Monday, July 24, 2006

RF is Kicking My Ass

Updated 7.25.06 8:33am
Updated 7.25.06 1:23pm



This is possibly Part 1 in a really stupid problem that is making me curious. It also caused me to cuss out loud twice until I started putting the pieces together.

First, some history. I went to meet friends one time at Caldonia's awhile back, and as I got out of the car and lock with my remote it would not lock. I thought the batteries were low or maybe there was something screwy with the receiver in the car, so I finally manually locked the car. After I got home, it was working fine. Weird.

On Thursday morning, I went to see a client and install some
network gear. I got out and unloaded the car, and then went to lock the car and alas, I could not. I even got retarded enough to try to put the remote under the car wheel well and it just would not lock the car. I was annoyed but again I manually locked the car and went in. When I came back out 2.5 hours later, strangely enough I could not unlock the car with the remote. Ok, fine. I drove back to the office, and the remote worked fine. Just another flook, it had to be.

Every where else I went the remote worked fine. I was scheduled to go back to the clients office and made it back there about 2:30. Sumanambeech. I get out of the car, and the fekker will not work. I lock the car again, go in. Rinse and repeat. Come back out, and I manually unlock the car again.

As I'm driving back to the office, I'm starting to put things together in my head. I can't remember where I had this problem before, but then it dawns on me finally, at fekkin' Caldonia's. Fekk me running.

In the photo you'll see two cross hairs and a RF antenna symbol. Not a very good one, but it's there. The lower one is Caldonia's and the upper one is the 'client's office'. The RF antenna is only there for reference for now. There used to be a TV station there but it's not operational. Although, there are microwave antenna's on the antenna tower. There is a Fire Station right next to the antenna tower which is the possible source since the lower spectrum from 225-400 MHz is for Public Safety, among other things. The TV and microwave facts are only noted for reference and not the source since those possible sources are not in the same spectrum, but the Fire Station keeps me wondering, and it's even more probable that the antenna tower is home to the Fire Station antenna.


The remote control to the car operates in the lower UHF spectrum at around 315 MHz which is considered Selected Bands at Issue, and for sure it competes in the spectrum for it's fair share, but there is a definite strong signal in the area with a high amount of intermodulation on that frequency range.

My plan is to move forward with a small site survey in about a one mile radius and to identify the signal source or the general source site and as well as the offending frequency. Not to say the frequency is not legitimate and that it should not be interfering with my signal, but I am just nosey now. Mega Mex and I have roots in signal locating, so I'll be touching base with my roots soon enough.


UPDATE #1: As I'm driving to work this morning, I am sitting at the stop light at Iliff and Parker and this is the perfect opportunity to get my site survey under way. I put the car in park (cause it's a red light) I kill the car, pull out the keys and try to lock the doors. Nothing. So I start up the car and drive on. I'll update the image shortly.

Update #2: At lunch I decided that it was time to go on the old site survey. At first I had screwed up my experiment so I had to start over, only on the initial spots. My control: Sit in the car, left hand out of the window with the remote which at max was only 3-4 feet away from the receiver, put the car in park and turn the car off. Remove the key from the ignition. Once the car was stopped then lock / unlock the car with the remote. It's simple. By placing my hand outside the car, I had simulated me getting out of the car and attempting to lock it. Since the body is a metal body and is grounded, it would work the same as if I were standing outside of the car, and the body of the car would still have an impedence on the signal strength to the receiver from my remote. Since the receiver in the car is in front of me and not behind or beside me while sitting in the car, sitting in car would have little to no affect on this.

My only dilemma is to figure out how to get my Yaesu VX-5 on FM instead of AM, or just figure out how to switch it period. I don't know where my manual is so I could not get a definitive source frequency yet, but it's only a matter of time. I'm coming to get you lower UHF...you wait and see.

Anyway. Instead of cross hairs, they are now simply red and green dots. The red dots indicate unsuccessful lock / unlock of the car. The green dots indicate a successful lock / unlock. Yoou'll notice that the green dots are located behind buildings in relation to the antenna tower. Pretty definitive so far on that aspect. More to come.

1 comment:

Rick Lee said...

uh...what the hell are you talking about? This is way beyond me I think...