102" whip SWR vs 4' Firestick - CB - Jeep Wrangler Forum
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Old 06-15-2018, 07:45 PM
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102" whip SWR vs 4' Firestick - CB

I _think_ I know the answer to this, but wanted to check with others more experienced

With a 4' Firestick antenna, I can achieve a SWR of about 1.2-1.3 on ch19.

With a 102" whip, I can achieve a SWR of about 1.6-1.7 on ch19.


Now, I believe the 102" whip is far, far more efficient than a 4' antenna, based on this, which I found online:

Quote:
If you put 4 watts into a four-foot antenna, you will get the same power out of that antenna as if you were putting 2 watts into a 102-inch whip.
If you put 4 watts into a 3-foot antenna you will get the same power out as if you were putting about 1.5 watts into a 102-inch whip.
If you put 4 watts into a 7.5 inch antenna on a hand held CB, it would put out as much power as a third of a watt into a 102-whip.
If you put 4 watts into a 102-inch whip antenna, it is the same output as if you put 11 watts into a 3-foot whip.
If you put 4 watts into a 102-inch whip antenna,, it is the same as if you put 14 watts into a 28-inch antenna.
If you put 4 watts into a 102-inch whip antenna, it is the same as if you put 54 watts into a 7.5 antenna.
If the SWR on channel 40 is greater than that on channel 1, your antenna is considered to be "LONG" and reduction of physical height and/or conductor length will correct this
situation.
Would it be correct to say, even if I didn't tune the 102" whip (I'd need to cut it down a bit, it's reading higher SWR on ch40, approachin 1.9, than on ch1 which reads similar to ch19), I am _still_ better off with the whip?

Thanks!
Scott

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Old 06-16-2018, 03:06 PM   #2
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I think it's hard to say. There's so many variables with antennas beyond efficiency.

You're probably getting additional gain from the 102" antenna, but that gain can come at a price of being more directional. Additionally, the take-off angles will probably change so that the signal is sent "skyward" more quickly.

So while you might have a more efficient antenna, that signal may not be reaching where you hope it is.

In the ham radio world, we often choose a less efficient antenna simply because the signal pattern is more in line with what we're wanting.

My suggestion for you is to do some testing and see which one works better for your application.

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Old 06-17-2018, 11:03 AM   #3
Knows a couple things...

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A 102" whip is so seldom the right choice of antenna for a CB on a Jeep that I wouldn't even consider one. Shorter antennas work fine in 99.99% of all situations a Jeep finds itself in. Not to mention if you take your Jeep to 4x4 events that many, including some Jeep clubs, long-ago banned 102" whip antennas due to how they can whip around and "nail" bystanders. And those who have their tips tied down in an attempt to avoid that issue still have that problem as the tips commonly end up pulling free to whip back and potentially seriously injure someone who happens to be behind the Jeep.

Heck even my 2' CB antenna mounted just above my tail light gets out fine and communicates for miles. I often lead large groups of Jeeps that get spread way out in mountainous terrain and my 2' antenna works fine for even those at the rear of the pack.
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Old 07-01-2018, 01:47 PM   #4
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Big quarter-wave whips often yield SWRs that are somewhat higher than shorter models, but they invariably yield longer ranges than shorter antennas that have coils to compensate for their short-man-syndromes (kind of like wearing elevator shoes doesn't fully compensate for longer torsos and legs).

The problem with the big guys, of course, is that nine feet of stinger on a mobile vehicle are hard to accommodate, and this is especially true on rough roads with low-hanging trees and narrow pathways. Being so tall, the nine footers often are placed down low on bumpers, which somewhat negate the value of their stinger heights because of their closer proximity to the ground and RF-reflective metal vehicle bodies.

I've seen tests where a magnet-base Wilson 1000 with 62 inches of whip will outperform a 108-inch tall boy, probably because the shorter Wilson is up high on a metal roof and the tall nine-footer is a few feet lower on the bumper.

All things being equal, the taller antenna has all the advantages. But often, all things are't that equal.
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