first of all im new to this site, guy from another forum referred me here, my names dillon, from southwest kansas, i have a cobra 29 and am looking at getting it tuned, needs a new mike, and im running it with a wilson 5000, but i havent cut my antenna to freq. yet
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CB tuning
- Thread starter fordfreak4life
- Start date
ya, i was wondering how much a cobra 29 could be tuned up, i have one thats about 2 years old and not used much, i need a new mike for it so would def like some suggestions on that, and living in southwest kansas who do i go to my tuning needs for? any ideas? thanks
dillon
The Astatic D104 is my favorite mic on any radio. The new RF Limited's CR-577 is an up-and-comer too. For a vehicle, the CR-577 might be better, as it is noise-cancelling. It won't be on the shelves for another two weeks or less.
As far as tuning your 29, see if there aren't any truck stops in your area that has a CB shop/repairman. Ask trucker in your area, they all know where these shops are at. When I drove across country last year, all of the truckers knew where they are at - since they need to know to keep their own gear in top shape. Tuning a 29 isn't as difficult as it seems, but if you have never done this before - forget about it if you want to get it right the first time. Take it to a local shop and be ready to spend ~$50 for modification and tune-up. Can't go wrong with that...
As far as tuning your 29, see if there aren't any truck stops in your area that has a CB shop/repairman. Ask trucker in your area, they all know where these shops are at. When I drove across country last year, all of the truckers knew where they are at - since they need to know to keep their own gear in top shape. Tuning a 29 isn't as difficult as it seems, but if you have never done this before - forget about it if you want to get it right the first time. Take it to a local shop and be ready to spend ~$50 for modification and tune-up. Can't go wrong with that...
welcome to the forum fordfreak,
my suggestion for a mic is the Astatic 636. this is a noise cancelling mic and is also a high quality, good sounding mic.
noise cancelling means that if you are driving with the windows down, and talking on the microphone, it will cut out the background noise.
these mics are meant to be "close talked", meaning that you want to be right up on the thing while talking.
buy a 4 pin version and it will already be wired for your 29LTD.
there is lots you can do to your 29LTD, but it depends on your operating style, whether or not you plan to use an amplifier, and what things are most important to you.
if you want to "do it up", and dont plan on running a linear behind it; i recommend having the shop do a full alignment, the 2SC2999/schottky diode receive upgrade, and convert the final to a MOSFET.
yes, it will cost some money to have all this done, but again, its up to what you want out of the radio.
if you just want to "make it loud", and dont want to spend any money, you can just go inside the radio yourself, and turn up VR4, which is the modulation limiter adjustment.
its very easy to do, and all you need is a small flathead screwdriver to do it.
just turn the dynamike all the way up, and after turning VR4 all the way one way; look at the radio's meter to see if it moves upward when you say "ahhh" into the mic.
one direction turns it down, and one direction turns it up.
pretty easy to tell when you get it right.
VR4 is located near the transformer in the rear of the chassis.
do this, use the 636 mic, and you will have a good sounding radio.
as for what shop to use, look around this forum for the recommendations from other members.
you can pretty much guarantee that if a shop is bad, they will be bashed here.
if they are good, they will be praised.
good luck,
LC
my suggestion for a mic is the Astatic 636. this is a noise cancelling mic and is also a high quality, good sounding mic.
noise cancelling means that if you are driving with the windows down, and talking on the microphone, it will cut out the background noise.
these mics are meant to be "close talked", meaning that you want to be right up on the thing while talking.
buy a 4 pin version and it will already be wired for your 29LTD.
there is lots you can do to your 29LTD, but it depends on your operating style, whether or not you plan to use an amplifier, and what things are most important to you.
if you want to "do it up", and dont plan on running a linear behind it; i recommend having the shop do a full alignment, the 2SC2999/schottky diode receive upgrade, and convert the final to a MOSFET.
yes, it will cost some money to have all this done, but again, its up to what you want out of the radio.
if you just want to "make it loud", and dont want to spend any money, you can just go inside the radio yourself, and turn up VR4, which is the modulation limiter adjustment.
its very easy to do, and all you need is a small flathead screwdriver to do it.
just turn the dynamike all the way up, and after turning VR4 all the way one way; look at the radio's meter to see if it moves upward when you say "ahhh" into the mic.
one direction turns it down, and one direction turns it up.
pretty easy to tell when you get it right.
