[eagle] Re: PAVE PAWS EMI

John B. Stephensen kd6ozh at comcast.net
Tue Sep 4 21:54:56 PDT 2007

Hi Juan,

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

> Lee,
> 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 
> to
> a mountain top that has line of sight to them, or moving into the local 
> area
> 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 
> was
> 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...
> 73,
> Juan
> -----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
> original
> files?  I know there was an upgrade done at Beal so it is now known as
> having
> 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 
> to
> 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 
> an
> 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 
> might
> avoid some of the problems the repeater owners are now having higher in 
> the
> band.  ARRL is reporting that some repeaters are being asked to reduce 
> their
> output by 7 to 54 dB.
> 73,
> Lee-KU4OS
> On Monday 03 September 2007 21:47:00 Juan Rivera wrote:
>> Bob,
>> We spent the afternoon trying to characterize the pulses that I see here
>> with my antenna pointed north.  See my last plot for details:
>> http://www.juanr.com/pages/hobbies/ham_radio/Eagle/PAVE_PAWS.htm
>> 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 
>> impact
>> reports from years ago.  Because of the recent push to clear ham 
>> repeaters
>> 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 
>> weeks.
>> 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
>> blanker.
>> > I'll take a look and try again if it was on.  Right now I can't
>> communicate
>> > with the CAN-Do module or I would switch to the 70 cm prototype 
>> > receiver
>> and
>> > 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.
>> Bob
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