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Re: [Discuss-gnuradio] Sharp BS2S7HZ1204 tuner

From: Krzysztof Kamieniecki
Subject: Re: [Discuss-gnuradio] Sharp BS2S7HZ1204 tuner
Date: Thu, 16 Dec 2004 15:30:36 -0500
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Thanks for the great report Marcus. 

This report has the first experimental data that I have seen of a DBS tuner
receiving a GPS signal (page 7). 

On page 11
I decided to measure the amplitude imbalance between I and Q using a known
signal&#151;the GPS L1 signal. I discovered that the actual amplitude imbalance
is closer to 7dB, which lead to rather suspicious-looking spectra.
Perfectly-symmetric responses of equal amplitude around the zero line,
regardless of which side of the carrier I tuned the tuner to, led me to suspect
a problem with the computed spectra.

Remember I'm not an EE. 

Could this be caused by the L1 signal being made up of two components, the C/A
(plus 50Hz data) and the P(Y) (plus 50Hz data) signals, which are broadcast in
quadrature? According to the GPS spec P(Y) has a signal strength of -161.5 dBW
and C/A has a signal strength of -158.5 dBW.

Quoting Marcus Leech <address@hidden>:
> I spent last winter playing with the Sharp BS2S series DBS 
> direct-conversion quadrature tuner module.
> I have full data on the module, and was able to use it in the following 
> project:
> http://www.propulsionpolymers.com/radioastronomy/seti_receiver.pdf
> The unit that I use is shown here:
> http://www.sharpsma.com/sma/products/rf/dbs2.htm              (BS2S7HZ1204)
> The unit is programmed via I2C, with the AGC voltage set via an analog 
> input between 0.8 and 2.7V.
> It's a direct conversion quadrature receiver producing I and Q outputs 
> stretching from
>   DC-<programmable bandwidth>.  The bandwidth is programmable from 2.5 
> to 20Mhz, and
>   the frequency is programmable in increments of 62.5Khz between 950Mhz 
> and 2150Mhz.
> Since this is an I2C unit, and Gnu Radio already has I2C routines, it 
> should be fairly straightforward
>   for someone to take the routines that I wrote for the above project 
> and integrate them into
>   Gnu Radio.
> I also have a .PDF of the datasheet for this device somewhere.
> I was able to get the tuner as a free sample, but even in 1s and 2s from 
> the local distributor, they're
>   only about CDN$12.00/apiece.
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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