Hello Hook948:
The higher priced coax will save only a insiginificant amount of loss at the HF Frequencies, as compared to say LMR400.
Remember that you want 170 Ft of coax but the ratios will be right on.
Here's how it figures out: (for 100 FT of Coax)
LMR400 = .7dB loss at 30 MHz
LMR600 = .42dB loss at 30 MHz
LMR900 = .27dB loss at 30 MHz
LMR400 = .7dB = 17% loss, at 1 KW = 870 watts delivered
LMR600 = .42dB = 10% loss, at 1KW = 900 watts delivered
LMR900 = .27dB = 6.4% loss, at 1 KW =936 watts delivered
So you can see that the expensive coax will have a lower loss, but not enough to justify the nut cake expense of LMR900, and the connectors for LMR900 will be close to 100 dollars a pop.
www.texastowers.com/lmrconn.htm
www.timesmicrowave.com/te...RGuide.pdf
I use a length of LMR400 that is 160 feet long, not a problem.
I keep getting e-mail on this so I will post some of this here as a guide to all the radio enthuists out there.
dB = P1/P2 Log x 10
Example:
What is the difference in dB from 936 to 870 watts, as shown above.
dB = 936 / 870 Log x 10
dB = 1.075 Log x 10
dB = .03 x 10
dB = .3
So the difference from LMR900 to LMR400 is .3 dB
To figure dB into percentages:
dB / 10 Anti-Log
Example:
.3dB / 10 Anti-Log 1/x
.03 Anti-Log 1/x
1.071 1/x
.93 or 93 % or 7% loss
These functions for the Log operations are in base 10, and a cheap 14 dollar Caculator from Radio Shack will do the trick. I use a Texas Instruments TI-30Xa.
Jay in the Mojave
www.A1antennas.com
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