The AM Forum

For at least 2 weeks there has been a spurious signal on 3570 KHz that has been heard by several members of the Old Mil Radio CW net,  at least around New England.  Consisits of a continuous series of slow CW dits ......possibly someone's cat knocked a keyer paddle onto transmit for a rig left on somewhere?  At any rate its kind of annoying, we have had to move the OMRN on Sunday nights to get away from it.  Can someone do some RDFing on it?

What kind of cat ?

A dit-zy one.

I just took a listen and didn't hear anything on 3570, but the static crashes are horrendous right now. 

When is the military CW net?

I am reminded of the old movie I haven't seen in 35+ years I believe is called "On the Beach" where the crew of a U.S. submarine returns to the U.S. mainland after a nuclear war.  On the way back, the sub hears a random CW signal on the air.  I don't remeber if the the transmitter was at a Navy base or not, but they tracked down the transmitter and found a window shade pull loop on the neck of a Coke bottle which was lying on a straight key.  The window was cracked open and hence the random CW being sent.

"On The beach"; some of the best CW you'll hear in a movie. When the shore party discovers coke bottle/key, one of the actors grabs the hand key and sends a short message back to the sub. Copyable about 15 wpm, it had prosigns and everything. As I recall, he sends something like "COKE BOTTLE ON KEY. RETURNING SHIP NW. AR SK"

(http://www.animation-station.com/cats/images/cat025.gif)

My kind of cat. FEARLESSLY defending his human from an arrogant and menacing turntable.

The Old Military Radio Net CW session is at 2100 eastern every Sunday night on 3570 (+/- kitten on the key!) through about 2200.  The AM net is at 0500 eastern every Saturday morning on 3885, through about 0700.

This guy needs a church key:

(http://prettyhazel.com/Graphics/Baseball%20Cat-2.jpg)

And a lime and a straw.

Chris,

I check in to this net as well and it just sounds like dah dah dah dah dah dah not di di di di

I'm learning about HFDF at my new Job at DRS. They use some cool hardware to do HFDF pronounced  "HUFFDUFF".

You want HUFFDUFF my friend.

The coolest aid in HFDF is to employ iono-sounder MUF data to tell how far away the station you are DFing is. It is all done through trig. If you know what layer is reflecting you can tell how far away the station is on a single bounce on a given frequency.

Ionosounders are located worldwide and they are used for propagation study. Here is a station that gives ionosounder data http://digisonde.haystack.edu/latestFrames.htm

Mike WU2D

Hi Chris, how is the Volvo's HF going, recovered from lighting strike?

As for your DF request, this is where several of the internet receiver sites can be helpful, I think Paul VJB published a list some time back.
You can select ones which will give you an idea of the geographic coverage of the signal in question.
Once you have a rough idea of coverage, you could ask local hams in those areas to track it down.

You could also informally request the OO team to get involved, Paul also posted the info for that, or contact me off board for specifics.

When does this occur, all the time, just during nets, evenings, etc.?
I'll listen out at my QTH if I know when to monitor.


73 Bruce W1UJR

HF DF on high angle of arrival signals is very hard to do.

Right on that one Steve.
At the freq Chris mentioned, I was thinking ground wave, if you can find internet stations close enough.
Think that would work.

Ground wave will work very well. But you would need to be within a few miles or so on 75 meters to receive groundwave. Using a bunch of Web receivers may allow you to narrow the signal down to a particular areas (maybe a few states or less). After that, somebody will probably need to go mobile. Try listening in the daytime, especially around noon. This time of the year, if a receiver can hear the signal at noon, it is probably fairly close.


I can take a listen with my directional antenna. But I will only be able to tell if the signal is coming from one of four quadrants on the compass.

Perhaps the deployment of EMP or HERF countermeasures would do the trick?  ::)

I was thinking of building a HF lojac system with 4 6830s.
It would be cool to get the matching DF processor

Bruce. spark gap machine....a big one

Luft Der Zeppelin!


Thus the value when you can do it.

Mike WU2D

The trig and geometry limitations are what make it hard. No one I know can do it with any significant accuracy, at least when compared to lower angle of arrival signals. A large baseline on the DF stations is very important.

Frank, what do you think about a Poulsen Arc transmitter?
Labeled as "1000" KW in photo.

(http://www.geocities.com/neveyaakov/electro_science/poulsen_arc2.jpg)

Conventional amplitude based systems which use monopoles do not work because all of the antennas will see about the same incident signal. This rules out many systems such as Watson-Watt and most conventional ham systems such as psuedo doppler (as used by LoJacK by the way).

If you can accurately measure phase and amplitude, and have good antennas it becomes possible to DF even high vertical incidence signals. Theoretically a zero phase angle would mean it is directly overhead! Steve You are correct - not easy..

Mike WU2D

And this is only for a single ray solution! Add in multiple rays (aoa's, phase, etc) and it gets even more tricky. That's why you get paid the big bucks!

Mark there is a lot of net data on chirp sounders. TCI makes a lot of that stuff.

Holy cow, this one brought Mark QHQ out of the woodwork!

Get out your loops men - we will triangulate!

Actually last week I switched from my inverted L which is pretty much a blob on 80M to my 3 element vertical array which is set up pointing west right now. Western stations are much louder on this. But I could not honestly say that the beeper was better or worse so I do not think it is west. 

Mike WU2D

I meant to post smething on this post last week...

With the issue of high angle waves, I wonder if anyone has considered using a Time Difference of Arrival (TDOA)method?  This would entail creating a "system" with networked receivers.  The receivers could be set up within a region, like New England.  Perhaps a half dozen or so or more.  This approach is how lightning strikes are tracked and also E911.  The signals are compared to each other and the shortest path is the most direct line to the transmitter of interest.  This way there is no concern as to whether you are tracking an incident signal (ground wave) or high angle path.

With everyone on high speed networks these days, I think many people could contribute with a "site". 

But there is no free lunch as the saying goes.  I'm not certain this would work.  And someone would have to come up with some software and receivers that would be compatible.  One receiver that may work are the software controlled types from Icom.  They have an electronic interface (CI-V) for frequency control and signal RSSI.

Anyway, an idea to consider. 
Peter
n1ps

I listened to the net Sunday night and there was no interference.  I also realized that I'm pretty rusty on code reception.

_._

I did not hear it either Sunday night. Gone hopefully.