Topics

digital modes on 2m 70cm


Andrew OBrien
 

Ok digital mode folks, now that I have an all mode transceiver that includes 2 mètres and 70cm , where/when is the action ? Is there much action outside of contests ?

Andy K3UK


Graham
 

FT8  -(

73-G


Tony
 

Andy:

The most popular VHF modes are FT8 for terrestrial propagation and MSK144 for meteor scatter. You can get an idea what the activity is like by checking out PSK Reporter with the 2 meter filter on.

If you're used to 6 meters, you'll find that Sporadic-E and other long distance propagation modes typically happen less frequently on 2 meters and a lot less on 432 so it pays to get email alerts to let you know when the openings occur.

If you're looking for daily propagation on 2m and 70cm, aircraft scatter is the most consistent mode out to a few hundred miles. It's easily recognizable by the Doppler shifted signals which FT8 usually handles well.

I've attached a PSK Reporter screenshot that shows the distances you might see on 2 meter A/C scatter. The other screenshot will give you an idea what the A/C Doppler is like on 2 meters.

There are several amateur satellites that you can try as well.

Tony -K2MO


Andrew OBrien
 

Thanks Tony . I have done quite a bit of MS on 6 but nothing on 2M . I’ll try FT8

Andy

On Oct 18, 2020, at 10:24 PM, Tony <73GUDDX@...> wrote:

Andy:

The most popular VHF modes are FT8 for terrestrial propagation and MSK144 for meteor scatter. You can get an idea what the activity is like by checking out PSK Reporter with the 2 meter filter on.

If you're used to 6 meters, you'll find that Sporadic-E and other long distance propagation modes typically happen less frequently on 2 meters and a lot less on 432 so it pays to get email alerts to let you know when the openings occur.

If you're looking for daily propagation on 2m and 70cm, aircraft scatter is the most consistent mode out to a few hundred miles. It's easily recognizable by the Doppler shifted signals which FT8 usually handles well.

I've attached a PSK Reporter screenshot that shows the distances you might see on 2 meter A/C scatter. The other screenshot will give you an idea what the A/C Doppler is like on 2 meters.

There are several amateur satellites that you can try as well.

Tony -K2MO









<2M FT8.jpg>
<ACS.jpg>


Bruce
 

Hi Tony
Interesting subject on Airplane scatter on 2 meters. Bouncing signals off of aircraft could that interfere with electronic systems or communications in the aircraft? If you bounced signals off of military aircraft, could that be tracked and bring a visit by MP's?
Also what antenna polarization works best for the path ? Do both stations need to be using the same polarization? How do you find stations and frequencies being used and arrange a contact?
Thanks for the education.
Bruce WA6DNT@...

On 10/18/2020 7:24 PM, Tony wrote:
Andy:

The most popular VHF modes are FT8 for terrestrial propagation and MSK144 for meteor scatter. You can get an idea what the activity is like by checking out PSK Reporter with the 2 meter filter on.

If you're used to 6 meters, you'll find that Sporadic-E and other long distance propagation modes typically happen less frequently on 2 meters and a lot less on 432 so it pays to get email alerts to let you know when the openings occur.

If you're looking for daily propagation on 2m and 70cm, aircraft scatter is the most consistent mode out to a few hundred miles. It's easily recognizable by the Doppler shifted signals which FT8 usually handles well.

I've attached a PSK Reporter screenshot that shows the distances you might see on 2 meter A/C scatter. The other screenshot will give you an idea what the A/C Doppler is like on 2 meters.

There are several amateur satellites that you can try as well.

Tony -K2MO








KD7JYK DM09
 

"Bouncing signals off of aircraft could that interfere with electronic systems or communications in the aircraft?"

No, for many reasons. But, in short, think of the amount of RF spew in a radio septic tank such as Los Angeles, and that there are no problems... They fly around in a cloud of GigaWatts, from "DC to Daylight", all signals bouncing off of them, all the time, without issue.

Kurt


Andrew O'Brien
 

but I did see a video latest week showing the drift briefly caused by a plane when using WSPR 

Andy K3UK

On Wed, Oct 21, 2020 at 12:11 AM KD7JYK DM09 <kd7jyk@...> wrote:
"Bouncing signals off of aircraft could that interfere with electronic
systems or communications in the aircraft?"

No, for many reasons.  But, in short, think of the amount of RF spew in
a radio septic tank such as Los Angeles, and that there are no
problems...  They fly around in a cloud of GigaWatts, from "DC to
Daylight", all signals bouncing off of them, all the time, without issue.

Kurt








--
Andy


KD7JYK DM09
 

but I did see a video latest week showing the drift briefly caused by a plane when using WSPR
Doppler shift of the signal bouncing off the craft, or sudden uncontrolled skewing of the crafts flight path when passing through one of a billion RF carriers?

