[hpsdr] Some answers to call for comments for the design of ALEX

[Graham Haddock]

Henry:
Thank you for your comments and ideas..
My comments below.
--- Graham


Henry Vredegoor wrote:
> ---> I think it will be most cost effective if the boards can be 
> assembled by DIY. (Saves us in the EU probably also up to 20 % VAT as 
> well.......)     A kit of pre-wound toroids could be easier for less 
> DIY experienced people and could have the advantage that the coils 
> could have a tested inductance.
>
>       Also another separate kit for all the other components please if 
> possible !
>
OK. I think we are headed this way.
>
>
> Additional/questions remarks:
>
> - Did I miss something and was the digitally continuously tuned 
> preselector/filter idea abandoned and are we back to a number of fixed 
> filters?
>
Phil H and I looked at a number of continuously tunable options, but each
had its special challenges.  We might come back and look at that at a later
date, but for now, to keep the availability of ALEX close to the same time
as MERCURY and PENELOPE, we will do this.  Phil H. also wants to
provide a dual receiver option in software, and the single tunable filter
would not enable this.
>
> - Where is the receiver protection? I think it should be closest to 
> the antenna and as far away as possible from the sensitive electronics.
>
I will provide some kind of transient protection at each receiver 
external input.
I have not decided what it will be yet.
>
> - Why not use relays for ALL the switches instead of using Hittite 
> switches for the receiver?
>
The Hittite switches are much smaller and cheaper than the relays.
>
> - What about daisy chaining of filter-boards (e.g. say I want a 16 X 
> RX bandpass filter configuration)
>
There is an external receiver filter insertion capability on ALEX.  You 
can insert
anything you want in line with the receiver using RCV AUX 1 OUT and RVC 
AUX 1 IN.
>
> - Since it seems we are back to individual filters and seeing the 
> resemblance between the RX and TX block diagrams, would there be a 
> simplification possible by designing just a single board for use in 
> both an RX- and a TX configuration?
>
I think they are different enough that they are different board designs.

>  Filters could be separate modules (as suggested already in the 
> previous discussions) layed out for individual preferences. 
> (Frequency, Filter architecture type, low- high- or band-pass, LNA)
>
> It would contain only the power supply, the  relays, the switching 
> logic and mounting space and connection points for the individual 
> filtermodules.
>
> This would require however another separate, (remote- ?) "RX/TX switch 
> over, SWR-bridge, antenna-select, receiver protection" board/unit of 
> some sort.
>
> (Quite a different setup, I am aware of that, but it would be my 
> personal preferred solution)
>
That is more than I want to take on right now.  It will be an effort to 
get the schedule for ALEX
as described close to MERCURY and PENELOPE's schedules, both of which 
started much earlier.

--- Graham / KE9H

==


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