WTF SWR

[roadrage]

I am getting frustrated. I bonded my truck last night and my SWR went off. I retuned my antenna but my radio meter is making me nervous.

I'll try to make this as non-confusing as I can. My extenal meter is showing a hair under 1.2 on Ch 1 & 40. When my external is taken away my radio's SWR meter shows 1.6 on ch 1 and 1.8 on ch 40. I click over to PWR and it shows a 20W DK. I hook up the external meter again and it shows the same SWR as it did earlier, 1.2 on Ch 1 & 40. The radio's meter drops its SWR reading to 1.5 on Ch 1 & 19 & 40. I click over to the PWR and it reads 32W DK (like it should). Why does my SWR seem to rise without the external meter hooked up? I know that the internal meter isn't accurate, but the power meter seems to see the difference as well. Without the external meter hooked up, the radio smells like its getting hot. Even the talkback is quieter than normal, just like as if I'd turned down the variable power. What the hell?

I checked SWR in a field, no nearby objects, all doors closed, the allen wrench wasn't left in the set screws either.
I am throwing that Wilson in the basement and putting up a 102" antenna. That ball mount can't get here fast enough. Freakin Wilson is probably made by barjan these days, like everything else, and turned to junk. I hope its the antenna system being faulty and not something with the radio. I can't afford to send this thing out again.

 

[oldslowchevy]

radio swr are never very good, if your radio has been modded then the radios meter may really be off. always go by the external swr meter.

 

[roadrage]

radio swr are never very good, if your radio has been modded then the radios meter may really be off. always go by the external swr meter.

I know it isn't the tune. It was done at DTB. I trust his work explicitly. It just came back. Everything was fine until I bonded my truck with grounding straps. Like I said, it isn't just the meter. When the external is not hooked up, my talk-back is quieter, my DK is dropped by 1/3, and my radio gets hot. I don't think its as simple as trusting the other meter. I literally have to keep it in-line, for some reason. As far as radio mods, its factory spec is 50W carrier and 150W peak. Mine is set for 32W carrier and peaks 150W. It isn't like its a Radio Active special. Something strange is afoot.

 

[Mudfoot]

I wouldn't trust the radios bridge. I would be looking at coax and connectors, also inspect the rigs SO-239. Try another rig.

 

[TonyV225]

I also always go with the external SWR meter readings I would take an SWR meter and hook it up right after the radio and double check that way

 

[reddog45]

Also if you know anyone with an analyzer like an MGM model. They are the way to go in my own opinion. I have the model 249.

 

[Captain Kilowatt]

In my 35 years of radio I have never really found the internal SWR meters to be that far off really so apparently I am in the minority. One thing to consider when looking at an internal and external meter at the same time and seeing two different values of SWR is that if the antenna is not a pure 50 ohms then the SWR will appear to be different values at different points along the transmission line. Since the external meter is not located at the same point as the internal meter they will read different values. You will see the same thing if you simply insert an extra couple feet of coax cable.I suspect that the internal meter is fine and is simply measuring the SWR at whatever point it is in the circuit. If you insert another meter inline then the point where the internal meter is gets changed and thus the SWR reading will change.

 

[reddog45]

Sorry. Spell check got me...meant to say MFJ!

 

[Mudfoot]

In my 35 years of radio I have never really found the internal SWR meters to be that far off really so apparently I am in the minority. One thing to consider when looking at an internal and external meter at the same time and seeing two different values of SWR is that if the antenna is not a pure 50 ohms then the SWR will appear to be different values at different points along the transmission line. Since the external meter is not located at the same point as the internal meter they will read different values. You will see the same thing if you simply insert an extra couple feet of coax cable.I suspect that the internal meter is fine and is simply measuring the SWR at whatever point it is in the circuit. If you insert another meter inline then the point where the internal meter is gets changed and thus the SWR reading will change.

