Author Topic: building yagi  (Read 627 times)

0 Members and 1 Guest are viewing this topic.

Offline kinkydoints

  • Newbie
  • *
  • Posts: 18
  • Karma: +0/-0
    • View Profile
building yagi
« on: January 30, 2017, 12:47:46 PM »
Here it goes ... I have noticed that in my area there is a broadcast signal being rebroadcast by some kind of
" loop"  the broadcast says " lizard test ..1..2..3.. lizard test " this is being sent out over the 27.185 MHz channel 19 every 15 seconds. It is so crystal clear that it has to be a base station . My thought is to build an yagi that I can drive to certain places and triangulate this broadcast. my question is can I use the dimensions for a yagi for the 11 meter band , that has lengths of 120 " s or so , can I cut it down by 1/4? It will give me a more manageable size to move around. I do use a tuner for my antenna projects , not really worried about the swr  I'm not sending, just trying to find the power out of this broadcast. is that kind of repeating illegal? constant all day long blocking most of the frequency every 15 sec.     trucker love it...

Offline Chuck

  • Forum VIP
  • Hero Member
  • *****
  • Posts: 503
  • Karma: +0/-0
    • View Profile
Re: building yagi
« Reply #1 on: January 30, 2017, 04:06:15 PM »
You could call the local FCC field office in your area to take care of it rather than confront this individual   ;)

Chuck

Offline k7rmj

  • Jr. Member
  • **
  • Posts: 69
  • Karma: +4/-0
    • View Profile
Re: building yagi
« Reply #2 on: January 31, 2017, 03:46:07 PM »
I agree with Chuck. DO NOT confront them with this. That is a good way to start a big rock fight. Contact the local FCC field office instead and let them deal with it.

HOWEVER...If you want to find out where it is coming from you could just build a simple dipole instead of a yagi. A dipole will have significant nulls off both ends of the dipole. That in itself will not give you the exact direction the signal is coming from but it will give you a line to draw on your map that is parallel to your dipole. Then just drive a ways down the road and make another reading for the second direction on the map. Mark both lines on a map and where they cross will be the location of the signal. It will get you within a block or two of the offending signal depending on how strong the signal is.

This method will be much more accurate than even a 5 element yagi because the null off the ends of the dipole are much sharper than the peak off the front of a yagi. You are right about not worrying about the SWR since you have no need to  transmit.

An easy way to determine the length for a dipole is to divide 468 by the frequency in MHz.  17 feet 2.5 inches will do the trick for a half wave dipole. You can do this with half of a dipole. A quarter wave wire or pole or whatever that is only about 7.5 feet long instead of 17 feet long will work fine for receive.

Just point it in different directions until you find the weakest reading on your S-Meter, drive a ways down the road and check it again. That will tell you where to draw the lines on your map. Of course, the lines have to go through your location on the map where you take the readings.

Good luck with it.

73 DE K7RMJ  Frank

Offline kinkydoints

  • Newbie
  • *
  • Posts: 18
  • Karma: +0/-0
    • View Profile
Re: building yagi
« Reply #3 on: May 24, 2018, 06:22:30 PM »
have an update to the post I started ...this loop broadcast was being tested by the Kentucky transportation board here in louisville. there is a new bridge called the Louis and Clark , and there is a tunnel that connects the east end in KY to the west end in IN. the KTB runs the maintenance building, this is were the broadcast  originated  . there is a huge antenna mast that has several different types of antennas leading to the main building.   I did contact the fcc and KTB to see if this was a contractor oversight ? for leaving the broadcast on a continuous loop?    for over a year !   after the email was replied to from the KTB. this broadcast was ended .