Re: {Collins} Need RCA SK3089 diode data (312B-4 mod)



You're right, they are the same, contrary to what I was told. Thanks for
correcting what I posted.

I'd like to know where I found those two mods. Maybe from Jerry, W7BUN
(SK).  I'm going through my Collins file now.

73, Mike
www.w0btu.com

On Fri, May 1, 2015 at 4:06 PM, Bill Carns <wcarns@xxxxxxxxxxxxx> wrote:

> I was replying about making them bigger.  Making kike Collins did was a
> very good design.
>
>
>
> The pickup is the same on the 312b-4 and the 302C-3
>
>
>
> B
>
>
>
> *From:* Mike Waters [mailto:mikewate@xxxxxxxxx]
> *Sent:* Friday, May 01, 2015 2:27 PM
> *To:* Bill Carns
> *Cc:* collins@xxxxxxxxxxxxx
> *Subject:* Re: {Collins} Need RCA SK3089 diode data (312B-4 mod)
>
>
>
> Hi Bill,
>
> Thanks for the info.
>
> I didn't know about the W8RO board, and don't doubt that it's better than
> adding the capacitors.
>
> However, from my old notes, it looks like Collins used those capacitors in
> their 302C wattmeter (IIRC, very similar to the 312B-4). There must have
> been a good reason.
>
> Adding those caps --as Collins did in the 302C-- made a tremendous
> improvement on SSB. I'd try and explain, but I have to get back to work.
>
> I'm not certain what you mean by "neither fish nor fowl". However, before
> I added those capacitors, my D-104 (with the 32S-3's 100K load) barely made
> the 312B-4 needle flicker off of zero on SSB, *regardless of the mic gain
> setting.*
>
> 73, Mike
>
> www.w0btu.com
>
>
>
> On Fri, May 1, 2015 at 1:58 PM, Bill Carns <wcarns@xxxxxxxxxxxxx> wrote:
>
> I will make a general comment to everyone..  Making the wattmeter (302C-3)
> "More Peak Reading" is not a good plan...  It is then neither fish nor fowl.
>
> To make it Peak Reading (nice to have), just use the very reasonable and
> very high quality peak reading wattmeter board mod that is offered by Floyd
> Soo, W8RO, and his company is Hi Res Communication. The contact info is in
> our Support Directory.
>
> Otherwise, it should be left configured as is so it is an average power
> meter the way it was designed.  It is a very good design and can easily be
> updated with modern Schottky diodes or modern germanium. Either will work.
>
> Bill
>
> [snip]
>
> On Fri, May 1, 2015 at 1:16 PM, Mike Waters <mikewate@xxxxxxxxx> wrote:
>
> > My RE 312B-4 has the following mods, which I highly recommend:
> >
> > 1.) 1N82A diodes replaced with RCA SK3089 diodes. I forget the details
> > on those.
> >
> > 2.) 7.1 uF tantalum capacitors to make it more peak-reading, as the
> > Collins 302C wattmeter has.
> >  One 7.1 uF capacitor goes between R3/R5/L1 and ground; the other one
> > between R4/R6/L2 and ground.
> >  The negative lead on each tantalum capacitor is grounded.
> >  Three 2.7 uF/20v in parallel = 7.1 uF.
>
> ...
>



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