intereference on MSP freq's

[Viperguynick]

anyone out there get static interference on MSP's SW Car-Car and SW Emergency frequencies? They are 154.695 and 154.710 respectively. It doesn't matter where I am in the Lewiston/Auburn or Brunswick areas. It seems to be quite random, but when it breaks squelch, I have to restart my PRO-106 in order to get it to stop. once I do that, it's fine until the next time...

I do sometimes get good transmissions on the SWCC freq when someone talks to Androscoggin SO to transport a prisoner, so I don't think what is happening are good transmissions that are just out of my area...

Thanks!

Nick

 

[02intlbluebird]

I get it on 156.150. Sometimes I thought a unit had an open mic, but it happened again for me last night around 10 PM and when officers are talking, it interferes and makes the audio gargled. Sometimes it will stop right after their squelch, sometimes a few seconds later as a tail, and sometimes I have to block the channel because it's several minutes long. It doesn't kill my radio, but is awfully anoying.

 

[NEK1213]

NH digital?

 

[Viperguynick]

Good to know that someone else out there experiences the same phenomenon!

It is quite possibly NH SP P25 transmissions. The only thing that is strange is that even on a search, I don't even get NAC codes coming up, it's strictly just noise...

Nick

 

[N1BHH]

Try using the attenuator on VHF signals. There have a few people reporting that their receiver front end gets overloaded and signal intelligibility improves with the attenuator activated.

 

[02intlbluebird]

NH digital?

I don't get it. This is Gray dispatch, which is all analog. Nothing that I know of is that NH SP shares similar radio frequencies. Are you saying a certain town that is digital is interfering with the radio transmissions.

Another thing I thought was in question is that I believe that MESP has different repeaters so, maybe a car transmitting is between two towers and can't decide which to send the signal to. Maybe I need to record some MESP Gray and put it up on here?

 

[Viperguynick]

I do remember driving home from Alton, NH one day and getting some P25 traffic on a freq I have listed as MSP C.I.D.2. I will have to check what frequency that is, but in my scanner it's programmed as a conv object with the SQ set to search, and normally comes up as analog. But that is why I thought it was strange not to see a NAC code when this happens, as soon as I got that transmission on the drive home, it displayed a NAC in the 800's.


Nick

 

[Maine45]

...Another thing I thought was in question is that I believe that MESP has different repeaters so, maybe a car transmitting is between two towers and can't decide which to send the signal to. Maybe I need to record some MESP Gray and put it up on here?

MSP has no repeaters on SWCC (154.695) or SWSP (154.710). There are remote base stations in various locations linked via telephone lines to the SP dispatch centers. Much of this infrastructure is very old (1974) and not always performing well. What I have been hearing on SWCC sounds like phone line noise.

Also, both these channels operate mostly without PL tones, so other types of interference such as adjacent channel & intermod have been a problem since the system was established.

Dick in Southern Maine

 

[NEK1213]

Could be the NHSP MDT in the cruisers. They share and create weird noise on a normal audio frequency.

 

[Maine45]

Could be the NHSP MDT in the cruisers. They share and create weird noise on a normal audio frequency.

Actually, they do not share. Per the FCC database, there are no NHSP licenses on either 154.695 or 154.71. There are a couple of NH towns with licenses on 154.71; but no NH licenses on 154.695.

If NHSP were a co-channel user, they would have forced Maine off these frequencies years ago. That is what caused the change in the MSP Zone 1 channel from 154.665 to 156.15 in about 2000. NHSP also created issues for the Rhode Island SP on 154.935, forcing them to change their North Zone frequency.

The problem here is that using VHF public safety frequencies without PL tones doesn't really work anymore. Too many new narrow band adjacent channels, too much intermod, too much rf noise everwhere. Plus, most of the populated parts of Maine are hit with long range stations from Massachusetts for much of the year. Plus the MSP system (and many others) is mostly 37 years old; ancient by today's standards.

The MSCOMMNET system will (perhaps) resolve most of this for Maine state agencies. The state should also address the common use channels such as State Fire and SWCC, since they largely control their use, and establish a standard PL tone for them.

Dick in Southern Maine

 

[ecps92]

156.1500 in NH for P25 would be the Sullivan County SO.

Waiting on someone in a NH list or closer to confirm the NAC as $117

IT could be from NH. Also remember, Cable TV loves to LEAK and interfere with not-only the VHF Bands, but the UHF as well.

I get it on 156.150. Sometimes I thought a unit had an open mic, but it happened again for me last night around 10 PM and when officers are talking, it interferes and makes the audio gargled. Sometimes it will stop right after their squelch, sometimes a few seconds later as a tail, and sometimes I have to block the channel because it's several minutes long. It doesn't kill my radio, but is awfully anoying.

 

[02intlbluebird]

156.1500 in NH for P25 would be the Sullivan County SO.

Waiting on someone in a NH list or closer to confirm the NAC as $117

IT could be from NH. Also remember, Cable TV loves to LEAK and interfere with not-only the VHF Bands, but the UHF as well.

