>The bands on my Kenwood AT-180 ATU are the following:
>
>MHz
>1,80
>3.80
>7,30
>14.20
>21.20
>28.50
>
>I have a narrowboat and intend to connect a "random wire" to the "Antenna 3" terminal.
>And am going to run the earth from the "GND" terminal to a copper pipe to place in the canal.
>
>Is this a good way to ground the set up or would I better grounding it to the actual steel boat hull?
>
>What is the optimum length for the random wire to make best use of the band coverage the ATU gives me?
>And what antenna cable would be the best to use?
>
>Likewise would AWG spec wire should I use from the "GND" Terminal to the copper pipe or steel hull?

Grounding the Kenwood AT-180 to the steel narrowboat hull provides a superior RF ground compared to a copper pipe in the canal. The hull acts as both a counterpoise and direct seawater connection, enhancing efficiency across HF bands, while a pipe may introduce higher resistance and corrosion issues.

| Length (m) | Closest Bands (MHz) | Wavelength Notes |
| ---------- | ------------------- | ------------------------------- |
| 8.8 | 14.20, 21.20 | ~λ/10 at 20m, ~λ/16 at 15m qsl​ |
| 12.5 | 7.30, 14.20 | ~λ/16 at 40m, ~λ/22 at 20m qsl​ |
| 17.7 | 3.80, 1.80 | ~λ/16 at 80m, ~λ/11 at 75m qsl​ |

For Antenna 1 and 2 SO-239: Tuner → PL-259 connector → RG-58C/U coax → PL-259 connector → 1:1 balun → 14-12 AWG antenna wire (e.g., dipole legs). SEE below, balun at dipole end
The Antenna 3 screw terminal goes to 14-12 AWG wire. SORTED

Dipole Lengths Confirmation

Yes, split each length into two equal legs for center-fed dipoles on Antenna 1/2 SO-239 ports:

8.8m total → two 4.4m legs (targets 14.2/21.2 MHz)
12.5m total → two 6.25m legs (targets 7.3/14.2 MHz)
17.7m total → two 8.85m legs (targets 3.8/1.8 MHz)
​
Practical Trimming

Start 5% longer, prune for lowest SWR at band edges using AT-180 meter; boat mounting may shorten effective length by 3-5%.

Only one balun per dipole, installed at the antenna end—tuner SO-239 → RG-58C/U coax → balun at dipole → 14-12 AWG legs.

https://www.hamradiostore.co.uk/ldg-rba-1-1-balun
https://moonrakeronline.com/ldg-rba-1-1-1-current-balun
LDG RBA-1 - 1:1 Current Balun

No, the LDG RBA-1:1 features a female SO-239 input for your RG-58C/U PL-259 plug, plus two top binding posts for dipole wire legs. Perfect feedpoint match.
​
Fit for Setup
Plugs directly into RG-58 end; attach 14 AWG wires to posts via ring terminals—weatherproof with silicone for canal use, QRP-ready 1.8-30 MHz.

RG8 Ultra Low Loss ideal compromise—minimal extra weight over RG-58
https://moonrakeronline.com/mini8-50-ohm-coax-cable-various-lenghts
OR
https://www.mcgillmicrowave.com/product/rg8/

Moonraker Mini8 vs McGill RG8

No, not the same: Moonraker Mini8 (6.1mm OD, RG8X-type, ~0.8 dB/30m loss at 1.8 MHz, 0.04 kg/m) is thinner/lighter/flexible low-loss. McGill RG8 (10.3mm OD true RG8, 1.0 dB/30m, 0.11 kg/m) thicker/heavier/higher power.

Mini8 vs LMR-400 Comparison

Moonraker Mini8 (RG8X-style) performs nearly as well as LMR-400 for your 30m QRP HF—losses ~0.9 dB/30m at 1.8 MHz (Mini8)
vs 0.7 dB (LMR-400), <0.3 dB difference irrelevant at 5W. Mini8 lighter (1.2kg/30m vs 3kg).

| Aspect | Mini8 | LMR-400 |
| ---------------- | ------------ | --------------- |
| Loss 1.8 MHz/30m | 0.9 dB kv5r​ | 0.7 dB youtube​ |
| Weight/30m | 1.2 kg | 3 kg |
| Flex/Dia | High/6mm | Med/10.3mm |

https://moonrakeronline.com/pl259-compression-plug-7mm-for-mini-8

Antenna - Gauge: 4.0mm Diameter
https://moonrakeronline.com/original-pvc-flexweave-antenna-wire

Ground to hull
https://moonrakeronline.com/eu/32-heavy-duty-antenna-wire-made-with-kevlar

​