Re: Heresy follows Re: [QRPLabs] IRF510 #alignment #magic of hollow state #alignment #magic


David Wilcox K8WPE
 

But even the new comers to this hobby should have at least ONE tube based rig. There is something special seeing a filament light up and even hearing the crackle as the audio starts. There is magic in tube rigs. With solid state there is only SMOKE or NO SMOKE and the rig either works or it doesn’t. I keep a Drake 2B on my bench and turn it on periodically just for the “joy”. Even today I enjoy the smell and the mental picture that comes in my mind of days gone by whenever I start to solder a part into a circuit.

Dave K8WPE

David J. Wilcox K8WPE’s iPad

On May 27, 2020, at 8:53 AM, James Daldry W4JED <jim@jimdaldry.com> wrote:

Hi, Brad

If I made a "set of boots" using one of the Loktal tubes I wouldn't make it a permanent attachment to the QCX, because Loktals were good up into VHF (little skinny pins) so it could be used to protect the Baofeng, at least on 2.

73

Jim W4JED

On 5/26/20 9:25 PM, Brad Thompson wrote:
Bill Cromwell wrote on 5/26/2020 6:40 PM:

Hi Gwen,

On another QRP list I make comments a couple of times per month about adding tubes to QRP projects. The fact is I used a 6146 as boots for an Argonaut 509 (once upon a time) when more power was needed. And yes to the sweep tubes. There are large sweep tubes and small sweep tubes. In fact there are audio output tubes that have done nicely as the finals in RF transmitters and those come in 'sizes' too. I play with some tubes to this day. They still do what they have always done. Some hams have even built rf stages with Nixie tubes!
Hello, Bill and the group----

Nixie tubes as finals-- I'd like to see how it's done.

Heresy follows.

Please don't read further if you have a mouthful of any beverage.

Caveats: I haven't assembled a QCX, nor have I thought through the
practicalities of the following proposal. What follows is an exercise in handwaving.

Based on the number of damaged output MOSFET accounts, maybe it's time to
interpose a linear buffer amplifier between the QCX and the unruly world of antennas.

In keeping with the QRP ethos, I'm imagining an add-on outboard linear amplifier built around
one or two vacuum tubes as designed for battery-powered radios of the 1950s.

(Pause to allow readers to dry their keyboards).

Dave Schmarder of Dave's Homemade Radios shows a two-tube regen design featuring a 1T4 untuned RF
stage and a 1T4 regen detector:

http://makearadio.com/tube/2-1T4.php

...Throw away the regen part.

Add electronic switching to heat the filament and apply B+ to th tube when the QCX transmits.

Another candidate tube would be the 3A5 dual triode used in a push-pull circuit.

Finally, if anyone might be interested in a grounded-grid(!) linear, there are the
Loktal-based 1LC6 and 1LA6 which have all of their grids brought out to separate
pins (and none returned to the filament as in the 1R5 and 1T4).

I have lost track of the image I have of a uBitX assembled with a pair of vacuum tubes sticking aout of it. It was all show and no go :
See? Someone has already tried this<g>.

Yours for protecting MOSFETs from abusive antennas, and 73--

Brad AA1IP


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