K1TTT wrote:
> Which one?? old rdf stuff used a loop or ferrite antenna to find a null in
> strength,
I'm referring to ADF, the old set of VHF, vertically polarized dipoles
on a pole that you'd see at most major airports. No loop was involved.
When you keyed your radio the ADF display would show a line on the scope
face in the direction to the transmitter. IIRC the antennas were small
for the frequency used to I figure it'd scale for most ham bands.
Of course, if you can find one, the ADF in the airplane could be adapted
to work in the ham bands.Complicated and expensive, but the NDB
approaches and hardware are being decommissioned. This means there
should be quite a bit of surplus, mobile equipment available. Standard
operation is at just over 100 KHz.. It's a rather complicated receiver
to set up as it uses a rotating loop and a sense antenna. It's sorta
like mounting your portable with its sense antenna on a turntable and
graphing the output versus position. All you need is a signal input
and noise will work. Unfortunately so does lightning, and lots of other
phenomena.
Because these things are expensive you don't see much ham
experimentation, but when they are phased out there should be plenty
available. The thing I have always liked about the ADF (NDB approach)
is you can also tune in the AM broadcast band and if you are stuck in
the middle of nowhere you can use a radio station to home in on and with
an accurate map make your own approach. Not legal, but in an emergency
...any port in a storm. Of course on a long night flight you can listen
to the news, music or what ever is being offered. I kinda prefer it as
a backup to GPS rather than the proposed *augmented* Loran.
73
Roger (K8RI)
> Doppler df uses electronically rotated vertical array to generate
> a synthetic doppler shift and determine direction by measuring the phase of
> the shift.
>
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt@arrl.net
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>
>
>
>> -----Original Message-----
>> From: Roger (K8RI) [mailto:k8ri@rogerhalstead.com]
>> Sent: Tuesday, July 14, 2009 01:35
>> To: K1TTT
>> Cc: rfi@contesting.com
>> Subject: Re: [RFI] Looking for ideas about yet another noise source
>>
>> I've never seen the circuitry, but how did the old ADF equipment work?
>> Might it be adaptable with a computer and display to display and overlay
>> on a GPS moving map?
>>
>> 73
>>
>>
>> Roger (K8RI)
>>
>> K1TTT wrote:
>>
>>> Those Doppler shift antennas won't work on noise. They require a
>>>
>> carrier,
>>
>>> preferably unmodulated, to detect the Doppler shift on while they rotate
>>>
>> the
>>
>>> array.
>>>
>>>
>>> David Robbins K1TTT
>>> e-mail: mailto:k1ttt@arrl.net
>>> web: http://www.k1ttt.net
>>> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>>>
>>>
>>>
>>>
>>>> -----Original Message-----
>>>> From: Roger (K8RI) [mailto:k8ri@rogerhalstead.com]
>>>> Sent: Monday, July 13, 2009 00:47
>>>> To: kb4t@arrl.net
>>>> Cc: rfi@contesting.com
>>>> Subject: Re: [RFI] Looking for ideas about yet another noise source
>>>>
>>>>
>>>>
>>>> Frank Haas KB4T wrote:
>>>>
>>>>
>>>>> Chris:
>>>>>
>>>>> The random nature of your pulsing interference means you will have to
>>>>> invest more time to find the source. It's not going to be easy and
>>>>> will likely be very time consuming because of its intermittent nature.
>>>>> You have the right tools so now you have to use them to the best
>>>>> advantage.
>>>>>
>>>>>
>>>>>
>>>> How about building up one of those "doppler shift" antennas? I've seen
>>>> them used on 2-meters and for close in work I'd think it could be
>>>> adapted to 20.
>>>>
>>>> For years I've chased what at times can be an obnoxious and loud hash.
>>>> It should be easy to catch as it's often on for some time, but
>>>> unfortunately when I get the chance to chase it, every time I get about
>>>> a city block to the SE it disappears and does not come back. It's like
>>>> they are watching for me...Nothing like a little paranoia.
>>>> When it's on it's loud at well over S-9 including the entire 6-meter
>>>> band, down to some where a bit above 40 meters. It's normally a day
>>>> time signal that is strong from the NE to S where it fades rapidly.
>>>>
>> The
>>
>>>> only electric fence in that direction is probably a bit over a mile.
>>>> While there is one to the S that I've never heard. There is one of the
>>>> big high tensions lines that at its closest is about a quarter mile to
>>>> the NE but I've never heard anything in that direction.
>>>>
>>>> OTOH I haven't heard it in over a year.
