[Radio Wrangler]

Hi Symon.

If you were going to build a loop to transmit with and you were going to resonate it to get the maximum current in it and hence the best radiated signal, copper pipe would matter.
The radiation resistance of a small loop is very low indeed, and the resistance of a few soldered pipe couplings can halve your efficiency.

Receiving MF and HF is different, you don't need that much care to get signals above your amplifier noise floor. terrestrial noise is more significant. Thickish wire will be more than adequate. The source impedance from the loop will be very low and it would be quite a special amplifier to get its front end noise-optimised for that sort of impedance. You don't need to go to that trouble to get satisfactory results. I'd expect amplifiers with grounded-base type input stages to have a bit of advantage.

I've built 'dead bug' prototypes for years without using lilypads much at all. Things were built flying in the air. Power rails mounted on a row of decoupling capacitors. ICs glued upside-down, legs in the air (dead bug!) I keep a stock of 1 meg ohm resistors as standoffs BNC and SMA connectors get soldered facing off board edges. You can get very creative and three-dimensional. It's also not so bad to tear a bit up and start again.

David