[hpsdr] [Flexradio] Teamspeak Audio - 05-13-06 lots of announcements

[Robert McGwier]

Chris:

AMSAT calls this approach to amplification HELAPS (high efficiency 
linear amplification by parametric synthesis).  DJ4ZC wrote his doctoral 
dissertation on "our brand"  of EER in the early 1970's.  Oscar 7

http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1974-089B


launched in  1974 had a 70 cm up,  2 m down crossband repeater 
(transponder).  It did EER (HELAPS).  Last fall AB2KT, KK7P, G6LVB, and 
I proposed to AMSAT-DL that we do this for P3E in an SDR transponder.  
That is called SDX (SDR transponder).  Karl,  DJ4ZC,  immediately 
recommended adding it to the spacecraft and we will now do that if all 
goes well.  It is called SDX (I think K3IO coined that acronym) and is 
one of the influences on Sasquatch/HPSDR.  Very soon AMSAT is going to 
open its Wikipedia (Eaglepedia) and the design documents for that will 
be open.  For those of you attending Dayton,  if you care to drop by the 
AMSAT booth,  you may see the SDX prototype in action and see the block 
diagram Lyle has drawn for the SDX where HELAPS (EER) is done. 

At http://www.gpstime.com  you can hear the first "QSO" through our SDX 
prototype built on SDR-1000's  if you scroll down the page and click on 
the audio.  This is a very exciting time for me personally because I see 
AMSAT,  TAPR, Flex,  HPSDR, GnuRadio doing things that commercial 
companies and even government institutions have lost the ability to do 
because of their organizational structures and because they cannot 
justify it in the quarterly reports/ bean counting or because of their 
"stove pipe, task oriented" nature.  If anyone hears ANYONE say that 
amateur radio is technically dead,  tell them to wake up and join these 
groups.  The only threat facing our health is demographics and loss of 
clout.

Bob
N4HY


Christopher T. Day wrote:
> Bob,
>
> There is another way to look at this. Any radio wave can be represented
> by a time varying complex number. The complex number, in turn, can be
> represented in rectangular coordinate - I and Q being the amplitudes
> along X and Y axes 90 degrees apart - or in polar coordinates - envelop
> amplitude A and instantaneous phase phi. In Envelope Elimination and
> Restoration, the amplitude is measured at a low signal level and passed
> along a distinct amplifier chain ending in a high-efficiency switcher
> amp that preserves the amplitude information but ignores the phase
> information. Meanwhile, the signal with the stripped amplitude still
> retains the phase information and goes through an amplifier chain that
> amplifies it via another form of switching amplifier that ignores
> amplitude but preserves phase info. In the final, these two chains come
> together to reconstruct the original complex number at a much high
> signal level and very high efficiency.
>
> My point is that all the SDR designs being discussed here do
> computations on the rectangular coordinateS of the signal - I and Q - to
> do sideband suppression. It is a very simple computation to then convert
> I and Q coordinates to polar A and phi numerically. The resulting A and
> phi can be converted to analog and fed directly into the EER
> amplification chains. Also, these signals can be pre-processed
> numerically to compensate for undesirable distortions of the amplifiers.
>
>
> 	Chris - AE6VK
>
> P.S. - Sorry for the brain dump, but I thought the idea ought to be
> spelled out explicitly in a public forum.
>
>   


-- 
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
Laziness is the number one inspiration for ingenuity.  Guilty as charged!