Hi Rick, I've been monitoring FO-29 on and off for the last few weeks as part of my AO-73 to FO-29 cross link experimentation. I have consistently seen FM on FO-29. In fact I played a video at the AMSAT symposium where I pointed it out in a spectral display (FFT and Waterfall) of the FO-29 downlink. We can see the entire noise floor of FO-29's passband with the VTGS setup, and when the FM activity jumps up, you can see the entire passband of the transponder drop in power as the FM signal sucks up all the power of the transponder.

I have detected, but have yet to decode AO-73's tlm beacon via FO-29. Right now I'm operating on a weak crosslink signal theory as the reason for failed decodes. I can hear FO-29 just fine (in fact VERY strong at VTGS), but AO-73 is barely making it into the uplink passband. I've come up with a simulation tool thats a mixture of STK output data and python that tells me when chain events will occur (a chain being AO-73 to FO29 to VTGS) and a whole bunch of other info like doppler offsets, crosslink path loss, etc.

In fact, this last Friday, around 1357 Eastern time, was one of the best opportunities to catch AO-73 via FO-29, in terms of minimum crosslink path loss, in a two week window. At the beginning of the FO-29 pass there was LOTS of FM activity on FO-29. I was cursing and pulling my hair out (to the dismay of the students who were watching) because I was worried that the FM activity would suck up resources on the transponder right when I'm hunting for a weak signal on the bird. BUT... as the satellite continued through the pass (an ascending pass) the FM activity died down, which was good for my experiment because the AO73 chain event was about the last 300 seconds or so of the pass. I still didn't decode (though I *think* I detected AO-73, I need to review the capture file more) because doppler shift had the AO-73 signal sweeping right through the center of FO-29's passband, where there was lots of normal SSB activity.

So yes, in the last couple weeks I've seen a LOT of FM activity on FO-29. And based on my experience with Friday's pass, which was ascending, I'm leading towards the Central/South America QRM theory. Lots of strong FM activity as the pass started and the satellite was over the lower latitudes, but as FO-29 ascended over higher latitudes towards the north pole, the FM activity died down.

-Zach, KJ4QLP

On 11/08/2015 03:25 PM, Jim Jerzycke wrote:

On 11/08/2015 07:03 PM, Rick Walter wrote:

...

I was just on the 18:44 Z pass of FO-29 and was certain I heard an FM signal around 435.869. There was a loud squeal and it sounded like an alien was talking! Should I get my hearing checked or did anyone else notice? Thanks. Rick - WB3CSY in FN10

I've heard FM on FO-29 before, but it's been a while. I forget if it was a Ham, or a Mexican/South American taxi or similar.

73, Jim KQ6EA _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb

Speaking of FM signals on FO-29, you'll be able to hear the AO-85 transponder through FO-29 when their paths cross as well. I wonder if you could get a high enough SNR to decode the DUV...

73,

Paul, N8HM

On Sun, Nov 8, 2015 at 5:30 PM, Clayton W5PFG w5pfg@amsat.org wrote:

I wouldn't recommend playing the FM audio heard via FO-29 to a group of children. Normally it's not English. It's most likely NOT a religious broadcast based on their choice of crude words.

73 Clayton W5PFG

On 11/8/2015 16:13, Zach Leffke wrote:

...

So yes, in the last couple weeks I've seen a LOT of FM activity on FO-29. And based on my experience with Friday's pass, which was ascending, I'm leading towards the Central/South America QRM theory. Lots of strong FM activity as the pass started and the satellite was over the lower latitudes, but as FO-29 ascended over higher latitudes towards the north pole, the FM activity died down.

-Zach, KJ4QLP

---

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Sweet, second cross link signal to look into! I missed that, you got the gears turning.......

So lets see.... 145.900MHz to 146.000MHz for FO-29 passband.

A quick look through JE9PEL satlist reveals these downlinks:

AO73 tlm bcn, 145.935 MHz AO73 transponder, 145.970-145.950 MHz AO85, 145.978 MHz First-MOVE cubesat (NORAD ID 39439), 145.970MHz DUCHIFAT, 145.980 MHz QB50p1/FUNcube3 (EO-79) transponder, 145.970-145.945 MHz VELOX-I, 145.980 MHz UKube-1/FUNcube-2, 145.915 MHz DeorbitSail, 145.975 MHz CAS-3E (XW-2E) transponder, 145.935-145.915 MHz CAS-3F (XW-2F) transponder, 146.000-146.980 MHz Fox-1B, 145.960 MHz Fox-1C, 145.920 MHz

I guess its not that surprising when FO-29 has half of the 2m Satellite Service allocation for its uplink. Next thing to do is figure out which ones are the most likely to be successful based on power levels, modulation schemes, transmission rate, which ones are using Forward Error Correction, etc. And then look at the orbits for possible chain events.

fun stuff!

