[Laser] first time, simple system, but problem

[Brent]

Paul M0EME wrote:
> 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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I just added in the bypass caps, seems to helped alot but still there 
some, ill move them right to the pins and also add in the cap w. 
resistor and see what happens. Thanks all for your suggestions and ill 
keep you posted. Gotta finish the TX and give it a try, still, any tips 
on a simple way to aling everything?