[hpsdr] CASMIR design v0.4 plus introducing COPERNICUS!

[John B. Stephensen]

Reed relays have an extremely high intercept point and last a long time.
Otherwise, PIN diodes with a 1.5 microsecond or longer carrier lifetime will
work on HF and VHF.

73,

John
KD6OZH

----- Original Message ----- 
From: <pvharman at arach.net.au>
To: "Lyle Johnson" <kk7p at wavecable.com>
Cc: <hpsdr at hpsdr.org>
Sent: Monday, June 12, 2006 01:05 UTC
Subject: Re: [hpsdr] CASMIR design v0.4 plus introducing COPERNICUS!


> ***** High Performance Software Defined Radio Discussion List *****
>
> I think we should avoid relays if possible. The latest switches should
have a
> high enough IP so as to not be the limiting factor on the receiver
> performance.   If we do have to use relays then bleed a little current
through
> the contacts to help keep them clean over the long term. The CDG2000 does
this
> along with a number of commercial designs.
>
> In my SDR I use the bandpass filters from the Pic-A-Star design. Each is a
ham
> band wide filter with good shape factor and low insertion loss on the high
> bands. The inductors were hard to find about 18 months ago so I expect we
will
> need to find alternatives. There are also lots of 1% silver mica
capacitors
> that I'm not sure have an SMD alternative. It was a lot of effort to hand
> build the board but the performance is excellent.
>
> I can provide a copy of the circuits and components that I used. I am
> currently using this in front of the LT2208, with a high performance
pre-amp,
> to test the Mercury design.
>
> 73's Phil....VK6APH
>
>
>
>
>
>
> Quoting Lyle Johnson <kk7p at wavecable.com>:
>
> > ***** High Performance Software Defined Radio Discussion List *****
> >
> > Hello Alex!
> >
> > > Personally it seems like a waste to use an ATLAS slot forducto
> > > COPERNICUS, maybe an external card. There's lots of room
> > > in my ATX case to mount it!  : )  (hint, hint, hint)
> >
> > Copernicus will need some sort of control logic to run it.  You could
> > reserve space at one edge for the ATLAS DIN connector and put another
> > connector in the same area. User than gets a choice of making it
> > Atlas-compatible or not.
> >
> > It would also need space for the DS2431 1-wire ID chip.  If the control
> > is via SPI or I2C, then the lines are already predefined for the ATLAS
> > bus, making things pretty simple.
> >
> > I suggest SPI, and use TI TPIC6C595, Allegro A6810 or similar ICs to
> > handle the control.  These can sink plenty of current for relay coils.
> >
> > Alternately, I2C and use PC8574 (or similar) parts with some means to
> > strap the address.  Not sure if these can directly drive relays.
> >
> > Almost as cheap, you could use a small PIC which can be set up as SPI
> > slave or I2C slave.  If you run the PIC from 6V, you may be able to
> > directly handle 5V coil relays.  Elecraft, for example,  has done this
> > for years in the various products.
> >
> > Finally, please consider the use of latching relays.  They're not
> > expensive, the board then remembers its last state, and operating
> > current is nil.
> >
> > 73,
> >
> > Lyle KK7P
> >
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>
>
>
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