VR4 is located near the transformer in the rear of the chassis.
do this, use the 636 mic, and you will have a good sounding radio.
as for what shop to use, look around this forum for the recommendations from other members.
you can pretty much guarantee that if a shop is bad, they will be bashed here.
if they are good, they will be praised.
good luck,
LC
i do plan to run a 100 watt linear behind it, and im pretty handy with electronics meaning circuit boards, just dont know how to go about doing anything to it myself, so a write up would be great
what amplifier are you going to use with it?
knowing that will allow me to be more specific with the requirements of the radio.
either way, you are going to have to lower the deadkey on your radio to mate it with the linear.
depending on what linear you are using, you want about a 1 or 2 watt deadkey, and you want the radio to swing up from there.
do the mod layed out in this article, turn up VR4, get the 636 mic, and you will be a very happy camper.
Cobra 29 LTD super modulation modification
as for the receive mod, if you want to do it, just buy one of the kits on ebay, and it should come with instructions as to what parts in your radio to replace.
basically, its unsoldering a transistor and 3 or 4 diodes, and replacing them with the parts you bought in the kit.
good luck,
LC
knowing that will allow me to be more specific with the requirements of the radio.
either way, you are going to have to lower the deadkey on your radio to mate it with the linear.
depending on what linear you are using, you want about a 1 or 2 watt deadkey, and you want the radio to swing up from there.
do the mod layed out in this article, turn up VR4, get the 636 mic, and you will be a very happy camper.
Cobra 29 LTD super modulation modification
as for the receive mod, if you want to do it, just buy one of the kits on ebay, and it should come with instructions as to what parts in your radio to replace.
basically, its unsoldering a transistor and 3 or 4 diodes, and replacing them with the parts you bought in the kit.
good luck,
LC
+1 for turning up VR4 and the 636 mic. I have a $10 Cobra 29 that I simply turned up VR4, spread 3 coils, and put a 636 mic on, and it rocks. It DK's 4 and swings to 20 or so. Plenty loud on the air.
Brandon,
not trying to be a smartass here, just trying to educate.
spreading the coils does not increase your output.
well, not your output on 27mhz anyway.
those coils are either part of a half wave filter, or a low pass filter.
either way, spreading them changes their inductance, and doesnt allow the circuit to perform properly. when this is done, you create harmonics.
these harmonics are 54mhz, 108mhz etc...
wattmeters are dumb, and when it sees signals on 27mhz, 54mhz, 108mhz, etc...
it just adds them all together and shows you the total.
this is why it looks like you have increased your power, when the truth is you are heating up your transmitter more without adding anything to your ability to get out.
if you would like to do a test to see how much of your power is actually on 27mhz, put a low pass filter in between your radio and the wattmeter.
most likely you will see your output go down, but at least what you do see is helping you get out.
hope this helps,
LC
not trying to be a smartass here, just trying to educate.
spreading the coils does not increase your output.
well, not your output on 27mhz anyway.
those coils are either part of a half wave filter, or a low pass filter.
either way, spreading them changes their inductance, and doesnt allow the circuit to perform properly. when this is done, you create harmonics.
these harmonics are 54mhz, 108mhz etc...
wattmeters are dumb, and when it sees signals on 27mhz, 54mhz, 108mhz, etc...
it just adds them all together and shows you the total.
this is why it looks like you have increased your power, when the truth is you are heating up your transmitter more without adding anything to your ability to get out.
if you would like to do a test to see how much of your power is actually on 27mhz, put a low pass filter in between your radio and the wattmeter.
most likely you will see your output go down, but at least what you do see is helping you get out.
hope this helps,
LC
On behalf of everyone who uses those frequencies, TV RADIO, thank you. Those are trap coils.
