Even as I play with the groundplane design, it is fairly clear to me that I will probably need a greater aperture for receiving at 1GHz. This means, simply, just as it does at HF - more wire in the air!
Theres lots of designs on the 'net, and there doesnt seem to be any obvious comparisons between them. I fancy a 12 section COCO (COaxial COlinear) but the necessary cutting of bits of coax isnt really a quick evening job. So, I thought i'd try this http://adsb.alle.bg/antenna/collinear/
My version doesnt follow exactly, but im hoping it will be 'in the ballpark'. For a start, im using 1.5mm wire, not 3mm (because I have some), and im also not worrying too much about weather protecting this one. So the specified dimensions will probably not be quite right for my version, but should at least give something on receive.
Ive cut, measured and bashed the wire into the required shape. Tomorrow i'll knock up the groundplane section as a few bits of wire soldered to a bit of PCB with a hole in it, and solder the lot to yet another TNC socket nicked from an old RC-690!