Henry Amps with roller inductor

[KE7ASO]

Well here goes. As the plate tuning is accomplished with the roller inductor.What is the criteria for the best setting of the roller inductor. We can monitor plate current ,grid current, power out with a given drive dead key,
at a given freq. So if the roller inductor is establishing Q. What parameters will tell if you have the right setting? The same power out can be obtained With different settings of the roller inductor. with the same drive. As henry was about the only manf. to use the roller inductor, I can't find any info on the subject. Any help will be appreciated.

[WA9WVX]

Hello King,

Here's what I think you are requesting regarding the Henry RF Amplifiers:

http://www.radiodan.com/hamindex.htm

Then scroll down the page to Miscellaneous and click on the Henry Tune Up Chart.

I suspect that W7RF is one of your area neighbors!

73,

Dan
WA9WVX

[N8BX]

Hello King, To properly tune your Henry amplifier (I presume you have a 2K Classic, or a 2KD Desktop, or one of the variants) I would recommend doing what Dan said and use the charts for a starting point. The bottom line is Henry intended the roller inductor to be the varible component in the resonant tank circuit. The fixed component is the doorknob caps on the bandswitch. This is kind of a novel idea. It works pretty well. Your ultimate goal is to tune the roller so as to get a dip for minimum plate current, much in the same way you would if it were a variable capacitor on the Plate Tune control of most any other amp. Once you have established the minimum indicated plate current, you then adjust the load capacitor to set grid current or reduce grid current to acceptable levels. When you are heading the right direction, a look at your watt meter will show a increase in output power for the same amount of drive (increase in gain). It will continue to increase up to a point at which no more gain can be had with any further adjustment. This is when you know you have properly tuned your amp up for the highest linearity in a high duty cycle mode like CW or RTTY. If you want to go one better for SSB use, after tuning up your amp in the way I mentioned above, turn the Load Capacitor slightly so as to decrease grid current a small percentage. How much? Well, I usually look at the watt meter and watch for a 5% decrease in output power (remember to watch the grid current meter and see it go down at this point). You could go as much as 10% but no more. Why on Earth would anyone do such a thing? Well, your SSB signal will be more linear due to that fact that your average plate voltage will be higher on SSB. The CW mode we use to tune up with causes the voltage to sag somewhat. But when you switch to SSB, your voltage does not sag nearly as much. Consequently, you are now actually running excessive grid current on your SSB voice peaks. This could make for a slightly dirty signal. It certainly will take its toll on tubes over time. It is easily overcome by reducing grid current with the load control slightly at the final tune setting.
I hope this information helps you and is not too confusing. It really is easy to tune up your amplifier properly and when done right, your signal will be as clean as anyone on the band.
73, N8BX

[KE7ASO]

Well this answer seems to be just what I was looking for.I had been going for the most output with the least plate current. But I wasn't watching the grid current very close because it was always below maximum. I will give this a try on both amps. 2k classic and 1kd-5. Need to make chart for all bands, as memory is begining to be slightly defective. Thanks alot for your help.
ke7aso 73's