Calling the SWR Masters! *

Bandwidth

 

Bandwidth?

You make no sense.

 

Most of the radio I do is around 28..400 MHz. The common practice for hams is to cut it to 96 inches which is obviously too short for CB, but fine for 10meters, Actually that's above 29mhz for the center frequency
98-99 inches though is a sweet spot that makes both bands usable, the portions I find relevant anyway.
I have a stock CB that I occasionally use and an unmodified multiband HF/VHF/UHF radio for my ham radio doings. Legal !
The actual resonant frequency for 102 inches is 27.52 MHz, outside ch. #40.
If we shorten it 3 inches it's still under 2:1 for CB, and nearly flat on the portion of ten that I use. I use an rf switch between the two rigs.
By the way, what little SWR there is is easily rectified by an inexpensive travel tuner from MFJ.

 

The typical 1/4 wave whip when tuned properly for CB usage would measure out to 108”, hence the reason a 102” is still slightly off, and the addition of the ever popular 6” spring. Trimming the whip down for 10M is in fact common, I know this trick, but I fail to see how it’s efficient for CB afterwards. I’m willing to bet it works fine for a low power stock radio, but I highly doubt it is in any way resonant on CB and 10M at the same time.

One or the other, you stated in the first post it was both, now the second post about it you mention you know it isn’t right for CB. A slight contradiction with words here.

 

Legal power on C.B is 4 watts AM and 12 watts SSB, both of which are qrp. So under those conditions yes it's low power. Anything above that is illegal.
I run an unmodified HF rig which is capable of 100 watts barefoot 1.8-54MHz. The SWR is fine under the legal limit for C.B. and the max power my HF radio is capable of, so the antenna operates perfectly well within the parameters that Iuse it.

 

It is common to trim the 102" stainless steel whip to 96" for 10meter use. Doing this places the center frequency at 29.25MHz, which is well away from C.B., gee I wonder why lol !
C.B. is a taboo subject around old school hams.
I cut mine at 99", actually I intended it to be 98.5 but bolt cutters just aren't that accurate, more of a hammer than a scalpel, and fiiled off the rough.
I have read different figures regarding the actual bandwidth of the 102" whip.
1.5Mhz is a figure I recall, although it is advertised as a 26-30Mhz antenna.
I do know that bandwidth is a function of the width/thickness, don't ask me to exppexp that though.
My 5/8th wave 2m (144-148Mhz)whip has a 4Mhz bandwidth. It also works on 6m(50-54Mhz).
A 5/8th wave 2m whip is also a 1/4 wave on 6. Conveinient how that works out.
Ten and Eleven are that close, neat how that works out for export radios ha.
That's no accident.

 

Gee, I didn’t know 4 watts was the limit for CB and 12 for SSB. I understand what you’re trying to get across, but saying it’s great on CB and on 10M is like saying a Ferrari and a Cadillac can be on the same level. It may work for you and kudos if it does, but it isn’t the most efficient on both, as stated before, it’s likely better on one than the other.

 

All mobile antennas are compromise antennas. The 102 trimmed antenna works fine on 10meters, and acceptable on 11meters for it's intended use.
If I want it to be even better, a simple MFJ-902b https://goo.gl/images/VddBqp travel tuner for about $109 can eliminate any swr. It is my belief that it can be "tuned" for 6meters no problem.

 

You're funny.

 

SWR on 11meters, is just under 1.5:1 on 40 and just over 1.7:1 on 40. I'll take that being as I trimmed it down to 99".