SWR question

[Duckodb]

I noticed taking a cobra 29 out of a truck with low swr and hooking up a Stryker in its place to the same antenna the swr is higher. You always read your tuning the antenna to the vehicle not to the radio but I think I disagree. My question is should the swr be checked with the 20 watt dk power wide open or backed off to around a 4 watt like a normal cobra 29? Wide open I’m showing 1.5s on both ends and about 1.3 on 20 but with the power cut back the swr meter needle barley moves off 1. I know it’s in good shape either way but was just curious if it should be set wide open or on low power.

 

[Crawdad]

It's definitely not about tuning to a different radio if using the same antenna and frequency band. Set it how you want. You're well within a good range either way. It doesn't hurt to know how much you're reflecting when cranked up either. It's not really about reading the lowest SWR if you're gonna turn the power up.

73

 

[144inBama]

Normally, the amount of power doesn't matter as long as the antenna is rated for it. Case in point, my SWR was initially set with a bone stock 29LTD, 4 watts max. I'm now running a Stryker 955 driving a 1X4 2879 box, the SWR hasn't changed a bit from the first time I set it.

 

[Crawdad]

Gotta differ with that one. My SWR changes upward slightly with more power. Always has. And the meter has to be re-calibrated with increases of power to accurately measure the amount of power reflected back. More wattage out = a higher level of wattage reflected back, no matter where the antenna was "set" or tuned.
I rarely monitor SWR, instead watching reflected power. If it goes up from normal @100w out then I know I have an issue to check.
In the end I reckon it's 6 to one, half dozen to another.............

 

[144inBama]

Can't cal mine, it's a MFJ 880 so it auto cals. If there's a difference, it has to be negligible because I really can't see it (ain't got the best eyes anymore though). It's running 1.2-1.3 barefoot or amp but that could just be how that meter calculates, no idea. As long as I'm not bumping 1.5-1.6 I feel safe.

 

[Duckodb]

Idk I had read on some website that you should set the power to low when your tuning an antenna and I was always doing it with it set as high as it would go thinking if I set it that way it would always be right no matter what power setting. I just hooked the meter to my work truck , the Ford that’s the topic of another thread that fried the first Stryker I put in it, on channel 1 on high with 20w dk it’s 1.4 on low with like a 2w dk it’s 1.1. That’s what it is where it’s sitting in the driveway at this moment anyway. Like I said I know it’s fine either way I was just curious mainly because it’s easier to tune on lower wattage.

 

[Crawdad]

I must have mis-read your post, thinking you were just checking SWR, not tuning an antenna. The SWR meters in some 11m radios and 10m "exports" are not terrribly accurate. I would not tune an antenna with one unless I had to. And I wouldn't have a great deal of confidence in it. You would at the very least want to use an external SWR meter. And then yes, I would use low power to tune.

The best way to tune an antenna is not with a radio or SWR meter but with an antenna analyzer. Maybe you know someone with an analyzer to loan. And a side benefit is that you can learn stuff about antennas and how they work while you use it.

73

 

[midnight special]

use a antenna anylizer,, harmonics can and will mess up a swr reading on external meters,,, using peaked and tuned radios and 10 meter radios and amps will create harmonics,,,

 

[nomadradio]

When changing radios makes the SWR higher, it's usually the radio's fault. As a rule, harmonic frequencies coming out of the transmit side (along with the desired frequency) are the most common cause. Your antenna is not tuned for RF energy that's way off frequency, and all that energy comes bouncing back to the "Reflected" side of your meter.

Doesn't mean the antenna went bad, just means the radio's transmit side isn't putting out a clean signal. If someone "tweaked" every adjustment he could find to see if it would make the wattmeter read higher, it can affect how clean the transmit signal is. Stryker radios have a good reputation with techs (until they break) but any radio can be 'tweaked' until it misbehaves.

73

 

[Beetle]

Some "SWR" meters have a switch that must be used in order to allow the meter to be adjusted for full scale deflection. Then the switch is put into a "quasi-SWR"mode. The meter now doesn't compute the actual SWR; it shows a slight upscale reading which can throw one off if he's not watching. Get a good wattmeter and SWR indicator and learn how they work. Then don't loan them out

 

[9C1Driver]

I noticed taking a cobra 29 out of a truck with low swr and hooking up a Stryker in its place to the same antenna the swr is higher. You always read your tuning the antenna to the vehicle not to the radio but I think I disagree. My question is should the swr be checked with the 20 watt dk power wide open or backed off to around a 4 watt like a normal cobra 29? Wide open I’m showing 1.5s on both ends and about 1.3 on 20 but with the power cut back the swr meter needle barley moves off 1. I know it’s in good shape either way but was just curious if it should be set wide open or on low power.

An antenna is in fact tuned to it's location on a given vehicle. Are you using an external SWR/Watt meter? I hope your not using the SWR meter in the radio's, those are ball park at best.

 

[Duckodb]

In my last post where I said I just hooked the meter to my work truck I was saying I hooked an external swr meter to it. I’m not tuning my antenna now that’s done and over. I just read an article on one of these cb shops website about antenna tuning and they said set the radios power to low that was my only question because I tuned the antenna with the power wide open and it was a little harder to get the lower readings that way. I’m under 1.5 on high or low and with a low power cobra in both my trucks. That article just did t make sense to me to set the power to low when high power makes the swr 0.3 higher, I would think you’d set it on the highest power you have and it would automatically be better on low which is what I did.