[amsat-bb] ISS Digipeater is back! On UHF this time (437.550MHz)!

Wed Nov 2 21:46:01 UTC 2016

OK, now it makes sense. I had to draw some pictures to get it straight in my head. Thanks for explaining.
I was attempting to compare it with SO-50, but since you TX on VHF it's not an issue.
Cheers, Michael KC4ZVA

      From: Bob <WB4SON at gmail.com>
 To: "mvivona at yahoo.com" <mvivona at yahoo.com> 
Cc: Robert Bruninga <bruninga at usna.edu>; AMSAT BB <amsat-bb at amsat.org>
 Sent: Wednesday, November 2, 2016 5:28 PM
 Subject: Re: [amsat-bb] ISS Digipeater is back! On UHF this time (437.550MHz)!

As the ISS is approaching, the Doppler Effect causes the frequency you need to listen to, to appear to be higher.  So you tune your RX to a higher frequency.
Likewise as ISS approaches you, the Doppler Effect causes you transmit frequency to be higher.  But the ISS isn't adjusting for that, so you need to transmit on a LOWER frequency in order to be heard by the ISS.
The adjustments are always in the opposite direction.
73, Bob, WB4SON

On Wed, Nov 2, 2016 at 5:06 PM, mvivona--- via AMSAT-BB <amsat-bb at amsat.org> wrote:

Robert,
I'm not following your explanation, please help me understand.

If the ISS is transmitting and receiving on 437.55, why would you split your TX and RX offset directions?Seems to me like you would TX and RX high on the approach and TX and RX low as it passes by. Both on the same frequency just like you would do on SO-50.

 Michael KC4ZVA

      From: Robert Bruninga <bruninga at usna.edu>
 To: AMSAT BB <amsat-bb at amsat.org>
 Sent: Wednesday, November 2, 2016 12:00 PM
 Subject: Re: [amsat-bb] ISS Digipeater is back! On UHF this time (437.550MHz)!

> I'm not so lazy that turning the dial is the end of the world,

I may be reading too much into that statement, but just to be clear...

it is not that simple...  On most FM rigs you cannot turn the knob both
ways at once, to the left for TX and to the right for RX .  You have to
tune the TX and RX in opposite directions at the same time every 2 minutes
or so.  Hence, the suggestion to pre-tune the -/+10, -/+5 , 0, +/-5, and
+/-10  kHz offsets in 5 memories to make it trivial to make the 5 steps
during the pass.

-----Original Message-----

From: Robert Bruninga
Sent: Wednesday, November 02, 2016 11:06 AM
To: AMSAT BB
Subject: Re: [amsat-bb] ISS Digipeater is back! On UHF this time
(437.550MHz)!

Great!    But... Everyone must remember, UHF packet is *not* appliance
operating.

You must oppositely tune for Doppler on the uplink starting low, and going
high, while tuning the downlink High and going low.  Best to pre-program 5
channels and switch during the event.  If you do not do this, you are
simplky QRM to everyone else, blocking their successes with your failures.

Bob

-----Original Message-----
From: AMSAT-BB [mailto:amsat-bb-bounces@ amsat.org] On Behalf Of John Brier
Sent: Wednesday, November 02, 2016 10:52 AM
To: AMSAT BB
Subject: [amsat-bb] ISS Digipeater is back! On UHF this time (437.550
MHz)!

I didn't see this on amsat-bb yet.

I plan on trying the upcoming 16:45 UTC pass.

https://twitter.com/RF2Space/ status/793559573240115200

"#ARISS ISS packet system now operational on UHF (437.550 MHz). #hamradio"

http://issfanclub.com/node/ 41954#comment-18163

"Due to the failure of the VHF radio in the Columbus module the packet
system on 145.825 is not possible. The crew just swapped the radio for the
UHF equivalent and packet is now operational on 437.550 MHz.

The Kenwood D700 radios were augmented a couple years ago by a Kenwood
D710E radio that was dedicated to SSTV operations. The Russian team soon
afterwards adopted the D710E as their only operational radio but it was
never configured for packet operations.

The ARISS team is working on flying replacement D710GA models to replace
and unify all the hardware. Target for delivery is late 2017.

Submitted by N5VHO on Tue, 2016-11-01 17:14."

73, John Brier KG4AKV

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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