As for RF drift, yes, the basis of "radar". The earliest I've heard noted was the 1920's, when craft, and broadcasts, were becoming more common, although it was noted that RF signals bounced off of metal objects in the late 1880's, with increasing experimentation until the creation of functional radar in the mid-30's.

Kurt


Tony
 

Bruce:

Commercial and military aircraft fly through a sea of RF including megawatt radars that track satellites in space without incident. If there was any risk, big-gun 2 meter EME stations would be outlawed : ) Aircraft scatter is probably not what you imagined - we don't point our antennas at the aircraft.

The mode relies on an aircraft crossing the path between stations; when the geometry is right, signal reflecting from the aircraft rises above the noise so the contact can be made. The reflection weakens as the aircraft continues along it's path so the signal doesn't last very long. Range is limited to 400 miles or so.

I produced a demo video that shows what A/C scatter looks like on a spectrogram.

See: https://www.youtube.com/watch?v=vYkaSuJkYrM

Tony -K2MO

On 10/21/2020 12:00 AM, Bruce wrote:
Hi Tony
Interesting subject on Airplane scatter on 2 meters. Bouncing signals off of aircraft could that interfere with electronic systems or communications in the aircraft? If you bounced signals off of military aircraft, could that be tracked and bring a visit by MP's?
Also what antenna polarization works best for the path ? Do both stations need to be using the same polarization? How do you find stations and frequencies being used and arrange a contact?
Thanks for the education.
Bruce WA6DNT@...

On 10/18/2020 7:24 PM, Tony wrote:
Andy:

The most popular VHF modes are FT8 for terrestrial propagation and MSK144 for meteor scatter. You can get an idea what the activity is like by checking out PSK Reporter with the 2 meter filter on.

If you're used to 6 meters, you'll find that Sporadic-E and other long distance propagation modes typically happen less frequently on 2 meters and a lot less on 432 so it pays to get email alerts to let you know when the openings occur.

If you're looking for daily propagation on 2m and 70cm, aircraft scatter is the most consistent mode out to a few hundred miles. It's easily recognizable by the Doppler shifted signals which FT8 usually handles well.

I've attached a PSK Reporter screenshot that shows the distances you might see on 2 meter A/C scatter. The other screenshot will give you an idea what the A/C Doppler is like on 2 meters.

There are several amateur satellites that you can try as well.

Tony -K2MO











Graham
 

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


Bruce
 

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
,_._,_


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

 

CONFIDENTIALITY NOTICE:  This email constitutes an electronic communication within the meaning of the Electronic Communications Privacy Act, 18 U.S.C. 2510, and its disclosure is strictly limited to the named recipient(s) intended by the sender of this message.  This email, and any attachments, may contain confidential and/or proprietary information of the United States Air Force.  If you are not a named recipient, any copying, using, disclosing or distributing to others the information in this email and attachments is STRICTLY PROHIBITED.  If you have received this email in error, please notify the sender immediately and permanently delete the email, any attachments, and all copies thereof from any drives or storage media and destroy any printouts or hard copies of the email and attachments.

 

EXPORT COMPLIANCE NOTICE:  This email and any attachments may contain technical data subject to U.S export restrictions under the International Traffic in Arms Regulations (ITAR) or the Export Administration Regulations (EAR).  Export or transfer of this technical data and/or related information to any foreign person(s) or entity(ies), either within the U.S. or outside of the U.S., may require advance export authorization by the appropriate U.S. Government agency prior to export or transfer.  In addition, technical data may not be exported or transferred to certain countries or specified designated nationals identified by U.S. embargo controls without prior export authorization.  By accepting this email and any attachments, all recipients confirm that they understand and will comply with all applicable ITAR, EAR and embargo compliance requirements.

 

 

 

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

,_._,_


Joseph Yuna
 

It is a matter of frequency and not power unless we are talking EW for us military types.

Front-end designs prevent a lot of EMI/EMC being addressed here.

-----Original Message-----
From: main@digitalradio.groups.io <main@digitalradio.groups.io> On Behalf Of KD7JYK DM09
Sent: Wednesday, October 21, 2020 12:12 AM
To: main@digitalradio.groups.io
Subject: Re: [digital-mode-radio] digital modes on 2m 70cm

"Bouncing signals off of aircraft could that interfere with electronic systems or communications in the aircraft?"

No, for many reasons. But, in short, think of the amount of RF spew in a radio septic tank such as Los Angeles, and that there are no problems... They fly around in a cloud of GigaWatts, from "DC to Daylight", all signals bouncing off of them, all the time, without issue.

Kurt


KD7JYK DM09
 

"It is a matter of frequency and not power unless we are talking EW for us military types. Front-end designs prevent a lot of EMI/EMC being addressed here."

Imagine if all the military RF was poured into ISDM bands like consumer garbage, and limited to 100mW!

Kurt