[Lowfer] UWL's new loading coil

[Eric Smith]

On Mon, 31 Mar 2003, Peter Barick wrote:

> 
> >>> eric@willow.nutstreet.net 03/29/03 08:10PM >>>
>> You can see my new loading coil and variometer under construction at 
>> http://www.nutstreet.net/radio/projects/lowfer/coil/ 

> Yeeks! It's the makings for a kid's tree house. Very nice rendering and      
> attention to detail, as per the Web pics.                                     

Yes -- I knew I'd be laughed at, but because my antenna is so short, I 
needed a lot of L.  The coil is so big because I was trying wanted Q as 
high as possible, and I read that something like twice as wide as long was 
good.  Don't know if this is true or not, but I did build the thing.

 
> Some questions, Eric:
> 1. I count 17 former rods, are they wooden dowel? Were they sealed up
> w/ say varnish (top and bottom plates too)?

Yes, I did coat the 1/2" hardwood dowel rods with spar urethane.  Also the 
end plates.  The frame is treated lumber and rough cut cedar, but I'll 
urethane them, too, once outside.  Same treatment to the 13 5/16" hardwood 
dowels and end plates of the variometer coil.  I weaved the variometer 
coil because I thought if it was good for the primary coil it should be 
good for the variometer :)

> 
> 2. I notice the end plates appear solid, so how does the vari-coil get
> into the interior? (May want to relieve the center area of outer plate
> to insert the vari-coil.)

They are solid.  The dowels are glued into the bottome end plate, but 
float freely in the top end plate.  It can be removed and replaced.  The 
variometer JUST fits, leaving a little room at the top and bottome when it 
rotates.

> 
> 3. How was the winding accomplished and ending up with the poles still
> aligned?  :-)
> 
> I asked Mitch the above question for his coil using PVC pipes. So I'd
> like to compare his solution, a temp bottom alignment plate to hold
> pipes rigid for winding, with yours.

Yeah, a little learning occurred here.  I started out winding too tight, 
and the rods did NOT line up with my top end plate holes when I finished.  
Took both me and XYL to force them into place.  (I live in Oklahoma and 
the Brute Force Method is very popular).

Since then, though, a few changes.  I've spread the coils out to cover the 
initial design length of 14.8 inches ... the coil looks much nicer, now.  
After spreading (which first required loosening) I was able to pull quite 
a bit of slack through, one turn at a time.  Now the coils are tight (but 
not too tight) and evenly spread.  I'll post new pix tonight. 


> 
> Liking your wood working skills so far, is there plans for a full
> enclosure of that coil? Further, there may be some advantage to raising
> the coil (legs?), both to lower needed L and to remove from children.

Heh heh ... my woodworking skills are a joke!  I did the best I could to 
plan in advance.  I looked at everyone elses coils and combined ideas, 
used what I THOUGHT would work/be advisable.

I do not (or did not before I read your email) have plans for a full 
enclosure.  I have seen on the web a coil with corrugated translucent 
fiberglass panels -- I kind of liked that and may do something like that.

The main thing is, I took most of my guidance from the work of others 
because I sure don't know what I am doing!

I did learn something, though, and when I wound the variometer I used nice 
even windings, not too tight.  When I finished the 72 turns the top plate 
fit on nicely without having to force (=bend) the dowel rods.

> 
> I'll be watching 185.3 more this week and matching Argo displays to
> those I find posted here. If lucky I'll make a match.
> 

Please do!  I'm very excited to receive contacts, and I'm working to 
improve my signal.  I WILL have the new coil in circuit tonight.

I noticed that by adding 1 ground radial that the voltage in my "RF probe" 
dropped by about .02V ... I THINK that is beacuse adding the radial 
changed the tuning.  Because my old coil can only be coarse tuned (via the 
taps every 10 turns at the bottom) I THINK adding the radial affected the 
tuning slightly but I couldn't change it.  I THINK that with the new coil 
(with variometer) I should be able to add radials and then re-tune and 
achieve HIGHER antenna current instead of lower :)

Thanks for listening, and let me know if I can explain my answers any 
better,

Regards,
Eric
KD5UWL