Re: [amsat-bb] Digital Satellites Question

2014-07-27 Thread Phil Karn
On 07/22/2014 08:50 AM, Douglas Phelps wrote:
 And, in a related question, wouldn't more proccessing demand more
 power from the batteries/solar panels?  I know my PC cetainly draws a
 lot more power when the CPO is working hard.

Not really. The biggest load in a communications satellite, or almost
any robotic spacecraft for that matter, is almost always the downlink RF
power amplifier(s). Using them more efficiently can justify almost anything.

Also, even highly efficient digital modes tend to be easy to generate;
many spacecraft do (or did) so purely in hardware. Demodulating and
decoding them is more work so uplink and downlink modes are often
different, each optimized for its purpose.

--Phil
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Re: [amsat-bb] Inclusion (satcoms?)

2014-07-27 Thread Phil Karn
On 07/22/2014 11:05 AM, Robert Bruninga wrote:

 The value of ham radio is providing communications where other systems
 cannot.  And of course, playing with toys just for fun.

I'd flip that around. With the Internet, mobile phones and other
ubiquitous communications, about the sole reason left for ham radio to
exist is **education**. And playing with toys just for fun is often
quite educational as well.

Ham radio provides a hands-on opportunity to teach and learn radio (and
electronics) technology, and you still can't find anything like it
anywhere else.

Emergency communications is still in there somewhere, but in all honesty
I now see it as a distant second.

And if one is to teach oneself communications and electronics technology
through ham radio, then ham radio really ought to use something like the
communications and electronics technologies that the outside world is
using today, not just those the world was using 40 years ago.

--Phil
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Re: [amsat-bb] AMSAT where are we going for what it is worth.

2014-07-27 Thread Phil Karn
On 07/22/2014 11:19 AM, Bryce Salmi wrote:
 All this requires much much much more power than a 1U satellite is
 currently capable of producing. At least for always on type operating.
 We'll get there eventually.

Only if you keep the analog modes since they hog nearly all the
available power and drive the spacecraft design in many other ways. Let
go of them, and many new things suddenly become possible for the first time.

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[amsat-bb] Yaesu G-5500 AZ/EL rotor for sale

2014-07-27 Thread John / NS1Z
This rotor is less than a year old. It works perfectly and is in very good 
condition. Works with any
of the ST series interfaces (ST-1 and ST-3). Selling the rotor, control box, 
Satellite serial port interfaces ST-3 and SAT668.

It really is Plug and Play

$450 plus shipping

Thanks

-Original Message- 
From: Phil Karn

Sent: Sunday, July 27, 2014 1:12 AM
To: amsat-bb@amsat.org
Subject: Re: [amsat-bb] going digital

On 07/22/2014 07:27 AM, JoAnne Maenpaa wrote:


When thinking of projects to enter into the digital communication
world plan on building or buying that digital interface to connect
your radio to the soundcard.


Soundcard interfaces to existing voice radios were a good start, but
it's time to move past them. I've designed several modulation and coding
schemes to fit existing radios, and their inherently limited bandwidth
is a major pain. For ARISSat-1 I agreed to cram everything through a SSB
filter, and I'm not doing that again.

Not only does the narrow bandwidth often limit the data rate to much
less than what the link budget could actually support, but it enormously
aggravates the Doppler problem. It doesn't help that there are no
industry-wide standards for SSB phase response or computer tuning, or
that every time you retune one (which is often) there is a poorly
characterized phase jump.

Doppler is much easier to handle at high data rates because it's the
ratio of the symbol rate to the Doppler that matters, not the absolute
amount of Doppler.

Now that we have a variety of pure digital radio front ends to choose
from, it's time to set aside the voice radio + soundcard model. Not only
do the SDRs support wider bandwidths but they tend to be considerably
smaller, lighter and easier to work with in software. Some, like the
Funcube dongle, are even considerably cheaper than conventional radios.

