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CX2SA > SATDIG 28.10.14 14:12l 322 Lines 9886 Bytes #999 (0) @ WW
BID : AMSATBB9367
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Subj: AMSAT-BB-digest V9 367
Path: IW8PGT<IZ3LSV<IV3SCP<IW0QNL<JH4XSY<JM1YTR<JE7YGF<7M3TJZ<CX2SA
Sent: 141028/1208Z @:CX2SA.SAL.URY.SOAM #:11827 [Salto] FBB7.00e $:AMSATBB9367
From: CX2SA@CX2SA.SAL.URY.SOAM
To : SATDIG@WW
Today's Topics:
1. AO-73 1st contact (Clayton Coleman)
2. Re: AO-73 1st contact (Paul Stoetzer)
3. Torque Coil turns vanish? (Robert Bruninga)
4. Re: Torque Coil turns vanish? (David G0MRF)
----------------------------------------------------------------------
Message: 1
Date: Mon, 27 Oct 2014 10:29:42 -0500
From: Clayton Coleman <kayakfishtx@xxxxx.xxx>
To: AMSAT-BB <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] AO-73 1st contact
Message-ID:
<CAPovOwfqELWt7kvXzy2-rZevoW_RtcC0OhrZ5GHyS0D5gT4L6g@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
It was nice to hear K4SQC making his first contact on AO-73 last night
with AC0RA.
Since the inception of the 73 on 73 award, over 100 unique call signs
have been copied by AC0RA over North America. Paulo, PV8DX has been
the only South American station I have personally heard and worked.
Others in the US have reported working him.
I've seen several emails implying it is somewhat esoteric to make
contacts via AO-73.
AO-73 remains the easiest bird to hear after the loss of VO-52. It
doesn't not require much power or high gain antennas to use
effectively. If you are not hearing it, you should not increase your
power. Many stations are successfully using Elk and Arrow-style
portable antennas with low-power QRP-style transceivers such as the
Yaesu FT-817.
Pick a clear downlink frequency in the transponder's pass band.
Adjust your uplink frequency until you hear your own signal. It's
that simple. Make adjustments to the uplink frequency as necessary so
that you do not "drift" across the pass band.
Manual tuning is probably best for most stations. Follow the rule of
tuning/adjusting your higher frequency (the UHF uplink.) You can you
use computer control via SatPC32 if you keep your fingers on the +/-
buttons and pay close attention to the frequency.
It's exciting to see some new stations getting on the SSB birds and
using AO-73 in their rover plans!!!
73
Clayton
W5PFG
------------------------------
Message: 2
Date: Mon, 27 Oct 2014 12:21:16 -0400
From: Paul Stoetzer <n8hm@xxxx.xxx>
To: Clayton Coleman <kayakfishtx@xxxxx.xxx>
Cc: AMSAT-BB <amsat-bb@xxxxx.xxx>
Subject: Re: [amsat-bb] AO-73 1st contact
Message-ID:
<CABzOSOqACvy29jxrZ4WazWS=6aAUBs5h3qYBtZHyZVPuGB3jeQ@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
Great post, Clayton! It really is an easy satellite to hear and work
once you get used to the the tuning quirks. The weekend passes are
generally at a convenient time and the evening passes will be more
convenient for us in the United States after Daylight Saving Time ends
this upcoming weekend.
Here are a couple of YouTube videos of an odd cast of characters all
working AO-73 using simple, QRP equipment as described in the original
post:
https://www.youtube.com/watch?v=wKQmilT636A
https://www.youtube.com/watch?v=UFSk1D0-d8w
73,
Paul, N8HM
On Mon, Oct 27, 2014 at 11:29 AM, Clayton Coleman <kayakfishtx@xxxxx.xxx>
wrote:
> It was nice to hear K4SQC making his first contact on AO-73 last night
> with AC0RA.
>
> Since the inception of the 73 on 73 award, over 100 unique call signs
> have been copied by AC0RA over North America. Paulo, PV8DX has been
> the only South American station I have personally heard and worked.
> Others in the US have reported working him.
>
> I've seen several emails implying it is somewhat esoteric to make
> contacts via AO-73.
>
> AO-73 remains the easiest bird to hear after the loss of VO-52. It
> doesn't not require much power or high gain antennas to use
> effectively. If you are not hearing it, you should not increase your
> power. Many stations are successfully using Elk and Arrow-style
> portable antennas with low-power QRP-style transceivers such as the
> Yaesu FT-817.
>
> Pick a clear downlink frequency in the transponder's pass band.
> Adjust your uplink frequency until you hear your own signal. It's
> that simple. Make adjustments to the uplink frequency as necessary so
> that you do not "drift" across the pass band.
