Cb Setup, Swr Swing off the scale!

[johnnyred]

Hello to all,

Here is what I have:

1. Magnum S980 new (stock mic)
2. Jetstream 35 amp max, 27 amp continuous power supply
3. 50 Ft. of RG 213 u coax cable. & 4 18" jumper of the same.
4. IMax 2000 with GPK Attached. on top of the roof that is 20 ft to the top of the roof, 10ft metal pipe attached to the vent pipe making the mast 30 ft off the ground, then the antenna is attached to the top of the pipe. So the tip of the Imax 2000 is 54 ft.
5. Dosy TFC3001S Cb Ham Radio SWR watt meter
6. MFJ-948 TUNER, 300W, 1.8-30 MHZ, PEAK READIND CROSS METER.

OK now I show a flat match, but when I talk the swr goes from a flat 1.2 and swings far right into the red.

and the radio has a built in swr warning light and it is always flashing.

any help here whould be great.

Johnny Red

 

[johnnyred]

I can also post a video if needed showing what is happing.

 

[undertaker]

Sounds like your swr meter is not calibrated..

 

[BOOTY MONSTER]

but when I talk the swr goes from a flat 1.2 and swings far right into the red.

you need a steady carrier to check vswr .
1.2 is more than good enough

these links will tell how to properly check your vswr .

http://www.cbradiomagazine.com/Articles/How to use a SWR meter.htm

http://cbradiomagazine.com/April 2007/SWR.htm

 

[Grogan]

I have Imax and Magnum S45HP 25amp MFJ switching power supply. Match on radio is close to 1:1 just with unmodulated carrier and when I talk into the mic I can make the needle move to 3:1 But Checking SWR I olny use a dead key. Also have a Cobra 29 LTD chrome model. An the match is great and with any amp or power Mic the antenna warning light was on, I asked the local tecks and was told to put a tiny bit of black electrical tape over the light. LOL I found that you can adjust the warning light in the radio, so I did and now it is off. But I allways check Swr,modulation and RF power so no big deal.

 

[Robb]

A few things . . .

If you have the MFJ antenna matcher inline; don't bother to have the Dosy inline at the same time. It has a cross needle that gives a really accurate SWR reading. Use that.

When checking SWR with the MFJ, set the radio to AM mode and turn the mic all of the way down/off. Then test it.

But not yet. Do the following FIRST:

Re-test everything inline on the way to the antenna but only after you test the basics first. So first remove the coax jumpers, the antenna tuner, and the Dosy. Everything. Now run only the radio, power supply, coax, and antenna inline together. Check the SWR using the S-9 radio's SWR function ONLY - with NO modulation/mic gain to 0. Then, check it again with some modulation.

If it goes into the red again, then either there is something wrong with your coax - or something is wrong with the antenna. Or the way the antenna is set up. Perhaps the antenna is next to a metal roof or metal pole - or anything that is large and metal and close to the antenna. That can/will affect SWR adversely. If you have a different piece of coax, try that too. If the SWR is OK after the coax was replaced with another one; then re-check your solder joints on the faulty coax. If the SWR is still bad when the coax was changed; then there is definitely something wrong with the antenna - or the way it is set up. Perhaps the ground plane is mounted in the wrong spot on the antenna. Maybe the antenna is faulty. The process of elimination is the best way to find the fault - IMO . . .

 

[Beetle]

"SWR Swing" says it all. Do NOT leave a typical "SWR" meter in line after you've checked things with NO audio. The meter is responding to reflected power in terms of the ratio of forward/reflected power.

SWR doesn't swing; it is what it is, and a dual-pointer meter (or a good digital meter) will show that fact pretty dramatically.

 

[W5LZ]

What you are seeing is normal when using an SWR meter that requires 'setting'/calibrating. Using a meter like that means that for it to be accurate the input signal has to be constant. If you vary the input signal by speaking, then you lave lost that calibration of the meter and it's reading doesn't mean anything. After checking for SWR switch out of the SWR mode, go to the power mode. Then, that 'swing' will be telling you something meaningful.
- 'Doc

 

[johnnyred]

So I hooked up the Dummy load from the radio to the dummy load and I show a flat match, but the SWR Warning light is still flashing. Must be a bad radio then.

 

[Beetle]

So I hooked up the Dummy load from the radio to the dummy load and I show a flat match, but the SWR Warning light is still flashing. Must be a bad radio then.

Possibly, but I'd look at the feedline, connectors and antenna (or dummy load) to see if they're intact and in good condition. Maybe substitute another radio and see how things react with it. This is where an antenna analyzer would pay for itself.

Flex the feedline, especially near the connectors, and watch the metering.

 

[Mudfoot]

I've had a few of those rigs with the SWR indicator light. I think most of them flickered a little.