[Amps] Restoring DX-100

[Glen Zook]

I know what the RCA transmitting tube manual and the specification sheets show for the output.  However, those are outputs which do not take into consideration things like losses in matching networks, etc.  In the "real world", at 3.5 MHz you are going to be lucky to see anything more than around 70% efficiency rather than the 77% theoretical efficiency shown in the tube manual.  Efficiencies between 60% to 65% are much more realistic in the long run.  However, with brand new tubes you may see efficiencies approaching 70% on the 80-meter band, but, as the tubes age, the efficiency is going to drop.

Also, as the frequency of operation increases the efficiency decreases.

The 6293, which is basically the same tube as the 6146A/8298 except that it has a more robust plate construction, is definitely a good choice and those tubes, generally, last a considerably longer period when run in the same operating parameters as the 6146.

Glen, K9STH

Website:  http://k9sth.com


--- On Sat, 1/15/11, Roger D Johnson <n1rj at roadrunner.com> wrote:

My RCA tube manual says (for 2 tubes ICAS) 600 volts Vp, 214 ma Ip, Po  104 watts! As you state in your article on 6146 series tubes, the 6293 is mo better in this application.