--Phil

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Re: [amsat-bb] Inclusion (satcoms?)

2014-07-27 Thread Diane Bruce
On Sat, Jul 26, 2014 at 11:31:51PM -0700, Phil Karn wrote:
 On 07/22/2014 11:05 AM, Robert Bruninga wrote:
 
  The value of ham radio is providing communications where other systems
  cannot.  And of course, playing with toys just for fun.
 
 I'd flip that around. With the Internet, mobile phones and other
 ubiquitous communications, about the sole reason left for ham radio to
 exist is **education**. And playing with toys just for fun is often
 quite educational as well.
 
 Ham radio provides a hands-on opportunity to teach and learn radio (and
 electronics) technology, and you still can't find anything like it
 anywhere else.

Agreed and this is the primary focus I took when doing up our club
brochure. http://www.db.net/~db/oarc_db_brochure.pdf
Our future is with the young is education. The idea of sitting in
your livingroom talking to people all over the world is something
doable with modern technology (even IRC!) not hamradio. This is the
wrong approach.
 
 Emergency communications is still in there somewhere, but in all honesty
 I now see it as a distant second.

I agree.

 
 And if one is to teach oneself communications and electronics technology
 through ham radio, then ham radio really ought to use something like the
 communications and electronics technologies that the outside world is
 using today, not just those the world was using 40 years ago.

Yes. SSB is a technology the phone company first used and they have
moved on to digital.

 
 --Phil
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-- Diane
-- 
- d...@freebsd.org d...@db.net http://www.db.net/~db
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Re: [amsat-bb] FM birds

2014-07-27 Thread Diane Bruce
On Sat, Jul 26, 2014 at 10:24:15PM -0700, Phil Karn wrote:
 On 07/22/2014 07:49 AM, wa4...@comcast.net wrote:
 
  SSB/CW birds are the only way to go and if you build it they will
  come  .
 
 Think about what it would be like to tune for Doppler while working SSB
 through a LEO satellite on microwave.
 
 Before you say computer control, work out the effect of even a tiny
 error in your clock or orbital elements on a high elevation pass and
 remember that SSB has no carrier or pilot tone for closed-loop frequency
 tracking.
 
 Sure, you could have a second receiver track the satellite's beacon. But
 if you're going to all that trouble, why not just have it track a
 single high speed data stream from the satellite, one that's much less
 affected by Doppler in the first place?

Exactly. It makes much more sense to go digital.

The crucial thing is *not* the complexity of the groundstation
it is the lifetime of the satellite. 

- 73 Diane VA3DB
-- 
- d...@freebsd.org d...@db.net http://www.db.net/~db
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Re: [amsat-bb] FM birds

2014-07-27 Thread Jim Sanford
Tracking doppler on 2m and 70cm was hard enough at field day.  I like 
2GHz and up, but do not want to even think about the doppler.


In the KITSAT days, I used an IC-751 as the receive IF.  It has a true 
FM detector, with discriminator centered at 0-volts.  It steps in 1 or 
10 Hz increments, even on FM.  I wrote a simple radio-control program 
which would take data from InstantTrack, calculate frequency from that, 
and set the radio on the expected frequency at the beginning of the 
pass.  Didn't matter if there was a little error, once AOS happened, the 
AFC put the receiver dead-on, and I got good data for the entire pass -- 
hands free.  It was a joy to watch.  And that was a simple digital mode.


The other thing that is exciting about going digital, is the idea of 
CAT-5 (or fiber) to the box at the antenna, not coax.


Digital will enable so much . . . .

73,
Jim
wb4...@amsat.org

On 7/27/2014 1:24 AM, Phil Karn wrote:

On 07/22/2014 07:49 AM, wa4...@comcast.net wrote:


SSB/CW birds are the only way to go and if you build it they will
come  .

Think about what it would be like to tune for Doppler while working SSB
through a LEO satellite on microwave.

