Talkback Cobra 29

Do you use a PA speaker alot?

Here is a thought, find a old cobra 29 that has other issues. Open it up and take the on/off and volume control out of it. Open up your working radio and remove the RF gain control knob. Solder the RF gain wires together and heat shrink them. This sets the RF gain at wide open.

Now place your extra on/off volume control into the RF gains spot. You will have to get your ohm meter out first to figure out which terminals you need to use to turn the talkback on and off as well as have volume control of the talk back. Should not be too hard to figure out. Now run a wire from each of your chosen terminals back to the ground sides of the PA and the external speaker. Solder them too the board and boom you are done. You know have talk back you can turn on and off as well as being able to control the colume of the talk back. When you want to use your PA then you just turn the talk back off and use your pa as normal.

I feel it is important to have a variable talk back so that you can control the volume of it or you might end up with a constant squeel due to feedback through the mic.

Or go buy one of the cobra models that already has talk back in it. I believe both the classic chrome and the black chrome models have talk back already setup from the factory.

As far as the ECO, not sure why you want it. Waist of money in my opinion. the majority of the people don't care to listen to eco and I have yet to find were any amount of eco actually made a radio sound better over the air. Most of them sounded 100 times better with the eco completely turned off.

 

Well you know Channel Jumper, if you don't have echo on your radio, you're not cool. Just ask some truck drivers.

 

I have the echo and talkback turned off in my radios. I think most that have to have echo and talkback just like to hear themselves talk, it makes them feel important and they think they're trucks go faster with it.

 

fsthawk I am sorry that on your first post to this site you have to be treated so poorly. I know you did not deserve to be berated for wanting to add talkback to your radio (or in general even being so stupid as to run a CB), by a bunch of ham operators most of whom have never even driven an 18 wheeler. Hopefully you will not take this poor treatment of your desire to run a CB radio in a truck on the CB section of a truck driving website by a group representing ham radio as an example of all those who do have a ham license. I have no idea why this site is the most poorly moderated board on the internet but there it is. Thread after thread, post after post everywhere on this forum the same thing goes on by mostly the same group of people. Every time a person innocently asks for advice the thread is hijacked to drive the topic in the same direction, namely:
1- ham is better than CB
2- you are a fool, a child, trailer trash, an ignorant moron for not knowing how much better ham is than CB
3- almost no one will try to help answer your question
4- run a repeater, use 2 or 10 meters, surely the loading dock will hear you, surely you will be warned by other drivers on the road about hazards or conditions up ahead if you will only throw away your CB and go ham
5- use your cell phone surely all other drivers have your number
6- I could go on but what is the point

If this is how ham operators set a shining example to others of what a great hobby it is, no wonder the numbers are dwindling and the spectrum space is being sold to big business by the government.

Not caring for the despicable treatment of poor innocent unsuspecting souls who dared to come to this site and ask for help for their CB, and the endless hijacking of threads by people dedicated to impressing you with how much better they are than you I will try to help. You can connect the grounds between the external speaker jack and the PA jack with a fixed resistor ranging from 22 to 150 ohms. The value will be determined by your radio model, choice of mike, and other conditions such as speaker type and placement. You will need to determine this experimentally to get the right level of talkback and no, it will not affect your use of the PA function. A typical example for a noise canceling mike on a Cobra 29 would be to start around 68 ohms. For a stock mike around 100 ohms. Listen to the sound and go from there. Use a resistor rated for at least 1/4 watt. If you have to lower your mike gain to stop squeal you are too loud, go to a higher value resistor so as to not excessively reduce your transmitted power. Rat was giving you a good idea except his choice of variable resistor is not all that optimum. A volume control is typically 50,000 ohms, much too high. Actually the 1,000 ohm RF gain control already in there is a better choice as you will have a wider range of adjustment in terms of degrees of rotation of the control. However I for one prefer to have the RF gain function so I believe picking the correct value of fixed resistor is a better method. As to echo I am kind of with Rat, it would be better if those actually using one would at least learn how to adjust it.

I have had many drivers over the years say talkback helps keep them awake during the long night hours over the road. Also the nonstop motion to the cord makes them fail often and it is good that you can immediately tell when there is a problem with the mike cord, or the switch since plating of contacts is a thing delegated to history.

 

If you don't us the PA function then you can get an external speaker that has talk back function. I bought one once. I believe it is a Cobra speaker. It has a dial on the back of the speaker turns it on/off and also controls the volume.

AB7IF, I used a volume control once on an older radio and it worked just fine. The first radio I had that had talkback in it was a cobra 29 that I had the talk back installed by a CB shop in Ann Arbor. He used a VR pot,much like the limiter VR. he installed it on the solder side of the radio near the speaker and PA ports. It worked fine but I had to remove the top cover to adjust it to get rid of feedback. Finally, I marked the spot on the cover and drilled a hole in the cover so I could get to it without having to remove the cover.

As far as using the RF gain control, well many people just crank it wide open and never ever touch it, they perfer to use the squelch to control noise. This is why I gave the option of removing the RF gain control or even using the RF gain control like you suggested and which I have done.

I am just nto big on installing a fixed value resistor. If it is too loud or not loud enough then you have to take it all apart and swap out the resistor and keep doing this till you find the correct resistor for the enviroment in which the radio is going to be used and if and were he may have an external speaker mounted in the cab etc.

