Hm.

All in the same sentence, that "line losses are negligible" and "line
losses will be about -3 dB"? I assume, of course that you mean 3 dB, not
-3 dB. But does this mean that you consider 3 dB to be negligible? And
how did you calculate that as the line loss?

Roy Lewallen, W7EL

Dave Shrader wrote:
Assuming a VSWR of 10 to 1, reasonable for 80 meters, and assuming line
losses are negligible for open wire tuned feeders, also reasonable for a
first approximation, your line losses will be about -3 dB.

EZNEC indicates that you will also have a VSWR of about 10:1 on 40 meters.

Conclusion: you will experience about -3 dB loss [1/2 S unit] on both 75
and 40 when fed with 500 ohm line.

Deacon Dave, W1MCE