Hi Neil,

an untuned wire has a very high (capacitive) reactance on 630m.

Your 10ft up / 30ft top wire = 40ft = 12m * 6pF/m = 72pF = 4650 Ohm @ 475kHz.

Assuming 50 Ohm TX output impedance 1W = 7V in 50 Ohm. Unloaded the TX output voltage must be about the double = 14V.

So 14V into 4650 Ohm = 3mA antennacurrent.

I do estimate that radiation resistance of the antenna = 0.025 Ohm, what with an antennacurrent of 3mA results in an ERP of about 2 microwatt.

Certainly a challenge to copy such a signal at distances beyond 10 or 20 miles (at best).

I think you can win a lot by resonating the antenna. 

72pF requires a loading coil of about 1.5mH.

With just 1W output power I wouldn't hesitate to wind it on a small PVC tube filled with some ferrite rods. Moving one of the rods will easily tune the antenna.

Even if the coil has a poor Q of 100 its loss will be only in the range of 50 Ohm. Add another 50 Ohm for the groundloss = total loss in the 100 Ohm range.

That would pump up the antennacurrent to something like 75mA = 0.14mW ERP and thus increase the signal by almost 20dB.

73, Rik  ON7YD / OR7T​