Re: [Discuss-gnuradio] 950-2150Mhz frontend

[cfk]

Dear Krzysztof & others:

    On the questions of the meaning of the -65dBm to -25dBm spec, what is
happening here is a definition of the minimum (-65dBm) signal level and
maximum (-25dBm) signal level that the Sharp module is designed for. I
believe that these front ends are intended to be used with an external LNB
(Lo Noise Block) converter to actually receive the signal from the
satellite. If you look at http://cfk.homelinux.com/gunradio , near the
bottom of the directory listing is sharp_BS2S7HZ1204.pdf . This file is 11
pages and shows more detail then the Sharp page you have below. I started
out with the two page document:
http://www.sharpsma.com/sma/products/rf/pdf/102.pdf and it just frustrated
me.

    In going through http://cfk.homelinux.com/gunradio/sharp_BS2S7HZ1204.pdf
, You can see that the DBS frontend supplies 25VDC @ 400mA to the LNB. Its
up at the LNB that the raw sensitivity is obtained sufficient to receive
either GPS or DBS signals. View the '1204 module and the little frontend
board as an interface to the USRP.

    If you go to http://www.sharpsma.com/sma/products/rf.htm , you can see a
picture of the LNB next to the '1204 module.

    The key question we have is "Is this an appropriate enough module for
the second frontend board?". I suspect there will be many frontend boards
for various purposes. The frontend boards are not complicated nor expensive.
We just need to move forward a little bit at a time to make gnuradio as
useful as possible as quickly as possible.

    Dont worry about bandwidth usuage of my computer, that is no problem.
All the files in the directory at http://cfk.homelinux.com/gunradio are for
the benefit of the gnuradio participants. This directory is just a
compilation of files including schematics and datasheets appropriate for
frontend work.


Charles



----- Original Message -----
From: "Krzysztof Kamieniecki" <address@hidden>
To: "GNU-RADIO DISCUSS MAILING LIST" <address@hidden>
Sent: Sunday, April 18, 2004 12:19 PM
Subject: Re: [Discuss-gnuradio] 950-2150Mhz frontend


> No helpful comments just more questions, and praise for your effort to
design boards for us RF
> illiterates.
>
> I'll refer to this spec to keep your websites "bandwidth" usage down.
> http://www.sharpsma.com/sma/products/rf/pdf/102.pdf
>
> The Sharp Module has this spec "Input signal level (dBm) –65 to –25"
>
> What does the lower limit mean in the analog domain?
>
> Here is an example based on my application:
>
> The GPS spec states that the Minimum received signal power (L1 C/A)
is -160dBW : -130dBm
> + a 40dB GPS Active Antenna
: -90dBm
>
> Does this mean that the amplified GPS signal magnitude is 25dB below the
maximum output of the tuner
> module, or 25dB below the noise floor of the module?
>
> Thanks,

> cfk wrote:
> > I have a preliminary schematic and parts placement for a 950-2150Mhz
> > frontend daughterboard on my web site at
> > http://cfk.homelinux.com/gnuradio . If you just enter this link, there
> > is a whole directory of files relating to three front ends. The files
> > with '4702' in them relate to the first frontend for 45-850Mhz of which
> > 6 boards were made. The second group of files have 'fedbs' in their
> > names. These files pertain to the Sharp '1204 module which is a DBS
> > 950-2150Mhz module. The third group are 'really' preliminary and
> > contemplate a Maxim 80211 chip.
> >
> > One the 950-2150Mhz frontend, which 'might' be interesting to GPS is a
> > schematic is in two parts, the first is
> > http://cfk.homelinux.com/gnuradio/fedbs_1.pdf and the second page is
> > http://cfk.homelinux.com/gnuradio/fedbs_2.pdf
> >
> > Perhaps Brian, Krzyztof and others might comment on it so we can get it
> > as useful as possible to the group.
> >
> > Charles