This post is an adaption of an article published in QTC Magazine. If you’re wondering why you’d bother with radials for a vertical antenna, read on…. it’s worth 6 dB
We recently relocated our QTH, and like any self-respecting amateur one of my first jobs was to get an antenna up in the air. I had a DX-Engineering multi-band vertical, and I figured this would be a good all-rounder and provide ready access to a good selection of HF bands.
Initially, I attached the antenna to a star picket and ran a few random radials across the grass. There wasn’t too much science or planning in this installation; it was more about having something to plug into the radio to get a bit of on-air time whilst I worked on medium term plans to re-install the Nally tower and consider other options for the lower HF bands.
Once we were settled it was time to improve the efficiency of this antenna. Living in the country and a reasonable distance from neighbours means I have very low QRM and improving the vertical’s efficiency made sense.
The obvious choice was to lay more radials.
I saw three main considerations:
- How many radials?
- What would I use to connect the radials; and,
- How would I bury the radials?
- How many radials?
I decided to aim for 32 buried radials, each ten metres in length.; anecdotal research indicated this to be a good balance between a reasonable efficiency dividend set against the effort required to cut and bury 32 lengths of wire.
2. What would I use to connect the radials?
DX-Engineering offer a very practical solution in the form of a stainless-steel radial base plate. But at USD$89.99 plus postage I figured this would add up to at least AUD$200 with postage. A friend suggested I use stainless steel rulers…. purchased from eBay.
This option required a bench drill; something I’d been wanting for some time. Now I had an excuse.
Well… AUD$4.92 postage paid, and I had four 30cm stainless-steel rulers. Never mind the $142 for the bench drill.
3. How would I bury and attach the radials?
The thought of using a spade to slice 32 ten-metre-long trenches for the radials had me reaching for the Panadol. I recall an amateur mentioning to me some time ago he had used an electric lawn edger for this very purpose.
What a great idea. A Ryobi battery powered lawn edger proved to be the ideal tool for the job. There is a special technique required, but after the first few runs, I developed a method that worked well. I also found that a heavier gauge wire (I ended up using house earthing wire) was much easier to push into the channels. To aid in deferring corrosion, I sealed the ends of each radial wire with liquid tape. Capillary action and corrosion should not be underestimated, especially if you live near salt water.
Even with all this planning, it still took about three weeks of dedicated radial laying sessions to cut the channels, lay and cover the radial wires. Not to mention cutting 32 lengths of wire, soldering lugs, applying liquid tape, and then breaking my back bolting each radial to the base plate rulers in cold Wintery conditions. (this is a job better suited to warmer weather).
Since completing the project, the vertical is now fed with RG-213 coax through some heavy duty hose buried about 10cms deep.
From the outset I was interested in measuring the effects of adding radials – if I was going to go to all this effort, it would be nice to measure the efficiency improvements.
Like many amateurs I have a bevy of measurement equipment in the shack. I chose a portable spectrum analyser for the job. If you haven’t seen one of these, they really are an incredibly handy tool and can be used for all manner of measurement, analysis, and problem determination. They’re also handy for hunting down QRM.
In this scenario the spectrum analyser was used as a Field Strength Meter. The test environment was as follows:
- Measurement frequency: 28.029MHz
- Measurement point from antenna: 70 metres
- Tx power: 5 Watts CW
Seventy metres placed me outside the near field. It’s difficult to know how much of the signal strength improvement is due to efficiency gain and how much to variation in radiation angle.
Of course, there is a lot that hasn’t been considered in my somewhat rough and unscientific measurement method… but as a relative measure of improvement these measurements clearly demonstrate the value of adding radials to a vertical antenna.
Bottom line… Going from 4 radials (-52 dBm) to 32 radials (-46 dBm) improved the Field Strength measurement by 5-6dBm.
On transmit, 6dB is the same as an amplifier from 100W to 400W. And of course, whilst I didn’t take any measurements, it’s probably fair to assume my SNR on receive will have benefited from 32 radials.
The whole radial project cost less than $100 and has provided my station with a very effective all-round vertical antenna for seven HF bands. It’s handy as a broadband propagation checker, works very well for broadcast station reception, SWL from 4-15MHz and gives me a nice all-rounder for my WSPR transmitter.
In researching this article, the following rules of thumb were noted:
- Buried radials are detuned: you don’t need to worry about trimming them to resonance;
- As a general rule, ground radials should be at least 1/8 of a wavelength in length;
- It’s better to have more short radials than fewer long radials;
- Broadcast stations generally have 120 radials: a practical amateur radio installation will get by with 12-16 radials; and,
- Adding more radials may not greatly improve efficiency, but it will provide redundancy where radials may suffer corrosion, continuity issues or complete failures due to external events (like a shovel, lawn mower blade or some other catastrophic event).
The law of diminishing returns applies to radials. Conventual wisdom suggests between 16 and 32 radials for most amateur radio applications is adequate. Some extremely dedicated top-band enthusiast will install 60+ radials. Even these mad-keen top-banders will more than likely confess to obsessive compulsive radial disorder!
If you’re intending to install a vertical antenna, you’re very first thoughts should centre on the radial system.
And here’s a pic of my new bench drill. Another very handy tool for the work bench.
Last modified: 28 April, 2026