Does anyone know the uplink receiver sensitivity and antenna gain/design on FO-29?

-Zach, KJ4QLP

On 11/08/2015 05:33 PM, Paul Stoetzer wrote:

Speaking of FM signals on FO-29, you'll be able to hear the AO-85 transponder through FO-29 when their paths cross as well. I wonder if you could get a high enough SNR to decode the DUV...

73,

Paul, N8HM

On Sun, Nov 8, 2015 at 5:30 PM, Clayton W5PFG w5pfg@amsat.org wrote:

...

I wouldn't recommend playing the FM audio heard via FO-29 to a group of children. Normally it's not English. It's most likely NOT a religious broadcast based on their choice of crude words.

73 Clayton W5PFG

On 11/8/2015 16:13, Zach Leffke wrote:

...

So yes, in the last couple weeks I've seen a LOT of FM activity on FO-29. And based on my experience with Friday's pass, which was ascending, I'm leading towards the Central/South America QRM theory. Lots of strong FM activity as the pass started and the satellite was over the lower latitudes, but as FO-29 ascended over higher latitudes towards the north pole, the FM activity died down.

-Zach, KJ4QLP

---

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Zach

On Sun, Nov 8, 2015 at 5:54 PM, Zach Leffke zleffke@vt.edu wrote:

well.. when I say students, I meant graduate students at VT that happened to be in the lab when I was doing the experiment. They work with me and Bob, so a few crude words here and there aren't uncommon to them.

But good point, probably not the best thing for a public demo if your audience is a bit younger.

Actually, I've seen so much FM activity (basically every time I've monitored FO-29 since we first came online in late september) that I've been toying with the idea of trying to locate where the source emitters actually are located based on doppler shift data. We know the doppler between the receiving ground station and FO-29, so we can back that out. We know the transponder mapping, so we can work through that to determine what the center frequency is as the signal enters the transponder uplink receiver. What we don't know is the uplink doppler, because we don't know where the emitter is and we don't know what exact center frequency they are on (but I bet you its in 5kHz steps, maybe 2.5kHz). So we have two unknowns. I'm betting there's a way to work through it though, and with enough observations and by watching the rate of change of the doppler, I bet there's a way to make an educated guess on what their center freq and location are.

Or if someone listening knows Spanish and/or Portugese, maybe we could get lucky and hear what cross streets the taxi is going to (if it is in fact a taxi).

-Zach, KJ4QLP

On 11/08/2015 05:30 PM, Clayton W5PFG wrote:

...

I wouldn't recommend playing the FM audio heard via FO-29 to a group of children. Normally it's not English. It's most likely NOT a religious broadcast based on their choice of crude words.

73 Clayton W5PFG

On 11/8/2015 16:13, Zach Leffke wrote:

...

So yes, in the last couple weeks I've seen a LOT of FM activity on FO-29. And based on my experience with Friday's pass, which was ascending, I'm leading towards the Central/South America QRM theory. Lots of strong FM activity as the pass started and the satellite was over the lower latitudes, but as FO-29 ascended over higher latitudes towards the north pole, the FM activity died down.

-Zach, KJ4QLP

---

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---

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Good point Bob. I haven't fully worked through the problem yet, but thats pretty much right in line with what I'm thinking. Thats what I meant by saying watching the 'rate of change of doppler.' When the slope of the doppler s-curve is at a maximum, that should be the point of closest approach.

Actually, that brings up a question. Do you know what type of equation would fit the doppler S-Curve profile? something that could be used to generate a regression equation from a few doppler observations?

-Zach, KJ4QLP

On 11/08/2015 06:12 PM, Robert Bruninga wrote:

Zach You dont need to know the senders exact freq, just a plot of his freq during the pass will form an "S" curve and once you have enough of the "S", you can know his center freq, and hence his closest point of approach. That gives a line of bearing. Anothe pass gives another one, and so on...

bob

On Sun, Nov 8, 2015 at 5:54 PM, Zach Leffke <zleffke@vt.edu mailto:zleffke@vt.edu> wrote:

well.. when I say students, I meant graduate students at VT that
happened to be in the lab when I was doing the experiment.  They
work with me and Bob, so a few crude words here and there aren't
uncommon to them.

