Excited by the possibility of adding to my DX worked totals on 80M during the ARRL DX CW contest a few week-ends ago, I hurriedly installed a new 80M ground plane (GP) antenna. Like the year before, I intended a single-band effort and the new GP was going to be my secret weapon.
I used my 50′ (15 meters) tall fiberglass mast and ran a 14 gauge wire vertical element of 44 feet. I also fabricated three 44′ long radials and fastened them in the yard at approximately 5′ high. I created a current balun by coiling side-by-side about 8 turns of RJ-213 coaxial cable leading to my remote coaxial switch. Tuning was to be accomplished by a LDG tuner in the Schack.
It took about an hour and a half to get everything placed and hooked up. I was done just before sunset, and I knew there would be some nice gray line enhancement for my testing. I turned the antenna selector switch to the correct position, found a clear spot around 3510 and pressed the tune button. The SWR came down to unity in a few seconds…beautiful! Tuning around the bands I did not yet hear any EU stations but DANG the whole band sounded extremely quiet! My anticipation grew awaiting the invevitable eruption of contest signals on a band as smooth as glass!
On a whim I dropped over to “Crappy”, my affectionately named G5RV. By the way, here is the EZNEC+ profile for Crappy. The feed point is at approximately 9 meters, or a bit less than 30 feet. Note the Y-axis is pointing Due North.
See what I mean? The antenna fits the name! Anyways, there was a bunch of noise on the G5RV that just wasn’t on the GP. I told myself not to be scared, this was all high-angle stuff and should be expected. That said, I did expect electrical noise to be much higher on the vertical (save this thought for later.)
Switched back the vertical in time for the starting bell at 0000Z…Ding! Yup, a bunch of signals erupted just like I knew they would. Took a few minutes to sweep up the band, copying calls calling into N1MM logger and storing them on the bandmap for pouncing on in a few minutes. Hearing the old faithfuls: OM7M, F2DX, Plenty of strong German stations…Nice!
Back to OM7M, hit F4 to send my call. Nope, didn’t come back to me. OK, no problem…it’s not even dark here. Next one…same thing. Next…huh? These guys are all contest super-stations running KWs and big antennas. They keep calling CQ so it is not as if I have competition at the moment. I make a station sweep: SWR is fine, transmitting at 100W. All seems good. I switch back to my old G5RV to tune up. SWR also fine, band is noisier, and received signals are still strong. It is now 0042z. I hit F4 to call OM7M again.
We exchange and I log.
I turned back to the GP and click on F2DX in my band-map. No calls returned. Switch back to my G5RV and call. I log F2DX at 0048z. DL9FBL a minute after that.
“Great,” I tell myself “This new antenna sucks.”
I let the failure wash over me for a few minutes, then switch back to the G5RV for good, and to better than expected results overall. I Actually try the GP throughout the contest just hoping it was propagation anomalies. It wasn’t propagation.
Modeling ex post facto reveals something a bit counter-intuitive about the antennas, but something I had seen expressed in the Low-Band DXing and ARRL Antenna books before: Low horizontally-polarized wires will often have better gain at low take-off angles than verticals especially over ground with average or lower conductivity. I modeled both antennas as accurately as possible and overlaid the patterns toward EU to validate if I were confronting this situation as well.
The GP looks pretty much like it does in the textbooks, except for the a slight reduction in gain toward the West. I could only accommodate radials in the North, East, and Southeast directions. Overall gain seemed to be pretty much as predicted as well. Not a high-gain antenna, but get a load of that classic low-angle pattern!
Then I placed the elevation slice trace from my G5RV model:
The outer ring scale being the same for each antenna, you can see the low G5RV is stronger by 3-4dB at 30 degrees. HFTA modelling indicates signals arriving from 28 degrees the majority of times. Less often signals arrive at lower angles (17, 12, and 4 degrees).
Here is the Azimuth slice at 30 degrees:
This pattern also reveals even better gain toward Africa and into the Pacific. And yes, I had no problem working KH6s during the contest (or any time), and around this time of year South Africa comes booming in (although not in the contest this year.) Morocco and Canary Islands are ear-splitting in contests on 80M…I can guarantee these multipliers.
I would say the overlay validates both the textbook knowledge and my own recent experience. My signal is just enough above the noise to work successfully into EU during contests on the G5RV. I was not being heard on the Ground Plane. If I were running 500 watts or greater I bet I would be heard on the Ground Plane.
There was not much difference between the G5RV and the GP on receive for large stations except into the Caribbean, where the GP had a slight edge. High-angle signals – state-side – were being attenuated by the GP pattern and thus made the Caribbean stations pop in comparison to the G5RV. That said, G5RV was better overall. For smaller stations from EU, the G5RV was a better RX and TX antenna.
The GP is not a bad antenna. Heck, I even worked YN2DD after the contest on 60M using the GP (a consolation prize…I don’t want to think how the G5RV would have been better. Must. Not. THINK) My ground conditions in Middle Tennessee are considered average at best. The comparison would be much different if I lived on the beach surrounded by salt-water where I am sure a vertical antenna would be the best antenna ever. I don’t have salt water anywhere near me so I need to work with what I got. Speaking of salt, I also take the models with a grain of it. I try to be conservative in my approach. My ground characteristics in EZNEC are probably worse than actual so that I don’t get inflated gain. I don’t get too worked up over a modeled dB here or there.
Remember my initial reaction to how quiet the GP was? I have a notion how vertical antennas are electrically noisy, and maybe true in theory. The lack of gain at high-angles has the effect of lowering close-in signals and static on 80M in this real-world exercise. This condition has inspired me toward thinking about a receive-only four-square for low-bands. I am sure it would play very well even on my small city lot. I would not have believed it unless I heard the noise reduction with my own ears.
Who would have believed that a low, non-resonant, much-maligned and poorly constructed antenna such as my bent G5RV, that goes by the name of Crappy, would be a superior antenna to a classically constructed ground-plane antenna on 80M.
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