[amsat-bb] ISS APRS Signal Quality? (tone skew?)

Wed Feb 13 15:42:10 UTC 2019

Bob, your guess would be more likely if the ground station was using
an external TNC whereby the settings might have gotten mucked up
somewhere along the way.  But, I, for one, am using the same TH-D74
and the same TM-D710G I was using before.  It's unlikely that both
radios went weird at the same time.

I really wish the problem was on my end.  It's a lot easier to fix
things on the ground than it is up there!

73,
Frank

FRANK W. KARNAUSKAS, N1UW
N1UW at GOKARNS.com
612-644-9174

-----Original Message-----
From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Robert
Bruninga
Sent: Wednesday, February 13, 2019 7:39 AM
To: AMSAT -BB
Subject: Re: [amsat-bb] ISS APRS Signal Quality? (tone skew?)

Im gonna take a stab with zero current knowledge.

Butover the years, one DIGI on ISS uses a radio and an external TNC
with
audio connections.  The other digi on ISS used a Kenwood with internal
TNC
directly connected to the discriminator and modulator.  One has a flat
response and the other has the normal preemphasis and deemphasis.

So if one transmits tones that are inbalanced, then one system does
better
than the other.  And in fact, with just a few dB of inbalance in the
wrong
direction, no amount of RF power will correct that.  It simply will
not
decode.

You can hear this on terrestrial packet frequencies.  Probably 80% of
all
the signals on the air "work" but have terribly misconfigured tones.
People just hook'em'up and "it works" to the local digi, but they are
not
aware that it might not work at all in weak signal realm where tone
settings must be ideal.

On my mobile, I see some signals that are dead full quieting with all
signal bars that do not decode, and then I see another kenwood with
only 3
bars and noisy that does just fine.  Tone balance is exteremely
critical.

Everyone should look at their tones on an oscope or at least listen to
their tones compared to a good known signal. (Factory TNC in a k
enwood).
Though, when you listen to or look at "your " tones, the
characteristics
of the audio in that receiver can also have a skew.

And, do NOT look at them one at a time.  That tells you nothing.
Since
the speech circuits will adjust them to the same level usually...
Look at
the relative amplitudes of the two.  You can fix them with the right
capacitor either in series to improve the high tone, or in parallel to
diminish the high tone.

But the right cap must perfectly match the impedance of your
particular
set up.

Bob, WB4aPR

-----Original Message-----
From: AMSAT-BB <amsat-bb-bounces at amsat.org> On Behalf Of Fernando
Ramirez
Sent: Tuesday, February 12, 2019 9:43 PM
To: walterh at k5wh.net
Cc: AMSAT -BB <amsat-bb at amsat.org>
Subject: Re: [amsat-bb] ISS APRS Signal Quality?

I have tried two different radios, an Icom IC-2820h and a Kenwood
TM-V71A.
No luck with the Icom at full power on a high elevation pass. Better
luck
with the Kenwood but only on higher passes and transmitting with 50w.

Other operators have been able to get their packets digipeated with
Kenwood APRS-Ready HTs, so it's kind of puzzling.

I'm using a Mobilinkd TNC3. I have no problem hitting distant
terrestrial
digipeaters with both setups.

73
Fernando, NP4JV

On Tue, Feb 12, 2019, 7:37 PM <walterh at k5wh.net> wrote:

> I definitely have to agree with you.
>
> The signal does seem to be less than half of what it used to be, and
I
> have yet to hit it myself. When it used to be so easy.
>
> Not sure what has changed, but it's certainly not the same as it was
> before the shut down several weeks ago.
>
> Walter/K5WH
>
> -----Original Message-----
> From: AMSAT-BB <amsat-bb-bounces at amsat.org> On Behalf Of Frank
> Karnauskas
> Sent: Tuesday, February 12, 2019 5:19 PM
> To: amsat-bb at amsat.org
> Subject: [amsat-bb] ISS APRS Signal Quality?
>
> Is it me or does the APRS signal not sound as strong as it was
before
> and is it not hearing quite as well?
>
> I am having a heck of a time pinging the digipeater and the signal
> seems to be down a bit.
>
> Could entirely be something on my end, but I would appreciate
others'
> opinion.
>
> 73,
> Frank
>
> FRANK W. KARNAUSKAS, N1UW
> N1UW at GOKARNS.com
>
>
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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.
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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
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Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
_______________________________________________
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