Self-Excited Type 27 Tube Hartley Oscillator (SEHO) Circa 1929
[A problem at Go Daddy who hosts my several websites showed one of my websites as being not Private and redirects you to a Porn Site where you do get to see Private Parts. I removed the link from a recent posting and Go Daddy is trying to fix it. What a way to start the New Year.]
Essentially the Self-Excited Hartley Oscillator is a high-power output VFO that is keyed.
Lots of problems with this topology such as vibration will cause a warble when you pound brass. The fix is to mount the SEHO on a shelf not connected to the operating table and to hold your breath while you key.
Another issue: the movement of your antenna (link coupled) can cause the frequency to vary. You must keep you EFHW taught and out of any breezes.
It drifts like a loose lady of the night way past her prime and the exposed wiring is a safety hazard. Did I mention key clicks and terrible chirp. But hey it was frequency agile, involved few parts and pretty cheap to build.
There is an annual competition using only the SEHO and it is called the Bruce Kelly Award. I guess if on 40M you hear a cluster of key clicks, warbly, chirpy and drifting signals then you found the contest. The link provides build info for the 1929 SEHO. [Check out the power supply in the build info. That is the 1st time I have seen a 450VDC three terminal regulator. This could be a great general-purpose power supply for Thermatron rigs!]
Replicas of the SEHO are selling on eBay in the range of $200-300 dollars and most do not include a power supply. This one uses an 01A tube.
A $235 SEHO
BTW I pay $300 a year to secure my websites and that did not work too well for one of the sites. I haven't changed anything or uploaded anything to that site in a long time and this anomaly is a recent event. Damn Chinese Hackers.
73's
Pete N6QW