[Elecraft] Tube radios and such

[N2EY@aol.com]

In a message dated 9/28/02 8:59:20 PM Eastern Daylight Time, 
DolfinDon@msn.com writes:

> It was common for many 8 to 10 tube communication receivers to draw 200 to 
> 300 watts (many TV's of that era 500+ watts) most of which was filament 
> current. 

Unless they were using 807s for RF amplifiers, that's a bit of exaggeration!

A typical 10 tube receiver might have a heater requirement of 3 to 4 amps at 
6.3 volts - that's 19 to 25 watts, max. Add 10 or 15 watts for a tube 
rectifier and the grand total is up to 29-50 watts. 

B+ requirements would typically be 250-300 volts at 80 to 160 mA - works out 
to somewhere between 20 and 48 watts. 

Add in some transformer and rectifier inefficiency and the typical receiver 
might draw 60-120 watts, tops. And most of that isn't to light the heaters.

Yes, tube receivers and QRP transmitters are inefficient compared to SS rigs, 
particularly SS rigs designed with energy efficiency in mind (like the K1 and 
K2). But let's be accurate about how much energy those ol' bottles actually 
need.

--

Prior to building K2 #2084, I had been 100% homebrew for most of my ham 
career. My "other rig" is a homebrew 100 watt 80/40/20 CW xcvr built in the 
early 1990s. It replaced a similar transceiver built in the early 1980s. 

This xcvr consists of a 13 tube receiver section, a 2 tube transceive 
adapter, and 3 tube driver/final amplifier section. Plus two power supplies. 
Receiver/transceive adapter draws 100 watts total. Driver/final amplifier 
section draws 80 watts on receive and 250 watts key down transmit (100 W+ 
output). 

This rig and its predecessors were built from junkbox and recycled parts for 
less than $100. Hamfests, dumpsters and other amateurs cleaning out their 
basements were prime sources for the parts. Often I'd get piles of NOS 
treasures for the price of hauling the stuff away.

One of the main reasons I built those rigs was so that I could repair or 
modify them if the need arose. Having to send a ham rig out for service just 
goes against the grain. The K2 fills that requirement, and many others. 

I was able to afford the K2 and accessories by selling off some of my excess 
inventory of tubes, sockets, and related parts. Seems there is a great demand 
for stuff that was considered "junk" about 20 years ago.

Funny thing - I originally intended to homebrew an outboard 100W amp for the 
K2. But I'm having so much fun with 5-10 watts that the amp project keeps 
geting put off. My "other" rig gets used regularly, just like my K2. 

I don't think Elecraft will offer a tube rig of any type - but imagine what 
it could do if they put their minds to it!

73 de Jim, N2EY