[hpsdr] preselector control

[Henry Vredegoor]

Hi All, Eric, Graham,

Sorry for being too early..... ;-)

Maybe I got carried away, but the point I just wanted to make was that,
while considering/designing/testing the possibilities, it would be good to
keep in mind where such a cut between the filter-section and the
control-section ideally could be made.

As far as I understand it, at least for the switched bandpass-filter section
that is, in the end it would come down to demuxing/decoding some (serial-)
control signals for the switching of the relays/semiconductor-switches for
the filter sections?
Or in case of an all-band-tunable filter, for the capacitors and inductors
or inductor-taps?

There, or thereabout, I think, could be the cut; a really dumb filter
section. ;-)

(Darn, I would like to have a look at the schematics of some of the
apparently already implemented commercial versions..... ;-) , Anybody? )

Sorry again if I am causing unwanted design-QRM.......


73's,
Henry.



> -----Original Message-----
> From: Eric Ellison [mailto:ecellison at gmail.com] 
> Sent: donderdag 15 maart 2007 0:03
> To: grahamh at verizon.net; 'Henry Vredegoor'
> Cc: hpsdr at hpsdr.org
> Subject: RE: [hpsdr] preselector control
> 
> 
> Hi Henry/Graham
> 
> I agree. Too early to call.  Graham you might consider calling a
> 'brainstoming session' on Teamspeak. Phil, Bill, Chris and 
> others are there
> on Friday's at 02:00. Would be fun to listen in! 
> 
> These were my thoughts, like Henry's in the Pandora thread with Ben.
> 
> > My feeling about Alex is it should be a 3 way.
> 
> > Put a DIN connector on it, to mount on Atlas, pick up power 
> and control
> from the buss.
> 
> > Also put external connections i2c connection, reset, 
> ground, JTAG and
> > whatever else is needed to control it from OZY. External 
> power connection
> from a standard PC power Molex 12v-G-G-5v.
> 
> 
> > Also make it 'stand alone for any receiver project going on 
> out there,
> > outside SDR.
> 
> 
> > Make it modular with plug in filter sections in any case.
> 
> ******************************************************
> That would be very hot!  Something that could be used outside HPSDR 
> would certainly increase interest!
> *******************************************************
> 
> Every time I see a project proposed in HPSDR my first thought 
> is can we get
> an equivalent 'off the shelf'. Second is can we make this 
> project board
> appeal to folks outside just Ham Radio. Third is is there any 
> 'duplication'
> of parts existing on other project boards (FPGA on Ozy for 
> example). In the
> case of Alex, almost any receiver/tranciever project in QST, 
> RadCom, QEX or
> other could benefit from an 'off the shelf' or easily 
> modified high quality
> filter board. Especially if it can take a few watts of 
> exciter power. Then
> instead of selling 300-500 highly customized (HPSDR) filter 
> boards we are
> into selling potentially thousands. I think ATLAS - OZY and 
> possibly an EPI
> board are in that category already if we hit the Robotics or 
> FPGA groups.
> 
> 
> Hi Henry:
> 
> Well, we are not far enough along to split the project yet.
> 
> Initial work will be focused on verifying that the topology we are
> considering can be made to work over the frequency range, and 
> whether we
> can use solid state switches and still make the filter performance,
> or whether we need to go to relays.
> 
> Packaging and control decisions will come later, after we 
> know how big it
> will be, and how sensitive the inductors are to picking up 
> local fields.
> 
> By going from a ten section fixed tuned preselector to a continuously
> tuned preselector, we have gone from something where a simple
> SPI bus was fine, and a small CPLD was overkill, to needing
> a small CPU or a large CPLD and a fairly large lookup table,
> or some clever algorithms to train and manage it.
> 
> --- Graham
> 
> 
> 


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