Re: [Discuss-gnuradio] Microtune 4937 RF module discontinued ...

[Alan Gray]

I've had the same problems finding the 4937 tuner, and am currently in the 
process of adapting the hardware design to use a 4702 tuner module with an 
IF output at 36MHz. When we contacted Microtune they suggested using a 
tuner such as the 4702 and an additional downconversion stage (they 
suggested the NEC Electronics UPC2798GR which is apparently what they use 
in the 4937 tuners anyway)

I've ordered a few of the NEC IC's but they're taking a long time to 
arrive. In the mean time I'm going to attempt to put together some hardware 
to use a 4702 module as is. I'm hoping that I should be able to sample the 
bandlimited signal without any downconversion (it's theoretically possible) 
and thus avoid the need for any more components.

Further to this, I've got just a quick question about the schematic design:
What is the purpose of the op-amp circuitry connected to the IF outputs of 
the 4937? It looks to be acting as a buffer and changing the output 
impedance of the system, however I'd like to be sure. I'll be dealing with 
a higher frequency output, and while the OPA691 appears to be able to 
operate at even higher frequencies I'm anticipating having to change that 
part of the circuit around a little, just need to know exactly what it does.

On a purely academic note, I'm curious as to why the 4937 has 2 pairs of 
I2C lines (the 4702 has only one SCL SDA pair) but that's just pure curiosity

If I make any significant progress, I'll be sure to send out a message
Alan
At 04:06 PM 17/07/03 -0700, you wrote:



hi all, i'm a student trying to get this software radio working but i'm
having difficulty finding the Microtune 4937 RF tuner module with IF
output 5.75MHz, because they discontinued the chip.  does anyone know
a good replacement for this module or alternative to use a high IF output
and use another module to reduce the IF output to what is needed for the
project.  I'm using the Measurement Computing PCI-DAS4020/12 as recommneded at
the website.

--
Thanh San D. Nguyen
The Marlan and Rosemary Bourns College of Engineering
Department of Computer Science and Engineering
University of California, Riverside
email: address@hidden
cell : 714-292-6783





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