Topband: What have I done?

[Carl Braun]

Topbanders

In the past, I've posted some questions related to making my 80 meter verticals (64' tall ground mounted) work on different bands.  The pair is spaced at ¼ wl on 80m and then I switch in base loading to resonate the same pair on 160m which are then effectively spaced at 1/8 wl.   Now I want to make them work on 40m which would have them resonate as ½ or 5/16 or 3/8 wl and would have an effective spacing at ½ wl.

So this is what I did...I installed an L network off of the vertical effectively tuning a 64' stick of aluminum to 7.050.  It took me a couple of tries as the first 1500pF (monster) variable capacitor wouldn't get down low enough to get me flat.  I had another 50-150pF Johnson variable cap available so I tried that and got the antenna to tune to 46 ohms at j+0.    Inside the shack I see 1.0:1 Vswr from 7.000 to 7.290...wow!

I measured the cap and it came to 70pf.  My cheapie Chinese meter doesn't register anything on the L scale but I have 7 turns on a 3 ½" inductor. The full coil is 33 uH at 25 turns so I estimate 8-12 uH of inductance.

But what have I done? Have I resonated a ½ wl antenna or have I resonated something else like a 5/16 wl or even a 3/8 wl antenna with the added inductance?

I plan on treating them as ½ wl spaced phased verticals on 40 and feeding them with equal lengths of ¾ wl feedlines for broadside phasing and then adding an additional 2/4 wl to get my 180 degree shift for end fire.

Please share your comments.

thanks

Carl de AG6X