Re Nautel, they have an offer that goes "Upgrade to a Nautel solid state and we'll buy back your last tube -- up to $10,000".

Yes, so it's not hard to guess how much they must cost to be able to offer that!

From what I hear, yes, expensive, but worth the money.

I didn't think that transmitters were still in such big cabinets though I suppose cooling is still a chief consideration. The last radio transmitter I saw was 2RRR's back in the 1990s, the main part is in a 4 unit rack cabinet though we are talking about an output of only 100W rather than 5,000W as would be required by a typical capital city commercial AM station.

Looks like the 5 and 10 kW are a single bay floor rack. They claim 86% efficiency for these models.

Some of the big valve transmitters were a lot more efficient than their predecessors, but it is not that many decades ago that transistors could not compete with valves when wattages started to get really big. I would in any transmitter expect that RF radiation, RF insulation, & cooling still become serious factors in construction of cabinets

Some of those big transmitter tubes gobbled up around 2KW 12 phase at 250 Amps just on the heaters.

We now have transistors that can handle several hundred volts. So we then have a choice of current, or Voltage loading the antenna & plate voltages of 30KV on the PA & 6 Kw into the grids of Push Pull PA's were not unusual on the big Transmitters.

I know just on the local station there had to be spare tubes as they had to be sent out to get rebuilt regularly.

2KW 12 phase

Assume you mean 2 phase.

Might up the gain on your Kriesler by replacing the IF 6N8 with a 6EH7, will require a few mods.

My Kriesler 11-81 that sits in the kitchen has that modification. However I found a 6EH7 was a bit much, on the edge of instability. So I used a 6BY7 instead - perfect. You still need to rewire the socket though.

Mention of big transmitter tubes brings back fond memories of a previous life as product specialist for the distributor of Eimac tubes in the 1960's.
In 2012, I gave a talk to the Sydney group of HRSA and ended describing one of the biggest, the 4CM500,000G.

Vapour phase cooling
500 KW plate dissipation
15 KV plate voltage, 75 A plate current
23 V heater 500 A

Its price tag was $75,000 at the time.

Harold

I am glad I wasn't paying the electric bill for that one.

Photo uploaded to Post 13 and 23.

VOA is US government funded.

I can double check what it was running but behind the Harris transmitter was a big oil filled transformer with 3 phase in and 12 out.

An odd thing about VOA, they don't have a callsign like WVOA or KVOA. Somehow, the FCC didn't make them have one. Seems that our National Telecommunications and Information Administration administrates VOA. NTIA acts like an FCC for federal government owned radio stations... Oh, federal law forbids the VOA from targeting listeners inside the USA, idea being that the government doesn't want to compete with private broadcasters.

Australia has certain oddities with its TV station callsigns too. One thing I was always wondering about was the structure of the ABC's callsigns. Commercial stations have a three letter callsign with the third letter representing the state the transmitter is located in. But outside the capital cities, the ABC uses four letter callsigns. I am not sure of the channel numbers for digital television but some of the rural stations in NSW included ABHN-5 for Newcastle, ABWN-5A for Wollongong, ABUN-7 for Tamworth, whereas in Sydney it was ABN-2.

In the two mainland territories, the territory name wasn't used for the third letter but the first letter of the name of its capital city was. ABC-3 & CTC-7 for Canberra and ABD-6 & NTD-9 for Darwin.

I think with a antenna on my roof I should be able to pick up 2cA in Canberra from Albury.
So far I can't ,,,but I picked it up in the car in day time from Holbrook to the north side of Goulburn. ... They were playing 60s music .
Pete