Bill Russell wrote:
> Hi folks,
> Just a note about my t'bolt operation. I installed the 50 ohm input
> resistor to see if my rig would "see" a 50 ohm load into the amp. Using an
> antenna analyzer looking into the amp, it saw 50 ohms at about 15mhz but
> the input swr went up sharply on either side of that frequency. The
> resistor was a non inductive 100 watt resistor. I DO understand ohms law
> and I did figure out that about 200 ohms would work to get the correct
> drive but that was NOT what I was doing.
> As for the HV under full load.............my t'bolt will run at about 2100
> volts loaded and about 2250 at idle. And yes I know the amp is a dog
> compared to the new multi megabuck stuff but I am not looking for the full
> limit. The difference the extra power would make is not worth the money in
> my humble opinion!!!
> I like to run AM and SSB and use the t'bolt for both although I use my
> trusty Valiant most of the time. If I use the t'bolt, I drive it with an
> FT-102 on both AM and SSB with the 350 ohm resistor installed. On SSB I use
> a tuner between the t'bolt and the 102 AND I parallel my 50 ohm dummy load
> with the t'bolt. On AM I use the same setup minus the dummy load. This is
> just temporary so I can use the amp for now. I will be doing the 200 ohm
> input swamping resistor soon.
> One more note, I am considering building a screen modulator for the t'bolt
> for AM. Now theres a project!!!!!! I have an IC746 that would make a dandy
> exciter and the 746 is a very good AM receiver.
>
> Bill Russell
> KC2IFR
>
SWAMPING RESISTOR:
If I remember right, the thunderbolt has a link coupled tuned input circuit
that can be used or not used. If not used then the 200 ohm resistor was used.
With the tuned input circuit no swamping resistor was to be used. ?? I think
they referred to it as hi and low drive inputs.
Using the tuned input circuit and if a 50 ohm resistor is placed at the input
it should provide a fair match to 50 ohms and require very little drive power.
Should be plenty of drive for AB1 or AB2 if you wish.
SCREEN MODULATION:
Screen modulation will not gain you anything over operating the amp as a linear
on AM. You will still be limited to about 25% carrier power out in either mode.
Linear AM operation will probably be a little cleaner (more linear) than screen
modulation.
73
Gary K4FMX
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