On 05/25/2018 06:43 PM, Dan Werthimer wrote:
b) you could make your own PCB, or perhaps use the downconverter boards
we made for arecibo multibeam receiver:
see section 4: "16-Channel Quadrature Downconverter (IF to IQ
Baseband Converter) of
https://casper.berkeley.edu/galfa/
lower parts cost but more work.
photos of this 16 channel downconverter are at:
https://casper.berkeley.edu/galfa/pictures/pictures.html
I'd probably go the PCB route if it were my problem.
The LT5512 looks appealing if you're going to do a low-IF
downconversion (as would be appropriate for my RTLSDR suggestion)
LeoBodnar enterprises has a GPSDO with synthesized output up to 800MHz
which could be used as the LO, and then you'd have
to distribute it to each mixer with equal phase lengths (or calibrate
out phase-offsets later in the chain).
My guess is that you could get 4 channels on a board cheaply.
best wishes,
dan
On Fri, May 25, 2018 at 9:04 AM, Michael Inggs <miki...@gmail.com
<mailto:miki...@gmail.com>> wrote:
Hi Dan
One of the tradeoff studies the guys are doing is the cost of a 48
channel analogue downconverter and low sample rate ADC. At
present, direct demod with a SNAP looks simpler in terms of
hardware complexity, but has not been costed.
One of the team has actually implemented all the digital backend
(including RFI excision) on a GPU, so in principle, all we need
are time stamped packets of samples, and nothing on the FPGA,
except demod, decimation.
Thanks for the ideas coming in to the team.
Regards
On Fri, 25 May 2018 at 18:59, Dan Werthimer <d...@ssl.berkeley.edu
<mailto:d...@ssl.berkeley.edu>> wrote:
if vinand,
if you want to digitize 48 signals with 250 KHz bandwidth, you
might want to consider
purchasing a 48 input PCIe ADC board and doing the signal
processing in a computer (in software).
(not use FPGA boards).
but then you'd have to mix the deuterium line to baseband, so
you'd need 48 downconverters.
if you want to use snaps, and you don't have much processing
to do on the fpga, and you want to save money, you could
plug in a ADC16 board into the snap -
this is a bit of a cludge, but would give you 28 channels per
snap (16 external ADC channels, and 12 on board ADC channels).
if you have a roach1 or roach2 lying around, there's a 64
channel adc board you could use that sample at up to 50 Msps;
i'm not sure about the analog bandwidth - you might not have
to use downconverters...
best wishes,
dan
On Fri, May 25, 2018 at 6:24 AM, Vinand Prayag
<vinan...@gmail.com <mailto:vinan...@gmail.com>> wrote:
Hi,
Please find attached the User Requirement. The bandwidth
is actually only 250KHz
Cheers,
Vinand
On Fri, May 25, 2018 at 5:20 PM Marcus D. Leech
<mle...@ripnet.com <mailto:mle...@ripnet.com>> wrote:
On 05/25/2018 07:28 AM, Vinand Prayag wrote:
Hi all,
We are looking at building a telescope in Mauritius
which is called the Mauritius Deuterium Telescope,
MDT for short. As the name suggests it is a Deuterium
focused experiment. We have planned for a pathfinder
station to be built for the end of this year and had
in mind the SNAP boards for the digital back-end. We
were set to buy four SNAPs by the end of next month
but a sudden slash in funding has put a dent in our
plans. I was wondering if anyone has any unused SNAPs
that we can get off their hands at a reduced price.
Currently one SNAP is sitting at $3500 from Digicom.
Anything below $3000 will greatly help us. We will
obviously be extremely grateful for donations. Hope
to have some positive feedback from some of you.
Kind Regards,
Vinand Prayag
Do you have a pointer to a project description?
Why such high bandwidth if you're looking at Deuterium?
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