Cobra 29 LTD Antenna Light - VR6 has No Effect

[rocknbil]

In reading I understand these radios are not what they used to be but I got it as a gift. I've been almost 3 months just trying to get it to work. :-\

This is a vehicle install. The Antenna light stays lit on keyup. I have a 4' Firestik FS in the truck, 18' coax, checked continuity/shorts including end-to-end of the coax itself, ground wire on mount, everything should be in order on the antenna end. All parts are new. I get an SWR reading barely at 1 to 1.5 (yup from the built in) but the antenna light shines bright on keyup.

I tried this fix from Cobra, but adjusting the VR6 pot has absolutely no effect. Turn it left, turn it right, nada, light stays bright. Among my meanderings I read that it's just that, a warning light, and it should be fine and ignore it. Can anyone confirm that? As mentioned the "close enough" internal meter shows under 2.

Imma bouta toss dis ding under a door for a door stop. :-D

 

[K9KLC]

Have you checked the SWR with a different device?

 

[WSAC829]

If the SWR checks out fine on an external SWR meter i’d just run it as is. Then maybe cover the warning led with a small cut circle of electrical tape to rid you of the annoyance.

 

[rocknbil]

Have you checked the SWR with a different device?

I don't have an external meter. I have dumped way too much money on this project already and my "financial manager" is giving me that look, you know the one.

I do have an IBA-5 5' antenna intended for a home station that I used to compare/bench test the cobra. Same result.

It really shouldn't matter though. The antenna is disconnected during the test, the light should go out on one side of the pot or the other and it doesn't.

 

[K9KLC]

I don't have an external meter. I have dumped way too much money on this project already and my "financial manager" is giving me that look, you know the one.

I do have an IBA-5 5' antenna intended for a home station that I used to compare/bench test the cobra. Same result.

It really shouldn't matter though. The antenna is disconnected during the test, the light should go out on one side of the pot or the other and it doesn't.

Ok. That test precludes that the antenna is in an "open state". I am not sure if the actual antenna was more towards the "shorted state" what would happen, but...carry on. If the final shorts out then, you're out a radio if the SWR circuit is actually working. "The financial manager" will probably like that too, I know mine always loves when things go out and I have to spend money parts and such. If you feel the radio is faulty, return it and try another one if it's only 3 months old.

 

[rocknbil]

If you feel the radio is faulty, return it and try another one if it's only 3 months old.

Well there's the thing. Immediately after Christmas tried to register. The registration form does not load on their site. Contacted support. The dopes send me a link to the same form that does not load. As a web developer of over 25 years this kind of crap really burns my tail. I basically can't register this product because some button-pushing dumbass out there says "it's working fine, it's your problem" and drives off in their BMW.

When the light won't go out, I call support. They need a proof of purchase to return, the time has passed and all wife's emails and orders no longer exist, so I'm stuck with a door stop if it breaks. It wouldn't matter anyway, the only thing they would do is replace it with the same model.

This question is just about the warning light. I know it's only supposed to light if the SWR is over 3, The problem is I haven't even gotten to the point of testing anything due to all these stupid little issues. I can fiddle with the SWR meter by setting the calibration way off and see the difference, so I'm pretty confident the actual SWR is "close enough."

 

[K9KLC]

Well there's the thing. Immediately after Christmas tried to register. The registration form does not load on their site. Contacted support. The dopes send me a link to the same form that does not load. As a web developer of over 25 years this kind of crap really burns my tail. I basically can't register this product because some button-pushing dumbass out there says "it's working fine, it's your problem" and drives off in their BMW.

When the light won't go out, I call support. They need a proof of purchase to return, the time has passed and all wife's emails and orders no longer exist, so I'm stuck with a door stop if it breaks. It wouldn't matter anyway, the only thing they would do is replace it with the same model.

This question is just about the warning light. I know it's only supposed to light if the SWR is over 3, The problem is I haven't even gotten to the point of testing anything due to all these stupid little issues. I can fiddle with the SWR meter by setting the calibration way off and see the difference, so I'm pretty confident the actual SWR is "close enough."

All I can say is good luck at this point. In the 90's we had a few of those come in with erratic SWR lights, frankly only one was narrowed to a radio problem, the rest antenna system issues. Like you said, 'these days' things are lacking somewhat in quality control so it wouldn't surprise me that it was a radio problem. Again, good luck to you getting it sorted out, sorry I can't be of more help.

 

[prcguy]

You need to prove the radio is actually broken by using a good 50 ohm load to simulate a perfect 1:1 match and maybe a 2:1 match with two dummy loads on a T connector. Since you diddled the VR6 all factory settings are out the window but if you can turn VR6 so its off with a good 50 ohm load on the radio and have it just go on with two loads on a T adapter then the radio is capable of working fine.

