[Milsurplus] Milsurplus Digest, Vol 227, Issue 21

[Mack McCormick]

Thank you to everyone for your suggestions on the ART 13 tuning. The issue
turned out to be a week 813 final and a shorted antenna, loading capacitor.

Mack

On Wed, Mar 15, 2023 at 20:43 <milsurplus-request at mailman.qth.net> wrote:

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> Today's Topics:
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>    1. Re: Suggested tuning for ART-13 into a 50 ohm antenna on 75M?
>       (B. Smith)
>    2. T-195 FSK IN and MO cables (B. Smith)
>
>
>
> ---------- Forwarded message ----------
> From: "B. Smith" <smithab11 at comcast.net>
> To: milsurplus at mailman.qth.net
> Cc:
> Bcc:
> Date: Tue, 14 Mar 2023 19:24:20 -0400
> Subject: Re: [Milsurplus] Suggested tuning for ART-13 into a 50 ohm
> antenna on 75M?
> Be very careful when extracting the 813 from its socket, the tube socket
> connections are very fragile and break loose from the ceramic.
> k4che
>
> On 3/14/2023 6:02 PM, Mack McCormick wrote:
> > Ken,
> >
> > These are all excellent thoughts and I too have arrived at the same
> > conclusion that the probable cause is a weak 813. I have others to test.
> >
> > The PS is stiff with low ripple. I completely rebuilt it for my
> > friend. 1100 VDC, 400 VDC, and 27.5 VDC. All very stiff and pure.
> >
> > Let me swap out a couple of 813's and I'll report the results back here.
> >
> > Thanks again/
> >
> > 73,
> >
> > Mack
> > W4AX
> > https://www.qrz.com/db/w4ax
> >
> >
> > On Tue, Mar 14, 2023 at 2:13 PM Kenneth G. Gordon
> > <kgordon2006 at frontier.com> wrote:
> >
> >     On 14 Mar 2023 at 5:17, Mack McCormick wrote:
> >
> >     >
> >     > Ken,
> >     >
> >     > Thank you. I  made a typo in my original posting. I am using
> >     2000pf not 4000pf.
> >     >
> >     > Mack
> >     > W4AX
> >
> >     Oh. OK.
> >
> >     Second question: are you sure your 813 is not weak or worn out? As
> >     I read it from various
> >     documents I have here on the ART-13, output should be around 100
> >     watts.
> >
> >     You are getting 60 even with SWR at 1:1. That almost perfect SWR
> >     means to me that your
> >     impedance-matching must be close to perfect.
> >
> >     And THAT sounds to me like a weak tube.
> >
> >     At this point, I sincerely doubt that your problem has anything to
> >     do with tuning. Yours sounds
> >     pretty close to perfect.
> >
> >     Lastly, how is your screen voltage? Low screen voltage to the
> >     final can also cause low power
> >     output.
> >
> >     But you know that.
> >
> >     I think that if I had the same symptoms you are experiencing, I
> >     would, at least temporarily,
> >     jack up the screen voltage to see what that does. The 813 can use
> >     up to 1100 VDC screen
> >     voltage for SOME services. If increasing the screen voltage
> >     significantly increases power
> >     output, then the tube is weak.
> >
> >     I am assuming you are using an AC supply with 28 VDC, 1150 VDC and
> >     400 VDC outputs.
> >     Are you certain your power supply is up to snuff?
> >
> >     A weak driver tube could also cause your symtoms, but that would
> >     show up with low grid
> >     current.
> >
> >     Ken W7EKB
> >
> >
> >
> >
> >
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>
> ---------- Forwarded message ----------
> From: "B. Smith" <smithab11 at comcast.net>
> To: Milsurplus <milsurplus at mailman.qth.net>
> Cc:
> Bcc:
> Date: Wed, 15 Mar 2023 21:42:22 -0400
> Subject: [Milsurplus] T-195 FSK IN and MO cables
> I've added some info on the T-195 FSK cables
> k4che
>
> http://k4che.com/T195%20FSK%20MO/T-195%20FSK%20MO.htm
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-- 
73,

Mack
W4AX
https://www.qrz.com/db/w4ax
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