[AMRadio] Motorized Variables

W5OMR/Geoff w5omr at satx.rr.com
Sun Jul 2 12:17:26 EDT 2006

Rick Brashear wrote:

> Geoff,
> Thanks!  You read my mind (short read!) about the potentiometer and 
> meter configuration to indicate the position.  

Another thought Rick, is that you could get a 10-turn pot, and gear down 
the motor to the shaft, if you want *precision* tuning.

>  I may have a couple of breadslicers that would work, but I thought 
> the vacuum variables would be the safer way to go.  I would really 
> like to have a roller inductor to use for the coil, but haven't been 
> able to find one I can afford.  I thought I had one, but have been 
> unable to locate it.  

I'm thinking that if someone had a lathe, they could wind their own 
coils fairly easily.  You'd just have to chuck up the coil form, and cut 
a groove in the form (think plexiglass tubing) then hand feed wire to 
the form, for a couple of turns... vary the speed of the lathe motor 
(VariAC?) so it's easy to handle...  You could probably build your own 
roller inductor the same way... AND be the size you want it to be.

> I'll either have to get one or use a relay to switch the coil tap when 
> moving between 160 and 75 and possibly 40 later on.

I was thinking this morning, that since I have another jack-bar and 
swinging link assembly, that I could mount the 2nd assembly somewhere in 
the final, and then have a big, high-voltage ceramic-insulated 
slide-switch, to go between 80 and 40m, but then I'd still have to get 
underneath the final chassis and change out the plug-in grid coil, so 
while I'm in the back of the rig anyway, might as well change 'em both.

It's not like I QSY from 75 to 40m on a daily basis, though... I -think- 
I've had the rig on 40m once, this year, so far.  Might have to check 
out 40m this afternoon on either 7.160 or 7.290, around 2 or 3pm.  Give 
a listen.. there'll be -someone- on, somewhere.

> When I get the capacitors in house I intend to set it up just as you 
> suggested,  in breadboard style, to do the mechanical and preliminary 
> tuning.  Hopefully, I can mount all of the components on a single 
> piece of aluminum and install it in the 1R2 as a unit in existing 
> holes. I like to keep things so they can be reversed without a trace 
> of ever being there. 

Those are the best mods.  I 'mod''ed a BC-610E once, by removing the 
grid connections to the 100TH's, and using the WA5BXO solid-state Class 
B Audio driver circuit.  the difference in audio was unbelievable, as 
has been reported.

That '610 is now on the air in Bevel Oaks, TX (near Beaumont) and can be 
heard most weekday mornings on 3.880 (about 7:30am on) and most 
evenings, around 5pm - same frequency.

And, for eveyrone else, a general FYI:
When Visiting in Beaumont thurday evening, I got up early and got on 
3.885 and worked a pissweak little portable signal emminating from New 
Mexico.. turns out to be none other than 'Double Yew A #1 acHe Yell Are, 
scrote 5'.  Tim's in New Mexico with Marcy durning her summer break. 
(mostly speculatoin on my part as to why they're there)

Driving your AM Rig without a scope, 
is like driving your car at night, without headlights. (K4KYV)

73 = Best Regards,

More information about the AMRadio mailing list

This page last updated 18 Dec 2017.