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SWR Issues....

T

T23

Active Member
Apr 17, 2010
645
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I am having some issues with my SWR, when I check the SWR on CW on my HTX-100 it reads a 1:1:3 on 7 and 25 watts out and when switched to SSB the needle never goes past where it was when I set the SWR cal. on CW, but when I put my JAWS II 150 ( a 150 watt amp) inline the SWR swings from nothing to full scale, I know your not supose to check SWR on SSB but I was concerned about this since when I switched to SSB from CW to cal. the SWR it never went past the SWR readout on CW until after I added the amp.

Update: just took an SWR reading with the amp inline on CW and it reads 1:3!?


T23
 

The bottom is never, NEVER, NEVER try and check SWR on SSB. Use ONLY a steady unmodulated carrier like AM, FM, or CW ONLY.

The reason the meter never went any further is because the peak SSB power is the same as the CW carrier power and as such the calibration setting would be the same.

BTW did I mention that you should NEVER check SWR on SSB? :whistle:
 
Ok, well I checked the SWR on CW with the amp in-line and it still gives me a 3, I have tried three different meters, the one that has the highest wattage rating I am not seeing the antenna tune to a different frequency, the SWR is never completely flat or close to it on any frequency, when I use the other two meters it will give a flat reading on the frequency the dipole is cut for, I am suspecting RF is getting back into the meter, while testing a 2 meter rig, the needle would swing and nothing would be connected to the meter. but the other two meters have metal casings which I guess is shielding it from the RF. The meters I compared it to though aren't rated for the wattage I need so testing was done within there limits. Could I possibly put one of the meters that has a lower wattage rating BEFORE the amp and still get a correct SWR reading?


T23
 
I'm still new and learning all of this, but have you tried using a dummy load just to verify what you are seeing with the live system? If you are able to eliminate one part of the equation and get the same result, then you can narrow down what may be the offender.
 
I'm a bit confused. Are you saying that the SWR when hooked up to the amp is different than when hooked up directly to the antenna? if that is the case it is because the input impedance of the amp is different than the antenna impedance. You would see this if the meter is between the radio and the amp. If the meter is after the amp it is because the amp has harmonics and the meter cannot tell the difference between the fundamental frequency and the harmonics.
 
That is exactly what I am saying, my SWR is much higher with the amp in-line. I can understand the SWR going up a little, but not from 1.3-1.5 to 3.

And a dummy load is on my to do list...
T23
 
Thanks for the offer it would be perfect for my station, but what I meant by "its on my to do list" is that I was going to build one.


T23
 
Captain Kilowatt said:
I'm a bit confused. Are you saying that the SWR when hooked up to the amp is different than when hooked up directly to the antenna? if that is the case it is because the input impedance of the amp is different than the antenna impedance. You would see this if the meter is between the radio and the amp. If the meter is after the amp it is because the amp has harmonics and the meter cannot tell the difference between the fundamental frequency and the harmonics.
Click to expand...

T23 said:
That is exactly what I am saying, my SWR is much higher with the amp in-line. I can understand the SWR going up a little, but not from 1.3-1.5 to 3.

And a dummy load is on my to do list...
T23
Click to expand...

What part is it that you are agreeing with? The first part about the amp input impedance or the second part about the harmonics? Simple way to find out is tell us where you have the meter placed,between the radio and amp or after the amp.
Since that amp is basically a CB amp with no quality control whatsoever it is to be expected that the input impedance would be anything zero to infinity. Well almost. :pop:
 
Well I have had the meter before and after the amp, I always get a lower SWR with the meter before the amp, And the part I was agreeing with was the harmonics, because I have tested this amp with two other setups and it does the exact same thing, SWR goes to 3 no mater what it was before the amp was put in-line.


T23
 
T23 said:
Well I have had the meter before and after the amp, I always get a lower SWR with the meter before the amp, And the part I was agreeing with was the harmonics, because I have tested this amp with two other setups and it does the exact same thing, SWR goes to 3 no mater what it was before the amp was put in-line.


T23
Click to expand...

Tell us what you are transmitting into when doing your tests. Dummy load or antenna. If antenna, what kind, feedline, etc. You really should do this kind of testing into a good dummy load. You can have a problem in the feedline or antenna that won't show up until you apply higher power levels.
 
I am testing my homemade vee dipole antenna. That's why I am concerned about my SWR. The SWR stays the same with a wattage increase from 7 to 25 Watts. My feedline is RG-58. The SWR is fine without the amp inline and with the meter before the amp. The amp puts out
150 Watts.

T23
 
I think what we're trying to find out is:

...if you have the meter before the amplifier, and the amplifier is shut off BUT STILL IN LINE, how the SWR?

Then, without doing anything else, turn the amplifier ON. Now, how's the SWR?

With a typical amplifier, if it's not turned on, the rf passes right through it; the amplifier is transparent as far as the radio is concerned. Then, when you turn the amplifier ON, the radio sees the input circuitry which, as Captain KW pointed out, may or may not be a good thing.
 
T23 said:
I am testing my homemade vee dipole antenna. That's why I am concerned about my SWR. The SWR stays the same with a wattage increase from 7 to 25 Watts. My feedline is RG-58. The SWR is fine without the amp inline and with the meter before the amp. The amp puts out
150 Watts.

T23
Click to expand...

Ok, do this. For now don't worry about the swr between the radio and amp. Install the amp in-line and the swr meter after the amp. With the amp turned off but still inline check the swr with a steady carrier. Now turn the amp on and do the same test. If the swr jumps at the higher power levels you probably have an issue with your rg-58 coax, feedpoint or connections. This is only going to be a guess since you are not doing any testing into a known good dummy load.
 
The SWR is fine with the amp inline and off with either the meter before or after it. I only have the issue with the amp on. The meter I am using seems to be acting weird it reads a little higher than my other two and it never reads flat on any frequency like the other two but has a higher wattage rating either with or without the amp inline or on or off.


T23
 

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