[Laser] first time, simple system, but problem

[Paul M0EME]

I found the LM386 a little noisy anyway.... I ended using a 8pin amp TBA820. 
You need a few more components but give it a try. I used this chip along 
with the KGP front-end and had heaps of success.... The one thing I did make 
sure was, that the whole thing was screened!! I built it in a 35mm film 
canister with a tiny hole for the sensor, and wrapped the whole thing in tin 
foil and earthed it to the screen of the cable. Give it a try, let me know 
how you go on.


----- Original Message ----- 
From: "Kerry Banke" <kbanke at qualcomm.com>
To: "Free Space LASER Communications" <laser at mailman.qth.net>
Sent: Wednesday, August 30, 2006 4:12 PM
Subject: Re: [Laser] first time, simple system, but problem


> The LM386 will oscillate at MHz frequencies if not dealt with properly. 
> The power needs to have bypass caps right at the pins. Also the output 
> needs to have a .05 uf  (0.1 ia ok) in series with a 10 ohm to ground to 
> prevent oscillation. We have several of those amps in use for our optical 
> receivers here in San Diego and those are the standard problems we have 
> found.
>  - Kerry N6IZW -
>
> At 04:57 PM 8/29/2006, you wrote:
>>hey all, KB1LQD here, built the simple RX'er out of a 741 op amp, and a 
>>386
>>amp with a photodiode. It works, but there is a terrible occilation when 
>>the
>>10k pot is at a volume point of anything decent, also, it seems like a
>>signal is there or not there at all, (No background noise), any tips? the
>>only long leads are the leads to the photo diode in the PVC pipe with a
>>lens. Also, any tips on making an aiming system for the RX and TX, Also, 
>>how
>>do I make sure the lens is perfectly in posistion with the photo diode?
>>
>>--
>>73's
>>_______________________________________________
>>Laser mailing list
>>Laser at mailman.qth.net
>>http://mailman.qth.net/mailman/listinfo/laser
>
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