I use a hex beam to operate from 20 meters to 6 meters with amazing results.
I wish to operate 40 meters and 80 meters also, and can only really install an end fed long wire due to my installation location.
Recently I installed an end fed long wire which comprises of a 9:1 unun with 25.6 meters ( 84 foot ) of wire. This is installed up high in a straight line. I don't have a counterpoise connected to the unun, and my coax cable feeder length from shack to antenna is 20 meters long.
The result is that the SWR is good on 40 meters, but extremely noisy on receive compared to the hex beam. So I use the hex beam for receive on 40 meters instead.
For 80 meters, my internal ATU can not even tune for this band which i'm surprised about.
Onto the main problem. As soon as I transmit on the end fed, it seems that RF is getting back into the shack, because the serial port on my computer locks up and I can no longer control the radio via the computer. This never happens when I transmit on the hex beam.
I have a 1:1 choke balun where the coax enters my shack but it still doesn't seem to solve the issue. I was advised not to put the choke at the antenna input because the coax must be used as the counterpoise. Others suggested to use a 49:1 balun instead of 9:1 balun, but this is not meant to be a perfect end fed half wave, more of a random length end fed.
Any experience with something similar or suggestions on how to improve this would be appreciated.
I was expecting an end fed with a length of 84 foot so high from the ground to perform incredibly well, but unfortunately it does not.