A quick NEC model of a 66 ft center fed horizontal dipole, at 35 ft, above
an average ground, indicates an input impedance of 307 +j708 ohms at 10.1
MHz.

For 70 ft of RG8X, using the ARRL's DOS program "TL", the matched line loss
is 0.63 dB, and an additional loss of 5.2 dB, for a total line loss of 5.83
dB. For an input of 100 W the ERP is therefore about 25 W. The coax input
impedance is 17.3 +j78.4 ohms.

73,

Frank


"Gary" wrote in message
...
I've got about a 70 foot +/- run of RG-8X that I use to feed my 40
meter dipole. I also use the same feedline and dipole through an
MFJ-949E tuner to operate on 30 meters with. Out of curiosity can
someone tell me about how much a a signal loss I've got compared to
having an antenna that's actually cut for 30 meters ?

Thanks in advance.

73 Gary K8IQ