DCFD trunked system question

[RS8]

Can anyone tell me why I get a strong signal during the day and it is all broken up at night?

 

[ka3jjz]

This is so broad a question as to be very difficult to answer. What are your conditions? Are you using indoor antennas? What scanner are you using?

Something in your area could be desensing you during the evenings....or maybe the system admins are changing the power/antenna config at night to concentrate their coverage. It's very hard to tell...Mike

 

[RS8]

DCFD trunk system

Mike I am using a Uniden BCD996T with an indoor antenna. I wonder about the desensing and is there anything I can do with the scanner?
At any rate thanks for your response.

 

[ka3jjz]

I'm going to assume here you're talking about DC Fire, since the cops are mostly encrypted, except for one or two talkgroups

My first suspicion would be a new cell tower going up near you. That would almost certainly nail you, if it's close enough. You might get around that with a small 800 Yagi with the offending tower off the back of the beam. There *might* be enough attenuation to solve the issue. In fact, you might just try kicking the attenuator on in the eves, just to see if it is indeed an overloading issue.

Moving the antenna a small amount may also make some difference. At these wavelengths, even an inch or two might change things. Also keep in mind that now that we're into Spring, near microwaves don't do quite as well with trees and shrubbery.

It's a little hard to be more specific - but clearly, you have some homework ahead of you. It's possible that the power on 800 is dropped in the evenings - you would think otherwise, but remember this is the District of Crackheads...er...DC...

Sri I can't do more...Mike

 

[ka3jjz]

One other possibility is that the antenna arrangement is changed in the eves to concentrate coverage in a particular sector. That would also explain the weaker signal. They could actually move the antenna or switch to a different tower.

When they moved to new systems, Baltimore county and city, Virginia Beach and Philadelphia all changed their antenna patterns (at least that's what is suspected), because hearing their respective systems became more difficult outside of their target areas (of course, that thrice damned LSM modulation scheme doesn't help matters). These moves were full time, of course, so perhaps DC is experimenting. We don't have anyone on the inside that could confirm that....Mike

 

[RS8]

DCD Trunked System

A contact of mine who is a retired member of DCFD and has a siginificant communications background told me that they got new consoles
and are currently working to get the system up to par.
We will see what happens.Today it is loud and clear.Last night reception was good.

 

[ka3jjz]

The it's quite possible that they're fooling around with antennas and/or power settings as they test the new consoles. I think you have found your answer...Mike

 

[brownlab]

Can anyone tell me why I get a strong signal during the day and it is all broken up at night?

It is a good question. Where are you (general area) in Loudoun? Sorry I did not see your PM

 

[ResQguy]

A contact of mine who is a retired member of DCFD and has a siginificant communications background told me that they got new consoles
and are currently working to get the system up to par.
We will see what happens.Today it is loud and clear.Last night reception was good.

That was only for audio levels (wireline from dispatchers mouth to system) and would not affect your ability to receive the system.

I suspect there is a source near RS8's QTH that increases when people come home at night, such as increased use of wifi & cell phones in the residential neighborhood causing the noise floor to be much higher than the daytime. I hate spending money, but this might solve your problem BPF-800N

Also, nobody anywhere would alter power levels or radiation patterns based on time of day. If that were the case, nobody would do interior attack when the sun went down because their radios would go out of range! There is no experimentation on a live 15 year old system. Also, this is a simulcast system. There is no transmitter steering based on location. All sites, all the time.

 

[ka3jjz]

That filter isn't even available yet...

Anyway it's not out of the question that some new or changed orientation of antennas is being tested. Keep in mind that the OP is in Loudoun county, not DC. If the antennas are being tested in some way to concentrate coverage inside of DC (instead of it bleeding into the suburbs), then he would indeed see a reduction in signal level at certain times. Firefighters inside the District might not see any change at all (or perhaps would see better coverage at times). I keep on hearing that there are several dead spots in the District where coverage is a bit spotty. Perhaps they're trying to fix that.

There's plenty of precedent for this. Look at what happened in Baltimore City (and I suspect Virginia Beach has also done this, talking to someone in that neck of the woods). That doesn't discount your suggestion, of course

Mike

 

[ResQguy]

That filter isn't even available yet...

Anyway it's not out of the question that some new or changed orientation of antennas is being tested. Keep in mind that the OP is in Loudoun county, not DC. If the antennas are being tested in some way to concentrate coverage inside of DC (instead of it bleeding into the suburbs), then he would indeed see a reduction in signal level at certain times. Firefighters inside the District might not see any change at all (or perhaps would see better coverage at times). I keep on hearing that there are several dead spots in the District where coverage is a bit spotty. Perhaps they're trying to fix that.

There's plenty of precedent for this. Look at what happened in Baltimore City (and I suspect Virginia Beach has also done this, talking to someone in that neck of the woods). That doesn't discount your suggestion, of course

Mike

1. BPF-800N Band Pass Filter
Stock Status:In Stock

2. It is out of the question. There is no such testing. Plus, sending up tower climbers is very expensive. You wouldn't do it until your planning was solid, and if it were wrong- you would fix it. You wouldn't do it again and again every night, and not tell anyone. That kills people.


Edited to include: Please understand, I'm not trying to be a prick. I just can't find a better way to explain what isn't happening.

 

[RS8]

DCFD trunked system.

Brownlab we are over in the Broadlands off of LC Pkwy.
This is a interesting situation. Last night was clear and very readable. Today it is still good and I am beginning to think it is local issue.

The suggestion of the filter might be a good idea.However I am using a back of set antenna.