I don’t have deatials on the tubes used, but it has been reported that BBC
radio 4 long wave have only ten tubes left, capable of handling the long wave
transmission.
There is an article on it here:
https://www.theguardian.com/media/2011/oct/09/bbc-radio4-long-wave-goodbye ;
<https://www.theguardian.com/media/2011/oct/09/bbc-radio4-long-wave-goodbye> I
have been unable to locate anything more technical than this.
Best
Laurence Cuffe
On 13 Jul 2018, at 19:18, `Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
I was thinking of that when I posed my question.
FWIW, pure water is a good insulator. It also has a high specific heat. For
those reasons water was used to cool the large vacuum tubes used in radio
transmitters and elsewhere. I think it still is for some applications. The
water had to be very pure otherwise there was enough leakage to cause
hydrolysis and deposition of material in the cooling system. After about 1935
air cooled tubes became available. The air cooled tubes were at first just
the same ones but with large finned radiators brazed to the plates. However,
while air cooling solved some problems the tubes had about half the power
handling capability of their water cooled counterparts. All replaced with
solid state devices in modern radio transmitters except for the very highest
power ones.
Many early high power broadcast stations (50KW or more) had a swimming
pool sized pond for cooling the heat exchanger water.
I can't remember what the source of cooling water was i.e. if the radio
stations had to have their own distilling apparatus or if they could buy
suitable water.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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