[linrad] Microtune AD board, chip front ends 88 - 862 MHz

[w3sz <w3sz@xxxxxxxxxxx>]

Hello, All!


Reading the ARRL SDR document (more below) has caused me to produce this 
rambling email regarding possible front ends to go in front of the 
Antennspecialisten modules (or what ever you are using).  Basically it 
focuses on some Microtune chips and preassembled boards.  I suspect they 
may not be suitable for weak signal work, but thought finding out why 
might be instructive to me and those who are, like me, pretty 
technically in the dark.

This is the blurb I  discovered from an archive of OLD gnuradio archives 
that got me started:.

The basic system is a downconverter (LNA, mixer, and LO) and a soundcard.
You could use a TV tuner to cover 50 to 900MHz, and then a fixed LO to
convert to baseband.  The fixed LO would be at 5.75 MHz, so it could be done
with 7400 or 4000 series logic parts, and it would be easy to get
quadrature.  With audiophile sub $300 soundcards, you can sample/output 4
channels (I/Q on 2 antenna polarizations?) at 96kHz.  That gives you 90kHz
of bandwidth from 50 to 900 MHz, which is plenty for some serious SDR.
Total cost is less than $500.

Those of us that have the microtune AD board (~$1200, 20 MS/s 4 ch), are
using a cable TV tuner.  It downconverts anything from 50 to 900MHz to a 6
MHz wide channel at 5.75 MHz.

Matt
N2MJI

:q end of blurb

Another posting on the gnuradio list said:

FYI, it's a Microtune 4937DI5 3x7702 module.  Tunes from 50M to 860M...

:q end of blurb

Does anyone have any thoughts or data on this microtune AD board? (other 
than the fact that its pricey)
It sounds interesting.  I can't find it anywhere, including on the 
Microtune website.  I emailed Matt Ettus to see what information he 
currently has.

There is also a Microtune 2050 single chip broadband tuner that has an 
input range of 48 to 860 MHz with a noise figure of 7 dB (not a problem 
with preamp ahead of it) and a first stage OIP3 of  77-79 dBm if I read 
it correctly, with a first stage gain of 18 dB.  Phase noise of the LO1 
is -86 dBm at 10 KHz, so its not great.  For LO2 is -94 dBm I think. 
 The first IF is 1220 MHZ.  The second IF is programmable from 30 - 60 
MHz.  Unfortunately that doesn't fit with any of the Linrad modules, but 
it could be converted.  You can view the specs at 
http://www.microtune.com/pproducts/PB-00038.pdf but you need to register 
first and they send you a password.  The chip costs $5.00 in large 
quantities.

I am sure there must be many things wrong with thinking of using this as 
a front end (maybe the phase noise alone is bad enough to be a 
show-stopper), but it might be helpful for those of us who are less 
technically inclined (and who want to improve in that respect) to hear 
about it via the list.  It might help us to figure out how to look at 
these things and decide what is and is not suitable.

Just off the top of my head, I see that:
the phase noise of the LO's is not spectacular
the OIP3s look pretty good
LO Spurious outputs are given as -60 dBc


There is a data sheet for the 2040 (a sister product) at:
http://www.microtune.com/pproducts/DS-00024%20rev%201.4%20MT2040%20Data%20Sheet.pdf
but again you need to have a password which you can get on their site, 
via email.

There is an MT4950 RF Tuner Module that comes complete with F connectors 
and that covers from 88 to 862 MHz and downverts to 5 - 65 MHz, so that 
might be connectable right to the 10.7 MHz Antennspecialisten Module? 
 Its URL is at
http://www.microtune.com/pproducts/PB-00022_MT4950.pdf password needed, 
again.
It looks like the phase noise of this is worse than what was quoted for 
the 2050 above.

I suspect that the specs for the AD board, which I can't find, are no 
better than the specs of the chips which I can find, but I don't really 
know this.

What started all of this was finding the Software Defined Radio Document 
by Leif, Bob Larkin, et al on the ARRL website and am chasing down many 
of the excellent references and URL's in the appendices.
http://www.arrl.org/announce/reports-0207/sdr.html

Thanks in advance, and

73,

Roger
W3SZ

-- 
Roger Rehr
W3SZ
2 Merrymount Road
Reading, PA 19609
http://www.qsl.net/w3sz




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