[amsat-bb] Re: Eagle U/V modes

John B. Stephensen kd6ozh at comcast.net
Wed Oct 11 00:14:05 PDT 2006

We're planing on 1 kW PEP EIRP (25 W into a 14 dBic antenna) U-band uplinks 
for SSB on Eagle.



----- Original Message ----- 
From: "Greg D." <ko6th_greg at hotmail.com>
To: <kb5mu at amsat.org>; <tmcgrane at suffolk.lib.ny.us>
Cc: <amsat-bb at amsat.org>
Sent: Wednesday, October 11, 2006 04:08 UTC
Subject: [amsat-bb] Re: Eagle U/V modes

> Two thoughts on Paul's comments:
> 1.  I was also excited by what I heard about the Text Messaging proposal.
> Has anybody approached (or future tense, could anyone approach) Kenwood 
> for
> a re-program of their TH-D7?  I suspect that the internal processing
> capabilities won't be sufficient, but if it worked, that might provide a
> readily available platform for a new product.  If not the D7, maybe the
> D700?
> 2.  What I thought I heard at the Symposium was that we wouldn't need such 
> a
> massive station to work Eagle's traditional UV transponder.  While I 
> expect
> there were many such "baseline" stations in existence around the planet, I
> wonder how many are still operational after years of no HEO UV birds and 
> all
> the affects of weather?  Then there are those of us who cannot put such a
> station on the air, lacking the space and/or neighborhood setting (cc&r) 
> to
> do so.  I managed a few contacts on AO-10 and one on AO-13 with my 8 
> footer,
> under unusually good conditions, but they were an ear strain.  I had 
> planned
> to need to go to LS on Echo until the Symposium convinced me that I'd be
> fine on UV.  Do I need to re-think that?
> Thanks to all the presenters at the Symposium.  Great event!
> Greg  KO6TH
> ----Original Message Follows----
> From: Paul Williamson <kb5mu at amsat.org>
> To: McGrane <tmcgrane at suffolk.lib.ny.us>
> CC: Amsat BB <amsat-bb at amsat.org>
> Subject: [amsat-bb] Re: Eagle U/V modes
> Date: Sun, 8 Oct 2006 09:39:56 -0700
> At 10:23 AM -0400 10/8/06, McGrane wrote:
> >Could someone please explain further the capabilities of the U/V text
> >messaging mode. Would this incude the use of typical packet equipment?
> No. In order to transfer information (even at low data rates) with
> very small antennas and low power, it's necessary to use every trick
> in the digital optimization book, so it won't be compatible with
> existing packet equipment.
> By very small, it's meant that the radio might clip onto the back of
> a handheld PDA, with an antenna system small enough to be manageable
> handheld. Probably not as small as a rubber duckie, but something
> that doesn't need pointing. Exact details are still to be designed.
> There's not a lot of detail yet about how the system will work from a
> user standpoint. The work so far has been on making the links work
> and determining the spacecraft requirements. For higher level
> architecture, one idea is to use Jabber, which is an open protocol
> for instant messaging (keyboard chat) used on the internet. It's
> thought that many of the applications that work on APRS would work
> great on this system (not just positioning).
> Now would be a good time to throw out your ideas for applications for
> a service like this, so the system designers can try to accommodate
> them.
> (The above info is based on what I heard at the Space Symposium and
> not to be considered official in any way.)
> >Could some old timers describe a typical AO-13 or AO-40 mode U/V station
> >for my education and to help me build a station.
> The baseline AO-13 Mode B station was a 20-foot-long circularly
> polarized cross-yagi for 2m, plus a 14-to-20-foot circularly
> polarized cross-yagi for 70cm, mounted for azimuth and elevation
> rotation. Rather short low-loss coax feed (e.g., Belden 9913) or a
> mast-mounted low-noise preamp on the downlink. On the uplink,
> operators who wanted to work under all conditions had about 100 watts
> available, but under good conditions much less power was needed.
> Continuously variable uplink power was considered mandatory since
> being too loud is bad practice and being too weak meant marginal
> stations couldn't hear you. SSB and/or CW capability on the radios.
> Most conveniently, a single-box "satellite" rig would allow the use
> of a single knob to tune around the transponder, but separate
> transmit and receive rigs were also common.
> Seriously hard-core stations who wanted to hear down to the
> transponder noise floor even when conditions were poor would phase
> two or more of the 20-foot cross-yagis. It was good to have a few of
> those stations around to pick out the very weak uplinks, but it
> wasn't really necessary for most users to have that much gain.
> Computer control of the rotators was convenient but not necessary,
> since the satellite moves slowly across the sky. Likewise computer
> control of radio frequency was generally not required, since the
> Doppler shift changed rather slowly.
> 73  -Paul
> kb5mu at amsat.org
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