But good point, probably not the best thing for a public demo if
your audience is a bit younger.

Actually, I've seen so much FM activity (basically every time I've
monitored FO-29 since we first came online in late september) that
I've been toying with the idea of trying to locate where the
source emitters actually are located based on doppler shift data. 
We know the doppler between the receiving ground station and
FO-29, so we can back that out.  We know the transponder mapping,
so we can work through that to determine what the center frequency
is as the signal enters the transponder uplink receiver.  What we
don't know is the uplink doppler, because we don't know where the
emitter is and we don't know what exact center frequency they are
on (but I bet you its in 5kHz steps, maybe 2.5kHz).  So we have
two unknowns. I'm betting there's a way to work through it though,
and with enough observations and by watching the rate of change of
the doppler, I bet there's a way to make an educated guess on what
their center freq and location are.

Or if someone listening knows Spanish and/or Portugese, maybe we
could get lucky and hear what cross streets the taxi is going to
(if it is in fact a taxi).

-Zach, KJ4QLP

On 11/08/2015 05:30 PM, Clayton W5PFG wrote:

    I wouldn't recommend playing the FM audio heard via FO-29 to a
    group of children. Normally it's not English.  It's most
    likely NOT a religious broadcast based on their choice of
    crude words.

    73
    Clayton
    W5PFG

    On 11/8/2015 16:13, Zach Leffke wrote:

        So yes, in the last couple weeks I've seen a LOT of FM
        activity on
        FO-29.  And based on my experience with Friday's pass,
        which was
        ascending, I'm leading towards the Central/South America
        QRM theory.
        Lots of strong FM activity as the pass started and the
        satellite was
        over the lower latitudes, but as FO-29 ascended over
        higher latitudes
        towards the north pole, the FM activity died down.

        -Zach, KJ4QLP

    _______________________________________________
    Sent via AMSAT-BB@amsat.org <mailto:AMSAT-BB@amsat.org>.
    AMSAT-NA makes this open forum available
    to all interested persons worldwide without requiring
    membership. Opinions expressed
    are solely those of the author, and do not reflect the
    official views of AMSAT-NA.
    Not an AMSAT-NA member? Join now to support the amateur
    satellite program!
    Subscription settings:
    http://www.amsat.org/mailman/listinfo/amsat-bb


_______________________________________________
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to all interested persons worldwide without requiring membership.
Opinions expressed
are solely those of the author, and do not reflect the official
views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb

No worries, I thought on it a bit more and I think a cubic polynomial is the right fit. I also found some python tools for regression calculations that I think will be useful for this. Also, I think this is pretty similar to how the COSPAS/SARSAT system used to locate lost ships (EPIRBs) and downed Aircraft (ELTs) before the proliferation of GPS and its inclusion in the locator beacons.

Concerning the lines of bearing. I'm still churning this one in my head, but I think basically point of closest approach will give us a line that is perpendicular to the ground track at that point. That should be the moment when range rate and thus doppler hits zero. Like you said take enough measurements over enough orbits and see where the lines begin to cross. I know there are some more algorithms for this, like Brown's Least Squares Triangulation Algorithm.

The work flow that's forming in my head is as follows: 1. Measure the signal doppler shift. 2. Work backwards through the transponder to get the uplink doppler as it enters the receiver (to remove doppler between measuring G/S and FO-29). 3. use regression to get the cubic polynomial S-curve of doppler. 4. Find the inflection point in the S-Curve (the zero crossing) that gives the instant in time for PCA. 5. Go back to SGPs+TLEs to determine subsatellite point and ground track at that instant. Which gives us the line of bearing for that orbit. 6. Repeat 1 - 5 over multiple orbits to get multiple lines of bearing. 7. Use triangulation algorithms to determine the likely lat/long of the emitter as well as the confidence interval (Error elliptical probable).

Things that kill this plan are multiple emitters on different frequencies. If its a taxi then the emitter is moving around which will dilute precision in the position estimate. Frequency drifts in the emitter and spacecraft can introduce errors. Stale TLEs will cause more errors.

A stretch goal might be to turn this into a Master's Level research topic for a graduate student, especially when trying to characterize all the sources of error and how that impacts the final estimate. If we could develop a working tool that AMSAT could use to locate illegal emitters, maybe that could provide a body of evidence that could be taken to say the IARU, to then maybe put pressure on the host countries to crack down on illegal use of the Amateur bands (likely a pipe dream to see actual political movement though, or see any real reduction in the QRM, but one can hope!).

