[amsat-bb] Ao 73 problems

[Bob]

Hi David,

You are spot on, fortunately, this old dog used to manual tune all the
time, so its just a matter of me going back to my original ways to doing
things.

Knowing that the the LO is changing around a bit with temp makes me
understand why the Doppler corrections never seemed to fit what I was
hearing from the bird itself, even thought most of my operation is during
Eclipse (before it emerges back into light, when the temp should be cold
and fairly stable).

AO-73 is a great bird, and a pleasure to work, but I do hear people time
and again saying they can never hear themselves on the downlink.  All it
would take is a published hint to try transmitting higher by about 8-12 KHz
for example, and I think folks would have much more luck.  The information
is out there, in various forum posts, personal blogs, and message systems,
it just hasn't been adopted by authoritative sources like funcube.org.uk,
or AMSAT itself (which list the original ideal UL/DL relationships).  Until
then it is sort of unconfirmed rumor.

Thanks again!

73, Bob, WB4SON



On Mon, Oct 26, 2015 at 11:06 AM, David G0MRF <g0mrf at aol.com> wrote:

> Hi Bob.
>
> AO-73 is difficult to track using a PC as there is a fixed offset on the
> receive crystal oscillator together with a variation in frequency which is
> temperature dependent.
> Consequently, the ideal midband frequency when the satellite is at TCA
> will be different for a pass in eclipse or a pass during the illuminated
> part of the orbit.
>
> As you know, it takes a bit of getting use to, but once you get the feel
> for it, manual tuning can get good results.
> I agree the published frequencies should probably include the fixed offset
> so people can get a little closer to the 'correct' frequencies for success.
>
> 73
>
> David
>
>
>
>
> -----Original Message-----
> From: Bob <WB4SON at gmail.com>
> To: George Henry <ka3hsw at att.net>
> CC: mm0kjg <mm0kjg at googlemail.com>; AMSAT-BB <amsat-bb at amsat.org>
> Sent: Mon, 26 Oct 2015 13:52
> Subject: Re: [amsat-bb] Ao 73 problems
>
> Hi George,
>
> You are one of many who have said manual tuning is best, and after
> so many
> similar comments, I should probably give that a whirl.
>
> Of course
> this will vary for rig and doppler, but I'd be curious to know
> what you find
> your tx frequency to be at mid pass?
>
> The reason for asking is the published
> spec is
>
> Uplink 435.150 - 435.130 MHz LSB (Inverting)
> Downlink 145.950 -
> 145.970 MHz USB
>
> Implying that a RX of 145.960 (mid band) would have a TX of
> 435.140.  From
> my tests it appears that I would actually have to transmit on
> 435.156 to
> hear myself at mid-pass.  That, of course, appears to be outside of
> the
> published passband, and those published specs probably prevent anyone
> new
> to the bird from ever finding themselves.
>
> I appreciate and data or
> feedback.
>
> 73, Bob, WB4SON
>
>
>
>
> On Mon, Oct 26, 2015 at 12:21 AM, George
> Henry <ka3hsw at att.net> wrote:
>
> > I have found that computer tuning for AO-73
> simply doesn't work...  the
> > satellite frequency drifts enough that your up-
> and downlinks won't stay in
> > sync for long.  I leave my downlink frequency
> alone as much as possible
> > (unless needed to chase the other guy), and
> manually adjust the uplink, and
> > that has worked well for me.
> >
> > George,
> KA3HSW
> >
> >
> > ----- Original Message ----- From: "mm0kjg via AMSAT-BB" <
> >amsat-bb at amsat.org>
> > To: <amsat-bb at amsat.org>
> > Sent: Sunday, October 25,
> 2015 6:24 AM
> > Subject: [amsat-bb] Ao 73 problems
> >
> >
> > Hello all.
> >> I
> seem to have a wee problem with working Ao-73. The problem I cant work
> >> it at
> all. I am hearing people talking but when I attempt to find my
> >> downlink
> nothing heard. I have tried sending cw up and tuning downlink and
> >> also
> tuning uplink and nothing.  I have set up tuning for 145.950 down and
> >>
> 435.150 up. Am missing something here?
> >> I spoke to my good friend and very
> good Sat operator Derrick Gm0fmw and
> >> he also cant access it with a fairly
> good antenna set-up. We are both in
> >> Edinburgh Scotland Is this the
> problem?
> >> Please all help will be appreciated .
> >>
> >> Thanks Kev MM0KJG
> >>
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