Before you say computer control, work out the effect of even a tiny
error in your clock or orbital elements on a high elevation pass and
remember that SSB has no carrier or pilot tone for closed-loop frequency
tracking.

Sure, you could have a second receiver track the satellite's beacon. But
if you're going to all that trouble, why not just have it track a
single high speed data stream from the satellite, one that's much less
affected by Doppler in the first place?
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Re: [amsat-bb] FM birds

2014-07-27 Thread Gus

On 07/27/2014 12:57 PM, Jim Sanford wrote:
The other thing that is exciting about going digital, is the idea of 
CAT-5 (or fiber) to the box at the antenna, not coax.


Yep.  Rig at the mast-head, fiber (RF noise-immune) to the shack, and a 
control head at the operators position.  Or a software-only control 
head, (but I like twiddling real knobbies and flipping real switches).  
Crunch numbers up the pole, at the desk, or both.


Will I live long enough?

--
Gus 8P6SM
The Easternmost Isle

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Re: [amsat-bb] I want this. I want that. Here comes another FM LEO sat.

2014-07-27 Thread Floyd Rodgers

I would also vote AO40 was not to complex, it was failed by an accident.
Not wishing to bring up bad memories, but two questions:
Did anything other than the plug incident happen? (In other words, did 
any systems fail before the explosion?)
Was there a backup bird built of the same design that just might be 
flyable if we could find a ride?


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Re: [amsat-bb] I want this. I want that. Here comes another FM LEO sat.

2014-07-27 Thread i8cvs
- Original Message -
From: Floyd Rodgers kc5...@swbell.net
To: bstguitar...@gmail.com; Phil Karn k...@ka9q.net
Cc: amsat-bb@amsat.org
Sent: Sunday, July 27, 2014 8:17 PM
Subject: Re: [amsat-bb] I want this. I want that. Here comes another FM LEO
sat.


 I would also vote AO40 was not to complex,

I agree ! Not to complex to be operated.

 it was failed by an accident.

Someone forgot to remove a red cap from a valv fuel and helium system.

 Not wishing to bring up bad memories, but two questions:
 Did anything other than the plug incident happen? (In other words, did
 any systems fail before the explosion?)

NO !

 Was there a backup bird built of the same design that just might be
 flyable if we could find a ride?

We got for years OSCAR-10 and OSCAR-13 in the Molnyia orbit
very similar to that of AO40 but with lover apogee and different
orbit inclination,

73 de i8CVS Domenico

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Re: [amsat-bb] I want this. I want that. Here comes another FM LEO sat.

2014-07-27 Thread Andre
Op 27-07-14 om 20:17 schreef Floyd Rodgers:

 Was there a backup bird built of the same design that just might be
 flyable if we could find a ride?
 
Not a backup for phase 3d but a satelite with simular spaceframe and
capabiletie to get in the same orbit, phase 3e is capable of being
flight test ready in a short time as it was intended to be launched
around 2007 if I'm not mistaken.

it has a simpler IF system but the signals should be just as strong as
ao-40 was.

73 de Andre PE1RDW
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[amsat-bb] LituanicaSAT-1 status update

2014-07-27 Thread Vytenis Buzas
Dear friends, FM transponder is OFF, it's mission is completed, thank you
for all the good responses. Based on this there will be more projects in
the future making benefit for HAM people of the World.

Currently only telemetry packets are to transmit data every 15 seconds.
On-board temperature is rising and the altitude is being lost quickly
therefore some peculiarities due to changing thermal environment can occur.

Would appreciate any of your reports tracking last orbits of LituanicaSAT-1.

Thank you for all of your support!

Vytenis B.
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[amsat-bb] CN88 on CW today

2014-07-27 Thread wa7...@frontier.com
I will be on FO-29, Mode CW on the 0048Z (July 28) and 0234Z passes, mode CW. 
Looking for some cw contacts.
.
73'...Ed  WA7ETH
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