This type of test would eliminate potential problems in your vehicle like inadequate ground plane and hot RF on the coax which can mess with SWR sensing circuits.

 

[rocknbil]

sorry I can't be of more help.

No this is all very helpful, thanks. I have seen at least three posts indicting it can be safely ignored, not a lot but enough to make me wonder . . . I've located a couple schematics for this radio, I might try to sort it out later and chase it down myself.

 

[K9KLC]

You need to prove the radio is actually broken by using a good 50 ohm load to simulate a perfect 1:1 match and maybe a 2:1 match with two dummy loads on a T connector. Since you diddled the VR6 all factory settings are out the window but if you can turn VR6 so its off with a good 50 ohm load on the radio and have it just go on with two loads on a T adapter then the radio is capable of working fine.

This type of test would eliminate potential problems in your vehicle like inadequate ground plane and hot RF on the coax which can mess with SWR sensing circuits.

And likewise, show the antenna system is good. I've seen a lot of good SWR on radio's built in stuff and not so good on a more accurate device and yes, "hot coax" is a thing that many don't realize.

 

[rocknbil]

So as mentioned, doing the VR6 adjustment per the manufacturer the light simply wouldn't go out. Gave up, put the unit back in the truck, pulled it out of the garage, cal'ed the SWR, hit transmit . . . .

No antenna light. At this point I can only presume the A.L. adjustment provided by the manufacturer is incorrect or this radio is just plain buggy. Or it's specifically designed to drive me up the wall before it makes any sense. Either way, I'm guessing the light is more unreliable than the internal meter.

Since you diddled the VR6 all factory settings are out the window

Unless a guy has the foresight to mark it before changing anything. I've taken apart so many complex auto parts and done enough hobby electronics I learned the hard way how to avert disaster (in this respect, anyway.)

Thanks again everyone, sometimes it just helps to walk through it, let's see if I can get any response now on my new pony express. (See . . . it took me three months, average mail time in the wild west was 1-3 months, okay not really funny but . . . )

 

[Chris155]

So as mentioned, doing the VR6 adjustment per the manufacturer the light simply wouldn't go out. Gave up, put the unit back in the truck, pulled it out of the garage, cal'ed the SWR, hit transmit . . . .

No antenna light. At this point I can only presume the A.L. adjustment provided by the manufacturer is incorrect or this radio is just plain buggy. Or it's specifically designed to drive me up the wall before it makes any sense. Either way, I'm guessing the light is more unreliable than the internal meter.



Unless a guy has the foresight to mark it before changing anything. I've taken apart so many complex auto parts and done enough hobby electronics I learned the hard way how to avert disaster (in this respect, anyway.)

Thanks again everyone, sometimes it just helps to walk through it, let's see if I can get any response now on my new pony express. (See . . . it took me three months, average mail time in the wild west was 1-3 months, okay not really funny but . . . )

The most important step in putting something together is taking it apart correctly. I learned that very early on working on transmissions.

 

[mmckenna]

The most important step in putting something together is taking it apart correctly. I learned that very early on working on transmissions.

On the other hand, if you take something apart and reassemble it enough times, you eventually end up with two of them.


I'd find someone with either an SWR meter or a 50Ω load and try setting this correctly. Sounds like the OP is assuming the antenna is tuned properly and using that to adjust the sensor for the antenna warning light.

 

[niceguy71]

In reading I understand these radios are not what they used to be but I got it as a gift. I've been almost 3 months just trying to get it to work. :-\

This is a vehicle install. The Antenna light stays lit on keyup. I have a 4' Firestik FS in the truck, 18' coax, checked continuity/shorts including end-to-end of the coax itself, ground wire on mount, everything should be in order on the antenna end. All parts are new. I get an SWR reading barely at 1 to 1.5 (yup from the built in) but the antenna light shines bright on keyup.

I tried this fix from Cobra, but adjusting the VR6 pot has absolutely no effect. Turn it left, turn it right, nada, light stays bright. Among my meanderings I read that it's just that, a warning light, and it should be fine and ignore it. Can anyone confirm that? As mentioned the "close enough" internal meter shows under 2.

Imma bouta toss dis ding under a door for a door stop. :-D

I would post some pictures of your antenna install, the guys here are pretty good at spotting something out of whack.
on the FireStiks they ALWAYS tune pretty good on SWR..... I just checked the SWR on my friends truck a few weeks ago and got a 1.6 SWR...... but it wouldn't work more than two miles and wasn't receiving very good????
so I had him pull it in my garage... I found the mounting bracket wasn't bonded to the truck's body panels ... he had screwed the bracket in with little screws and didn't grind the paint off the truck......
what was happening was the antenna didn't have a ground plane because RF will not travel to body panels of the truck through little screws and paint..... so the antenna was using the coax as a ground plane.... it obviously didn't have a ground plane... but it still showed me a good SWR on my $400 antenna analyzer.
so even though the radio shows a good SWR, your antenna may not be working.
the bottom of antenna must be grounded to the bracket ( GROUND ALL THE POWDER COATING OFF ).... the bracket must be RF grounded to the body.... using larger bolts and lots of bare metal.... the antenna has to have lots of flat metal under the antenna to work. ... don't have the bracket lower than the metal you're using for a ground plane.

