Re: digital modes on 2m 70cm


Joseph Yuna
 

First, there are other hyper-spectral systems on the market for the blind.

 

Second, the Tomcat (US Navy not USAF) F-14A+ is no more, The “Falcon” F-16N is an USAF fighter, not long-range fighter interceptor.

 

Third, the F-16N systems were not affected by that radar gun. If so, the Program Office and AO supporting the aircraft should be relieved of all and any future duties within the USAF Acquisition Corp.

 

 

 

Regards,

 

Joseph D. Yuna

Joseph D. Yuna

Principal Systems Engineer

 

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From: main@digitalradio.groups.io <main@digitalradio.groups.io> On Behalf Of Bruce
Sent: Wednesday, October 21, 2020 6:18 PM
To: main@digitalradio.groups.io
Subject: Re: [digital-mode-radio] digital modes on 2m 70cm

 

Hi Graham

You brought back a memory of when I was working for the County as a radio tech. I was troubleshooting a pesky problem with a speed radar gun used by the Sheriff. The needle would hang up about half scale instead of falling to zero. Out of desperation I installed a headphone jack in the Doppler Radar audio path. I found the switching power supply was introducing a whine which was seen as a "signal." After I repaired the power supply, I took it on a test run. With the headphones I could hear the Doppler shift as I panned the dish antenna. Pan the signals up a stairway and I could hear the steps. I could tell where walls were. (Note: this could be developed into a useful tool for the blind) If I aimed it at a vehicle that was using a stick shift I could hear the shift points. Hmmm I thought what would it do with Military aircraft landing at a nearby Navy base? We drove to a frontage road that crossed the landing pattern, stopped and waited. Sure enough, a "Tom Cat F16 was landing. There are no "sights" on the gun to aim the marrow beam - but I was able to get a return and the audio tone went thru a screaming 8-10 KHz and the meter pegged hard well above 100 MPH!! I did not stick around for the MP's to show up! I wonder if the F16 IFF alarm went off?!

73 Bruce WA6DNT       

 

On 10/21/2020 1:34 PM, Graham wrote:

Bruce 

Interesting  point on the  military aircraft , popular rumer had/has  it , that one of the  local  police , out on traffic speed  duty , close to a  scottish air base , out of curiosity , pointed his  hand held 'speed gun' at one of the  aircraft coming  into  land , which lit up the  counter measures suite , end of career .. 

Its more to  re-radiation , most of the  aircraft to  day are  composite hulls ,  [one of the reasons for the  11 meter  ww2 radar , was aircraft wing was round 35 feet , so it gave a  good  return  signal]  so the  signals are not as  good as  in the past , polarisation ,  probably Horizontal , I would  expect the  return  signal to  be modified  , dopper plays a part as well , so the  decoder needs  to have a  wide  acceptance 
bandwidth , I think the  doppler shift is up to  x2  if the  target is  advancing ,  first shift  tx> a/c  then a/c >> rx  , at 600 mph , that's  round  +150 Hz on 2 meter's  ?

Ive  found this  write up  by two  spanish  stations  using a  plotting/ prediction software package to  give the  expected  angles / range , google translate makes a  good  job  of converting  to  english , just noticed it was  back in  2014  , when the  decoder was re-worked  during the  eme  testing

http://hamlincs.blogspot.com/2014/04/aircraftscatter-144mhz-con-opera.html?fbclid=IwAR3KXz9kxfm9-ePVvANjWkI4iOAfG0JtbV76Jps3TC4TXv3gQZUbTHYgJ5Y

This was a  scatter  spot , from a French  10 watt  70 cm  beacon, using a  halo round  Ae to  south of france   to paris 704 Kmt , confirmed by 
the  keeper 

19:56 432418 F5ZAS de F1RJ Op05 -19 dB F:2% in JN18AT 1390,6 Hz

>> Foxsix Htj Yes, Aircraft Scatter, big airplane above Clermont Ferrand (matching with AirScout software).

73-Graham
g0nbd

,_._,_

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