Perhaps the biggest thing my station is missing is an 80m antenna. I really don’t have room for a full, half-wavelength dipole, so I’m looking for options. For a while, I used a W3EDP antenna, but to be honest, results were mediocre at best, and since the tuner I used was in the shack, there was always RF in the shack. I took down that antenna when the tree supporting it had to be cut down, and I never put it back up again.
As far as I can see, I have three options:
- End-fed, half-wave (EFHW) antenna. My EFHW 20m antenna is a decent performer, so I’m thinking that an 80m version could be an option. Googling around, I found a commercial design for $75 and a homebrew design that I could make for a lot less. The schematic of the homebrew matching unit is shown below.
- 43-ft. vertical. A couple of days ago, I worked a station in Maine that was using a 43-ft. vertical. I asked him if it worked well for him on 80m, and he was very enthusiastic about its performance. I do have an automatic tuner that I could put very near the base, and one advantage of this antenna is that I could use it on other bands as well. A couple of disadvantages are that it would cost a fair amount and I’d have to run some radials.
- Shortened, loaded dipole. Another option is a shortened dipole using loading coils. A design by VK3JEG is only 66-ft. long, about the size of a 40m dipole. Another design by KB0ZZ is a little longer, but resonates on both 40m and 80m. Basically, the loading coil is operating as a trap. More designs can be found by Googling “80m loaded dipole.”
At this point, I’m leaning towards the EFHW, but any of these antennas seem like interesting options. If you’ve had experience with any of these antennas, I’d love to hear from you.
Walter Underwood K6WRU says
I’m using a loaded 80m dipole from Hy Power Antennas. It is loaded to half-size, which should make it about 3dB down from a full-sized dipole. I checked that on a site for designing loaded dipoles.
http://www.hypowerantenna.com/products/dipoles
I actually use his 80-40-20 fan dipole (3B2080LFAN), which is a clever setup. It is a full sized 40m dipole, and the 80m loaded dipole is cut so that the center part is a 20m dipole. The loading coils isolate the extra wire. That is 70 feet long. I use a Balun Designs QRP balun on mine. That dropped the noise by about 6dB.
http://www.hypowerantenna.com/products/fan-dipole
K9YC said good things about the construction of the Hy Power antennas and I agree.
The end-fed design is not an end-fed half wave, because it is not a half wave long. That is a non-resonant wire with an impedance transformer. That can be a good antenna, but it isn’t an EFHW. For more details and more options on wire length (53 feet is good), look at the info from Balun Designs.
http://www.balundesigns.com/servlet/the-106/9-cln-1-9-dsh-1-unun/Detail
http://www.balundesigns.com/Wire%20Lengths%20for%209-1%20ununs.pdf
Finally, an 80m full wave loop is only 67 feet on each side, so often fits where a dipole can’t. I’m thinking about putting up one of those with posts along our fence.
Walter Underwood K6WRU says
Interestingly, this exact antenna, the Hy Power LD8073 loaded 80m dipole, was reviewed in the September QST on page 57. Steve Ford, WB8IMY, likes it.
Dan KB6NU says
$73, including shipping, seems like a decent price for the antenna as well. Maybe I’m missing something, but do you know if the antennas come with some kind of center insulator if you don’t purchase the optional balun? The website doesn’t seem to say anywhere.
Walter Underwood K6WRU says
Yes, they come with a nice grey PVC center insulator. The wire is tied through the PVC and soldered to a UHF socket mounted in the center.
Here is my antenna before I added the balun.
https://www.flickr.com/photos/walter_underwood/5854611660/in/set-72157626885239329
Here is a link to the original size photo. You can scroll around to get a zoomed-in look at the center insulator.
https://www.flickr.com/photos/walter_underwood/5854611660/sizes/o/
AJ W5HEH says
Have you seen the SV9 43′ vertical? They are on closeout at Cheapham.com for 125 bucks.
I have the SV31. It is very good. You can wind a couple of PET coils as described on the yahoo group site for these SV9s. There are pics and good instructions in file section. You still might have to add 4 radials for 80meters and maybe a loading coil. You will have to try one thing at a time to check on performance , depending on your soil ,etc.
Another option is a Sterba Curtain ? Might fit and they work great from what i have read . Also, there is a Super C antenna that does not take up much space. Operators even put them in their attics.
Let us know what you come up with. I am not partial to traps.
