Re: Vacuum-tube final for QRP transmitters?
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Well, nuvistors would be an excellent idea, except for their relative scarcity nowadays.? Same with the 1V filament tubes. ?
How about a 6- or 12-volt filament miniature tube?? I won't suggest compactrons, which would be an excellent idea except?for their scarcity. ?
Weight will impose a penalty if you?need to string a bunch of 9 volt?batteries together and carry spares,especially for SOTA and hiking up 5,000 vertical?feet.
Still, there's nothing wrong with tubes for QRP.? After all, we did it for decades, back in the beginning.
73 Jim N6OTQ
Nuvistors anyone?
73 John F5VLF
> On 13 Sep 2023, at 21:14, Brad Thompson <brad.thompsonaa1ip@...> wrote:
>
> Hello--
>
> Please note that I currently do NOT have a dog in any of the current digital dogfights
> which are consuming quantities of various MOSFETs used as final amplifiers in
> QRP equipment.
>
> Has anyone considered experimenting with such vintage tubes as the 1T4, 3V4,
> 1U5, 1LN5, 1A5-GT ?. These are available in the $5.00-$10.00 NOS price range.
>
> Objections in no particular order:
> Filament power? 1.4 volts @ 50 mA -- 2.8V@ 100 mA (3V4)
> Warm-up time? Consider running the filament at a fraction of full
> power; switched by MOSFET
> High voltage for the plate and screen?? Three 9-volt batteries connected in series = 27 V., falling to
> 18 volts at dropout.
> Bulky, fragile tubes? Don't over-miniaturize the project, and don't use it as a football.
>
> 73--
>
> Brad? AA1IP
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