70 Mhz Hentenna
The Hentenna was developed by JE1DEU / JH1FCZ/ JH1YST in Japan during the 1970's. The Hentenna is well suited to working on any band
The Complete Hentenna Trial
After looking at many designs for a 70mhz antenna that has a limited profile and is easy to build. First I looked at a Co-linear but I have serious problems with mast space for antennas of this type, so then I thought what about a Yagi, again I don't have the space on the mast to put a Yagi, I could do with raising the mast and putting a rotator on the top, which will happen early next year (hopefully) so ruling out colinears, yagis I then looked at a Dipole, I've built a dipole for SOTA and whilst that works quite well I am looking at encapsulating the coax built antenna for erecting on the mast for running a beacon off of. I will detail this in another document.
The Hentenna Frame (reverse side of the antenna)
Firstly I built a wooden frame, as you will notice I am no Carpenter and I made a number of errors that I would recitfy if I where to build another. The frame is basically a wooden rectangle with an extra peice across the middle forming a sealed H design.Then I measured 1 λ + 1/3λ of antenna wire I then formed a Loop out of the wire soldering the ends shut this was then attatched to the frame using wire clips (nails with plastic cable holders afixied) then I measured 1/10th λ from the bottom and then created the feed points using two lengths of antenna wire and two crocodile clips which where attached to the outer ring, the inner sections where then soldered to the feeder, one side to the shield one to the inner (live). Using an antenna analyser I then checked the SWR to optimise the antenna. (by moving the feeds up or down the length of the antenna.) When I had this optimised, I then Soldered the positions to make it permenent. Whilst the diagrams show the bottom loop being rectangular, I couldn't get it to match up very well that way, I may be out slightly on the measurements of the initial loop. However it SWR's well at 1.5.1 so I am happy.
The jointing to Create the second loop.
The Feeder 
connected to the antenna.
Following this I intend to redo the whole thing in Copper piping to make the unit more stable and get the bottom rectangle shaped properly. However this is reliant on finding a decent supplier of copper piping and Morecambe Bay ARS letting me borrow the Antenna Analyser again.