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Catawba EMS Frequency Interference

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msigmon3306

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Any of you guys that monitor Catawba, particularly in Hickory, I've beat this horse to death and I need any help or suggestions anyone can give me.

Our frequencies are 159.495 transmit, 159.960 receive. Right in the area of Hickory Base and extending about .5 miles east and west of that position we are getting terrible interference on our mobiles and base station. It sounds like a paging signal and completely blocks the comm center out. It's so bad that we've had units tell the comm center to hold their traffic until they can move out of the "interference zone".

I'm pretty sure it's coming off the WHKY tower but can't pinpoint it. This tower is about .25 miles from Hky base. I've sat at Hickory Base for hours with scanners and can't catch it while it's killing our signal but I haven't been able to pinpoint the frequency yet. I think it's maybe in the 158.000-159.000 range. I've ruled out Arch paging, they are 900 mhz on the tower and their 158.700 antenna on St. James Church Road has been ruled out.

I've searched the FCC database every way I could think of and can't find any paging companies using VHF in that area or in our range.

Any help or suggestions would be very much appreciated.
 

pboy

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152.48 is the frequency on WHKY's tower. Metrocall USA. 350 watts output with 1,000 watts ERP.

It has been a thorn in the butt for scanner listening even three miles to the north where I am.

Another pager is on Barrett Mtn. in Alexander County.
 

msigmon3306

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Thank You!!!

Thank you so much for this info. This has been a major problem for us for the past two years and it's getting worse. I'm going to monitor this frequency tomorrow night and see if it correlates with what we're picking up. If I can confirm it hopefully we can file an FCC public safety interference complaint.

Strange thing is, it doesn't affect the walkies, just mobiles and base.

I don't know how I missed it with all the FCC searches I did.
 
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qball

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Check the frequency 159.540. Eastern Radio in Charlotte (ALLTEL used to resell pagers on that channel) used to run a paging system on that channel. I had problems on more than one occasion with interference from that channel. I have not listened to see if the channel is still active, but if it is....it could be hitting you right where it hurts!

Also, I wouldn't immediately file a complaint with the FCC....it sounds GRAND, but that is the slow way to handle things and will do nothing but get an extra party involved. If you can confirm who the offender is and the only way to do that is with some time and a service monitor/spectrum analyzer, the best approach is to call the offending party and discuss it with them. You will otherwise put them on the defensive and you will have a heck of a time getting it worked out...even with the FCC.

Every paging company I have had to work with to resolve problems has been very accomodating. They know that they occasionally will have a spur or otherwise dirty transmitter and will usually be more than willing to help get it fixed. If you can come close to confirming that it is someone else's equipment...I will be happy to help you get in contact with someone at the appropriate paging company.

Good luck!
 
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msigmon3306

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Thanks gball, I'll try that frequency also.

The only route that we knew of to deal with frequency interference was the FCC public safety complaint. I'm not a radio expert by any means so everyone's input is much appreciated.

And thank you Jeff. I'll try that frequency also. This is a huge safety issue for our guys in Hickory. It doesn't seem to be a problem north of the tower just south and extending from South Center Street to 15th St SE. They literally have to tell the comm center to wait until they've cleared the area before they can receive traffic.

I spent an entire afternoon at Hky Base listening to scanners trying to pick it up while going through the FCC database and missed all these frequencies on that tower. This is new territory for me.
 
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qball

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A couple of other thoughts as well...

Your EMS frequencies are extremely close to that paging channel, and mobile radios do not have very selecive front-ends. This means that just because you are receiving "interference" doesn't mean that the paging transmitter is at fault. Mobile radios are intended to listen to a wide range of frequencies and only a well-designed radio will reject those off frequency signals at such high signal levels without external filtering devices.

Here is an example....

I am talking on a 100watt mobile radio at 151.835Mhz. You are parked next to me listening to 151.850Mhz. Everytime I transmit, your radio goes quiet and you can't hear your dispatch. The problem is not mine that you aren't able to hear your intended message....those are just limitations of the mobile radios. My radio is on frequency and has a clean signal and your radio is limiting as much unintended RF that it can, but you still have desensitization of your receiver. This could be the problem that your EMS is experiencing...slightly different circumstances!

On the other hand, paging transmitters should have filter cavities to "clean up" the transmission so that only the intended RF energy is presented to the antenna. If there is no cavity and the transmitter is spurring (tranmitting unintended energy off of the center frequency) then it may interfere with other receivers in the area. The only way to determine if this transmitter is working properly is with a spectrum analyzer.

So, just be careful about making accusations, even if you find a correlation between the EMS problem and the 159.540Mhz transmitter, as you will have to prove to them that the problem is theirs and not your mobile radios. Their transmitter maybe working just like it should and within legal specifications!

I am not a proponent of Nextel rebanding and am surely not taking up for Nextel, but the same idea here is the same reason that all NPSPAC channels are being rebanded. Nextel's frequencies are too close to the pubilc saftey channels and it just drowns out the intended traffic. Is Nextel at fault....not really....according to the FCC. They are, however, accepting blame.

I hope that this helps!
 
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msigmon3306

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gball,

We're using MCS 2000's, CDM 1550's and Kenwood TK 790's. Is there anything programming -wise in these radios that I can look at?
 

gmt0000

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Try talking with Mr. Tom Long at WHKY about your problem, he is the station eng. and part owner, and a real nice guy.........

gmt0000
 

msigmon3306

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Thank you all for your input on this. I found where the problem is coming from, the frequency, etc. I'll be taking your suggestions up the chain and see if we can fix it.
 

msigmon3306

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I'm reviving this thread just briefly to thank all of you who helped me out with this problem. This issue was resolved about two weeks ago (the wheels of local government move slowly) and we haven't had any interference problems since.

Everyone's guidance and suggestions were instrumental in getting the problem fixed and our guys working Hickory are very happy. Plus, I learned a lot of good stuff.

Thank you all very much,

Mark
 

KE4ZNR

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msigmon3306 said:
I'm reviving this thread just briefly to thank all of you who helped me out with this problem. This issue was resolved about two weeks ago (the wheels of local government move slowly) and we haven't had any interference problems since.

Everyone's guidance and suggestions were instrumental in getting the problem fixed and our guys working Hickory are very happy. Plus, I learned a lot of good stuff.

Thank you all very much,

Mark
Good to hear the good news bud! :) Another example of a community coming together to help get a problem solved! Great job guys!
Happy Monitoring,
Marshall KE4ZNR
 
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