[amsat-bb] doppler shift

John john at amber.org.uk
Thu Jan 4 19:46:20 UTC 2018


Hi Nick,

It all depends on the knowledge and skillset of the scouts in question. My
last significant AMSAT demo was done during JOTA, and at that point we had
between 100 and 150 young people come through the shack doors throughout the
weekend. We didn't have a huge amount of time to explain everything or go
really interactive with the control or tracking, and to be honest most of
them were amazed enough that they could hear voices coming back from space,
so when we listened in to one of the Italian ARISS contacts, they were even
more thrilled! My trusty FT-847, SatPC32, ERC-M interface and Kenpro KR5600
did the job nicely, we made quite a few QSOs, and we got to listen to a full
ISS pass - something the 80 odd people who poured into the shack when it
started will likely not forget for a long time yet.

If your group of scouts is at a level where they've got the understanding,
accuracy and, most importantly, the concentration to follow the full pass,
then there's no reason not to try it manually with them. If, however,
they're less experienced/interested/accurate, then you might find that it's
hard to keep them all doing their respective jobs at once. Remember that
there's only one of you trying to manage four different teams at that point,
so how far you can stretch yourself is another consideration. Especially if
your primary focus is on the actual operation of the QSO.

If you want to demonstrate that it can be done on a budget, get them to
bring those tape-measure yagis they built with them. Hook up a couple of
handhelds or FT817s to them, and demonstrate an FM bird (AO-91, SO-50, or
similar?) for the simplest approach. Then step up the game a bit, adding a
little more challenge. Even if you just listen during the first pass or two,
you'll see the thrill they'll get from knowing it's working with the yagis
they built themselves at the last club meeting, and that's where you can
gauge whether they are ready to step it up. If you want to add a bit more
'competition' to it, then have them run the yagis and handhelds alongside a
full auto-tracking station and see if they can 'match' it (or even 'beat'
it). Never underestimate the power of some healthy competition - give 4
teams identical sets of gear, show them where to point, and you'll find that
they're competing to see who can hear the satellite the loudest in no time.
If, however, you want some successful QSOs, then it's worth having a back-up
plan that you can roll out if you aren't getting success.

One of the biggest things I've found in the past with demonstrations is that
whilst the latest and greatest kit isn't necessary, having a decent setup
that's hassle-free and 'just works' can bail you out of a huge hole. We
found the same thing with HF a few years ago - whilst you can theoretically
make that QSO to the opposite side of the planet on 1W with a wet piece of
string up a tree in the right conditions, it's a lot easier to put on a
successful demonstration with an 8 element HF beam at 80 feet on a tower,
plenty of TX power and a radio with an excellent receiver. And very often
the quality is what will determine whether or not you keep the interest.
Making them work for that contact is all well and good, but sometimes
instant gratification is better for the uninitiated or more casual folk.

There's no hard and fast formula for what will or won't work. You gotta read
your audience, respond to it, and work from there. If you can see they're
getting more and more into it, then teach them a bit more, and add to the
level of work they have to do to make the pass happen. As a wise scouter
once said to me, many years ago (when talking about campfire songs, but the
principle applies to this too): If you're drilling for oil, and you don't
strike it within the first couple of minutes... stop boring!

In short (or long, as it seems to have become)... See what works for you,
but plan to start simple and work upwards! You know your young people better
than I do, so assess their capabilities and challenge them, whilst staying
within those capabilities.

73, and a firm left handshake,
John (XLX)

-----Original Message-----
From: Nick Hart [mailto:nickhart at usa.net] 
Sent: 04 January 2018 19:16
To: John <john at amber.org.uk>
Cc: jim at k6ccc.org; amsat-bb at amsat.org
Subject: Re: [amsat-bb] doppler shift

I'm glad you mentioned scouts, John. 

I counsel for the radio merit badge for our local scouts, and Elmer our
local middle school's radio club. In the club last month, we completed tape
measure yagis. And, for this month's radio club meeting, I was planning on
having the kids working a couple of birds passing during the meeting time. 

I figured that with 10 kids, we could have them in teams for tracking,
tuning, recording and operating under my supervision. I thought it would be
good for them to try to do everything manually once for two reasons. One is
to show that's it's doable on a minimum budget by a teenager. And, the other
is so they'll have an appreciation of everything our more automated rig will
do during our ARISS QSO in March. 

>From your comments, I'm rethinking that strategy a bit. Do you think that's
too much?

73!

Nick

> On Jan 4, 2018, at 9:57 AM, John <john at amber.org.uk> wrote:
> 
> Hey now, don't shoot the messenger! The vast majority of my AMSAT 
> demonstrations are done with groups of scouts of various ages, and the 
> last thing they need to see is me focussing more on the radio than 
> making sure they understand what's going on!
> 
> If I've got a piece of software that can correct for doppler shift for 
> me, and it can manage pointing my antennas in the right direction, 
> then it leaves my focus available for the actual operating, and the 
> explanations to the young people who could well be the next generation 
> of amateur radio and AMSAT enthusiasts ;) I think that's a far better 
> use of my resources than sitting there with my back to the people I'm 
> supposed to be introducing to the hobby, and focussing on turning 
> dials and pushing rotator controller buttons...
> 
> John (XLX)
> 
> -----Original Message-----
> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of 
> jim at k6ccc.org
> Sent: 04 January 2018 17:46
> To: amsat-bb at amsat.org
> Subject: Re: [amsat-bb] doppler shift
> 
> 
> 
> Ya know, you could MANUALLY tune.  It does work.  In fact I strongly 
> preferred manually tuning for doppler shift vs computer corrected.
> 
> Jim
> K6CCC
> 
> -----Original Message-----
> From: "John" <john at amber.org.uk>
> Sent: Thursday, January 4, 2018 02:10
> To: "'Dave L'" <kb0rfy at q.com>, amsat-bb at amsat.org
> Subject: Re: [amsat-bb] doppler shift
> 
> 
> 
> Hi Dave,
> 
> When you say your doppler is too far ahead or behind, do you actually 
> mean your overall frequency, or do you mean your split distance?
> 
> If you mean your overall frequency then that's really odd, as SatPC32 
> has always put me smack bang in the middle of the pass-band if using 
> linears (with the correct locator set on login). If this isn't the 
> case you can adjust it in the settings files, but it's generally 
> calculated based on your locator and the Keplerian data you can 
> download (and should be updating every time you open up the app). If, 
> however, you mean your offset (ie finding your own downlink) then this 
> is always a bit variable for me, but usually pretty close.
> 
> SatPC32 does, in my experience, remember your offsets when you adjust 
> them (in my case either with the + and - buttons, or the pot at the 
> top right of the rig), so that next time you hit that satellite it 
> keeps the same offsets. You may find your offset is slightly different 
> on different passes, or you may find it's exact every time, but that's 
> part of the fun with linears - finding yourself first!
> 
> Hope that helps.
> 
> 73,
> John (XLX)
> 
> -----Original Message-----
> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Dave L
> Sent: 03 January 2018 23:32
> To: amsat-bb at amsat.org
> Subject: [amsat-bb] doppler shift
> 
> I'm useing satpc and a Yaesu ft-847.
> 
> Fm birds are not a problem. SSB I'm either to far ahead or behind.
> 
> Any hints or advice would be appreciated.
> 
> radio and ant are comp controled
> 
> thanks
> 
> dave
> 
> kb0rfy
> 
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> _______________________________________________
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> the official views of AMSAT-NA.
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> _______________________________________________
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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
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> _______________________________________________
> Sent via AMSAT-BB at 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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