Fun Stuff!

-Zach, KJ4QLP

Research Associate Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305

On 11/9/2015 9:54 AM, Robert Bruninga wrote:

No, I’m all talk and no do… compared to whiz kids and Matlab… Im old fashioned enough to just plot it on graph paper and LOOK for the middle hi hi…

*From:*Zach Leffke [mailto:zleffke@vt.edu mailto:zleffke@vt.edu] *Sent:* Sunday, November 08, 2015 6:55 PM *To:* Robert Bruninga *Cc:* amsat bb *Subject:* Re: [amsat-bb] FM signal on FO-29?

Good point Bob. I haven't fully worked through the problem yet, but thats pretty much right in line with what I'm thinking. Thats what I meant by saying watching the 'rate of change of doppler.' When the slope of the doppler s-curve is at a maximum, that should be the point of closest approach.

Actually, that brings up a question. Do you know what type of equation would fit the doppler S-Curve profile? something that could be used to generate a regression equation from a few doppler observations?

-Zach, KJ4QLP

On 11/08/2015 06:12 PM, Robert Bruninga wrote:

Zach

You dont need to know the senders exact freq, just a plot of his
freq during the pass will form an "S" curve and once you have
enough of the "S", you can know his center freq, and hence his
closest point of approach.  That gives a line of bearing.  Anothe
pass gives another one, and so on...

bob

On Sun, Nov 8, 2015 at 5:54 PM, Zach Leffke <zleffke@vt.edu
<mailto:zleffke@vt.edu>> wrote:

well.. when I say students, I meant graduate students at VT that
happened to be in the lab when I was doing the experiment.  They
work with me and Bob, so a few crude words here and there aren't
uncommon to them.

But good point, probably not the best thing for a public demo if
your audience is a bit younger.

Actually, I've seen so much FM activity (basically every time I've
monitored FO-29 since we first came online in late september) that
I've been toying with the idea of trying to locate where the
source emitters actually are located based on doppler shift data. 
We know the doppler between the receiving ground station and
FO-29, so we can back that out. We know the transponder mapping,
so we can work through that to determine what the center frequency
is as the signal enters the transponder uplink receiver.  What we
don't know is the uplink doppler, because we don't know where the
emitter is and we don't know what exact center frequency they are
on (but I bet you its in 5kHz steps, maybe 2.5kHz).  So we have
two unknowns.  I'm betting there's a way to work through it
though, and with enough observations and by watching the rate of
change of the doppler, I bet there's a way to make an educated
guess on what their center freq and location are.

Or if someone listening knows Spanish and/or Portugese, maybe we
could get lucky and hear what cross streets the taxi is going to
(if it is in fact a taxi).

-Zach, KJ4QLP

On 11/08/2015 05:30 PM, Clayton W5PFG wrote:

I wouldn't recommend playing the FM audio heard via FO-29 to a
group of children. Normally it's not English. It's most likely NOT
a religious broadcast based on their choice of crude words.

73
Clayton
W5PFG

On 11/8/2015 16:13, Zach Leffke wrote:

So yes, in the last couple weeks I've seen a LOT of FM activity on
FO-29.  And based on my experience with Friday's pass, which was
ascending, I'm leading towards the Central/South America QRM theory.
Lots of strong FM activity as the pass started and the satellite was
over the lower latitudes, but as FO-29 ascended over higher latitudes
towards the north pole, the FM activity died down.

-Zach, KJ4QLP

_______________________________________________
Sent via AMSAT-BB@amsat.org <mailto:AMSAT-BB@amsat.org>. AMSAT-NA
makes this open forum available
to all interested persons worldwide without requiring membership.
Opinions expressed
are solely those of the author, and do not reflect the official
views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb


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to all interested persons worldwide without requiring membership.
Opinions expressed
are solely those of the author, and do not reflect the official
views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
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Hi Daniel, Thanks for the info. I'll look into it more when I get a free moment. And for the cubic thing, I just meant that it appears that the doppler S-curve looks like a third order polynomial over the course of a full pass. After a quick google search, the first image at this link is what I mean (in this case envision time along the y axis and doppler offset along the x axis).

http://www.biology.arizona.edu/biomath/tutorials/polynomial/graphingpolynomi...

But I haven't looked into this fully yet, and it sounds like you might be saying that its not that simple. I was just looking into regression equations for the purposes of curve fitting from a number of discrete doppler offset observations. At a quick glance, the cubic polynomial seemed like the right 'shape' for the regression.

