I experience that kind of issue all the time while scanning the 160 rail band. I live on the fringe of any train tracks and sometimes I will hear nothing for a week and then the signals come back. I blame propagation.

 

[tvengr]

155.64 appears on 4 different sites. If all transmit at the same time, you could very well be experiencing simulcast distortion. On your scanner at home, disconnect the rooftop antenna and try using the back of scanner antenna.

 

[emsflyer84]

155.64 appears on 4 different sites. If all transmit at the same time, you could very well be experiencing simulcast distortion. On your scanner at home, disconnect the rooftop antenna and try using the back of scanner antenna.

Would this issue potentially be worse if you have a tall antenna that is receiving more then one site? Versus, say, a mobile antenna on your car that is only receiving one site maybe?

 

[a417]

Would this issue potentially be worse if you have a tall antenna that is receiving more then one site? Versus, say, a mobile antenna on your car that is only receiving one site maybe?

Yep, pretty much it in a nutshell. Sometimes the answer is less antenna.

 

[emsflyer84]

Yep, pretty much it in a nutshell. Sometimes the answer is less antenna.

I suppose this is possible. Can my bcd996 not handle simulcast? It’s weird that is seemed to work fine before though.

 

[a417]

It is well documented on here that it has trouble with, and was not designed for simulcast environments.

It may have worked "just fine" before for Many Reasons™. They could have made a slight improvement to one site/tower/antenna to solve a problem for them (like a deadspot, etc) and now it means you get too much signal at your house, in the form of multipath from several sites...and your BCD996 just barfs on it. Before the possible improvement, you were only getting a signal from one tower/site/antenna and your unit was none-the-wiser.

 

[emsflyer84]

It is well documented on here that it has trouble with, and was not designed for simulcast environments.

It may have worked "just fine" before for Many Reasons™. They could have made a slight improvement to one site/tower/antenna to solve a problem for them (like a deadspot, etc) and now it means you get too much signal at your house, in the form of multipath from several sites...and your BCD996 just barfs on it. Before the possible improvement, you were only getting a signal from one tower/site/antenna and your unit was none-the-wiser.

All very possible. It seems like everything I’ve read on simulcast issues, you still hear something, just broken, digital sounding, choppy, etc. In my case I’m mostly not receiving anything at all. Sometimes it does come in brown. But mostly it misses everything.

 

[a417]

All very possible. It seems like everything I’ve read on simulcast issues, you still hear something, just broken, digital sounding, choppy, etc. In my case I’m mostly not receiving anything at all. Sometimes it does come in brown. But mostly it misses everything.

That sounds like a non-simulcast reciever being presented with simulcast signals to me... your solution might be attenuation or less antenna, or even a directional that nulls out a second site.

Lot of options, and lots of potential solutions.

 

[Ubbe]

I recommend to always have a variable attenuator at hand when dealing with external antennas and connect inline with the coax and check if a weaker signal might be a better option. ScannerMaster have a $50 one but there are also other $10 ones that can be used and look for those that can be set between 0-10dB or 0-20dB.

Instead of spending money on a LMR400 and the work involved of installing it, and especially when having connections to an existing lower quality coaxes, you could have used an antenna amplifier, good ones are $17 to $25, and would then not be bothered by any coax loss or splitters and connectors. Just use that variable attenuator to get best possible reception from the scanner. Some amplifiers need a direct DC power connection and others can be powered from the coax by using a bias-T.

If only that 150MHz frequency needs more attenuation then a $20 diplexer can be used to split up the signal into VHF and UHF and add a fixed 10dB attenuator to the antenna coax, if a 20dB amplifier are used, and the additional variable attenuator only to the VHF band and then connect the two signals back together again.

/Ubbe

 

[emsflyer84]

Hey all, thanks for all the reply's. I think I've narrowed this issue down to some interference at my house that probably is effecting reception across the board but I'm noticing it on this particular frequency because it's the one that's farthest from my house. I've now discovered that I can pick this frequency up while sitting in my car in my driveway, about 30 feet lower then my rooftop antenna. Something in my house is screwing with my base scanner I think. I'll cut the power to my house and connect a handheld to my roof antenna and see if I can pick them up that way, the I'll know for sure.

 

[tvengr]

Have you recently installed any new electronic devices? USB switching power supplies are notorious for wideband interference.

 

[emsflyer84]

So I’ve added a few things, wired mouse, mouse pad and keyboard with rgb lighting, a small strip of LED accents lights on the mantle near my computer that plugged into the wall. My son has a gaming computer with all kinds of crap plugged into it, multiple keyboards, monitors, etc. But he’s on the other side of the house. I’ll have to start playing with all this stuff to see.

 

[a417]

So I’ve added a few things, wired mouse, mouse pad and keyboard with rgb lighting, a small strip of LED accents lights on the mantle near my computer that plugged into the wall. My son has a gaming computer with all kinds of crap plugged into it, multiple keyboards, monitors, etc. But he’s on the other side of the house. I’ll have to start playing with all this stuff to see.

Start throwing breakers.

Eliminate stuff by room, and then by outlet.

 

[Ubbe]

You can pretty much hear interference in AM mode if you have a scanner that can be set to it to that frequency. Set squelch to 0 and then in AM and tune around that frequency in smallest steps possible as it could be heard stronger on another nearby frequency. Then try and pinpoint the source where you get the strongest signal.

/Ubbe

 

[emsflyer84]

Hey all, I've got some interference I believe with my scanner setup at my house. Running a BCD996p2 to a Diamond dual band antenna on my roof with a short run of LMR-400. I have trouble getting a particular frequency that I can get in my car with a handheld scanner connected to a glass mount antenna. So something is going on my my house. The coax is new, connections are good, etc. I've had interference before from power line noise when the utilities were being worked on in the area but that was cleared up years ago when the work was done. I know basically how to track it down, but it's going to take some work for sure. Just looking for any tips or tricks anyone has who has gone through this before. Any help would be great. Thanks!