Hi all,

As I recall, there was a bit of a "horsepower" (er, Peak Envelope Power - PEP) thing going on during the late 60s and 70s where manufacturers focused on the 'peak' power (PEP) rather than average power or CW power. It was also a time when TV sweep tubes were inexpensive and if pushing the power a bit resulted in a shorter tube life, so be it. The plate dissipation of the 6DQ6/12DQ6 is only 18 watts, so figuring a typical efficiency of 50% to 60% for class AB1 operation, the "key down" power would be limited to about 70 watts input for a pair of tubes. Fortunately most ham operation is not continuous key down and we are able to get away with more peak power. One common assumption for SSB operation is that the peak power (PEP) is about twice the average power (the duty cycle is about 50%). Given this, a pair of these tubes could conservatively be used at about 140-150 watts input without stressing the tubes. The intended application for the sweep tubes as horizontal output tubes in TV requires high peak power (plate current), while the average dissipation is significantly lower. I have attached a small file comparing the ratings of several of the sweep tubes used in ham and CB equipment during this time frame. Note that the largest plate dissipation is about the same as the venerable 6146B at around 30 watts. The difference is that the 6146 is designed for continuous duty operation vs. low duty cycle operation. A number of hams have been bit by not being aware of power requirement when using modes that are in fact 100% duty cycle such as RTTY and (I think) FT-8.

I suspect the use of PEP was mostly a marketing statement intended to provide a simple number that could be used to compete against other manufacturers using PEP in their advertising, much as we see the same thing today in marketing 1kw amplifiers vs 1.5kw amplifiers. The difference is less than 1/2 of an "S" unit but, golly, its 50% more power.

Anyhow, almost all of these tubes are getting harder to find and more expensive as the existing supplies gradually dry up...

Bob,? K7DYB

On 2/23/2025 1:36 AM, HF via groups.io wrote: