So for the 1/4 wave (81mm) section of the antenna the loss would be
about 0.05dB ? at 915 MHz.

I typically have between 150mm (When antenna mounted on enclosure) and
2m length (when antenna external to enclosure) cable between transmitter
and Antenna. (Around 1.2dB max. loss in coax between transmitter and
antenna). Would this usually be acceptable or do you aim for much lower
loss in the transmission line ? Max. power is 1 Watt. Most of the
transceivers I play around with are around 10mW.

Thanks

Cecil Moore wrote:
David wrote:

If I scale that up to 915MHz, the dimensions are almost perfect for
using RG58 coax ...


I wouldn't use RG58 for anything above HF. It has 20 dB
matched line loss per 100 ft at that frequency.