[ARC5] OT? bc-348 bfo question

[Fuqua, Bill L]

    A bit of information of copying SSB with diode detector and BFO.
The BFO injection must exceed the peak signal at least several times.
The diode detector is a square law device. The output is proportional to the square
of the input voltage which works well for receiving AM. 
  So the output of the diode detector when two signals are provided is as follows.
Iout = Vsquared. 
So 
I out=(Vsignal+Vbfo) squared
Expanded you get
I out= Vsignal Squared + 2xVsignalxVbfo+Vbfo squared

The Vsignal Squared represents the AM detection of the signal
The Vbfo squared term is DC from rectified BFO signal
However,
The 2xVsignalxVbfo is the part of the expression that is the product of the two signals (product detector)
That detects the SSB signal.

If the BFO injection is too low you get some AM detection and SSB detection. Thus it sounds bad.
If you increase the BFO signal the product detected signal exceeds the AM detected signal and it 
sounds much better. 

73
Bill wa4lav






________________________________________
From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on behalf of Fernando - LU2DFM [lu2dfm at gmail.com]
Sent: Sunday, September 15, 2013 7:59 AM
To: Robert Eleazer
Cc: arc5 at mailman.qth.net
Subject: Re: [ARC5] OT? bc-348 bfo question

On Sat, Sep 14, 2013 at 06:35:39PM -0400, Robert  Eleazer wrote:

> So you might try plugging in a fresh tube.

Thank you. I've found the problem and it's working fine now.

I have not another 6F7 so testing other tube should need at least an
adapter for the UX to octal.

--
73 de Fer, LU2DFM
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