[Laser] Stepper motor control of laser communication unit

[Andrew T. Flowers, K0SM]

Kerry,

I don't have a simplex option in the SW, but I suppose I could make 
one.  As long as you don't drive your soundcard into clipping it should 
be okay.  You need to set one station to transmit on the "top" band and 
the other on the "bottom" band.  The only QRM you will get from your own 
signal will be spectral bleeding from your own signal several bins 
away.  If this is a problem you might try the "Blackmann" window 
function as it is designed to attenuate the bleeding into bins removed 
from the signal.  A good way to test is to try transceiving in full 
duplex ((TX high, RX low) with one station and seeing if you get a 
significant amount of energy filling up the receive band.

Even if your own signal is way above the noise floor you shouldn't have 
any trouble resolving much weaker signals at other frequencies.  A 
computer FFT has much longer integration time than our ears and thus 
better frequency resolution.  For example, we can't separate two CW 
stations 20Hz apart by ear, but we can see it fine on a spectrogram.

Andy

Kerry Banke wrote:

> Andy - That's great hat you have someone there to play with:) Good 
> luck on your 47 GHz and laser contacts. We have four 47 GHz rigs in 
> our group but have only done the 1KM required for the contest each 
> year.  Sometime we need to get out & see what they will really do 
> since we have already done a lot farther with lasers.  I'll certainly 
> send you the info as soon as I get it together over the next few 
> days.  I kind of got sidetracked from the NLOS experiments when these 
> steppers came along but I think they will be useful for those 
> experiments as well.  I need to finish getting setup to try 
> communicating one way using your Laserscatter SW and then build a 
> second set of equipment.  I'm kind of assuming we'll have to run in 
> simplex mode to avoid clobbering our local receiver with our local  Tx 
> signal.
>  Let me know how you make out on you hilltopping.
> Kerry N6IZW -
>
> At 02:52 PM 10/21/2004, you wrote:
>
>> Kerry,
>>
>> I'd like to see a copy of that word document when you get a chance.  
>> I won't get a chance to do any building any time soon, but it will 
>> give me something to think about.
>>
>> BTW, I just assembled a second laser aimer using a couple of Daedal 
>> stages  It very much like my other aimer which uses a big Zeiss 
>> translation stage, only much lighter.  With any luck we'll be 
>> lighting up for a real QSO around here in a couple weeks.  K2AXX is 
>> planning a big tower party to put up the uW antennas and It looks 
>> like we are going to try a 47 GHz shot from his hill.  If we do that 
>> then I'll tag along with the THz gear :-)
>>
>> Andy K0SM/2
>>
>> Kerry Banke wrote:
>
>
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