Ham receives ISRO Mars Orbiter

Hello, and greetings from Boston!

So, are you saying that we are looking at ILLEGAL data captures (that may or may not be of Mom in orbit seen with a 3 foot chicken wire dish)? Are you also saying that my opinion on these matters COINCIDES with the law?

Is that an unreasonable point of view to articulate and defend my friend? If so, why?

I am law abiding, very productive, and enjoy a good life at the border of a ripe old age.

And I have 42 years of radio astronomy background--pure and (one of the few doing it!) applied;-)

73
Chip W1YW

 

Ron,

I feel like you just ignored my analysis and swept it under the rug.

Assuming reading is a viable option, I invite you to go back and look again.

But for the reading-challenged, I provide the following:

1) A good rule of thumb is that a system temperature of 290 degrees K with one second integrations at 1 Hz yields -174 dBm for a 1 sigma noise . Easy to remember. Motivated by the average earth temp, and simple time-bandwidth product=1. Ron tried to beat this down by assuming that detection was at 1 sigma. Ron, I am sorry, but that is just not true. In spectroscopy, which is what you have here with oodles and oodles of channels and a hunt for spikes, the probability of a false detection sky rockets with more and more channels, so the usual 3 or 5 sigma detection threshholds do not apply. And 1 sigma is NEVER a detection threshhold... Sheesh! Ten sigma is usually the conservative min in the absence of multiple, independent observations(which we are not provided), if you wish to prove that a given channel's 'detection' is real.

2) Please get real on the system temperature. The data shown --that is not with the 'may be bogus' disclaimer--was at roughly ten degrees elevation at his location on 26 Sept. But his alleged chicken wire dish has a 3 dB beamwidth of about 10 degrees (9 something). So the dish is seeing a big swath of hot earth on side portions of the main lobe. Thus your -178 dBm for 1 sigma applies (won't quibble on a dB or so). BUT THE NOISE CEILING STAYED THE SAME AS HIS PREVIOUS DATA ALLEGEDLY TAKEN AT MUCH HIGHER ELEVATIONS. Please: doesn't that raise your suspicions?

3) Combining 1 and 2 your detection threshhold is 10 dB + -178 dB = -168 dBm. Not -182.8 dBm.

Reviewing the ERP /Friis side next (again).

73
Chip W1YW

 

M0EYT is either unwilling or unable to provide even modest info on ability to track, and do on-offs...

But hey--we're all HAMS we can DO WHAT WE WANT!

73
Chip W1YW

 

...except I gave you the compelling reasons already: the data itself--allegedly Mom RX'ed with a 3 foot chicken wire dish-- shows mulitple detected spikes in several channels. So the power in the one (apparently arbitrarily selected) is diluted by the power distributed to other channels. There is no evidence that ISRO uses a monochromatic narrow band carrier for its link. That would be data throughput challenging. Not Morse code.

Probably down at least 6 dB based on the mimimum number of spikes seen in the data, and that's ignore what TX spikes are extant OUTSIDE of the shown passband. And you are dreaming on full throttle. Spacecraft only run full throttle when the RX link shows flakiness. Thus my estimate of roughly 100-150 watts, say, down another 3 dB. That's at least 9 dB addition loss. Could easily be 10+dB down from your assumed value of 230 watts in that one channel..

73
Chip W1YW

 

Can you provide a reference for this "sigma" stuff?

 

I imagine everyone's basic, original source on all these noise vs signal issues is from the MIT Rad Lab series of books. There are plenty of folks reading the mail. I invite them to pipe in on that.

Let me motivate it a bit more. Let's say you have one passband. For convenience, let's say its a MHz wide. You use the noise formula and you get the RMS (1 sigma) value of the noise. Then you measure the 'signal'. You know the noise has Gaussian statistics (actually not, but pretty close) so you want to define a detection threshhold that is statistically significant above the noise. IF YOU ARE ONLY LOOKING AT THAT ONE 1 MHz passband, then the probability statistics tell you that there is only a small fraction of 1 % probability that a 'signal' at 3 times RMS will occur--as noise. I will let you look up the usual Gaussian probability profiles---kids get them nowadays in intro stat courses.

Now. Let's say you have an additional million 1 MHz passbands and you are trying to decide which, if any have a 'signal'. If you defined that threshhold as 3 sigma, you would be astounded to find that there are dozens and dozens of 'signals' that are actually noise.

What happened? How can that be?

73
Chip W1YW

 

BTW Ron,

I am so old that I remember doing an 8 point FFT--BY HAND--in my radio astronomy class at Cornell. Frank Drake co-taught ;-) God bless Cooley and Tukey!

Man, you guys have it easy these days!

73
Chip W1YW

 

You know, an online reference. A set of books from 1945 isnt exactly in every engineers library. And BTW, I'm retired.

 

Paul,

Could you kindly explain the legalities involved in your sat measurements? The Wireless Act of 2006 may preclude these efforts. I would appreciate knowing more, some clarification,and your thoughts.


Thanks,

Chip W1YW

 

Nah. Someone else can dig that out for you online . I have a 3000 volume library.I collect the tech books that others chuck.

I' m not retired. I have no concept of that, but respect that others do.

And the Rad Lab series is a popular DVD BTW.


73
Chip W1YW

 

Come on Chip. If you can't back it up, then I'll have to assume it's just hand waving on your part.

 

No Chip,

You are going 'off topic' yet again. The topic is 'ham receives ISRO MOM orbiter'. The WT act is relating to 'communication' not the presence of a carrier signal or its frequency.

You may explain to myself and the rest of the amateur community how this so called 'bogus' signal can remain within a 0.76Hz FFT bin whilst being Doppler corrected using JPL ephemeris data during its flight to Mars... Are you really telling me that 'QRM' happens to exhibit the same drift etc, as the legitimate MOM S-Band signal? Take http://pjm.uhf-satcom.com/twtr/mom_150614.jpg as an example, the coherent signal from MOM is within this FFT bin after Doppler correction - some sort of random 'artifact', or could it REALLY be the signal from MOM?????

I would REALLY like to hear your expert consultation on that since the chances of it happening are probably about the same as me receiving an apology from you....

I'm REALLY looking forward to your explanation of that one.....

Have a GREAT day Chip,

regards,

Paul M0EYT.

 

Not a dumb question. But it's a reason confirmation from ISRO would be a good thing.

 

He claims pure and applied radio astronomy experience for 40+ years. Silly me, I thought he turned away from Drake to Mandelbrot and has been bending little wires all that time.

 

Of course it is THE question. But Paul has provided sufficient evidence (Doppler correction) to prove the signal came from MOM. And of course everybody doing this kind of experimenting is checking the signal's origin by turning the antenna away and back to confirm the right direction. This is a matter of course. Nobody, not Paul, not myself and not the other guys receiving interplanetary spacecraft would even think about talking to anyone before they successfully performed this test.

W1YW is not really interested in the subject. He only wants to bully. He ignores any explanation. He has lost his face and now he can't go back to a reasonable position. In my eyes he is completely disqualified in technical matters. I wouldn't take him serious in any regard any longer. Maybe he has made some money with his obscure fractal antenna stuff. Doesn't matter. You can sell any nonsense to sufficiently ignorant people with a lot of money if you have the right story. Evidence is not required.

And let me add: I am receiving MOM's signal almost every evening. It is getting more difficult because of the low elevation but it is still possible. Here is a recording a few hours before Mars orbit insertion. http://edgarkaiser.homepage.t-online.de/MOM_140923_1645_2292.96.jpg

Cheers
Edgar