The QRPer Board

as for the radiator length, see here https://k7mem.com/Ant_End_Fed.html#Not_Random_Multi ensure to add a good guanella choke after the 9:1 and use at least one counterpoise wire with a lenght around 1/16 Lambda at the lower frequency (e.g about 5m if the lowest frequency is 3.5MHz, eventually add a ...

https://www.alphaantenna.com/wp-content/uploads/2022/09/What-Coax-Should-I-use.jpg https://www.alphaantenna.com/wp-content/uploads/2022/09/What-Coax-Should-I-use.jpg consider that every 3dB of gain or loss the power doubles or halves, so a 3dB cable loss means that the antenna will receive half of t...

looks good !

the carabiner hole is useful both when the antenna is deployed and to hang it to a backpack wnen the antenna is wrapped, the velcro stripes will help keeping the wire/coax wrapped

Just to try explaining it better, see the image below (ugly but hopefully "readable")

Please, post an update when you'll try it !

A suggestion, make the "box" hosting the 9:1 and choke a bit longer so that the two toroids will sit flat side by side laying on the bottom and not one over the other, also consider enlarging the sides a bit and having some rectangular slot holes at the sides, these will serve to host some...

Ok, now I feel like a dummy. I have a TransWorld TW2010 (pretty much a commercial version of your double T bar) but I was concerned about taking up too much space in the car. Next time... if the antenna is this one https://www.dxengineering.com/parts/dxe-tw-2010-p then once closed it isn't too big ...

Considering how easy it is to build https://vk6ysf.com/unun_9-1_v3.htm I think it won't be a problem building one of them as desired :) the "ground" goes to the counterpoise(s) or to ground stake, a small IP66 electrical junction box will host the toroid, the wire connectors and the coax o...

the double t-bar may be unsuitable for some spots, but imVVHo will serve you well in all other cases when you can't set up an endfed wire

for "no tree" or "no wires up trees" situations, consider the *double t bar" antenna

https://www.qsl.net/hb9mtn/hb9mtn_vertdip.html

a ground stake or a tripod will support it, and while the gain isn't high, the takeoff is low, even if the antenna is near ground