[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: AO-54?

Couple of things ..

The vector they throw it on would need to be calculated pretty  
carefully to get the HT-sat into any kind of predetermined orbit, and  
throwing it on a random ad hoc vector could have pretty  
counterintuitive results.  More than likely the best vector will be  
up and behind ISS, putting your sat in more or less a SuitSat-like  
orbit with a time to reentry somewhere around a month or so, and a  
useful lifetime of maybe a few orbits.

Also, HT's are sort of designed to be held in the hand when they  
transmit, and don't have a ground plane to speak of.  If you set up  
an HT floating in a vacuum with nothing touching it, the impedance of  
the antenna is going to be way off and it will be seeing high SWR,  
which will make it .. well, do whatever it is that HT typically does  
on high SWR, either burn out the finals or reduce its output power.   
Either way you won't hear much on the ground.

I'd say the factory ducky is probably about the **worst** choice for  
an antenna if you really want to launch an HT-sat and have it work.   
Better would be a tuned 1/4 or 3/4 wave whip of music wire or copper  
tubing with suitably long ground plane radials on the BNC/SMA  
connector (I've built these for enhanced performance in marginal  
areas) with suitable droop to give the radio exactly 50 ohms at its  
downlink frequency.

You might get a few useful orbits out of a configuration like that,  
although you'd need a radio that can transmit on the downlink more or  
less continuously (UHF up and VHF down might be easier on the finals  
thermally) .. bear in mind that you can absolutely positively count  
on it transmitting continuously while over North America, Europe, and  
most other areas .. and doesn't desense on crossband repeat at all ..  
and can put up with being hit by extremely strong signals from people  
running 100W into EME arrays, etc.  I don't know of many HT's that  
will meet all those design constraints.

On Feb 8, 2006, at 11:24 AM, John W Lee wrote:

> Do ya think they could throw it "UP" into a higher orbit ?
> And of course the cross-band repeat and maybe a AL800
> antenna?
> On Wed, 08 Feb 2006 08:48:38 -0800 AL7CR <al7cr@punakea.com> writes:
>> So a handheld thrown out the door DOES qualify if it is turned on.  I
>> agree it should be programmed for cross band repeat first though ...

           --... ...-- -.. . -. ..... ...- -...
                   Bruce Bostwick N5VB

[demime 1.01d removed an attachment of type application/pkcs7-signature which had a name of smime.p7s]
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org