CDM1250 VHF technical woes

[Josh]

Ok, so here's the deal, and I need this for clarification

The local cab company has a horrible continuous duty data transmitter that send out signal to the taxi's MDTs or whatever the hell they use.

They're located about a mile from my house, license KQD351, 80WERP on 152.33, which I can hear loud and clear from 30 miles away on an HT... 80Watt ERP my ass. http://wireless2.fcc.gov/UlsApp/UlsSear ... ey=1921969

Here's the issue, it's bleeding over onto 161.22Mhz and swamping my receiver. It used to only destroy my radio's receive within about 1/3 mile of the place, but now it seems to have ventured to my radio at home with loud, noisy interference which is highly annoying. Is this an image or something? Or is their crappy loud, continuous 24/7 POS transmitter throwing spurs like the local paging companies used to?

I think it's the latter... unless it's an image or something. Again, I'm using a CDM1250 as a base station at home and have one while mobile. I don't remember if I was getting the same problems when I ran a GM300 in the car or not, I don't know if HTs (like the HT1250 I had or the XTS5k I have now) received the same interference locally or not. I'm not around.

It's just annoying as hell and it pisses me off. If all my radios do get the interference because of a spur from their transmitter, then the CN/GTW railroad should have attention called to it since it's their frequency for yard operations in the area local to the transmitter. I don't doubt they get noise all the time on their HT1000s and Spectra railroad radios.

Any insight? For now it's just locked out. If you're local to Downriver Michigan, I'd say withing 30 or so miles you can hear it on 153.22, it's probably the most annoying noise ever.

-Josh

[W2MB]

First order of business is to determine if their transmitter is operating within specs as far as spurious and harmonic emissions are concerned. It could be due to some other complex issue involving other nearby transmitters. You can try listening to the frequency with another receiver and see if you hear the same trash, but you can't really pursue it unless you have someone qualified with the proper equipment look at it. If it's dirty, they have to fix it. First step is letting them know of the violation if it exists.

[jackhackett]

Correct me if I'm wrong, but with a 20K0F3E emision type on the license, aren't they in violation by transmitting data?

[Josh]

I dropped them an e-mail that I was receiving much more interference than I usually do, but I have a downriver connection with a spectrum analyzer that can possibly check the signal.

I just wanted to rule out that it wasn't my radios creating it. I'll be in the area tomorrow and will take a couple HTs and other radios and see what happens.

-Josh

[escomm]

Correct me if I'm wrong, but with a 20K0F3E emision type on the license, aren't they in violation by transmitting data?

Seems to me that E would have to be a W to allow data, no?

[jackhackett]

Well, if they're only using it for data it would probably need to be 20K0F1D. The MDT sites around here appear to be licensed with both the F3E and F1D designators as they were originally used for voice, and I guess the FCC just appended the digital emission type. I suppose a dual use site could also be something like F9W.

http://en.wikipedia.org/wiki/Types_of_radio_emissions

In any case, the current license doesn't appear to cover what they're using it for.

[Josh]

Well, I found the source of the interference as being what I said before.

It only poses a problem when I'm using a CDM1250 radio. I tried getting the spurious bleedover on my XTS5k, but it remained clear. It was able to properly filter it out.

So, I guess technically my radio is at fault, but it doesn't help having an 8-bay folded dipole array (yes, that's right... pointed right to my home, and myself having a dual 4-element yagi array pointed in the general direction of their continuous duty transmitter (which isn't at the location they're licensed for and is at a new location from where I normally got the interference from (they moved across town, so technically they're now like 2 miles away).

Anyway, there may be some math involved that would couple how it could bleed over and cause interference (while mobile) for about 1/2 mile or more from the site, on the CDM1250 radio. I don't have a lot of waris or GM type radios to test other models other than my XTS5k. I still have my connection analyzing the signal when he gets back from vaca.

-Josh