[hpsdr] A/D

[Jason A. Beens]

Sweet.  It would be nice to design the filter bypass to provide a
controlled impedance path up to 700 MHz (or as high as practical) so we
can attach band-select filters on the Mercury for direct conversion.  A
full bandwidth scenario might not be practical, but we should consider
the bypass bandwidth in the layout of the design.    


-----Original Message-----
From: hpsdr-bounces at hpsdr.org [mailto:hpsdr-bounces at hpsdr.org] On Behalf
Of Phil Harman
Sent: Saturday, April 21, 2007 10:27 PM
To: 'High Performance Software Defined Radio Discussion List'
Subject: Re: [hpsdr] A/D

***** High Performance Software Defined Radio Discussion List *****

My current Mercury prototype works fine on 2m with the input filters 
bypassed - it will  need a suitable preamp and bandpass filter for
serious 
use but for monitoring  the local repeaters it's OK as is.  I think the 
LT2208 input is specified to 700MHz.

So the answer is Yes!

73's Phil... VK6APH


----- Original Message ----- 
From: "Lyle Johnson" <kk7p at wavecable.com>
To: "Jason A. Beens" <jbeens at sensetechnologies.com>
Cc: <hpsdr at hpsdr.org>
Sent: Sunday, April 22, 2007 7:22 AM
Subject: Re: [hpsdr] A/D


> ***** High Performance Software Defined Radio Discussion List *****
>
> Hello Jason!
>
>> Is there any plan for undersampling the incoming signal?  You can
recover
>> the information on a carrier by satisfying Nyquist over the bandwidth
of
>> the modulated signal.  You cannot recreate the carrier in this
manner,
>> but the contents of the carrier can be demodulated.
>
> As long as the information is band-limited, you can certainly
> undersample the RF and downconvert in the A/D.  You should be able to
> bypass the filters in Mercury, allowing you to do this sort of thing
> using external filters.
>
> I have done this with my SDR-14 to listen to 2 meters, for example.
>
> 73,
>
> Lyle KK7P
>
>
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