Technical Note · Feed System · ATU Configuration
Do I Need a Tuner at the Base of My Greyline Antenna?
Short answer: no — but understanding why helps you build the most efficient station for your situation. Remote tuner at the feedpoint is the engineering ideal. Desktop tuner in the shack is what roughly half of Greyline operators run, including working RF engineers. Both work Real DX. Here's the full picture.
The Engineering Ideal — Remote Tuner at the Base
Placing an automatic tuner at the base of the antenna is the most efficient matching configuration. The tuner matches the antenna directly at the feedpoint — so the entire coaxial run back to the radio maintains a near-perfect 1:1 SWR. Feedline loss becomes negligible. Maximum power reaches the antenna.
Most 100W remote tuners operate via power-over-coax — one feedline handles both RF and DC power. No separate control cable required. For high-power applications, 1,500–3,000W remote ATUs are available, though some require a separate 12V supply at the antenna base.
Popular with DXers, contesters, and EmComm operators who want the cleanest possible signal chain. The LDG RT-100 is the standard Greyline bundle configuration — 125W, weatherproof, DC over coax, base-mount. That said, there are many ATUs on the market, most work great with Greyline VDAs. See antenna + ATU bundles →
The Practical and Popular — Desktop Tuner in the Shack
A high-quality desktop tuner is a proven and popular configuration. Roughly half of Greyline operators run one — including RF engineers who've looked at both options carefully and chosen the shack tuner deliberately.
In this configuration, the tuner matches the radio to the entire system — coax and antenna together — so the transceiver sees a clean 1:1 SWR. The SWR on the coax between the tuner and the antenna will remain elevated, which increases feedline loss. With short runs of high-quality low-loss coax, that loss is often minimal and the on-air difference is negligible. Thousands of operators work the world this way.
The Key Variable
When running a desktop tuner, feedline choice matters more. High SWR on the coax amplifies any loss the cable already has. The solution is simple: use the best coax you can. LMR-400 minimum, which a majority of our buyers use. LMR-600 better. Hardline or heliax is a step up too. Bury it and forget it.
The Feedline Makes the Difference
Feedline choice becomes critical when using a shack-based tuner. Three options, ranked by loss performance:
Option 1
450Ω Ladder Line
Lowest possible loss. Requires shack ATU. Cannot be buried without large conduit. Weather can detune. Best performance, hardest install.
Option 2
Two HV Silicone Wires
Lowest loss, lowest cost. Run (and bury underground) in flex conduit. Harder install than coax but excellent performance. Underused option.
Option 3
Coax
LMR-400 minimum. LMR-600 better. Hardline or heliax for lowest loss in the coax family. PVC insulation not suitable for HF/VHF. Bury it and forget it.
Greyline Recommendation
For most operators: Get the widest diameter coax you can afford, bury it, and let the ATU do its job. LMR-400 or better. A clean install with good coax and a quality desktop tuner will work the world. Most do exactly that.
For the RF purist: Open wire ladder line to a shack tuner is the lowest-loss path and there's real merit to it. If that road interests you, call us — it's a topic worth a longer conversation. 435-200-4902.
Want to go deeper: Antenna Physics: An Introduction, Robert J. Zavrel W7SX, ARRL 2020. The physics foundation behind every Greyline technical claim.
A Note on the Rig's Internal ATU
The automatic tuner built into most modern transceivers is a fine-tuning tool, not a primary matcher. Internal ATUs are designed to correct small SWR mismatches from an already near-resonant antenna — typically 2:1 or less. They work well for trimming small deviations after your primary external tuner has done the heavy work. This is the way the pros trim the last bit of SWR.
The Greyline VDA is a non-resonant all-band system. It requires a wide-range external tuner to present the full 160–6M operating range to the radio. The rig's internal ATU alone won't get there on every band — but it's a useful tool for those small mismatches you encounter moving across a band.
For complete signal chain configuration — tuner placement, choke position, coax routing — see the Feed System Configuration guide →
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Ham Radio is fun again! Pass it on… 73, The Greyline Performance Team · Sun Valley, Idaho · 435-200-4902