Frank WA8WHP says
I am currently playing with a continually loaded design using “Slinky” toys. I am trying two per side of a dipole. I found the metallic versions at Walmart for $3 each. I plan to check resonance at various lengths as soon as I get my analyzer back. I will let you know what I find.
Dan KB6NU says
I’ve used a Slinky antenna, but never for a frequency that low. Please do let me know what you find out.
Dave KU4B says
Something you might consider is a single band version of the Double L antenna. It is nothing more than a dipole with the center vertical and what you can’t fit in the lot folded to suit. That keeps the efficiency fairly high, and eliminates the need for radials. Just take the 160 stuff off of this, and it should work fine.
David VE3KGK says
I built KB0ZZ’s shortened 40/80 dipole and as I have it set up it works very well.
I found the lengths he gave to need some adjusting. My antenna has been up for a couple of years and I work European DX on both 40 and 80 with no trouble I have it set up as an inverted V with the center about 35′ above ground on my tower. It is oriented roughly north/south.
I found the PVC for the coils at Lowe’s and a ten foot length cost me about four bucks.
When I raised the antenna and used a Rig Expert to tune the length I found the 40 m measurement was good for a less than 2:1 SWR across the phone portion of the band. I found the 80 m lengths quite a bit short and I had to add about a foot of wire to each leg. I used standard 14 swg copper house wiring and made up a center insulator like ZZ shows on his web site. I did not use a balun. I found that the length I added just coincidentally put me right in the DX window on 80 m. I will say that on 80 m without a tuner the swr rises quite rapidly to unacceptable levels once I get out of the DX phone window on 80 m.
I contacted ZZ after I had the antenna set up and he suggested that I could have taken off about four turns on both coils, but since the antenna was resonant where I wanted it to be after adding the foot or so of wire to the 80 m part of the antenna I decided to leave well enough alone.
I am very happy with the antenna and it has worked well for me since my lot is very wide but not very deep and I had supports for the ends from front to back over the very end of the garage on my house where going east/west I’d have been over the roof and the anchor points were not as convenient.
Dan KB6NU says
Hi, guys. Thanks for your comments. Since I wrote that blog post, I put up a homebrew version of the Cobra Antenna. With my Dentron Super Tuner, I can tune the antenna on any HF band 80m and above, and it seems to work just as well or better on 40m and 30m as did the fan dipole. That might be due to using ladder line, but it could also be that the coax I was using with the dipole was starting to deteriorate. In either case, I’m very happy with the antenna.
jeff says
How about a “Bent Dipole?”
I’m using a 135′ doublet (67.5′ on each side) but the last 18 feet on each end hangs down vertically, making the whole arrangement about 100 feet long, plus support ropes. Fed with 450 ohm window line to a DXE 1:1 balun (the most expensive part of the antenna system) and about 8 feet of RG-214 into the shack. 66 DXCC entities confirmed on 80M with this antenna.
L.B. Cebik wrote that if you had to bend your doublet, a Z shape was good, but I don’t have enough trees in the right places for this…
Joseph Cotton W3TTT says
I use an INVERTED VEE. The one big tree in my yard supports the center, and the legs are tied to the fence left and right. It is the same as a dipole, just adjusted to fit my yard. Works just as well as a flat top dipole. How do I know? Because it used to be a flat top dipole, using a tree in a neighbor’s yard as the second support. when the rope broke, I just pulled the other side up over the branch and made it into a inverted vee. In fact, it might work better, because the center is now higher than when it was a flat top dipole. It then used to sag in the middle. hihi.
The vee is fed with ladder line and tuned in the shack.
John says
I also put up a 75m loaded dipole by HyPower. Performance was excellent. Everywhere I went I was told the signal was good. It was 68 ft long. I had a problem with stray RF going into my shack and my neighbors. I thought a good low pass filter would solve it. It had a rotary knob for 2.3-4..4-8.8-14.5-21.6 and 30 MHz. Nope. Didn’t help at all. I put ferrite beads on my coax. That didn’t help either. I cut back from 100W all the way back to 25W and still had RF. Everything was grounded; the radio, tuner, and filter. I tried my vertical antenna. No stray RF at 100W. The problem is it didn’t get out for beans so I couldn’t use it. I’m looking at an antenna made my Mapleleaf that’s 70 ft long, no coils or traps, uses open wire to coax feedline. I never liked the open loading coils on the HyPower but tried it anyhow. That’s my story & I’m sticking to it.
Dan KB6NU says
Sounds like you might want to use a balun at the feed point of that dipole.