1/2" vs 7/8" coax for low band a 180' tower?

nmfire10 · Post by **nmfire10** » Wed Apr 07, 2004 5:19 pm

Would there be a significant difference in performance between 1/2" Heliax and say 7/8" for going up to the top of a 180' tower on low band? Our low band fire antenna on top of this tower is using 1/2" heliax all the way up. All the UHF stuff on it is using 7/8" coax. Does it not really change much on low band at that height?

ARZ902 · Post by **ARZ902** » Wed Apr 07, 2004 5:51 pm

loss per 100 ft of 1/2" hardline at frequencies below 2.5 Mhz is less than .1 db

loss per 100 ft of 7/8" hardline at frequencies below 6Mhz is less than .1 db

Post by **HumHead** » Wed Apr 07, 2004 5:57 pm

At 50MHz, 1/2" would lose around 0.833dB over the 180' run. The 7/8" would lose around 0.455dB over the same run. So, the difference would be 0.377dB. If you're running closer to 30MHz, the difference gets even smaller (0.291dB).

All things considered, I probably wouldn't lay awake at night worrying about it.

By comparison, at 450MHz, you would be losing 1.16dB between 1/2" and 7/8"

nmfire10 · Post by **nmfire10** » Wed Apr 07, 2004 6:09 pm

Cool. Thats kinda what I thought so I guess the 1/2" on the low band is perfectly fine. Just wanted to confirm it to ease my mind (or answer someone else in the dept who wants to know)