if you mount the firestick to the bed rail.. it really doesn't have much metal under it.. the bed rail is only about 3 inches wide. and if you have it near the back glass of the pick-up like on a tool box... it will kill it's performance.

as I've said before I HATE FIRESTIKS... I've never gotten one to work... NEVER!... 2 miles range is the best I ever got

when my friends buy a CB they ALWAYS get a Firestik????... they spend $25 bucks and expect it to work??? then when it won't work, they come over my house and ask me if I can get it to work.
I normally let a friend try one of my spare Tram 3500 magnetic antenna's and send them out 10 miles for a range test as I talk to them on my base station... they get 6 to 10 miles range generally and come back after the test and usually throw the Firestik away!!
you can get a Tram 3500 for $69.99 at amazon and your 2003 Tacoma has a steel roof.. it would be simple and easy and a good test to see if your radio is working... once you know your radio is working and your talking back and forth with people... then you can always go back to trying to get your Firestik to work
Tram 3500 at Amazon for $69.99
or for $48.00 you could try a Wilson "LiL WiLL" antenna they seem to get 3 to 4 miles but it would be a cheap test to see how the radio is working.... but for another $22 bucks I would get the Tram 3500.....
for $69.99 it would stop you from all the hair pulling frustrating problem hunting!

I personally think the Tram 3500 would far outperform your Firestik..
if you have to pay more than $75 bucks for the Tram... then get something better... but for the price it will work good for you.

for a CB to perform really well you want your antenna in the center of a lot of metal... like the roof.... the antenna sitting next to a fender or on a bumper or on the bed rail... only has a few inches of metal for a ground plane to reflect the signal.... VS the 5 or 6 feet of metal that the roof has!!!!

or if you want, you can do as WSAC829 brilliantly said put black tape over the light ( I'm kidding don't do that.. the light is telling you your antenna system is not working correctly ) people only try to adjust the light setting because they didn't realize there is a problem with the antenna system... if they only put a good magnetic antenna on the center of the roof they would KNOW it's not the radio warning light!
(99% of the time )
looking forward to the pictures of your antenna install.

I put my Tram 3500 in the middle of the roof and have the coax hanging into the bed.... DON"T go between the bed and the cab ...... in the corner of a pick-up bed is a plastic drain plug ( usually) I drilled a hole in the plastic drain plug and stuck a gromet in it and siliconed over it... then I drilled a hole in the back of my cab... painted the bare metal ( I only had grey paint) put a gromet in it and siliconed over it.... now when I go through the car wash, I can unstick the magnet from the roof and lay it down on the floor of the bed and stick the magnet to the back of the bed to keep the magnet from picking up metal and rolling around in the back of the bed...... this way the coax is not on the bed rail where it could get sucked up in the car wash brushes...... works great for me.... hope this helps.

 

[WSAC829]

you can do as WSAC829 brilliantly said put black tape over the light

Dude….. can you READ? I said if the SWR checks out on an external SWR meter then run with it. Then cover the warning led with tape if it gets annoying.

 

[rf_patriot200]

In reading I understand these radios are not what they used to be but I got it as a gift. I've been almost 3 months just trying to get it to work. :-\

This is a vehicle install. The Antenna light stays lit on keyup. I have a 4' Firestik FS in the truck, 18' coax, checked continuity/shorts including end-to-end of the coax itself, ground wire on mount, everything should be in order on the antenna end. All parts are new. I get an SWR reading barely at 1 to 1.5 (yup from the built in) but the antenna light shines bright on keyup.

I tried this fix from Cobra, but adjusting the VR6 pot has absolutely no effect. Turn it left, turn it right, nada, light stays bright. Among my meanderings I read that it's just that, a warning light, and it should be fine and ignore it. Can anyone confirm that? As mentioned the "close enough" internal meter shows under 2.

Imma bouta toss dis ding under a door for a door stop. :-D

The Antenna light is like the Oil light on your dash, which lights when your Cam, pistons, and valves are red hot and deforming due to Lack of lubrication... Uh Oh.

 

[rocknbil]

Thank you everyone, these are all good learning points and I am definitely paying attention, but this thread has gone way off topic. This adjustment provided by the manufacturer doesn't, or didn't, seem to have any effect. The point is moot, as mentioned when I put it back in the truck, no more antenna light. I don't know how or why but it has stopped.

Again, note that the manufacturer "fix" is done without an antenna. So I'm not sure why we're discussing the details of antennas.

