Galaxy 99v SWR High on SSB

[Shadetree Mechanic]

Hi everyone,
I just joined and this is my first post. I have read a lot here over the past few weeks and have learned a ton. I was into CB back in the 70s as a kid and now I have a little money to spend on myself to have a little fun around the house. Enough about me and on to the subject:

I just got a Galaxy99v from a buddy of mine and it seems to work great except the SWR is over 3:1 on SSB. On AM the SWR is between 1:1 and 1.3:1. I am using a Starduster 400 antenna about 30ft up and 100ft of CA400 coax. I turn the RF power all the way down and key the mic on SSB and the SWR needle pegs the scale. Switch back to AM and SWR reads normal. If there is already a thread about this please point me to it. The first thing I did when I got the radio is look up all the mods that can be done to it. I found that the modulation limit resistor has already been clipped and is the only mod I found. I am willing to send the radio out to have it checked, but I wonder if the problem is with the antenna install or a setting on the radio. Thanks in advance for any and all replies.

808 Under the Tree

 

[undertaker]

SSB does not have a carrier like am..

 

[Shadetree Mechanic]

Thanks for the quick reply. So standing waves are not a problem on SSB or FM? Just trying to understand.

 

[nomadradio]

Let's back up a step here.

How do you measure SWR on sideband? There should NOT be a steady carrier coming out of the radio in sideband mode when you key the mike.

If there is, the radio has a problem, not the antenna.

73

 

[fourstringburn]

Welcome to the Forum!

Undertaker is correct, there is no carrier on SSB so this mode can't be used to check SWR. Only carrier modes like AM & FM can be used with your radio. The SWR shouldn't change if you change modes.

If you are seeing the needle rise on SSB, you either have way too much mic gain modulating the ambient noise or an adjustment out of whack on the radio like the SSB carrier balance pot.

Either way, there should be no modulation on SSB when deadkeying.

Also I wouldn't rely too much on those radios internal SWR meter. Always best to have an external meter. Even a $30 cheapie is good enough.

 

[Shadetree Mechanic]

Thanks for the replies guys. I just went out to the garage to try it again so I can give more detail. For measuring SWR I am using a radio shack power / modulation / SWR tester. When I dead key on SSB with the mic gain all the way down, the power comes up, the modulation needle makes a small bump and returns to zero and the SWR goes all the way to the right. I only hold the key for about a second because I am afraid that I will hurt the finals. What should the SWR meter do on SSB? Stay at 1 or the same thing that it does on AM? Sorry if it sounds like I don't know what I am doing. Hopefully with everyones help I can get pointed in the right direction. Thanks again.

 

[309hellinois]

You can't check swr on ssb. You have to use am or fm. Your swr will not change from one mode to another.

 

[Shadetree Mechanic]

Ok so I can just ignore the SWR meter when in SSB mode?

 

[309hellinois]

Ok so I can just ignore the SWR meter when in SSB mode?

As long as your swr is good in am or fm, you're good to go.

 

[Shadetree Mechanic]

Thanks Everyone for your help! I am going back to the garage to do some talking!

 

[Captain Kilowatt]

SWR is dependant on the frequency that you are operating on. Frequency does not change when switching modes between AM and SSB or FM etc. Those are just different methods of modulating the same frequency. SWR is the same on all those modes as long as you are on the same channel. I suspect that since SSB has more power output you are seeing an apparently higher SWR due to the higher power output and that the meter is not recalibrated to that higher power level. Also as said before here, SSB is not a good mode to check SWR as there is no carrier and simply whistling into the mic is far from accurate.

 

[Shadetree Mechanic]

Thanks for your input Captain. On SSB it pegs the SWR meter when dead keyed even with the RF power all the way down. I figured a standing wave is a standing wave but on SSB mode it must be reading something else? I guess I have a lot to learn and I appreciate all the help I can get.
Ps. I am reading the Wikipedia page on SWR. https://en.wikipedia.org/wiki/Standing_wave_ratio

 

[9C1Driver]

Thanks for your input Captain. On SSB it pegs the SWR meter when dead keyed even with the RF power all the way down. I figured a standing wave is a standing wave but on SSB mode it must be reading something else? I guess I have a lot to learn and I appreciate all the help I can get.
Ps. I am reading the Wikipedia page on SWR. https://en.wikipedia.org/wiki/Standing_wave_ratio

Since SSB mode has no carrier you cannot use the calibrate control on the SWR meter BEFORE you get an SWR reading. Since you cannot calibrate first you don't have a valid or correct reading. This is why you check it on AM or FM. I'm sure your good to go.

 

[nomadradio]

The power stage of the radio is oscillating.

Normally, the output from a SSB transmitter is zero until you talk. The power that comes out and is seen on a wattmeter is directly in step with your voice audio. No Voice, no RF.

But your radio shows output when you are NOT talking.

That's wrong. Most of the time, this is because the power stages in the radio that should only be amplifying your voice modulation are instead creating their own RF power.

As a rule, when this happens, the frequency coming out of the radio will not be anywhere near the channel frequency you have selected. Only the voice-modulation SSB power will be on the channel.

The power coming out of the transmitter when you DON"T speak on SSB is called a "spur", short for "spurious output".

Most of the time, this is because the power sections of the transmitter have developed a feedback issue. Consider what happens if you turn on the talkback, key the mike on AM and hold the mike directly against the speaker. You will get a feedback howl.

What I think you are seeing is the RF equivalent to the audio feedback that causes the "talkback howl".

The SWR reads high because that spurious RF power will NOT be on a frequency near the channel you selected. Since the antenna is not tuned for that spurious frequency, the SWR will be high.

Frequently, switching to AM mode will make this spurious RF output disappear when you transmit. If so, the SWR reading returns to a more-reasonable level, since you are now only feeding the correct frequency to the antenna.

Sometimes the cause is as simple as a loose screw grounding the circuit board to the metal chassis, or the nut securing the antenna socket has worked loose.

On a good day.

73

 

[357]

Ya something not right.
Either the car. bal. is cranked, the mode knob is on pointing to USB when its really on FM or like nomad its oscillating.
Does the back get hot on receive on ssb?