[R-390] 3TF7 Substitutes

[David Wise]

Right.  (I presume you mean "switching regulator circuits", not
linear.)  By the way I did a linear regulator too.  It worked
fine but I didn't like the extra stuff cluttering up the view.

I once put a Sangean ATS-803A at maximum gain right next to the
3DW7A when it was still a breadboard, and with certain antenna
orientations I could hear a little bit of hash around 150-300kHz.
I don't hear any noise in the R-390A itself, at any frequency.
My circuit uses reverse phase control at 120Hz, which is much
quieter than anything one can do with the kind of switcher you're
probably thinking of.  The MOSFET pass elements are on at zero
cross, and softly turn off part way through the waveform.

I'm not arguing that my circuit is simple, far from it.  Some
would call it an obsession gone wrong.  But to my knowledge
it's the only good regulator that is also 100% nonintrusive.
You don't so much as have to loosen a screw, you just plug
it in like a 3TF7 and it plays.

73,
Dave Wise

> -----Original Message-----
> From: Cecil Acuff [mailto:chacuff at cableone.net]
> Sent: Friday, September 24, 2004 2:25 PM
> To: David Wise; r-390 at mailman.qth.net
> Subject: Re: [R-390] 3TF7 Substitutes
> 
> 
> There are any number of complex ways to solve the 3TF7 issue 
> but we should
> not be short sighted and forget about any noise that might be 
> generated by
> the solution.  Linear regulator circuits work great but are 
> quite noisy.
> 
> The new fangled sand box radios suffer from many problems 
> associated with
> noise generated by devices internal to the radio...fortunately the 390
> series doesn't have that problem....that's one of the things 
> that makes it
> such a stand out performer.
> 
> Cecil...
> ----- Original Message ----- 
> From: "David Wise" <David_Wise at Phoenix.com>
> To: <r-390 at mailman.qth.net>
> Sent: Friday, September 24, 2004 3:29 PM
> Subject: RE: [R-390] 3TF7 Substitutes
> 
> 
> > -----Original Message-----
> > From: mikea [mailto:mikea at mikea.ath.cx]
> > Sent: Friday, September 24, 2004 10:29 AM
> > To: r-390 at mailman.qth.net
> > Subject: Re: [R-390] 3TF7 Substitutes
> > cause of this drift.
> >
> > Thanks _very_ much for your research results. I have had the benefit
> > of your expertise for some years now, and think it is appropriate to
> > give you your due in public.
> >
> > I feel some construction coming on.
> 
> If you're in the mood for construction and would prefer to make
> *no modifications whatsoever* to your radio, you might consider
> the 3DW7A, which I designed a while back.  Thanks again to Roy Morgan
> for massaging the picture into a portable format.  I tried to post
> it here, but the listserv rejected the .jpg attachment.  Contact
> me off-list and I'll email it to you.  The single-source items
> (the MOSFETs and the RMS converter IC) are available at DigiKey.
> Everything else is generic.
> 
> It's a cool-running two-pin module, although you'll
> need a magnifying glass and tweezers to cram it into
> the "tubester" form factor like I did.  Maybe I ought to
> post a photo of the completed unit to prove it can be done.
> 
> By the way, I'm still working on the 3DW7D, which does the
> same job digitally at about 1/2 the parts count.  Somebody
> asked for a LED to simulate the olde-tyme glow, and I got
> carried away.  Soon (but that means < 5 years :)
> 
> 73,
> Dave Wise (SWL)
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