[AMRadio] Ranger... good news, bad news


Peter Markavage manualman at juno.com
Fri Nov 3 23:33:42 EST 2006


Why not just make the screen voltage adjustable by using either a
variable pot or some solid-state circuitry with a variable pot. Pot can
be mounted behind the xtal socket with a small knob or shaft protruding
through the center hole of the xtal socket. Electric Radio, not to long
ago, had a simple circuit for this that worked very well. And the plate
current meter still worked and no diddling behind the Ranger with the
accessory socket.

Pete, wa2cwa

On Fri, 03 Nov 2006 21:02:54 -0500 Larry Szendrei <ne1s at neandertech.com>
writes:
> Jack Schmidling wrote:
> > I have read page after page of mods and changes to the Ranger to 
> make it 
> > suitable to drive an am and wonder why I can't just reduce the 
> drive to 
> > get about 15 watts out and be done with it.
> > 
> > What am I missing?
> > 
> > js
> > 
> 
> The problem is that in a Class C amplifier the grid is driven well 
> beyond "saturation" (no additional power output with increasing 
> drive). 
> If this wasn't the case, you would have no increase in output with 
> increasing plate voltage on positive modulation peaks - so there 
> would 
> be no positive peaks in your "AM" RF output! Also, reducing drive 
> will 
> reduce your plate efficiency greatly and you may exceed your plate 
> dissipation in the 6146 PA tube (in case you wanted to try this for 
> CW).
> 
> IMHO the best way to reduce the output from a Ranger to drive an amp 
> is 
> to use the LV power supply (~300V) for the PA plate supply instead 
> of 
> the HV plate supply. This can be done right at the accessory plug in 
> 
> back of the rig, but you'll lose your plate current indication on 
> the 
> panel meter. You can either rewire the Ranger internally so that it 
> will 
> read Ip no matter whether you use the LV or HV plate supply (as I 
> have 
> on mine), or use an external plate current meter wired to the 
> accessory 
> plug. Of you choose the latter you can leave the Ranger stock and 
> not 
> even take it out of the cabinet!
> 
> You can still use the HV supply on the modulator plates for lots of 
> 
> audio headroom, but turn the audio gain pot will be way down from 
> where 
> it is when running the rig at full output.
> 
> With this approach you'll get about 12-15W out, perfect for driving 
> a 
> linear amp.
> 
> This is the Timtron-approved way of doing it, and I can vouch for 
> it, as 
> it has worked well for me.
> 
> 73/GL,
> -Larry/NE1S



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