>>>>
>>>> 73
>>>>
>>>> Roger (K8RI)
>>>>
>>>>
>>>>> Keep a log and note the day(s) and time(s) that the interference
>>>>> occurs. Is there a time/day when it seems to occur more frequent. If
>>>>> you keep a log for several days, do you note an increase or decrease
>>>>> in activity.
>>>>>
>>>>> Is the activity level affected by environment? Day or night, warm or
>>>>> cool? Prime time vs. Daytime? Trend analysis may show you better times
>>>>> to hunt the source.
>>>>>
>>>>> If you are convinced that the source is not in your home, you will
>>>>> have to start walking around the neighborhood particularly at times
>>>>> your trend analysis says you are likely to hear the source.
>>>>>
>>>>> If the signal level varies from moment to moment you will have to note
>>>>> the highest and lowest levels and try to find an attenuator setting
>>>>> that gives you something in the middle. Another approach might be to
>>>>> set the attenuator so the level is more or less consistently low and
>>>>> start moving around to see if there are any locations where the signal
>>>>> strength seems higher?
>>>>>
>>>>> I could go on and on but hopefully by now you see my point. Thorny
>>>>> problems like yours require collecting more data and thinking more
>>>>> about how you can use your tools to your advantage. Invest the time
>>>>> and use your tools wisely and you will locate your source.
>>>>>
>>>>> I can't encourage you enough NOT to SPECULATE as to what the source
>>>>> might be. In my experience, guessing what the source might be has been
>>>>> a waste of time. Even with all the experience I have now, I rely on my
>>>>> tools to lead me directly to the source. The only meandering I'll do
>>>>> is in the early stages of the hunt when I'm trying to find the general
>>>>> direction I must take to the source. Once I get a "lock" I focus on
>>>>> that direction. Sometimes it takes a bit of effort to get the "lock"
>>>>> but that's what the trend analysis and wide open receivers do for me.
>>>>> I prefer to work smart rather than work hard. I hate to waste time so
>>>>> I limit guessing as much as possible.
>>>>>
>>>>> Good luck & 73,
>>>>>
>>>>> Frank N. Haas KB4T
>>>>>
>>>>> -----Original Message-----
>>>>> Message: 4
>>>>> Date: Sun, 12 Jul 2009 02:33:05 -0500 (CDT)
>>>>> From: "Christopher E. Brown" <cbrown@woods.net>
>>>>> Subject: Re: [RFI] Looking for ideas about yet another noise source
>>>>> To: kb4t@arrl.net
>>>>> Cc: rfi@contesting.com
>>>>> Message-ID: <Pine.LNX.4.64.0907120217560.19313@tree.woods.net>
>>>>> Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
>>>>>
>>>>> I have a Grundig SW rig, but I find the HT (wideband receive w/ AM)
>>>>> with a step attenuator and a small shielded loop to be more useful.
>>>>> Also have a simple coax faraday pickup for in close.
>>>>>
>>>>> The issue is that the signal is strong but *SHORT*, think snap your
>>>>> fingers short, and while it may repeat after a few seconds the long
>>>>> term average is a couple times a minute or less.
>>>>>
>>>>> If I had a second or 2 to rotate the loop... But I don't.
>>>>>
>>>>> I even tried connecting the loop to the main tranceiver mounted to the
>>>>> desk so that I could try to plot long term averages while rotating the
>>>>> loop 5 deg every 10 minutes. Only problem, the peak reading for the
>>>>> pulse varies up to 40db from pulse to pulse.
>>>>>
>>>>> I am pretty much down to guessing likely canadates, adding enough
>>>>> attenuation to lose the pulses, and then placing the loop phyically
>>>>> close to suspect devices and waiting. The only thing I do know is
>>>>> that it is not in home or a reciever generated issue. All AC power
>>>>> cut, still there.
>>>>> 2 seperate HF rigs and an HT on three seperate antennas, still there
>>>>> on all three.
>>>>>
>>>>> Even went as far as listening on one receiver/antenna, then cutting
>>>>> power to that receiver and powering up another just to totally rule
>>>>> out the radio gear as a source.
>>>>>
>>>>> I keep hoping that whatever the device is it is some form of
>>>>> "statekeeping" status, and that I can catch it in an active state
>>>>> generating pulse trains of 10 seconds or longer so I can properly DF
>>>>> it.
>>>>>
>>>>> _______________________________________________
>>>>> RFI mailing list
>>>>> RFI@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/rfi
>>>>>
>>>>>
>>>>>
>>>>>
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>
>
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