spyro at armlinux.org
Fri Jun 14 15:48:07 PDT 2002
On Fri, 14 Jun 2002 21:25:07 +0100
Chris Lingard <chris at stockwith.co.uk> wrote:
> Ian Molton wrote:
> 10GHz is near an amateur band so you will find plenty of designs
> at rsgb.org or arrl.com. What sort of bandwidth would you want?
I havent the foggiest. whaty sort of bandwidth does radio astronomy use?
> But how are you going to steer it? Equitorial mount and geared
> down motor. Loud grinding noises from Ian's home
This is the 'easy' bit. Its a cunning plan to use the huge stepper
motors and optical shaft encoders I have lying around ;-)
I assume an 'equatorial' mount is one with a plane parallel to the earth
and the 'scope would pivot up / down from it and swivel round?
> Get a multi mode receiver and use it as a tunable IF.
A what now?
> Feed the
> output, via analogue to digital, to a comms port; and write a
> driver for the port.
I was going to feed the analogue into my much underused sound cards
> Write some patern recognising software, then sit back and wait.
My problem is I havent the first CLUE about RF electronics, let alone
IF. all I know is Im going to need some EXPENSIVE transistors and be
VERY careful about signal routing and shielding...
what exactly IS bandwidth? (no, I dont mean in the sense of 'how fast is
as I understand it, if I have a 900MHz carrier and modulate it with a
5KHz signal, I not only alter the amlitude, but also the frequency,
causing it to deviate either side of the 900MHz carrier, although I dont
fully understand WHY changing the amplitude affects the frequency...
and if altering the amplitude alters the frequency, surely the reverse
so, surely then, amplitude modulation and frequency modulation are /the
same thing/ ?
Also, what /is/ a down converter? how does it work?
if I have a 10GHz band to observe, and beat it against a 10GHz
oscillator, then a 10.001MHz signal would resolve to a 0.001MHz signal?
so, to observe the 10GHz band with (is this the right term) a bandwidth
of 100MHz, I should beat it against a 10GHz osc. and low pass filter it
so I lose anything above 50MHz ?
Is that a down conversion or direct conversion?
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