Yes Ian, you are right.
Pressurizing the anode compartment and let the hot air out through the anode
chimney is the more common way.
I saw that kind of cooling first time with a Lorenz UHF TV translator using
the TBL2/500 and later in a Siemens RS1062 cavity.
73
Peter
-----Original Message-----
From: Ian White [mailto:gm3sek@ifwtech.co.uk]
Sent: Dienstag, 18. März 2014 15:38
To: 'Peter Voelpel'; ka4inm@gmail.com
Cc: amps@contesting.com; ham_amplifiers@yahoogroups.com
Subject: RE: [Amps] 4CX5000A in grounded-grid
>
>The main air flow is through the anode by the large blower.
>That is quite common with VHF/UHF amplifiers in Europe.
>The cathode area is cooled by that separate fan. Of course the amp is
>mounted with the tube vertical.
>
>Cooling through the anode and use of a bypass duct to the cathode area
is
>quite common in Europe.
>Almost every commercial VHF/UHF amp is constructed like that.
>
Am I seeing this correctly? It looks like he is blowing cold air <into>
the end of the anode line, so the anode compartment becomes filled with
hot air.
That is not the way it is normally done. Normally cold air is blown into
the side of the anode compartment, so it keeps the tuned circuits cool,
and then the air flows outward through the anode cooler (or though a
separate chimney).
This cooling system was first published by K2RIW (who got the idea from
WA7TZY) although it may have been invented separately in Europe as well.
With cool air filling the anode compartment, it is then possible to
bleed 25-30% of the airflow downward into the input compartment to cool
the base as well... but it wouldn't make sense to use hot air to do
that.
73 from Ian GM3SEK
>-----Original Message-----
>From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Peter
>Voelpel
>Sent: 18 March 2014 14:10
>To: ka4inm@gmail.com
>Cc: amps@contesting.com; ham_amplifiers@yahoogroups.com
>Subject: Re: [Amps] 4CX5000A in grounded-grid
>
>Hi Ron,
>
>The main air flow is through the anode by the large blower.
>That is quite common with VHF/UHF amplifiers in Europe.
>The cathode area is cooled by that separate fan. Of course the amp is
>mounted with the tube vertical.
>
>Cooling through the anode and use of a bypass duct to the cathode area
is
>quite common in Europe.
>Almost every commercial VHF/UHF amp is constructed like that.
>
>73
>Peter
>
>
>-----Original Message-----
>From: KA4INM [mailto:ka4inm@gmail.com]
>Sent: Dienstag, 18. März 2014 14:52
>To: Peter Voelpel
>Subject: Re: [Amps] 4CX5000A in grounded-grid
>
> Hi Peter DJ7WW Voelpel:
>
>> That 2m amplifier is not run zero bias but with normal screen and
grid
>voltages for AB1.
>> Power gain is about 13db.
>> I know the builder quit well.
>> You see more photos on his web site:
>
>> http://www.dj5dm.de/DJ5DM%20R17%20QRP%20Tube/index.htm
>
> Does he operate it with the blower on top or with the blower on the
>bottom?
>This is the first time I ever saw a tube being blown from the top.
Very
>unusual construction.
>--
> Ron KA4INM - Youvan's corollary:
> Every action results in unwanted side effects.
>
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