Wading in excrement

[Moleculo]

On your chart it says an SWR of 2.0:1 reduces your power by 11.1%

And don't forget that what the chart says isn't exactly accurate, either. A high SWR does not by itself cause any loss in ERP. It is the act of the RF traveling through the feedline that causes the loss. Just because there is a mismatch of 2:0:1 at the feedpoint doesn't equate to a magic 11% loss of ERP. Depending on the length and loss characteristics of the feedline, the actual loss of ERP may be much higher or much less.

The only thing SWR really tells you is whether or not it is safe to transmit. For most people running a CB, that's probably really all they need to know anyway once they've chosen the antenna that suits their needs.

 

[CDX-007]

Make sure you aren't accidentally using Base SWRs for the mobile.

J/K, that's one I just heard on Ch.17 last night...

I checked the SWR of my 102" whip I have mounted on a quick release atop a 4-magnet mount on the roof with a direct ground directly beneath it, and it was 1.4:1 and 18-over 9 on my friend's iCOM Pro3 analog meter. I then cut it down so I'd have a 1:1 SWR and lost 2db on his meter. When I finally checked the reactance on an MFJ-259B tester I found I had added reactance by lowering the SWR and lost performance.

In my case Higher SWR = better performance, not because a little SWR is good (one common CB myth) but because less reactance is good for better performance, even though in my case it causes an higher SWR.

I fabricated a shorting / shunt inductor and was able to bring the reactance down to 14 at 1.2:1 SWR and in that same test spot his Pro3 meter now consistently shows 19 over 9, 10 miles, both preamps. I picked up ~1dB by lowering the reactance but raising the SWR.

Wilson 1000 = 15 over 9
Wilson 5000 = 16 over 9
5' tunable tip Firestik = 17 over 9
Extended 10m Hamstick = 18 over 9
96" 'Imax 700' & 102" ss WHIP = 19 over 9

 

[jazzsinger]

its rare that i agree with doc but he is right, vswr tells you little about how well your antenna is operating, that list of loss vs vswr is the excrement you are wading through,
reflected power due to antenna mismatch is only lost at those percentages in the mythical world of cb radio, in the real world the loss is much less, especially when using transmitters that don't fold back tx power when vswr goes above a preset value such as a cb radio,
if you want something that does not smell like shit when wading through it read walt maxwells "reflections"

a wilson 1000 beats a k40 which is the worst performing 60" antenna i ever had the displeasure to own 3 times,
the 1/4wave whip talks further than the silverload regardless of it having 1:1 vswr or 1.5:1 vswr

its miles further not feet

Like Bob 85 it's not often i agree with Doc, but in this case he's bang on.vswr is irrelevant,many antennas are resonant without being 1.0:1 vswr,as others have said resonace occurs when reactance isn't present, it doesn't matter what the feed impedance is at resonance the antenna will still be most efficient,

if you tune an antenna with only a swr meter you risk the chance of reducing the performance if you tune for 1.0:1 vswr,very few antennas are designed to be resonant with the feedpoint around 50 ohms.

that is why an antenna analyser that shows reactance is a much better tool for tuning antennas than a swr meter,a swr meter is only efficient for antennas that are 50 ohm at the feedpoint by design,they are far less effective for tuning antennas that have characteristic feedpoint impedances outwith 50 ohms.


as bob says a read at maxwell's reflections should shatter many of the myths that are perpetrated by cb'ers and others about losses due to a less than perfect 1.0:1 vswr,you will be surprised, a lossy coax cable is far more critical to losses than a high vswr will ever be.