My SWR makes no sense.

[N8N]

So I finally got around to "installing" everything in my car (consisted of running the antenna wire and putting a lighter plug on the power cord, I still haven't actually mounted a radio yet) - got a Cobra 29 NW/WX/ST/whatever (everything but bluetooth, basically) used 'n' cheap off "a certain auction site" and a little wil antenna on the trunk lid. So I slap it on and fire it up and took the long-ish way home so I could get on the Interstate. Did pick up some chatter on 19, WX works great, haven't tried tx yet. When I check SWR with the built in meter it appears to be great - barely over 1 on 1, 19, and 40. (easier to check that way than 1, 20, and 40 when you have a switch for 19) Hooked up my cheap Para Dynamics meter and it says that my SWR is awful - about 2:1 on one end and over 3:1 on the other (forget which way) now here's the funny thing, when I check the SWR at the CB's meter with the external meter hooked up, I'm also getting bad SWR's - not as bad as the external meter indicates, but 1.5:1 to over 2:1. So basically I don't know what the heck I'm doing now. (I never have adjusted the length of the antenna; when I checked SWR on my cheap Uniden CB with my external meter, it appeared to be OK.)

Soooo... any ideas why this might be happening?

I think I will just try to get my butt up and over to the CB store tomorrow even though it is a 30 mile drive, just because a) now that I have two CBs, I ought to have two antennas, for convoying on road trips etc. and b) it might be time to have someone that knows what they're doing take a look at this. But I thought I'd just post and see if anyone had any bright ideas.

I did meter out the antenna connector thinking I might have pinched something, but no, it measures about 2,000,000 ohms center to shield. (using my trusty old Simpson 260) That was about the extent of my bright ideas for troubleshooting.

I also noticed that according to my meter I'm DK'ing at about 9 watts or so... either there's something more than just a "peak and tune" going on here or else I really can't trust this meter...

One thing I found odd was the *lack* of chatter... only really overheard one clear conversation the whole way home from work and that was on I-66. that and a prerecorded announcement telling truckers not to use the right lane between certain mile markers because of bridge damage. That certainly was reassuring... <G> I was pretty much sitting on 19 because I figured that would be where most of the action was. I don't have any previous experience with CB so I'm not really sure what to expect; just wanted to have two good working rigs for driving long distances with another car around and also to get a heads up for traffic, weather, smokeys, etc. Noticed the same thing last weekend with the Uniden in the car - only time I really picked anything up was actually driving through DC...

[heavyD]

Sounds to me that likely the connection, the jumper coax, or the meter itself could be doing you wrong. If you have no experience with radios my recommendation would be take it to a tech..this kind of thing could be simple or complex. If it were me I'd try another piece of coax first

['Doc]

What you are seeing, the internal meter not agreeing with the external meter, is fairly common, it happens quite a lot. What most people do is take that external meter's word for things instead of the internal meter's. That assumes that the external meter hasn't been 'diddled' a bit, is of typical/normal quality, and if you do know how to use it correctly.
One solution is as you suggested, take it to someone who is familiar with all this stuff and see what they say. Another solution is to substitute various things to see what happens, what might correct the 'problem'. One result of that substitution method is that you tend to acquire various extra 'parts', the ones not producing any benefits are always nice to have around for doing this sort of thing again later, maybe. (Typically how 'junk boxes' are built up! The really good guessers usually don't have a 'junk box'. )
I won't try to make a guess at what your problem is, there are just too many variables here. I think that since the radio seems to have been 'peaked and tuned', and that everything is 'used' anyway, there are just too many possibilities for an accurate guess.
Good luck!
- 'Doc

[231]

Yea, I'd be inclined to agree that there are too many variable to consider here. The biggest to me is the fact someone has already been in the radio and the fact you really don't know it's history (other than what's been shared with you by the seller). This is part of the reason why so many of us take the internal SWR meter's with a grain of salt most of the time and prefer external meters. The horizontal s-meter on the Cobras has been known to be problematic ever since I've been using them (especially in the older rigs). What I usually do is trust the external meter WAY before the internal, and merely use the internal as a second reference point...nothing more.

Best of luck.

[N8N]

Forgot to follow up. I did stop by the CB shop Sat. and now I am shopping for a new SWR meter. guy said it was off (and tuned the antenna,) so the one in the Cobra wasn't right, but I checked it with my own external meter when I got home and on that meter it read way high, so it disagrees with his meter too...

[jopcobra89]

Yeah... forget that Para Dynamics meter. The one I own shows very generous dead key readings averaging 3 to 5 watts higher than my trusted meter. I purchased several cheap used radios over a short time period and thought I had gotten lucky since each one seemed peaked and tuned on the PDC meter... but my new Radio Shack AVG / PEP meter shows them all putting out the customary 4 to 5 watts.

I have to admit I do like the built in tuner function in the PDC5. The meter is only good for rough ballpark figures... but the tuner does wonders when you're running a "less than adequate" antenna.

[North Texas Mudduck]

there you go just throw up an antenna and slip a tuner inline
same antenna same coax nothin gdone to antenna
just something stuck in the middle to lie to the swr meter
bottom line is the problem is still there

wanna check it out

try this
radio into swr meter out to antenna tuner out to a swr meter to antenna
set the tuner to lwest swr and wow its nearly flat swr in the first swr meter then the swr meter going to antenna is still the same swr when it was installed

['Doc]

Tuners don't change anything with the antenna system, feed line or antenna. They do act as an impedance transformer and converts whatever the combined impedance of that feed line and antenna to something closer to what the transmitter want's to see. That's the whole point to using a tuner. (Same basic idea with using a transformer to convert 120 vac to 12 vac so you can rectify it and have 12 vdc. There are losses involved, but those losses are going to be less than trying to use 120 vac straight to a 12 vdc device! Same with antennas and impedance.)
Now, if you could put that tuner at the feed point of the antenna, it's exactly the same as using a gamma, delta, hair-pin, whatever device to tune that antenna. Usually a bit harder to reach to re-tune if needed, but...
- 'Doc

And then there's always those auto-tuners. They aren't a 'cure-all' by any mean$ but they certainly do make thing$ ea$ier.

[heavyD]

$itting here thinking about what you $aid about tho$e auto tuner$. $o are the are the$e tuner$ rea$onably priced? Rhetorically speaking of course

[N8N]

well I bought a RS meter and it makes much more sense now. Damn near 1:1 on CH1, about 1.2:1 on 19, about 2:1 on 40. will check again with shop next time I'm in Manassas but I think I just had a crappy meter

['Doc]

heavyD,
That's a good question, that you will have to answer for your self. I don't have a stand-alone auto-tuner. I do have a manual tuner and think it's just a dandy thing to have around. So far, I've been able to load dang near anything I can connect to it. That doesn't mean those 'things' are any good as antennas really, but I can make them work.
I think the 'LDG' brand is an up-n-coming one, sorry, no idea about prices. I do know they will be considerably more than what I gave for the manual tuner. It ain't easy being this cheap you know!
- 'Doc

[heavyD]

Sounds to me that likely the connection, the jumper coax, or the meter itself could be doing you wrong. If you have no experience with radios my recommendation would be take it to a tech..this kind of thing could be simple or complex. If it were me I'd try another piece of coax first

BTW. I TYPED THIS FOR A DIFFERENT THREAD, NOT THIS ONE...WEIRD