Trying to track down interference

[markab]

Hi,
I live in Cambridge Ontario and I'm hoping someone here might be able to make some suggestions on helping me track down an interference problem I'm having with the Fleetwood zone 1 system which I use to monitor the OPP. I'm currently using a GRE PSR-500 scanner attached to a Watson W-889 antenna which I've had for about six weeks.
I receive the signal very strongly (4-5 bars) but about every 10-15 transmissions the transmission will get badly garbled and then will mute out for the duration of the transmission. I use the scanner primarily in and around my house. I have noticed when I'm in my driveway that several AM radio stations have an annoying buzz on them that disappears when I get on the road. I'm wondering if this may be affecting the front end of the scanner intermittently and causing the problem? I was also wondering if the zone 1 system is a simulcast system, as I know this can cause reception issues? I generally find that I can't use the attenuate option on the scanner as it makes the signal too weak pick up. One thing that I have found that helps, but doesn't eliminate the problem is if I leave the antenna fully collapsed. I also have the Waterloo police/fire, and the Guelph EMS systems programmed in my scanner and they work flawlessly.
Does anyone else in the Waterloo region using the 500 have similar problems monitoring the OPP on zone 1? Thanks in advance for any suggestions.

Mark

 

[Forts]

Sounds like your scanner is overloading on the VHF end of things (Waterloo is 800mhz so that would explain why it's not affected). I have the same problems here due to a paging transmitter about 1km from me that is broadcasting in the 159mhz range. Turning the attenuator on can help a great deal in these cases. You may find that antenna is just too hot for your location and you may need to try something else.

 

[markab]

Thanks

Hi Forts,
Thanks for the advice. How are you handling the front end overload in your situation?

Mark



in

Sounds like your scanner is overloading on the VHF end of things (Waterloo is 800mhz so that would explain why it's not affected). I have the same problems here due to a paging transmitter about 1km from me that is broadcasting in the 159mhz range. Turning the attenuator on can help a great deal in these cases. You may find that antenna is just too hot for your location and you may need to try something else.

 

[nova1010]

Does anyone else in the Waterloo region using the 500 have similar problems monitoring the OPP on zone 1? Thanks in advance for any suggestions.

Mark

I used to get the local AM station come through my old Pro-96 but with my PSR-500 I use a stalk antenna indoors with no problems.

Im in Guelph and pretty close to the Woodlawn tower.

 

[Forts]

Hi Forts,
Thanks for the advice. How are you handling the front end overload in your situation?

Mark



in

Well, for the most part I just live with it. Fortunately most of my listening is done at night so the paging transmitter isn't as busy. I looked into having a custom filter made to block out the offending 159mhz frequency which would have ran me about $100. I decided just to put up with it for now and use the ATT function on the scanner.

 

[markab]

Stalk antenna

Hi Nova,
Thanks for your reply. I'm going to have to dig up the stock antenna and give it a whirl. I've only recently noticed the interference, and this evening I've been running the scanner locked on the OPP for about half an hour so far with no reception issues. I not sure however if the steady rain outside might be attenuating any interference?

Mark

I used to get the local AM station come through my old Pro-96 but with my PSR-500 I use a stalk antenna indoors with no problems.

Im in Guelph and pretty close to the Woodlawn tower.

 

[gary123]

It does sound like you are getting pager intermod. A single Vhf cavity would get rid of the interfearing page signal. You can usually find these at ham radio flea markets for a very good cost.The set up and tuning is easy and can be done with no special equipment.

 

[markab]

Thanks

Hi Gary,
Thanks for the info. It's still too early to tell but over the last 24 hours I've found if I have my antenna completely collapsed -which would act as an attenuator or sorts- that I'm getting far less interference. In fact, in the last 5-6 hours of monitoring I've only had interference break the squelch twice, and i've not had it interfere with a single voice transmission. If it stays this way for a week or so I'll consider this a cure

Mark

It does sound like you are getting pager intermod. A single Vhf cavity would get rid of the interfearing page signal. You can usually find these at ham radio flea markets for a very good cost.The set up and tuning is easy and can be done with no special equipment.

 

[gary123]

you can also make a trap using 18 in of coax and a 2p-30p trimmer capacitor. The cap goes inline with the ceter conductor. the assembly can be put on a bnc connector and connected to your scanner with a "T" connector. Note this works but is not very narrow, it will attenuate about 3 megs on each side peaking where you tune it. This option would allow you to run your antenna at full leanth for best operation on other services.

 

[SCPD]

Bcd996xt

I have the same OPP problem with a BCD996XT and a back-of-set whip antenna. I was wondering if it had anything to do with encrypted transmissions breaking the squelch?!?

I will also try the attenuate thing.


Cheers

 

[motomeso]

What part of Cambridge are you in? I know a few paging companies have their transmitters at 190 Hespeler rd near the Police station. Any chance that you are line of site to that building?

I was getting nearly a 7300uV signal from the Bell paging site on Queen north until I installed a notch cavity and brought it down to around 700uV. No sooner do I do that does a 4000 watt FM station called KFUN FM show up on the Bell Microwave site behind my house which has been vacant for years other then a few ham repeaters.

Needless to say I have a new project on my hand.