- Amateur Radio has many diverse interests. CW, Rag Chew, RTTY, SSTV, Contests, DX, Repeaters, D-Star, EME, Phil's latest digimode ...
- These diverse interests can coexist. There are occasional gripes about things that conflict but for the most part it is live and let live.
- Amateur Radio satellites are different. Unlike other aspects of Amateur Radio it requires a group to make it happen.
- What the majority wants is more important than any individual want.
How do you determine what the majority wants.
- Voting People will vote one way or another. If people are not given the opportunity to vote they will vote with their feet and walk away if they are not happy. In the absence of voting a small group or individual will get what they want. That may or may not be the best thing for the group.
I used to think that voting in AMSAT was necessary. Working a linear satellite pass with very little activity followed by an FM satellite that is packed is perhaps the best indicator of what the group wants.
- 'Better than Dead' I am not a fan of LEO FM satellites but it does seem to be what people want and it is something we can do. I saw a crippled old guy wearing a cap that had 'Better than Dead' embroidered on it. When I feel disappointment in what is happening I think of that guy. Is an LEO FM satellite better than no satellite at all - for me it is certainly at least a little bit better than dead. For the group it seems like the only logical choice.
73 W9KE Tom Doyle
On 07/20/2014 06:10 AM, Thomas Doyle wrote:
- What the majority wants is more important than any individual want.
How do you determine what the majority wants.
- Voting
The results of an election are strongly determined by who gets to vote.
If you poll the tiny fraction of the amateur community currently active on satellites, you'll get one answer.
If you poll the much larger pool of people (including people who aren't even hams yet) who might be interested in something else, you may well get another answer.
But not right away; it's been shown time and again that people often don't know they want something until you show it to them, and then they simply have to have it. Think mobile phones and Internet, the two things I spent my career on. It wasn't long ago that people (including most hams) rolled their eyes whenever I talked up the idea of global computer networking and mobile personal communications. Who couldn't wait until they got home to make a phone call? Who needed to send a letter instantly when they had the phone or the US mail? Who cared about talking to other countries unless they had relatives there?
Don't also forget that the AMSAT membership hardly pays for its satellites. The volunteer engineering that goes into each one of them is easily worth millions of dollars at market rates. And it must be understood that there is no such thing as a volunteer willing to work for nothing, even though they don't get paid in money. You have to give them something else, and in the case of engineering an amateur satellite that "something else" is an interesting technical challenge that makes them feel like they've really accomplished something.
Doing the same thing over and over certainly doesn't make me feel like I've accomplished something.
--Phil
I'll finally charm in on this.
Don't also forget that the AMSAT membership hardly pays for its
satellites. The volunteer engineering that goes into each one of them is easily worth millions of dollars at market rates. And it must be understood that there is no such thing as a volunteer willing to work for nothing, even though they don't get paid in money. You have to give them something else, and in the case of engineering an amateur satellite that "something else" is an interesting technical challenge that makes them feel like they've really accomplished something.
Doing the same thing over and over certainly doesn't make me feel like I've accomplished something.
Most of this is true. However, you're looking at a narrow slice of the Fox-1 satellites, that being the operating mode of FM/Analog.
I'm currently building the Fox-1 series satellite Maximum Power Point Tracker. It's a hell of a project. Could AMSAT have bought one off the shelf, yes. However, it's also true that what the majority wants is what the majority gets. In the cubesat world Universities are the majority. They have money, lots of it. Their missions are 6 months to a year. Most commercial cubesat MPPTs are not designed for much longer of missions.
In contrast AMSAT is gaining a huge amount of Intellectual property by designing an analog MPPT where the algorithm is completely stateless and part selection is aimed at helping guarantee that a 5+ year mission is possible. Most of the market doesn't care about this, it's hard to do and using a microcontroller is ridiculously more straightforward. Just do a Google search for MPPT, nearly everything you find will be using perturb and observe with a microcontroller or super pricey/almost non-existant analog multipliers or the maximum current method (which relies on the battery being present). The Fox-1 MPPT is specifically designed to not need a battery at all for nominal operation.