There is another option, Cobra radios go on sale all the time at truck stops. Some of the cobra models have talk back already in them and it is variably controlled via a knob on the front of the radio. I have seen them as low and 100 bucks.

How about a double control or a control or what ever it is called. You know like some of the controls you see on some Uniden models. Were the center knob controls one function such as volume and the outer ring controls another function. Do you think there could be one that has the proper values to be but in place of the RF gain control and use that from both the RF gain and talkback? The center knob could control one and the outer ring could control the other? This might be a better option if we had an idea what control would have the proper values.

I would not mind rehooking the RF gain control back up on the one I did and use a double control so that I could also have the variable talkback.

I have an old doner PC 68 LTW sitting here that I could rob the control out of. One of them controls the mic gain and the RF gain via the center knob and outer ring. Would the mic gain section work for controlling talk back?

 

With a volume control (50K ohm) the talkback is all or nothing near one end of the range. Plus volume controls have a Log taper making it worse. A linear taper pot like the RF gain of 1K is going to give you a more precise adjustment with a wider range of rotation. 500 ohms would be better still but not easy to find especially with identical mechanical configuration such as knurled shaft of proper length, so as to keep the same radio knob. I have done the dual pot before, you can find combos of 1K/50K that work out OK, 50K being too high for mike gain in some models but it will work fairly well. Too much mismatch over design values can introduce distortion in the audio. Hard to find with switch combo making it harder to replace the volume (single) in a Classic 29 to add talkback there. A dual 1K to make RF gain a combo with TB is a good choice. Wiring RF gain full is not a good idea. If you only have squelch you lose range. It takes more signal to trip if RF is full on. In average noise conditions you will find about 3:30 on the RF gain, with squelch just at threshold gives you quieting yet someone can be 2 to 3 times further away and still break your squelch as opposed as a tighter squelch setting because RF gain is full on with no way to adjust. The ratio of the two settings varies with conditions which is why the engineers gave you both controls. Likewise only using RF gain to quiet the radio (many run it like this) kills the receiver. A poor way to run a radio since the dynamic range has been wrecked by shutting the receiver off too hard. Your talkback speaker choice works too, my only problem is the quality of the speaker in most of them is so poor.

 

" Thread after thread, post after post everywhere on this forum the same thing goes on by mostly the same group of people. Every time a person innocently asks for advice the thread is hijacked to drive the topic in the same direction, namely:
1- ham is better than CB
2- you are a fool, a child, trailer trash, an ignorant moron for not knowing how much better ham is than CB
3- almost no one will try to help answer your question
4- run a repeater, use 2 or 10 meters, surely the loading dock will hear you, surely you will be warned by other drivers on the road about hazards or conditions up ahead if you will only throw away your CB and go ham
5- use your cell phone surely all other drivers have your number
6- I could go on but what is the point

If this is how ham operators set a shining example to others of what a great hobby it is, no wonder the numbers are dwindling and the .....................

spectrum space is being sold to big business by the government

Sadly I have to agree some are posting things about the "dumb " CBers ...

That said EXCEPT for 220-220 what bands have the hams lost since 1990 ? I have been on 220 since 1974 and still am.
Most are shaired like the 440 band some are HAM only ......

Again that said I can see microwave bands going by-by I have been on 1296 and up at 96 Ghz and there is not many to talk too ......

One good reason I did not spend $600 to put the 1200 mhz box in my TS-2000

 

For a long time many die hard Morse code advocates including the ARRL considered quality over quantity was most important. After loss of band space and pressure by business to buy more room (at around a million dollars per megahertz), the 'use it or lose it' forces won out, thus the dropping of code standards. In effect you might say further loss of band allocation was abated by surrendering the idea that if it was worked hard for it would be respected more. Anyone can memorize questions especially when the answers are already known. Having to pass 20 WPM forced people to really work very hard and therefore respect highly that which was gained. So you could say nothing more has been lost but I for one would not brag about since I think much more was lost than many realize.

 

Well.....

My older brother passed his extra at 20 WPM and loves code ..... I don't know what speed my younger brother did it at but both of us took our Tech class at the FCC because of a problem the FCC had with the local club and someone giving the tests back in the mid 60's.
Except for my moodbounce days I have never used it now i try and copy it but with my days starting at 4AM and never quiting to midnight It has
been on the back burner for 3 decades now. My FT-840 and FT-100D have CW filters I have many good keys like several J-38's and on a rare time I have little to do lissen to 20 CW there is little to match the sound of someone who knows how to send it right ......

I have worked at UHF/VHF since I finshed school in the ARMY and in many engineering or production places mainly on FM UHF but we had stuff going down to 26 mhz and up to 196 GHZ.

The NEED for space is going to be above 400 mhz little today is going to be in places that there are HAM bands and with the loss of TV to digital
there is a lot of HIGH VHF and some UHF now becoming unused.

I do feel it was over kill to kill the code for all classes the extra would have been a place to have kept some kind of requirement but with the FCC in its state of mind it is in today and few HAMS in the FCC code is something even they don't understand. Look at enforcement the head is not a HAM or CBer just another lawyer ....