[Skywave]

Any resistor in parallel with the RFC in the cathode produces a parallel tuned circuit whose bandwidth is made wider by that R by lowering the Q of that tuned cct. A resistor in series has much the same effect, but that also changes the bias arrangement for the valve. So in either case, for an oscillator covering a wide range, there is an obvious trade-off. My analysis above refers.

In the cathode of the Model 59, I would expect that the inductance of the choke to be approximately determined by noting the highest freq. that the GDO goes to and estimating (or by measurement) the self-capacity of that choke, plus a small allowance for stray C at that point in the cct. The classic formula for a tuned cct. applies.

Above, you refer to a GDO tuning from 5-150MHz. In an earlier post, I made reference to a GDO that I built many years ago to a design by G3TYJ (featured in Practical Wireless). Haven't used it for years, but from memory, it uses 7 plug-in coils, a split-stator capacitor (25 pF + 25 pF ?) and an EF91. Tunes from < 1.8 MHz → 150 MHz+. I'll see if I can dig it out from the archive - and be a bit more specific. I used it extensively during the mid-1970s when building home-brew TX gear for 144 MHz and later for 432 MHz.

Al.