[Boatanchors] Re SX-130 question

Bill Fuqua wlfuqu00 at uky.edu
Wed Feb 1 09:08:43 EST 2012

   It does have a product detector however, the bias on the tube seems a 
bit strange.
Perhaps it is to reduce the gain so that AM and SSB reception audio levels 
are about the
same. The screen voltage is about 24 volts and plate about 65V. Perhaps the 
detector is being driven by the IF signal. 6BE6 pentagrid converter tubes 
were primarily
intended for low level mixing, not high level and  have considerable 
conversion gain.
Bill wa4lav

At 03:05 AM 2/1/2012 -0500, John Kolb wrote:

>This is common to most (all?) receivers which do not have a product
>detector for SSB but simply
>add a BFO signal to the IF signal going into the AM detector.  This
>is true even of the R-390 receiver.
>For the BFO signal to replace the missing carrier of the SSB signal,
>it needs to be much stronger than
>the SSB signal components.  If the SSB signal is strong, the BFO may
>not be enough stronger to
>serve as a carrier.  In this case, turning down the RF Gain reduces
>the SSB signal to a proper level
>to work with the BFO signal.
>With the RF gain turned down, the AGC will probably be less
>effective, so constant adjustments
>of it may be necessary (riding the gain).
>At 08:49 PM 1/31/2012, Ron Barlow wrote:
> >Many thanks to all who replied to my request for info on the SX-130.
> >The owner (a member of the Hallicrafters mailing list) states that
> >the RF gain control must be reduced to obtain good copy on SSB. He
> >states that if the RF gain control is advanced, the audio distortion
> >becomes severe.
> >  He asks if this situation, is normal, for this particular receiver.
> >  He sent along a copy of the owners manual, which states that
> > "under certain conditions, it may be found advantageous to reduce
> > the RF GAIN setting for improved reception." Judging from the
> > owners description, his receiver seems to require a great deal more
> > attention, to the RF gain control, than the owners manual suggests.
> >  Unfortunately, I do not have access to the receiver, and I have
> > never operated an SX-130. Therefore, I am not in a good position to
> > judge whether his receiver is operating normally. Any and all
> > advice is greatly appreciated, and I will forward it to the owner
> > of the receiver.
> >                                        Many thanks & 73 de Ron  N4GJV
> >
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>Boatanchors at puck.nether.net

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