I agree with your entire post. I have always noticed most internal meters to be fairly accurate, even on CB rigs. if I noticed the meter acting flakey, then I usually would not trust it. I have only had/noticed problems with the 2950/2970 flavors. They just never seemed to be consistent. I just don't trust them to make excursions up and down from a known resonance.

 

[W5LZ]

Leave the jumper used with the external meter in-line, just remove the meter it's self (barrel connector). What does the internal meter say now?
I'd recommend using that analyzer any way. If that jumper added to the feed line makes the SWR meter in the radio appear 'happy', then it means the antenna isn't tuned correctly. The reason to find that analyzer...
- 'Doc

 

[Zman]

just sell everything and use your cell phone. Ive always had issues getting a mobile installation to work.....

 

[Mudfoot]

Lol

 

[roadrage]

I also always go with the external SWR meter readings I would take an SWR meter and hook it up right after the radio and double check that way

Its a radio only. No external amplifier. What I don't get is why my radio's power meter gives me a lower reading without the external SWR meter inline and a higher reading with it. The radio's SWR meter reads higher without the external meter inline, it reads lower with it inline.

Before I bonded my truck, my radio's SWR meter read 1.4 on ch 1 & 40 and 1.2 on 19. The external meter was reading 1.1 on ch 1 40 and it didn't move on 19. Now, the radio meter shows 1.6 on ch 1 and 1.8 on ch 40 with the radio hooked directly to the antenna. With the external meter inline, the radio's meter changes to 1.5 on ch 1, 19, & 40. The external meter reads 1.2 on ch 1, 19, & 40.

Is the radio chassis being grounded to the truck body, via the bracket bolted to the floor, a bad thing? I have always been under the impression that it was a good thing. Maybe I should try putting some rubber tubing over the thumb screws and a rubber gasket between the bracket and radio. This same thing happened when I installed my new 9" bracket and bolted it to the floor. The only thing different was that it was corrected when I took apart the Wilson, cleaned all connections with a wire brush, and retuned my antenna. It has been fine until I installed the ground strap bonding of my body panels. Only, this time, I can't seem to get my radio right without the external meter inline. If I take away my external meter, the radio gets hot and smells hot, the talkback gets quieter, and my power meter reads lower. For now, I am leaving it inline until this problem gets solved. Something is causing a mismatch that is corrected when I add the external to the mix. Maybe just having there with the jumper is whats making it happy. At the very least, it could be fooling my radio; and any reflected power is going into the meter instead of agitating my finals? I am going to try to change out the coax on my Wilson to the RG58 I have, currently, on the base. Maybe I am getting a bad connection to the radio's SO239, as already stated in m24duster's reply. I'll see at lunch. I wish I had an analyzer. It would make my life easier.

 

[roadrage]

Leave the jumper used with the external meter in-line, just remove the meter it's self (barrel connector). What does the internal meter say now?
I'd recommend using that analyzer any way. If that jumper added to the feed line makes the SWR meter in the radio appear 'happy', then it means the antenna isn't tuned correctly. The reason to find that analyzer...
- 'Doc

I would buy one if I could afford it. I don't know anyone who would have one either. Someday I'll have one, but that doesn't exactly help me out now, lol.

I will try the barrel connector between the coax and jumper. I have to have it shipped so it will take a couple days. Closest radio shack is 65-70 miles away, so ebay it is.

 

[W5LZ]

Buying an antenna analyzer isn't all that practical for most people. If you do more than casual antenna work, then it's certainly worth it. If not, don't waste your money for a 'one shot' thingy.
If it were black/white with no shades of grey, then the best device for tuning an antenna is the one that tells you the most pertinent information. There's so much gray in antennas that unless you are really serious about tune them, an analyzer is just too expensive.
I like playing with antennas and have played with enough so I think an analyzer is worth having. If I didn't do that much 'playing', I certainly wouldn't buy one (borrow one instead!). You have to decide for your self.
- 'Doc