Both my antennas at home are earthed on the lightning conductor network, which provides a good enough ground plane to allow me to use a mobile centre loaded whip for 80m and brings the SWR down to 1.3 without a tuner. With the OCFD, it is important to remember that whilst it is connected at the end, like a normal EFHW, the actual feedpoint is one fifth of the way along the antenna where the centre conductor of the coax meets the long pvc wire. The impedance at this feedpoint is not more than 300 ohms, easily dealt with by most auto ATUs. If the coax were grounded on the antenna side of the current balun, close to the true electrical feedpoint, it would no longer be a dipole, but something like a long wire working against a ground. That said, a relay switch to ground on the antenna side would perhaps allow a 20m long OCFD (lowest band 40m) to be tuned up and radiate effectively on 80m, which would be useful for restricted spaces. Here is an updated link to the page maintained by M0RZF on the End Connected Windom:
Whilst the grounding helps, the hybrid SDR function of the KX3 allows me to use full pre-amp on 80m whilst only getting about S1-2 noise in HDSDR. On the KX3 side, there is about S8-9 noise in the receiver. Antennas aside, I wouldn’t be on 80m at my home QTH if it wasn’t for HDSDR.
73 de OE6FEG / M0FEU
Matt