Harry (and Allen),
you wrote:
>>Built an NN1G (Mk II) rig fer 20m a couple (2-3) years ago and have enjoyed
using
it very much; however it has recently developed a problem.
When on my dummy load it shows one watt output and (almost) no reflected
power, but when switched to the antenna SWR shoots up to above 4:1.<<
Allen's conclusion was also my first (I have two of these rigs, Mk2 and MK3,
as well as a SW 40 and GM 30..which use the same TX amps). When the amp just
before the final (the driver?) is over driven.. the rig makes a lot of power
but it is all harmonics. The later rigs used a pot on the emitter of this
transisitor instead of a fixed resistor. Seems like on mine the power comes
up pretty fast as the pot is "turned up" and then at a specific point starts
to come up more slowly or vice versa (seems like mine was at around one watt
at 13 volts). This was the spot to leave the setting. Dave's notes said
that going past this point was not good for the rig. I'd also check the
resistor on the emitter of the driver and would be sure that the operating
voltage is not much more than 12 or 13 volts and regulated.
Please let me know what it was.. when you figure it out.. I've got 4 rigs to
maintain here with this set up!!!
Harry KG5LO
Saline MI
(another Harry.. we've got to stick together)
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