Interference help

  • 1
  • Question
  • Updated 4 years ago
  • Answered
Good evening Flexers,

This QRM is driving me crazy.  It's a 1 second down frequency sweep about 1 second apart.  Please see the pic of the interference.  I'm assuming it's some kind of a timer but I can't seem to locate it.  Has anyone seen/heard this before and have any suggestions about what it might be?  I've been monitoring some AF MARS Freqs and I only see this on the freq indicated.  I hear it on all my antennas no matter what time of day at the same level so I'm assuming it's a local problem.  Any help would be appreciated.

 

Thanks.

Tom
WQ5O
Photo of Tom - WQ5O

Tom - WQ5O

  • 40 Posts
  • 4 Reply Likes

Posted 4 years ago

  • 1
Photo of Stu Phillips - K6TU

Stu Phillips - K6TU, Elmer

  • 642 Posts
  • 256 Reply Likes
Tom,

I suspect what you are hearing is CODAR - its a system used to measure wave heights on large bodies of water - usually the ocean.  I realize you are far from the ocean and I have no clue whether they have such systems deployed on Lake Michigan.

Stu K6TU
Photo of Tom - WQ5O

Tom - WQ5O

  • 40 Posts
  • 4 Reply Likes
Stu,
I found the CODAR signal on youtube and it's similar to what I'm hearing on 4.5MHz.  It seems faster, 2 pulses a second vice the 1 a second I'm hearing, but the wave form and the display are identical.  Ok, I guess I'll just have to live with it since I don't expect the FCC to chime in on something like this.  I swung my hex beam around 360 and found that the signal strenght didn't change no matter which way the antenna was pointed.  Thanks.
(Edited)
Photo of George Molnar, KF2T

George Molnar, KF2T, Elmer

  • 1639 Posts
  • 599 Reply Likes
Welcome to the most frustrating part of modern HF radio. Start with KY6LA's excellent guide on building a quiet station. Rule out everything in your house by literally shutting it all down at the breakers (run the rig on battery, use a laptop). Drive the neighborhood while tuned to the offensive frequency. I spent about a year cleaning up my end as best possible before finally buying an MFJ noise cancelled (phasing unit) to knock down the worst off-premise noise.

If you get "lucky" and identify an external source that is owned by someone who wants to fix it, bonus points.

It's a pain, a lot of work, but you can make a very big improvement. And that makes it worthwhile.
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 4166 Posts
  • 1329 Reply Likes
I hear it in Indiana right now (02:42Z).  Actually I hear several of them.
One sweeps from 4.550 down to 4.500 MHz.
another overlaps it from 4.588 down to 4.5280 MHz.
there are still others up and down the band.
and a much faster sweeper sweeping up from 4.420 to 4.445 at about 4 sweeps per second.

I always thought these were a form of over the horizon radar, but Stu's theory might be a better one.


 
Photo of Stu Phillips - K6TU

Stu Phillips - K6TU, Elmer

  • 642 Posts
  • 256 Reply Likes
There are many of these things here in California and this is a common frequency range in which to find them. I tried searching to see if there was anything about wave radar deployment on the Great Lakes but didn't find anything.
Hard to know for sure.

Stu K6TU
Photo of dan martin

dan martin

  • 7 Posts
  • 2 Reply Likes
For what it's worth it shows up in Florida as well... There are so many strange signals outside the ham bands that we may never ID or locate, but it's part of the reason I purchased the 6500 I like to listen have from the time I was 12 and go an old Philco radio with Short Wave...
Photo of Tom - WQ5O

Tom - WQ5O

  • 40 Posts
  • 4 Reply Likes
Thanks everyone.  It seems to be CODAR. 

George, I have a very quiet station and very little interference in the ham bands.  Fortunately I live in a very small neighborhood outside of town on a hill and all the homes were built within the last 10 years.  My place is quiet as a mouse.  Thanks for all the suggestions.  I'd never heard of CODAR before and was thinking it was something that had a built in timer that was causing the noise.  Glad to know it's not something in the house, neighborhood or ham bands. 

My 6500 is great and receives better than any radio I've ever owned or operated.  The receivers I used while on active duty back in the 70-90s were bricks compared to the 6000 series.  We had the Collins 651-1S receiver that was state of the art when I was pounding brass for a living.  They were really good but don't even compare with the SDRs. 

Thanks again.  73.

Tom
Photo of Doug K0DV

Doug K0DV

  • 142 Posts
  • 17 Reply Likes
Another thought, is your or your neighbor's plasma TV .  My Plasma TV's really tear up the bands with noise similar to the spacing you show in the screen capture.  Router and switching power supplies can also be a problem, however the panadapter display usually shows these more as spikes.
Photo of Tom - WQ5O

Tom - WQ5O

  • 40 Posts
  • 4 Reply Likes
Not sure what TV they have.  I have nothing but LEDs in the house but had a Plasma when i was in Oklahoma.  Never had any interference from that TV.  Other than that 4Mhz CODAR it's really quiet RF wise.  My shack is wall wart city and no problem so far.  Seems everything has a wallwart attached now days. 
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 3636 Posts
  • 876 Reply Likes
I have the same thing here, I am sure a neighbor's tv is doing it, they stay up late at night and when they go to bed it disappears. I wish it would blow up soon....

This conversation is no longer open for comments or replies.