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.
73,
John KD6OZH
----- Original Message ----- From: "Juan Rivera" juan-rivera@sbcglobal.net To: "'Lee McLamb'" ku4os@cfl.rr.com; eagle@amsat.org Cc: "'David Smith'" w6te@msn.com; "'Dave Black (Work)'" dblack@mail.arc.nasa.gov; "'Dave Black (Home)'" dblack1054@yahoo.com; "'Samsonoff@Mac. Com'" samsonoff@mac.com; "'Juan.Rivera (Work)'" Juan.Rivera@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 PAVE 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@cfl.rr.com] Sent: Tuesday, September 04, 2007 7:38 PM To: eagle@amsat.org; juan-rivera@sbcglobal.net Cc: 'Robert McGwier'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)'; 'Samsonoff@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@gmail.com] Sent: Monday, September 03, 2007 10:11 AM To: juan-rivera@sbcglobal.net Cc: 'Dave hartzell'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)'; eagle@amsat.org; 'Samsonoff@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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