Question about Cobra 29 LTD CB Radio
Posted by Anonymous on
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Posted on Jan 02, 2017
SOURCE: cobra 29 delta tune
For normal operation, set this control to the center position.
This feature has several uses and can help receiver operation.
If a received signal is slightly off frequency, the Delta-Tune control can be used to òfine-tuneó your receiver. Fine tuning is accomplished by listening for a more readable signal at the speaker or by noting the Smeter reading when the Delta-Tune control is operated. Another use of this control is eliminating adjacent interference (bleed over from other channels). If an exceptionally high level signal from an adjacent channel is creating interference on the channel being used, the Delta-Tune can be used to minimize or eliminate the interference. Rotate the control until you obtain minimum adjacent channel interference. NOTE: Delta-Tune is operable only in the receive mode.
It doesn't actually help receive any better, just can help kinda like a clairifier.
Mt. Vernon, TX
Posted on May 22, 2008
Wow. That's not at all a solution to what this guy is asking. And why all the caps??
The one point jm77437 has that is correct is that you do not set the radio, you set the antenna. The rest is blah blah.
Here is how you tune your antenna for you radio. First off it depends on what kind of antenna you have. most fiberglass antennas have a tunable tip to adjust the height of the antenna. Metal whips either have a collar at the base that the whip will either slide up or down in to adjust the height. The other type of metal whip's you have to physically clip to shorten the antenna, you must be careful with this type because once its clipped, that's it. You cannot add what you cut off.
I am going to give this example using a metal whip with an adjustable collar.
First after your radio is hooked up in the vehicle, drive to an open lot. Buildings and other structures can cause extra reflection. turn to channel 1. Flip the meter to CAL. Key the mic without talking. Now turn the CAL knob up until the needle reaches the little upside down triangle all the way to the right marked CAL. Now you have just celebrated your radio for your setup to measure you SWR. Now while still holding the key, flip the meter switch to SWR. The needle will move, and where it stops is your SWR reading. The lower the better. Anything under 1.5 is considered really good. But still, the lower the better.
Make note of what your SWR was on ch 1.
Now flip to channel 40. Repeat the SWR process. You must recalabrate each time you take a reading.
Now like jm77437 said. If your SWR reading is higher on 40 then 1, then your antenna is too long, and you must make it shorter. Loosen the collar and lower the antenna in the collar 1/4 inch at a time. check the swr each time you adjust the antenna.
If your SWR reading is higher on channel 1, then your antenna is too short. You must make your antenna longer. Do this by loossening the collar and pulling the antenna upward in the collar 1/4 inch at a time, again checking the swr each time you adjust the antenna.
What you want to achieve is having the same SWR reading on channel 1 and 40. then you have the best match you are going to get with that antenna.
If your swr is under 1.5 on all channels, you don't need to fuss unless you are a perfectionist. then by all means go ahead.
If your reading is higher then 3, or your ant light comes on, something is really wrong. Make sure your antenna is connected all the way, and the coax is not damaged.
Its important to have an appropriate SWR because if you do not, you are reflecting too much signal back into the radio, and eventually you will burn out your final transistor, and your radio will be toast.
Some tips: make sure you check the swr with the doors and windows shut. Make sure you are in an open lot. Remember to calabrate ecah time you take a reading. If you have had your radio peaked by a radio shop, and they have lowered your dead key, or have done a swing modification, then the meter in your radio will not work when taking an SWR reading and you will have to use an external meter.
Posted on Apr 24, 2009
SOURCE: cobra 29 ltd classic ant light
Your SWR is probably NOT fine. You need to use an external meter if you have had work done to the radio. Especially if you have had a swing mod done to the radio. When you do this, the dead key of the radio is lower then the calibration knob on the radio can adjust for. It will always come up lower then it actually is.
Your radio might have been fine before the work was done on it because it was putting out very little power. Now you are most likely putting out 50 watts or more. Big jump from 4 watts.
When your raise the power in a radio, you will notice more when the antenna is not properly tuned.
In most cases with a stock CB, even when the antenna is not even near tuned, you will get a reading less then 1.5 anyway.
the more power you put out, the more important it is to have a good match.
But an external SWR meter, and check it. be careful if the ANT light is on.
You might also want to check your coax, connections to it, and your antenna for anything wrong.
Posted on Apr 24, 2009
Only a qualified technical person is allowed to do so per FCC, (Federal Communications Commission). That means what it says. If you are not one, then you cannot do this procedure....hope this helps....
Posted on Mar 12, 2010
SOURCE: how do i tune my cobra 29
Depends on what you mean by "Tune"
If you are talking about aligning the radio, you need the factory service manual, a watt meter, volt meter and oscilloscope to align the radio.
If you are talking about a peak and tune, that all depends on what you want. If you are just trying to peak it out, the easiest thing to do with out having to know about what you are doing is to turn the modulation to max. In that radio you do that by turning VR4 all the way to the left. That will get you around 20 to 25 watts of modulation.
There is more you can do, but it gets technical. But over all you will be pleased with just the modulation increased.
Some times people have the radio tuned to be run on an amp, which is necessary so that you do not blow up the amp. This involves un-soldering parts and replacing them with other parts to achieve the desired dead key.
Posted on Oct 21, 2010
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