Texas Star 350 concerns.. SWR jumping

[CB590]

Ok.. been running my TS350 just fine with most of my rigs wide open on SSB and according to my MFJ822 all was well at 1:3-1 on 1 and 1:1-1 on 40 and very little movement of SWR when modulating on sideband at full tilt (aka no Varible switch on)

I admitedly did a few times hit the MFJ822 without pushing the 30/300 button..

Anyway. The last 2 radios when TS350 is on full power has made my SWR do crazy jumps when talking like 1.4-1.5.

If I push the Varible and run at full clockwise I get no bounce and it reads the normal 1:1-1.2 when modulating..

The radio currently is a good running Uniden PC122XL and audio reports are on frequency and great.. pushing 18w max on SSB with a whistle.. usually 7-9w with my voice modulation..

Could the meter have gotten goofy after hitting it with 200-250w on the 30w setting?? And why when running with the Variable on and swinging 60-140w on the MFJ822 the SWR seems fine.?

I was going to order in a 100w dummy load but this issue is occurring over 100w..

Suggestions or tips?

No other changes in my system. Same coax jumpers and such .

 

[Shadetree Mechanic]

Maybe cmc on the coax braid? I would not worry about 1.5 .

 

[jessejamesdallas]

You "DON'T" check SWR while modulating period...Whatever you see when doing that is a false reading...Don't check SWR while moving either....It will jump all over the place...

 

[CB590]

You "DON'T" check SWR while modulating period...Whatever you see when doing that is a false reading...Don't check SWR while moving either....It will jump all over the place...

Well even on AM it seems to be jumping a little bit as well, with the Amp wide open. When I do the variable I get my 1:2-1..

What's cmc??

 

[mrgumby]

It’s most likely a bad variable they are known to go bad just leave it all the way up I use the buttons to lower power those dial a watt pots don’t last

 

[338_MtRushmore]

You "DON'T" check SWR while modulating period...Whatever you see when doing that is a false reading...Don't check SWR while moving either....It will jump all over the place...

Which part of the reading is false, forward or reflected?

 

[CB590]

It’s most likely a bad variable they are known to go bad just leave it all the way up I use the buttons to lower power those dial a watt pots don’t last

Actually with dial a watt' on, the readings are normal..

With wide open amp, they bounce on SSB to 1.5-1.7 and 1.3-1.5 on AM..

I did recently add the power for the SWR meter light.. maybe that is catching the stray RF and sending up to the meter??

 

[jessejamesdallas]

Which part of the reading is false, forward or reflected?

forward would be anyway...guess if your using a cross needle meter you could get a idea whats going on while talking...didn't think about that.

 

[Tallman]

Well even on AM it seems to be jumping a little bit as well, with the Amp wide open. When I do the variable I get my 1:2-1..

What's cmc??

https://myantennas.com/wp/tech-info/about-cmc/
To define “common mode,” I must define “mode.” The concept involves nothing beyond electricity and eighth-grade algebra. Consider a cable of two insulated wires, like zip cord. Imagine this cable delivering power to a 12-VDC lamp. The current flowing in one wire of this cable has the same magnitude as the current in the other wire, but the currents flow in opposite directions. For a 24-W lamp, the magnitude of the current in either wire would be 2 A. The net current in the cable (i.e., the algebraic sum, considering both the magnitudes and the directions, or signs, of the currents in the individual wires) would be zero.

 

[nomadradio]

What's "jumping" is probably the harmonic-frequency content of the amplifier's output.

The antenna is not tuned for the harmonic frequencies. As soon as the amplifier starts feeding energy to the antenna at those frequencies, the reflected power jumps up. The antenna won't accept those frequencies, so nearly all the power in the harmonics gets reflected back to the meter.

The SWR/Wattmeter can't tell one frequency apart from another. It just lumps together all the power you feed into the antenna, and all the power that gets reflected back down from the antenna.

A dummy load won't show this behavior. The dummy's impedance is the same at all frequencies, including those harmonics.

But the antenna's SWR is only low for the frequencies it's built to absorb efficiently. It will reflect nearly all of the 54 MHz, 81 MHz, 108 and up frequencies an amplifier may feed to it, especially on modulation peaks.

This is usually the explanation. Your amplifier is not the first one to show this behavior.

73

 

[CB590]

Well I am moving in about 45 days and the amount of time I get to use the setup is minimal. All reports are good thus far.

I know the SWR is set at 1:1 on channel 18+ and 1.2-1.3:1 down on 1 and below abit.. I talk on 38, 415 where I'm know x10 to be flat SWR as I set the A99 for the higher channels..

I temporarily pulled the meter out of the line yesterday in case it was bad I didn't want an issue backing up into the amp etc.. if that's even a possibility.

Should I put the meter back at the end of the line and just keep a weary eye on it? Run the TS350 with the Variable?

 

[CB590]

Ok. I put my old PDC1 on it without amplifier.. got same 1.2:1 on 1 and flat up above 18.. on AM mode

I took MFJ822 and got same.

I added TS350 after the 822..

I get same with AM..

I kick on amp and I get a 1.3 on channel 1 with deadkey on AM. So the amp is throwing some. I also noticed with amp on my DK wattage from radio goes up almost 1w..

Also checked sideband and same results..

Should I just run with the 822 between radio and amp for now?? That should tell me if there are at least major issues all of a sudden??

 

[338_MtRushmore]

Are you sure your 1 watt dead key increase isn't reflection from a higher swr?

 

[CB590]

Are you sure your 1 watt dead key increase isn't reflection from a higher swr?

That's what I'm thinking.

Increase in SWR and 1w up on the DK..

 

[999]

The output tuning cap in the amp might be going south.