[hpsdr] [Hpsdr] Call for Comments - ALEX

[Robert McGwier]

Graham:

Thank you very much for the work you are doing here.

The relays should be chosen with some care so that they provide 
sufficient isolation against leakage paths.  I hope you will allow for 
full duplex operation when connected to separate antennas for crossband 
operation and support of satellite operations (sorry for my personal 
biases!).

I would not limit the surface mount parts.  Through hole parts may be 
thought of best as good parts attached to (may be poor but) antennas.
The lower profile of surface mount parts contributes significantly to 
reduce emission and susceptibility to emission.

If the Elecraft experience is any indication,  people like to buy and 
are more comfortable with prewound toroids.  Some of their after market 
winders might even be willing to do this work for us as well.

The cores need to be chosen with care or they will contribute to a 
decrease in IP3 as I think you already know.

The insertion loss in the filters can be high.  I would consider an 
elliptic design as well and compare the results.  You can certainly 
afford to prototype these (in a good shielded box).

Thank you!

Bob
N4HY


Graham Haddock wrote:
> ***** High Performance Software Defined Radio Discussion List *****
> 
> All:
> 
> Well, the refelector seems so quiet that people are sending
> themselves test messages to make sure it is still working. 
> 
> For those who need something to do, I have a "call for
> comments" on ALEX.  All the information has been posted on the
> updated ALEX Wiki page. 
> 
> http://hpsdr.org/wiki/index.php?title=ALEXIARES
> 
> Please review the Wiki page for the overview, and if you want
> to dig deeper, download the three ".pdf" documents at the
> bottom of the Wiki page. One is the overall ALEX package, and
> one each for the filter simulations for the two filter boards.
> 
> The ALEX project has evolved to the description as now
> presented. I would like comments before we finish the PCB
> layout for first prototype units.
> 
> 
> Comments solicited:
> 
> Too many external (BNC) connections?  Or not enough?
> 
> Would you be willing to assemble this yourself, as opposed to
> purchasing a manufactured module?  It is a mix of through-hole
> and some surface mount components, and will also require some
> mechanical assembly.  It is not the kind of assembly
> that most contract manufacturers are used to dealing
> with.  I could limit the surface mount
> components to larger pitch ICs and larger passives.
> 
> There are about 20 ea. T-50 toroids and 5 wire coils that will
> need to be wound.  Would you prefer a kit of pre-wound toroids?
> Or would you rather wind them yourself?
> 
> Any concerns or alternative ideas you might have.
> 
> --- Graham / KE9H
> 
> ==


-- 
AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair
"If you're going to be crazy, you have to get paid for it or
else you're going to be locked up." Hunter S. Thompson

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