

The "wet" numbers represent worst case for lines covered with ice or snow. 
Here's a quick line loss calculator to use Note that the simple program used for this web page gives a very close approximation for additional losses due to SWR.


Online Coax Cable Loss / Antenna Gain Calculator
This program is provided "asis". It is thought to be accurate but it is the responsibility of the user to verify the accuracy of the calculations when using this program.
INTRODUCTIONThe longwire antenna is a very effective antenna for the listener who wants
to cover all of the shortwave bands from 530 KHZ to 30 MHZ. However if you have some
favourite frequencies that you listen to on a regular basis you may wish to consider a dipole
antenna. This antenna is a fairly easy to construct antenna and will give you better reception on
the frequency it is cut for. Think of a dipole as a longwire that has a insulator in the middle.
FREQUENCYA dipole antenna will not only work well on the frequency it is cut for, but also
for the multiples of that frequency. For example if you cut a dipole for 7.0 Mhz will also
work well on 14 Mhz, 21 Mhz and 28 Mhz. This way if you can pick and choose your frequency
you can make one antenna work on two or three bands.
LENGTH To find out how long the antenna should be all you have to do is fill in a simple
formula:
468 divided by FREQUENCY IN MHZ = LENGTH IN FEET
300 divided by FREQUENCY
IN MHZ = LENGTH IN METERS (wavelength)
168 divided by FREQUENCY IN MHZ = DIPOLE LENGTH
(with end effect
calculated in)
That is the only formula you need ever know to build a dipole antenna.