160 / 80 meter antenna

[W4DNR]

My next door neighbor has offered me the use of a tree in his yard .

60 feet tall to a limb that has no branches in the way.

Currently, I am end feeding a slope top-fed 1/4 wave on 80 meters.   More vertical than horizontal.
It works pretty good out in the first skip zone and has a decent match to my 50 ohm coax line.

The tree is 145 feet away from my tower, and I could make a horizontal wire that is 60 feet tall at both ends.

My question is how to make a 160/80 out of that wire without getting into a high impedance feed point at the tower end.       Center feed would be difficult.

Traps come to mind or maybe a 1/4 wave shorted stub at 62 feet or so... coaxial or open wire line.

I wonder what the extra length of the stub would do to  160 meters  ( or 80 for that matter )

Anybody tried this before ?   I'd rather not get into the 3000 ohm feed point impedances.   The slope wire is less than 2:1 at the center of the band and the tuner in the shack handles that well across the band.

I'd just like a two band "cloud-burner" for local nets and stuff.

Don W4DNR

[W1ITT]

Do you have the arboreal geometry to do an Inverted-L that's three quarter wavelengths on 80 meters?  I'm thinking that you could start a 120 foot horizontal run from the tower top, feeding it there with coax, running towards the borrowed tree, then dropping down another 60 feet vertically, or at least fairly vertical.
This would be 3/4 wave on 80m, and show 50-ish ohms.  On 160m it would also approach 50 ohms, but with inductive reactance that could be tuned out with series capacitance, similar to the famous W1BB 160m scheme from the 1960s.  Conceivably, you could have the capacitor in series in a box at tower top, with a relay to short it out for 80m operation. 
Before I built my TallT for 160m, I had a 120-by-60 foot inverted L and worked Stateside and DX with it.

[W4DNR]

3/4 wave on 80 would be doable.  If I "borrow" my 432 coax at 140 foot up ( 7/8 heliax ) ,
I could get a 180 foot run out to the tree.   

Matching on 160 could be done at the shack end of the heliax
since coax losses due to VSWR souldn't be large.

Ahhh ........spring-time and antennas  !!!


Don W4DNR

[N7ZDR]

"Ahhh ........spring-time and antennas  !!!"

Our snow has finally all melted here at my QTH , I  went out last night and attempted to dig a hole to plant a 4 x 4 post-- I hit water at about 16 inches, I looked this morning before work and the water was about 1 inch below the top of the hole   . Sorry-- it will be another month before much in the way of new antenna planting here in northern Utah takes place .

Cheers,
Larry