Excellent explanation.
If it were me.....I wouldnt do much to the radio at all,if anything I would put a good quality mic on it and leave the insides alone,you start tinkering around inside you could cause the radio to splatter across the entire CB band as well as the harmonic distortion...Just get a good mic and have a trusted radio friend help you to adjust the mic and mic gain to where it is plenty loud without overdriving(start with the mic gain at about 50% and go from there)
The Cobra 29 is a nice radio that has plenty of audio right out of the box and the 100 watt kicker will give you a good boost ......
The Cobra 29 is a nice radio that has plenty of audio right out of the box and the 100 watt kicker will give you a good boost ......
kd-5-bgt,
i do agree with your recommendation to have a radio friend listen and set the mic gain where it sounds good without distorting.
that can still be done after turning up VR4. really, the mic gain's value at max with the amc adjusted from the factory is somewhere between 70-90% modulation.
they NEVER turn it up to 100% because they want to make sure it passes mustard with the FCC.
when you turn up VR4, yes, you can overmodulate the radio, but you dont have to, thanks to that now very handy modulation control on the front panel.
everyone with a stock radio runs their mic gain at 100% because its a passive device and doesnt actually provide any gain at all.
it only reduces gain when you turn it down.
max is 0. anything less is, well, less.
as you can tell, im certainly not a purist. im a die hard cb enthusiast, but i dont like the sound of a muffled, nasaly, overdriven radio any more than ham ops do.
just my 2 cents,
LC
i do agree with your recommendation to have a radio friend listen and set the mic gain where it sounds good without distorting.
that can still be done after turning up VR4. really, the mic gain's value at max with the amc adjusted from the factory is somewhere between 70-90% modulation.
they NEVER turn it up to 100% because they want to make sure it passes mustard with the FCC.
when you turn up VR4, yes, you can overmodulate the radio, but you dont have to, thanks to that now very handy modulation control on the front panel.
everyone with a stock radio runs their mic gain at 100% because its a passive device and doesnt actually provide any gain at all.
it only reduces gain when you turn it down.
max is 0. anything less is, well, less.
as you can tell, im certainly not a purist. im a die hard cb enthusiast, but i dont like the sound of a muffled, nasaly, overdriven radio any more than ham ops do.
just my 2 cents,
LC
If you still feel you need more modulation after you adjust VR4, remove C71 and replace it with a 33uf 25v capacitor (make sure you get the polarity right). I never liked the idea of clipping the diode...
Jim
I have never heard a standard single final CB radio sound distorted by clipping the limiter..........never. Export radios are a different story though.
Clip the limiter and set the dead key to 3 watts, done. Don't spread the TVI trap coils, they serve a purpose.
Steps for tuning radios.
1. If you don't know what you are doing, then don't do it. If you have to ask, then you don't know what you are doing.
2. If you don't have the equipment to do it right, then you won't do it right.
3. If/when you get that equipment the first step is learning how to use it correctly. Read the instruction. Don't throw them away.
4. Not knowing 'why' is as bad (if not worse) than not knowing 'how'.
It's really that simple.
- 'Doc
1. If you don't know what you are doing, then don't do it. If you have to ask, then you don't know what you are doing.
2. If you don't have the equipment to do it right, then you won't do it right.
3. If/when you get that equipment the first step is learning how to use it correctly. Read the instruction. Don't throw them away.
4. Not knowing 'why' is as bad (if not worse) than not knowing 'how'.
It's really that simple.
- 'Doc
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@ AWP:Is it possible to be on a lake and have a homing directional beam being emitted from the shore so a person could navigate to that beam's source? For example at night to a jetty.
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@ BJ radionut:
June VHF
The American Radio Relay League (ARRL) is the national association for amateur radio, connecting hams around the U.S. with news, information and resources.www.arrl.org
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