Cobra 29ltd classic antenna light coming on

[phic4538]

Have a cobra 29 ltd classic that when I key up antenna light is coming on. I have checked antenna grounding an everything. Even put a spare radio in the truck to make sure that the setup is good. It just happens with this radio?? Any help would be appreciated!!

[Slyguy]

What's the SWR looking like?

[phic4538]

Believe it was around 3 to 4. I replaced coax and antenna aswell to make sure

[sonoma]

running 3 to 4 swr is why the light is coming on. it is set at the factory for around 3. better get the swr down to 2 or less. the lower the better. I try for 1.5 on my radios or lower.

[MDYoungblood]

Hello phic4538,
Welcome to the forum. I hope you aren't depending on the SWR meter in the radio. Get a good external meter and adjust the SWR to less than as close to 1:1 as possible. You never mentioned what antenna you are using.
As a new member could you post an intro in the "Welcome to the Forum" topic, [Please login or register to view this link], so other members can say "Hello", thanks.

3's

Greg

[MDYoungblood]

After you get the SWR problem with the antenna done a "poor man's" way of adjusting the antenna warning light is to purposely detune the antenna (mark it so tuning it back to 1:1 is easier) to 2:1 on channel 19 or 20 using a reliable SWR meter and adjust VR6 on a Cobra 29LTD so the light just comes on at 2:1.

3's

Greg

[Deleted User 14541]

A 25 or 100 ohm resistor used as a dummy load will simulate a 2:1 swr. There's not a thing wrong with the internal swr meter in that radio. It may not have super accuracy but tune the antenna so the swr is as low as possible and that's the best you can do. It may show 1.5:1 and your external meter may show 1.3:1 but if you've already tuned it as low as possible what else are you going to do?

Most external meters marketed towards cb are pretty crummy. If you want super accuracy buy an antenna analyzer or use a bird meter to measure reflect. If you want to test the accuracy of an swr meter you can do so with an old coax jumper and some resistors. Cut an end off the jumper. And connect the center and shield to a 50 ohm resistor you should see 1.1:1. With a 75 ohm you should see 1.5:1, with a 100 ohm you should see 2:1, with a 150 ohm you should see 3:1. Use 2 watt carbon resistors and only your radio...no amplifier or high power radio unless you have big enough resistors to take the power. Don't stay keyed for too long as the resistors will heat up. Just key long enough to calibrate and get a reading.

[TheCBDoctor]

Have a cobra 29 ltd classic that when I key up antenna light is coming on. I have checked antenna grounding an everything. Even put a spare radio in the truck to make sure that the setup is good. It just happens with this radio?? Any help would be appreciated!!

Good morning phic4538,

Your radio was "Peaked and Tuned" which means D-11 is cut or VR-4 was adjusted to disable the audio limiter. The SWR meter on the original Cobra 29 LTDs work fine. Well enough to determine if you have problems with your antenna system. You need to readjust the "Idiot light"

The adjustment is the variable potentiometer at the very right rear of the radio (VR-6). Adjust it counter-clockwise until the "Antenna warning indicator" stops coming on. This circuit has no affect on the calibration of the radio's built in SWR meter, which despite what others may believe is fairly accurate in the older models.

The new LX digital series has issues and I would not depend on that radio's SWR meter.

Respectfully

[phic4538]

Thanks for all the advice!! Planning on tuning the antenna which has never been done on the antenna which is a steel whip 120" I believe is the length on it.. Will post results

[795]

Where is the antenna mounted?
DOCTOR/795