SWR Question

[clantonman1983]

I have a Galaxy 979, it has an SWR meter built in, and I know those aren't the most accurate ways to check your SWR. With that said, My SWR usually is low, around 1:2 or 1:4. But, the other day, I was driving through a fast food restraunt and noticed that when I keyed up the SWR warning light lit up just barely. It quit doing it once i left the restraunt. Then, it did it again a few days later when I was at another restraunt area. I noticed that there was a small roof built over where my truck was parked and wondered if that was the reason.

If there is a roof of some kind over your truck and your antenna is close to it, can that sometimes cause your SWR to go higher?

[Gadfly]

Yes, that is likely the reason (being under a roof or cover). Often these things are metal which CAN drastically affect SWR. I would avoid transmitting while under a drive-thru or other roof. It is even possible for other trucks (while driving a tractor rig) to do the same thing at times. It is not a huge problem since you say it only happened when going under or around a drive-thru restaurant.


GF

[Turbo-T]

If there's any metal close to the antenna it can do it. I.E. you could be parked next to a metal light pole with nothing else around and key up and the reflection off the light pole could cause the SWR's to go up.

[clantonman1983]

Originally Posted by Gadfly

Yes, that is likely the reason (being under a roof or cover). Often these things are metal which CAN drastically affect SWR. I would avoid transmitting while under a drive-thru or other roof. It is even possible for other trucks (while driving a tractor rig) to do the same thing at times. It is not a huge problem since you say it only happened when going under or around a drive-thru restaurant.


GF

Thanks for the civil replys.

[Flying Dutchman]

Yes, walls, light poles, trees, power lines and any other large physical obstruction can raise you SWR. The best way to set it is a wide open space with nothing within 50 feet of you or more (getting harder and harder to do here in California!). Once everything is dialed in there, you are good to go. As far as talking on your radio barefoot (no amp) next to an occasional obstruction, that is not an issue. But I would not be talking on my amp with that warning light on, just to be safe!

[clantonman1983]

Originally Posted by Flying Dutchman

Yes, walls, light poles, trees, power lines and any other large physical obstruction can raise you SWR. The best way to set it is a wide open space with nothing within 50 feet of you or more (getting harder and harder to do here in California!). Once everything is dialed in there, you are good to go. As far as talking on your radio barefoot (no amp) next to an occasional obstruction, that is not an issue. But I would not be talking on my amp with that warning light on, just to be safe!

What can happen if you use your amp while the warning light is on?

[Turbo-T]

You run the risk of destroying it.

[Flying Dutchman]

You will smell a certain smoke that you never want to smell again. It means you toasted your amp, and your out a bunch of money to repair or replace!

[WA4GCH]

Try this .....

Put a dummy load ( not your mother-in-law ) on the radio

CHECK SWR IT SHOULD READ ALMOST 1:1

I always then use a 100 OHM resisror wired into a pl259 for this next test .... HOWEVER YOU CAN USE A 24 OR 27 ohm resistor too .....

CHECK SWR WITH THE 100 OHM PL-259 LOAD

It should read about 2:1

If your meter reads this it is WORKING .......

[Hardlyevr]

Always be careful to NEVER let out the magic smoke, that's what makes your radio really work!