Cubesats are standardizing AMSATs satellites and there's much much more to the satellite than simply the amateur radio mode used to communicate. If I do my job right, and others working on their Fox-1 subsystems do their jobs right too, you will never know it... it will be invisible to the average user.
Once AMSAT can rapidly and reliable get basic cubesats into orbit, then it can start going wild on experimental modes and such.
For the record, I'm all for digital satellites. I also understand how too much complexity too quickly isn't a good thing either.
Bryce KB1LQC
On Sun, Jul 20, 2014 at 8:00 PM, Phil Karn karn@ka9q.net wrote:
On 07/20/2014 06:10 AM, Thomas Doyle wrote:
- What the majority wants is more important than any individual want.
How do you determine what the majority wants.
- Voting
The results of an election are strongly determined by who gets to vote.
If you poll the tiny fraction of the amateur community currently active on satellites, you'll get one answer.
If you poll the much larger pool of people (including people who aren't even hams yet) who might be interested in something else, you may well get another answer.
But not right away; it's been shown time and again that people often don't know they want something until you show it to them, and then they simply have to have it. Think mobile phones and Internet, the two things I spent my career on. It wasn't long ago that people (including most hams) rolled their eyes whenever I talked up the idea of global computer networking and mobile personal communications. Who couldn't wait until they got home to make a phone call? Who needed to send a letter instantly when they had the phone or the US mail? Who cared about talking to other countries unless they had relatives there?
Don't also forget that the AMSAT membership hardly pays for its satellites. The volunteer engineering that goes into each one of them is easily worth millions of dollars at market rates. And it must be understood that there is no such thing as a volunteer willing to work for nothing, even though they don't get paid in money. You have to give them something else, and in the case of engineering an amateur satellite that "something else" is an interesting technical challenge that makes them feel like they've really accomplished something.
Doing the same thing over and over certainly doesn't make me feel like I've accomplished something.
--Phil _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 07/20/2014 08:42 PM, Bryce Salmi wrote:
Cubesats are standardizing AMSATs satellites and there's much much more to the satellite than simply the amateur radio mode used to communicate. If I do my job right, and others working on their Fox-1 subsystems do their jobs right too, you will never know it... it will be invisible to the average user.
This is absolutely true, especially for the power subsystem you're working on. So it's vital that the payload use that power as efficiently as possible.
The biggest load in a communications satellite (most spacecraft, actually) is the downlink power amplifier, and that's why it's so important that the downlink use the most power-efficient communications mode available. And that's not FM, SSB or any other analog mode, not by a long shot.
Here are some numbers for comparison. NBFM typically uses 15 kHz bandwidth, and a SNR of at least 10-12 dB in that bandwidth is required for acceptable performance. That's a P/No (power to noise spectral density ratio) of about 53-54 dB-Hz.
A CODEC2 encoded voice signal at its highest rate (and quality) is 3200 bps. (Codec2 was specifically developed for ham radio digital voice by VK5DGR, and outperforms many commercial voice codecs.)
The CCSDS-standard turbo FEC codes require an Eb/No (energy per bit to noise spectral density ratio) of -0.25 to +1.5 dB, depending on code rate and block size (the lower the code rate and the bigger the block size, the lower the required Eb/No). This is remarkably close to the Shannon limit.
Assuming an Eb/No of +1 dB and a CODEC2 data rate of 3200 bps, a single voice signal therefore requires a P/No of 10*log10(3200) + 1 = 36 dB-Hz, 17-18 dB less than the FM voice signal.
That's a power savings of something like 60x, which in a power limited system like a communications satellite turns directly into a capacity increase of 60:1. That is, you could carry 60 digital voice signals with the power required by a single FM voice signal. Or you could carry a single digital voice signal with 1/60 of the power required for a single FM voice signal.
This should give some clue as to why almost the entire (non-amateur) world has gone digital.
--Phil
participants (3)
-
Bryce Salmi -
Phil Karn -
Thomas Doyle