Yes I know I can look this up....

Am currently feeding a 20M single triangular quad loop about 3 metres
off the ground with a 1/4 wavelength 75r Q section. Modelling the loop
shows a high-ish Z of 180 ohms. Not a problem for this feed method
though. (I expected it to be around 120 ohms)

Thinking of making it work on 10M and Z I think is around 350 ohms, but
I havent modelled it.

If I use a 4:1 coaxial balun cut for 20M, does the 4:1 effect (now a
full wavelength) also occur on 10M?

(Thinking a 3/4 wavelength Q section is the same as a 1/4 wavelength one
when it comes to translating the Z)

I am not and will not be using a tuner... (in case anyone wants to
suggest it)

TIA Bob VK2YQA