[eagle] Re: PAVE PAWS EMI
juan-rivera at sbcglobal.net
Tue Sep 4 22:08:55 PDT 2007
Whatever it is that we're seeing here, it's not an artifact of the spectrum
analyzer since we see the same thing using the USRP DSP board.
I had what I thought was a brilliant idea -- since the TS-2000 has two
receivers (a main one and a sub-receiver) I could put them in different PAVE
PAWS channels and record stereo. I did and sure enough the pulses don't
correlate at all. Then I moved the two receivers to opposite ends of the
same channel (or at least what looks like a channel) and they still didn't
correlate, or maybe they do and I'm not used to the freeware I just
downloaded... Finally I put them both on the exact same frequency. They
still look different. I think some if this can be explained by the fact
that they are completely different designs - one is complex and the other is
simple. They both have DSP processing so there could be different delays
through both. Net result - I still don't know what I'm looking at. I tried
to upload all of this to my web so everyone could take a look but the files
are so big I have to scale everything down and try again tomorrow.
From: John B. Stephensen [mailto:kd6ozh at comcast.net]
Sent: Tuesday, September 04, 2007 9:55 PM
To: juan-rivera at sbcglobal.net; 'Lee McLamb'; eagle at amsat.org
Cc: 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)'; 'Samsonoff at Mac.
Com'; 'Juan.Rivera (Work)'
Subject: Re: [eagle] Re: PAVE PAWS EMI
The spectrum that you posted didn't look like the radar interference that I
would see on 70 cm in Los Angeles when the Navy conducted exercises off the
coast. It looked like dozens of emitters, each sweeping more or less
synchronously across a few MHz, since the sweep speed on the spectrum
analyzer was much lower than the repitition frequency of the radar.
----- Original Message -----
From: "Juan Rivera" <juan-rivera at sbcglobal.net>
To: "'Lee McLamb'" <ku4os at cfl.rr.com>; <eagle at amsat.org>
Cc: "'David Smith'" <w6te at msn.com>; "'Dave Black (Work)'"
<dblack at mail.arc.nasa.gov>; "'Dave Black (Home)'" <dblack1054 at yahoo.com>;
"'Samsonoff at Mac. Com'" <samsonoff at mac.com>; "'Juan.Rivera (Work)'"
<Juan.Rivera at gd-ais.com>
Sent: Wednesday, September 05, 2007 02:55 UTC
Subject: [eagle] Re: PAVE PAWS EMI
> I think you may be correct - my data may in obsolete. I think we will be
> able to determine if what I am seeing here is really PAVE PAWS by moving
> a mountain top that has line of sight to them, or moving into the local
> near the base. I am going to try to make a stereo .wav file with my main
> receiver on one channel and the sub receiver on the other. By tuning the
> two receivers to what appears to be two different PAVE PAWS channels I may
> be able to see if the pops I hear are correlated across both or not. If
> they are not I think that strengthens my feeling that this probably is
> PAWS. Once we get up on a mountain we can tell with much more confidence,
> but I can try this now.
> I may have the original files, but I extracted everything that I thought
> pertinent and put it in the ATP already.
> Once we get the CAN-Do module running again, and we see if there are guard
> bands, then I can tune the 70 cm receiver into one to see if that improves
> the situation.
> I'll post my .wav file if I get it done this evening...
> -----Original Message-----
> From: Lee McLamb [mailto:ku4os at cfl.rr.com]
> Sent: Tuesday, September 04, 2007 7:38 PM
> To: eagle at amsat.org; juan-rivera at sbcglobal.net
> Cc: 'Robert McGwier'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black
> (Home)'; 'Samsonoff at Mac. Com'; 'Juan.Rivera (Work)'
> Subject: Re: [eagle] Re: PAVE PAWS EMI
> Another source you could be seeing is the airborne AN/APS-145 UHF radar
> although it typically has a fairly distinctive 6 second pattern looking in
> the time domain due to the antenna rotation rate.
> The web site cited in the ATP has been taken down. Did you save the
> files? I know there was an upgrade done at Beal so it is now known as
> both the original EWR and the UEWR modes. I'm wondering if perhaps the
> frequencies in Table D-2 are for the EWR. Also with the 1 MHz
> chirp, "channel 11" will be creeping into the satellite sub-band as well.
> Another thought that comes to mind is that we might be well served to try
> pick our uplink passband in the guard bands if we can determine what they
> are. AO-40's 70cm analog uplink was 435.550 - 435.800 MHz. That gave it
> almost perfect worst case frequency alignment with channel 13. We'd
> probably need to check all three sites, Beale, Cape Cod and perhaps
> Flyindales, UK to feel sure we had a good handle on the spectrum. Another
> advantage to putting ourselves in the 'quiet zones' is that our Users
> avoid some of the problems the repeater owners are now having higher in
> band. ARRL is reporting that some repeaters are being asked to reduce
> output by 7 to 54 dB.
> On Monday 03 September 2007 21:47:00 Juan Rivera wrote:
>> We spent the afternoon trying to characterize the pulses that I see here
>> with my antenna pointed north. See my last plot for details:
>> You'll see several evenly spaced areas showing many hits over about a 30
>> minute span. They are too evenly spaced to be random but they don't
>> conform to the PAVE PAWS band plan that I pulled from environmental
>> reports from years ago. Because of the recent push to clear ham
>> off of the air anywhere in the vicinity of a PAVE PAWS site, we know
>> something has changed, but what?
>> To resolve all of our questions we'll need to move to an unobstructed
>> location atop a local mountain and try again. That will take a few
>> Until then I would be cautious about using my .wav file. It might be the
>> neighbor driving around the block on his Harley.
>> 73, Juan
>> -----Original Message-----
>> From: Robert McGwier [mailto:rwmcgwier at gmail.com]
>> Sent: Monday, September 03, 2007 10:11 AM
>> To: juan-rivera at sbcglobal.net
>> Cc: 'Dave hartzell'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black
>> (Home)'; eagle at amsat.org; 'Samsonoff at Mac. Com'; 'Juan.Rivera (Work)'
>> Subject: Re: [eagle] Re: PAVE PAWS EMI
>> Juan Rivera wrote:
>> > Hi Dave,
>> > I noticed that too. I killed the AGC but didn't think of the noise
>> > I'll take a look and try again if it was on. Right now I can't
>> > with the CAN-Do module or I would switch to the 70 cm prototype
>> > receiver
>> > repeat the test.
>> > Juan
>> Yes, please. I have some interesting noise blanker stuff I want to work
>> on to eliminate PAVE PAWS pulses on board the SDX transponder. This is
>> the PERFECT set of signal collection (SDR-IQ of IF) for doing that work.
>> Thank you very much once again Juan for your extremely valuable
>> contributions and your unbridled enthusiasm. It is very welcome indeed.
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> Eagle at amsat.org
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