From this web site, it is 227.

http://www.swnh.org/nh-police-frq.htm

Sullivan Cnty NH Sullivan P .. 156.1500 .. 136.5 .. .. .. .. Claremont SP343
Sullivan Cnty NH Sullivan P .. 156.1500 .. .. P25 227 .. .. Claremont .. 11/1/2006 1/17/2011 11/1/2006 1/17/2011

 

[12dbsinad]

Actually, they do not share. Per the FCC database, there are no NHSP licenses on either 154.695 or 154.71. There are a couple of NH towns with licenses on 154.71; but no NH licenses on 154.695.

If NHSP were a co-channel user, they would have forced Maine off these frequencies years ago. That is what caused the change in the MSP Zone 1 channel from 154.665 to 156.15 in about 2000. NHSP also created issues for the Rhode Island SP on 154.935, forcing them to change their North Zone frequency.

The problem here is that using VHF public safety frequencies without PL tones doesn't really work anymore. Too many new narrow band adjacent channels, too much intermod, too much rf noise everwhere. Plus, most of the populated parts of Maine are hit with long range stations from Massachusetts for much of the year. Plus the MSP system (and many others) is mostly 37 years old; ancient by today's standards.

The MSCOMMNET system will (perhaps) resolve most of this for Maine state agencies. The state should also address the common use channels such as State Fire and SWCC, since they largely control their use, and establish a standard PL tone for them.

Dick in Southern Maine

The fact of the matter is it doesnt really make a diffrence if the system or any system is "ancient". That part of it is really has nothing to do with interference. It doesnt matter if you are analog or digital, if there is a co-channel user it will cause problems. May not here them, but i assure you they didnt go anywhere! Also, not only co-channel, but adjacent channel interference is just as common. Excpecialy since a user on wideband can be right next door to a narrowband user.

 

[Maine45]

The fact of the matter is it doesnt really make a diffrence if the system or any system is "ancient". That part of it is really has nothing to do with interference....

Yes, except it does. The issue here is "noise" not necessarily typical rf interference. Old, poorly maintained telephone line links to remote sites may be causing the noise that the op was hearing. There may also be coax, connectors or other componenerts that were installed at remote sites in 1974, which may be damaged & allowing stray rf to be picked up. And as Bill suggested, cable TV lines adjacent to these parts of the system are always suspect. How many of the remaining 1974 transmitters/receivers (and there are supposedly quite a few) still operate within their original specifications? It is kind of amazing that any of them still work at all, a testament to the quality of the American-made electronics of that era (and the skill of the state radio techs!).

PL tones of course do not eliminate noise or actual rf interference, only mask it. However, the presence of external noise & rf interference may well not be enough to create issues for the operation of the system such as blocking transmissions; only sufficient to cause annoyance to the users. When the MSP system, including the SWCC and SWSP channels was established in 1974, it was apparently not considered necessary to employ PL tones on those channels. You would never do that today on a new public safety system!

Dick in Southern Maine

 

[ecps92]

SPOT ON - Dick !!!

How many folks get TV Land in the 467.7500-467.8000 Mhz

Yes, except it does. The issue here is "noise" not necessarily typical rf interference. Old, poorly maintained telephone line links to remote sites may be causing the noise that the op was hearing. There may also be coax, connectors or other componenerts that were installed at remote sites in 1974, which may be damaged & allowing stray rf to be picked up. And as Bill suggested, cable TV lines adjacent to these parts of the system are always suspect. How many of the remaining 1974 transmitters/receivers (and there are supposedly quite a few) still operate within their original specifications? It is kind of amazing that any of them still work at all, a testament to the quality of the American-made electronics of that era (and the skill of the state radio techs!).

PL tones of course do not eliminate noise or actual rf interference, only mask it. However, the presence of external noise & rf interference may well not be enough to create issues for the operation of the system such as blocking transmissions; only sufficient to cause annoyance to the users. When the MSP system, including the SWCC and SWSP channels was established in 1974, it was apparently not considered necessary to employ PL tones on those channels. You would never do that today on a new public safety system!

Dick in Southern Maine

 

[Maine45]

SPOT ON - Dick !!!

How many folks get TV Land in the 467.7500-467.8000 Mhz

Thanks, Bill. I receive cable leakage in many parts of the spectrum on my car radios when in my garage, including nasty noise on Marine Ch. 16, Statewide Car to Car and frequencies associated with a certain federal agency known to use many channels in the 167 MHz. range! Mercifully it disappears when out of the garage and is not heard elsewhere in the house. Goes away when cable is out!

It should also be clarified here that some users of both the SWCC and SWSP channels DO employ PL tones; generally the old Maine "standard" 192.8. I believe they are (and certainly should be) on transmit only in those radios. There are still some base stations out there that do not transmit with a PL, so these would not be heard on a radio with a fully PL'd channel. Why do they do this? I suspect it is a holdover from an attempt to fully PL these channels sometimes in the past. They would have started the process by adding tones only to the transmit side of mobiles. It obviously was never fully implemented. If anyone at the Maine State level involved with the new state system should read this, please please please push for full implementation of PL tones on the above mentioned channels plus State Fire and all the "CONOPS" channels. All potential users of these channels will have to reprogram for narrowband use between now and 2013 anyway, so it's not like it's going to cost us more to add the tones!

