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

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




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 <> 


On Fri, May 1, 2015 at 1:58 PM, Bill Carns <wcarns@xxxxxxxxxxxxx <mailto: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.



On Fri, May 1, 2015 at 1:16 PM, Mike Waters <mikewate@xxxxxxxxx <mailto: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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