Don’s Antenna talks by N4DJ

The amount of power lost in a short coax is pretty small with a 2:1 SWR. In fact I doubt if you could even measure it. Look at the chart I included. The matched loss of your coax is going to be very low if short. That’s on the X axis. If it were, say, 0.4 dB then a 2:1 SWR would only cause 0.1 dB additional loss. 100 foot of RG8X has about 1.5 dB loss per 100 feet at 30 MHz, so even in this case, using 100 feet of cable on 30 MHz and having a 2:1 SWR will only give you an additional loss of maybe 0.25 dB.  If only using 20 ft of RG8X at 30 MHz, your matched loss would be 0.3 dB and the loss due to  2:1 SWR is so low it’s not on the chart. It would take a SWR of 15 to have even almost 1 dB additional loss caused by high SWR.