>
> Manual tuning is probably best for most stations. Follow the rule of
> tuning/adjusting your higher frequency (the UHF uplink.) You can you
> use computer control via SatPC32 if you keep your fingers on the +/-
> buttons and pay close attention to the frequency.
>
> It's exciting to see some new stations getting on the SSB birds and
> using AO-73 in their rover plans!!!
>
> 73
> Clayton
> W5PFG
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. 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://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 3
Date: Mon, 27 Oct 2014 16:35:25 -0400
From: Robert Bruninga <bruninga@xxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Torque Coil turns vanish?
Message-ID: <2ff0b291e19defe9383aa26d97182c5b@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
I keep coming up with the number of turns of a torque coil vanishing with
respect to torque (for a given wire size).
Given that Torque = A x B x I x n where A is area, B is field, I is current
and n is number of turns.
But I is inversely proportional to the length of wire (resistance). I = V/R
but R is proportional to n.
Hence the number of turns. So I is proportional to V/n.
But V is fixed in the cubesat, (5v) area is fixed (where we can put the
coil) and so plugging in,
T = A x B x V/n x n and the n?s cancel.
So I can get the same torque with ?any- number of turns for a given size
wire.
What changes with turns, of course, is the current. So to save spacecraft
power, the more turns, the less current, and thus, the least power for the
same torque.
Interesting result.
We ended up with 600 turns of #34 wire to keep the current at 25 mA so we
can drive it directly from a CPU pin.
I wonder where?s the limit? Infinitie number of turns? Zero current? I
guess you run out of space.
AH HA! Yes, that was it. We started with #30 wire but it took so many
turns to get to below the 25 mA, that there wasn?t room for the coil. So
we went to smaller wire and ended up with the #34 to give us a ?? thick
coil with 600 turns to give 25 mA.
But I just always found it interesting that once you have chosen the wire
size, the number of turns is only determined by the current you want. The
Torque is constant.
Bob, WB4APR
------------------------------
Message: 4
Date: Tue, 28 Oct 2014 06:00:15 -0400
From: David G0MRF <g0mrf@xxx.xxx>
To: bruninga@xxxx.xxxx amsat-bb@xxxxx.xxx
Subject: Re: [amsat-bb] Torque Coil turns vanish?
Message-ID: <8D1C0AD1B56C0F7-151C-988C@xxxxxxxxxxxxx.xxxxxx.xxx.xxx>
Content-Type: text/plain; charset="utf-8"
That's an interesting technique, but as the CPU pin turns off and the
magnetic field collapses, don't you get a huge spike in voltage due to dI/dt
that could kill the CPU I/O port?
We ended up with 600 turns of #34 wire to keep the current at 25 mA so we
can drive it directly from a CPU pin.
73
David
-----Original Message-----
From: Robert Bruninga <bruninga@xxxx.xxx>
To: amsat-bb <amsat-bb@xxxxx.xxx>
Sent: Mon, 27 Oct 2014 20:35
Subject: [amsat-bb] Torque Coil turns vanish?
I keep coming up with the number of turns of a torque coil vanishing with
respect to torque (for a given wire size).
Given that Torque = A x B x I x n where A is area, B is field, I is current
and n is number of turns.
But I is inversely proportional to the length of wire (resistance). I = V/R
but R is proportional to n.
Hence the number of turns. So I is proportional to V/n.
But V is fixed in the cubesat, (5v) area is fixed (where we can put the
coil) and so plugging in,
T = A x B x V/n x n and the n?s cancel.
So I can get the same torque with ?any- number of turns for a given size
wire.
What changes with turns, of course, is the current. So to save spacecraft
power, the more turns, the less current, and thus, the least power for the
same torque.
Interesting result.
We ended up with 600 turns of #34 wire to keep the current at 25 mA so we
can drive it directly from a CPU pin.
I wonder where?s the limit? Infinitie number of turns? Zero current? I
guess you run out of space.
AH HA! Yes, that was it. We started with #30 wire but it took so many
turns to get to below the 25 mA, that there wasn?t room for the coil. So
we went to smaller wire and ended up with the #34 to give us a ?? thick
coil with 600 turns to give 25 mA.
But I just always found it interesting that once you have chosen the wire
size, the number of turns is only determined by the current you want. The
Torque is constant.
Bob, WB4APR
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx. 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://amsat.org/mailman/listinfo/amsat-bb
------------------------------
_______________________________________________
Sent via amsat-bb@xxxxx.xxx.
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 member? Join now to support the amateur satellite program!
http://amsat.org/mailman/listinfo/amsat-bb
End of AMSAT-BB Digest, Vol 9, Issue 367
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