I would post some pictures of your antenna install, the guys here are pretty good at spotting something out of whack.

Sure I can do that, it is bumper mounted and mount is grounded to frame. Appears to work . . . SWR on 1,20, 40 are all very close. Continuity test and resistance is < .003 on the ground. Mastech MS8268.

when my friends buy a CB they ALWAYS get a Firestik????... they spend $25 bucks and expect it to work???

It fits in the garage, that is why. It's also more than $25. In comparison and review of hundreds of articles, many that came from this very site, it was the best break-in option. I can always upgrade later.

or for $48.00 you could try a Wilson "LiL WiLL" antenna they seem to get 3 to 4 miles but it would be a cheap test to see how the radio is working.... but for another $22 bucks I would get the Tram 3500.....

There's a couple unimportant reasons I didn't get a roof mount, at least for now (1, I measured them out and it would hit the garage door pulling in.) I'll look at those for the next upgrade, maybe I can bury the costs so my "financial manager" doesn't notice. I'd like a 102" whip but unmounting/dealing with it every time I pull in the garage would get very troublesome, very fast.

But . . . none of this has anything to do with the Cobra antenna light when there's no antenna connected.

The Antenna light is like the Oil light on your dash, which lights when your Cam, pistons, and valves are red hot and deforming due to Lack of lubrication... Uh Oh.

Well that's a stretch. The oil light only triggers if the level is low, it's your temperature gauge you really have to look out for (I hate vehicles with just a light for temperature.)

Point taken, but I'm not so sure I agree. Given the flaky manufacture of this unit it wouldn't surprise me a bit if it's just a bell or whistle to impress consumers. It's only supposed to light if SWR is over 3, my SWR shows under 2.

As mentioned multiple times, this is about the manufacturer's fix for the light and why the VR6 has no effect. But then I put it back in the truck and no antenna light, all with SWR less than 2 across the spectrum.

Thanks again everyone, it's all learning so all good.

 

[K9KLC]

I do have one question, at some point you said you backed out of the garage and the light stopped coming on. Were you in the garage when the light was coming on and it was hooked to the antenna?

Regarding the initial question. I saw what you posted, and FWIW, I took a two 29s made in the Philippines and tried that adjustment with no antenna. One I got to finally go off and the other light never did go off adjusting that pot. When I hooked it up to two dummy loads on a t connector however (giving 25 ohms of impedance emulation or 2:1), I was able to make the light go on and off on both radios. (which I find odd). We had never used anything but the T back in the day to help get that set as I was always more worried about a more towards shorted connection rather than an open connection. I do seem to recall using a couple of 100 Ω resistors in parallel to emulate 2;1 on the open side but we never used that one too much. at times the way that circuit works, it was hard to get good balance between the two. We honestly didn't use that method much( the built in antenna test this was in the 90's) and used actual MFJ antenna analyzers to set SWR then, and when we had good SWR on the vehicles we did, the light never came on so we just went with that. We honestly didn't sell or service a whole lot of 29's back the day, the export stuff was already catching on but this is what I remember from way back then.

 

[rocknbil]

I do have one question, at some point you said you backed out of the garage and the light stopped coming on. Were you in the garage when the light was coming on and it was hooked to the antenna?

Hehe . . . no I said after I gave up trying to get the light go out, I threw the 29 back in the truck and turned it on for a sec, no light. Yeah it was in the garage but I pulled it out on the street to check the SWR, etc.

Regarding the initial question. I saw what you posted, and FWIW, I took a two 29s made in the Philippines and tried that adjustment with no antenna. One I got to finally go off and the other light never did go off adjusting that pot.

Thanks, that kind of confirms it's just a bug, even though those are the old ones.

<OT>
Not to divert the topic further, but I bring this up only as a testament to some flaky things about these. I came across the way they do "reverse voltage protection" on these and I think it's dumb. The N400 diode on the power in goes directly to ground. If reverse voltage is applied, it blows the diode (and fuse,) causing it to short to ground and requiring the diode to be replaced. I always do my electronics so the diodes actually protect against reverse voltage, doesn't blow anything but the unit just won't work until you get it right. Not quite sure why they used to "crowbar" approach, probably to contribute to the service industry.

Edit: a quick fix is to cut the diode, but would highly recommend against this, then the reverse voltage would definitely damage other components. Replace the diode.

 

[K9KLC]

Not quite sure why they used to "crowbar" approach, probably to contribute to the service industry.

It certainly helped the industry, that was used in most radios and still is. That being said, it "mostly" worked. I had a customer cut his when it shorted out and he hooked it up wrong again (like probably more than once) and did some pretty severe damage in the radio.

I always do my electronics so the diodes actually protect against reverse voltage, doesn't blow anything but the unit just won't work until you get it right.

That would be too easy, and also add a few bucks to the price. You know the old adage, "ain't broke don't fix it".