inverted l on 80 meters

hi i have an inverted l with 50 ohm coax to the end of my garden aprox 80 ft in all what balun can i make for the coax termination i only use this inverted l on 80 meters and for listening for hf am broadcast stations thanks for looking stay safe do radio

What length is the antenna radiating element, and do you have a way of measuring the feedpoint impedance?

You don't need a BALUN as you have an unbalanced antenna and unbalanced feedline, so what you really need is either a matching network or unun built to give you as close to 50 ohms impedance as possible from what it currently presents. 

For example, if it's a quarter wave, it'll present something like 20-30ohms.  If it's half wave and end-fed, it'll be thousands of ohms.  If it's a non-resonant length, a few hundred or so ohms....

Or have a misunderstood, and you're looking for a choke?

hi thanks for your reply i have an mfj  i will be able to get some readings with it 80 meters and 40 meters does work thats the only 2 hf bands i use with it i have a ts 2000 x auto atu fitted and using an mfj auto tuner extenda get it to load up i live in teesside  and work into scotland and south uk 40 meters with  some continental europe  so it does work  i also use it for rx with icom 71e hf receiver with a global rx atu or a 4 to 1 balun in the shack the noise drops a lot with this balun  i will get back to you with the results from my mfj thanks for your help paul m0kbd stay safe do radio 73s

This is my current project.
I have never done this before so don’t be too tempted to follow me!

RG213 out of house and to the end of 75ft garden, buried approx 6” under the soil. Comes up and winds round a 4” diameter pipe, making a 1:1 choke (19ft 7” of coax). Then into 9:1 unun at base of polyweave inverted L.
Vertical section rises from 2’ to approx 20’, passes through dogbone insulator, 90 degree bend then horizontal run of approx 46’ to another dogbone where it terminates, suspended by loop of Kevlar paracord from K bracket on house.
The dogbone at the 90 degree bend is held up by paracord through a pulley, running down to a cleat hook (a giant washing line, in effect) allowing the whole aerial to be lowered and stashed along hooks on the fence.
The pole which supports the pulley is sprayed brown to camouflage against trees. (This is also telescopic but I don’t lower it).
From the unun ground, this weekend I will run several polyweave radials 2” under the surface of the lawn, fanning out under and away from the long wire.
At the unun end, these radials are connected to a stainless earthing terminal block, with one single 5” length connecting to the unun ground terminal.

It is basically a collapsible ~20m long inverted L, with buried counterpoise, 9:1 unun, and 1:1 choke to prevent common mode currents on the coax braid. Height above ground is 20’, giving height above sea level of 332’.
It offers 1/4 wave on 80m (well, that’s the plan.....).

Original plan was to double this length, making a V shaped wire, however weight v’s droop v’s visual appearance made me abandon this.

I used to run an 80ft long inverted L, 25ft vertical section, the rest horizontal. I used a SGC230 antenna coupler at the antenna and used it on all bands from 160m to 10m and it worked great. You can use MFJ's Bias T to feed 12V to the SGC through the coax.

hi thanks for your replys the balun i made with coax is a 1.1 choke  i have a 9.balun i made with an amidon toroid while the lock down i will get out the mfj analiseir and take some readings i rig i use is a ts 2000x built in atu and an mfj  auto tuner extender thanks for looking stay safe do radio 73s paul m0kbd