[AMRadio] tube shields on radios used by the military

[Doug Hensley]

I think Nick is correct.  Maintaining the tube seated in its socket was more of a concern than heat.  Where the heat became an issue, you see the shields with cut away sides.

Doug W5JV

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Message: 3
Date: Sat, 28 Aug 2021 15:27:15 -0400
From: Nick England <navy.radio at gmail.com>
To: CL in NC <mjcal77 at yahoo.com>,       "amradio at mailman.qth.net"
        <amradio at mailman.qth.net>
Subject: Re: [AMRadio] Another question to ponder
Message-ID:
        <CAB55hNevXhvPbuP8t4wE3k7bigtxyWLn5tgqNQUE3vVDKonoEw at mail.gmail.com>
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Possibly just a requirement for tube retention. Perhaps glass protection.
Perhaps thinking that it will conduct some heat to the chassis while
reducing radiated heat to other components. In other words, I dunno.
But yes it is surprising that the glass doesn?t melt in a shielded 6AQ5.
Nick K4NYW

On Sat, Aug 28, 2021 at 3:19 PM CL in NC via AMRadio <
amradio at mailman.qth.net> wrote:

> Has anyone ever researched the need for tube shields on all tubes, versus
> just some tubes?  Talking about the standard shiny metal ones, not the heat
> dissipating ones.  On this SP600, there is a tube shield over the 6AL5 bias
> rectifier.  Why?  Did Hammarlund get a deal on 7 and 9 pin sockets with
> integral shield bases?  If you have a string of IF tubes, what is to be
> gained by shielding every one of them, maybe just every other one if they
> are in a line.  Even the HFO, unless you are running multiple receivers
> side by side at the same time, what issue from the HFO radiating a signal
> is there?  If you remove shields and re-peak circuits, would things drift
> around?  Does the shield keep the tube at a constant scorching hot temp and
> that keeps things stable?  You can find shielded 6AQ5's, the hottest, leave
> your finger prints on the envelope tube ever, some are shielded, and some
> have a cutout shield and many are open to the air.  Is there a real use for
> a shield in a  vintage r
>  eceiver in a heavy metal cabinet, other than to protect the tube if you
> drop something in there?  Other than a heat reducing shield, is there any
> benefit for the shiny shields that reflect heat back into the envelope on
> every tube in a radio?
>
> Just wondering.
>
> Charlie, W4MEC in NC
> _____________________________________________________________
>
--
Nick England K4NYW
www.navy-radio.com<http://www.navy-radio.com>


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