I think what you might be warning about is that, in doing so, because there are a large number of parameters that go into the generation of the doppler (and its s-curve), that we might be losing necessary fidelity in the data by assuming a cubic polynomial? Honestly this all kind of new territory for me, so any and all advice is welcome.

Thanks again for the info, much appreciated.

-Zach, KJ4QLP

Research Associate Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305

On 11/9/2015 3:29 PM, Daniel Estévez wrote:

Dear Bob and Zach,

This paper might be worth looking at: http://www.dtic.mil/dtic/tr/fulltext/u2/409103.pdf

As far as I know, it started the whole business of location by measurement of Doppler shift.

Apparently, according to the success of project Transit, it is possible to:

a) Compute the TLEs of a satellite by using just a few minutes of the Doppler curve of the beacon of a satellite, as received on a ground station with known location.

b) Compute the location of a ground station, by using just a few minutes of the Doppler curve of the beacon of a satellite with known TLEs, as received on said ground station.

Of course, several variation on this are possible, such as the one which is discussed here:

Compute the location of a ground station by using the Doppler curve of its transmissions during a pass, as received on a satellite with known TLEs.

It seems that the key point in all this is that the Doopler curve depends independently on all the parameters in question (so not a cubic polynomial, which depends on fewer parameters).

73,

Dani M0HXM/EA4GPZ.

El 09/11/15 a las 17:59, Zach Leffke escribió:

...

No worries, I thought on it a bit more and I think a cubic polynomial is the right fit. I also found some python tools for regression calculations that I think will be useful for this. Also, I think this is pretty similar to how the COSPAS/SARSAT system used to locate lost ships (EPIRBs) and downed Aircraft (ELTs) before the proliferation of GPS and its inclusion in the locator beacons.

That makes sense Hector. I've seen the FM activity kind of all over the transponder. More so than I would expect if it was the same transmitter each time on the same frequency and the different pass geometries causing a bit of swing due to doppler.

-Zach, KJ4QLP

On 11/08/2015 06:34 PM, Hector W5CBF/CO6CBF wrote:

Hi Zach and group

I think, the main problem is they are not always the same stations. I have heard several different stations in terrestrial QSOs QRMing FO-29; majority of them speaking Spanish and without any kind of ID. I have not heard them recently, though.

73!

Hector, CO6CBF/W5CBF

-----Mensaje original----- De: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] En nombre de Zach Leffke Enviado el: Sunday, November 08, 2015 4:54 PM Para: amsat-bb@amsat.org Asunto: Re: [amsat-bb] FM signal on FO-29?

well.. when I say students, I meant graduate students at VT that happened to be in the lab when I was doing the experiment. They work with me and Bob, so a few crude words here and there aren't uncommon to them.

But good point, probably not the best thing for a public demo if your audience is a bit younger.

Actually, I've seen so much FM activity (basically every time I've monitored FO-29 since we first came online in late september) that I've been toying with the idea of trying to locate where the source emitters actually are located based on doppler shift data. We know the doppler between the receiving ground station and FO-29, so we can back that out. We know the transponder mapping, so we can work through that to determine what the center frequency is as the signal enters the transponder uplink receiver. What we don't know is the uplink doppler, because we don't know where the emitter is and we don't know what exact center frequency they are on (but I bet you its in 5kHz steps, maybe 2.5kHz). So we have two unknowns. I'm betting there's a way to work through it though, and with enough observations and by watching the rate of change of the doppler, I bet there's a way to make an educated guess on what their center freq and location are.

Or if someone listening knows Spanish and/or Portugese, maybe we could get lucky and hear what cross streets the taxi is going to (if it is in fact a taxi).

-Zach, KJ4QLP

On 11/08/2015 05:30 PM, Clayton W5PFG wrote:

...

I wouldn't recommend playing the FM audio heard via FO-29 to a group of children. Normally it's not English. It's most likely NOT a religious broadcast based on their choice of crude words.

73 Clayton W5PFG

On 11/8/2015 16:13, Zach Leffke wrote:

...

So yes, in the last couple weeks I've seen a LOT of FM activity on FO-29. And based on my experience with Friday's pass, which was ascending, I'm leading towards the Central/South America QRM theory. Lots of strong FM activity as the pass started and the satellite was over the lower latitudes, but as FO-29 ascended over higher latitudes towards the north pole, the FM activity died down.

-Zach, KJ4QLP

---

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---

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