Dick in Southern Maine

 

[ecps92]

I've seen many a code plug for Port/Mobile radios and a few base stations all programmed with PL / DPL Transmit, yet CSQ RX. Amazing. Why use PL or DPL then.

Thanks, Bill. I receive cable leakage in many parts of the spectrum on my car radios when in my garage, including nasty noise on Marine Ch. 16, Statewide Car to Car and frequencies associated with a certain federal agency known to use many channels in the 167 MHz. range! Mercifully it disappears when out of the garage and is not heard elsewhere in the house. Goes away when cable is out!

It should also be clarified here that some users of both the SWCC and SWSP channels DO employ PL tones; generally the old Maine "standard" 192.8. I believe they are (and certainly should be) on transmit only in those radios. There are still some base stations out there that do not transmit with a PL, so these would not be heard on a radio with a fully PL'd channel. Why do they do this? I suspect it is a holdover from an attempt to fully PL these channels sometimes in the past. They would have started the process by adding tones only to the transmit side of mobiles. It obviously was never fully implemented. If anyone at the Maine State level involved with the new state system should read this, please please please push for full implementation of PL tones on the above mentioned channels plus State Fire and all the "CONOPS" channels. All potential users of these channels will have to reprogram for narrowband use between now and 2013 anyway, so it's not like it's going to cost us more to add the tones!

Dick in Southern Maine

 

[12dbsinad]

Alright... so im a bit confused here. Are you talking about interference from your own scanner or interference actually coming over MSP? Seems like you guys are talking about both. Leaking cable TV, bad telephone lines, leaking cable and connectors at the site? Im plain 'ol confused! Im sure things have been upgraded at the sites since 1974, I understand they run a 1974 vintage microwave system, and not phone lines. If a cable was that bad at a radio site, it wouldnt go un-noticed to the techs during a check up. Plus, even if a cable was "bad" it would not cause interference to a scanner. You could hack saw the connector off and it would radiate about 300 feet, and burn out the transmitter. It sounds like everyone here is talking about local scanner interference on a particular frequency.... which is common and getting more common as the RF world keeps increasing.

 

[Maine45]

Alright... so im a bit confused here. Are you talking about interference from your own scanner or interference actually coming over MSP?

... Im sure things have been upgraded at the sites since 1974, I understand they run a 1974 vintage microwave system, and not phone lines.....

Well, this discussion has drifted "off frequency" slightly, however the original topic was interference on the SWCC (154.695) and SWSP (154.71) channels. There are a number of remote transmit sites for these channels around Maine. Some are linked back to the MSP or local dispatch centers by phone lines; some by microwave relays. Due to the age of many parts of the system, there is a strong possibility that there are components including phone lines, coax, etc that are injecting "interference" into what is heard on the channels. In addition, there may be some adjacent channel interference and intermod issues. It seems less likely that co-channel users in NH are causing the noise that is heard since there are non on SWCC and few on SWSP. SWCC can be a particularly noisy channel; not only is one or more sites perhaps transmitting phone line noise, but receivers (scanners and two-way radios) also receive noise interference from other sources such as leaky cable systems.

Why are you sure that the "things" at the sites have been upgraded? My understanding is that there is still some very old equipment in place.

Dick in Southern Maine

 

[12dbsinad]

Well, this discussion has drifted "off frequency" slightly, however the original topic was interference on the SWCC (154.695) and SWSP (154.71) channels. There are a number of remote transmit sites for these channels around Maine. Some are linked back to the MSP or local dispatch centers by phone lines; some by microwave relays. Due to the age of many parts of the system, there is a strong possibility that there are components including phone lines, coax, etc that are injecting "interference" into what is heard on the channels. In addition, there may be some adjacent channel interference and intermod issues. It seems less likely that co-channel users in NH are causing the noise that is heard since there are non on SWCC and few on SWSP. SWCC can be a particularly noisy channel; not only is one or more sites perhaps transmitting phone line noise, but receivers (scanners and two-way radios) also receive noise interference from other sources such as leaky cable systems.

Why are you sure that the "things" at the sites have been upgraded? My understanding is that there is still some very old equipment in place.

Dick in Southern Maine

Thanks for the reply Dick. From a technical standpoint, it doesnt sound like the interference is caused by the states equipment. (but doesnt mean all). Most of it is injected into a reciever by all kinds of external sources like you said, the list goes on and on including street lights. PL on RX mutes that sort of things out as you explained, but its still there. SWCC and SWSP are both simplex, so there is no possible way that any type of coax issue (or any other RF issue) would cause it to recieve interference and transmit at the same time. Phone lines interference will typically not cause the transmitter to key if there was such, most use Tone control which is current in todays newer systems.

Im just guessing on the equipment. But i cant imagine why they wouldnt replace repeaters and such over the years since its a very simple system. I have heard that before in other parts of the country and come to find out most equipment was current production except a few things. I do think though that the system being implemented is a bit much for the State. Way to expensive considering economic times and the States finacial position. But that anouther story and topic! See i get off frequency too dont feel bad!