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Hello all, i am new to this site but not new to electronics and cb's, not new to the two of them together if that makes any sence I have a cobra 29 that was given to me and is going to be my test subject untill i get comfortable with modding radios. I keep reading about swapping out finals and drivers and my question is; is there any step by step guide for this? I know how to solder, i guess my biggest issue is knowing which component to swap out, and also what pots i need to turn once im finished? i read for 5 hours last night and never really found what i was looking for or any information. i read a couple of things about following a guide on cb tricks, but i could not find it for the life of me. I am 23 years old and am trying to learn the ways the the "cb shop" so that i can carry on a profession that seems to going by the wayside in my area. Thanks in advance for any help you all may me able to give me.
Well for the finals I'm not 100% sure. I know a lot of ppl go for the RFX 75 I think is the name. That comes with instructions. As for Modulation, Carrier adjustments etc, cbtricks.com has the manuals for that radio. All you have to do is download it and skim through to the alignment procedure and it'll tell you what pots are for what. Then scroll down a little and find the diagram showing you where its located.
I'm 33 and same as you, Soldering etc is no big deal, I can read a schematic and I know what a diode, resistor, cap etc looks like but put them all together and I'm lost! I am in the process of reading a first year electronics text book. Knowledge is power errrr Knowledge will make power?? haha
Anyways sorry I can't be of more help but making a radio into dual final shouldn't be that hard. Ill take a look around today and see what I can come up with for ya!
350jeepcj5 wrote: I keep reading about swapping out finals and drivers and my question is; is there any step by step guide for this? I know how to solder, i guess my biggest issue is knowing which component to swap out, and also what pots i need to turn once im finished? i read for 5 hours last night and never really found what i was looking for or any information. i read a couple of things about following a guide on cb tricks, but i could not find it for the life of me.
Here you go have fun
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You can either find and follow other peoples mods or do your own. CBTricks has the majority of them. You'll occassionally find others elsewhere, like the 2SC2999/Schottky diode mod, etc. etc.. CBTricks is the de-facto repository for such things however.
As far as do your own.. well.. You need to be able to read AND understand schematics.
Best advice I have is to think of everything as 'modules'. They even illustrate this in their block diagrams (Although it's still too high level). Somewhere in between the block diagrams and the schematics, there's a happy medium of understanding.
You don't look at each individual nut and bolt in an engine, you think of the whole thing as the 'engine'. The nuts and bolts are just supporting parts and everything combined forms the engine..
Because of this, you don't look at just 'the final', you look at the whole 'final stage' with all of its supporting parts.
You might have put a 350 engine in your volkswagen bug, but if the bolt patterns don't line up, you have to adjust the supporting parts. Same thing here.. Swapping finals, etc, requires readapting the other parts to make the whole thing work.
Knowing what a diode or resistor or capacitor or whatever is and what it does won't get you very far. Several resistors/capacitors/inductors in a group form a 'module' and identifying those 'modules' and what they do, and what you want to make them do is whats important..
I etch my own circuit boards, draw up schematics, program microcontrollers and make entire embedded electronic automation systems from scratch, but I still don't have a clue when it comes to drivers/finals, etc, I have to rely/reference the work of others. If the capacitance of an IRF520 is meaningless to you, you have more learning to do and should follow guides that other people have done.
As far as the audio chain, learn about opamps and low pass filters/high pass filters..
I wouldn't replace the final in that cobra 29 unless it's already gone out.. It'll do about the same power regardless if you single mosfet it or single transistor it.. If you're doing dual finals, then that would be a worthwhile upgrade..
I have a 29 I've been playing with and have read guides claiming 35 to 40 watts from a single 2030. Is this correct or is that a smelly load as I have suspected. You do have to be carefull what you read and not blindly follow.
Galaxy 959 mobile 1969 final, with extra channels
Cobra 142 base, with extra channels
Galaxy 959 mosfet final
Nobody can go back and start a new beginning, but anyone can start today and make a new ending.
wyatt knight wrote:I have a 29 I've been playing with and have read guides claiming 35 to 40 watts from a single 2030. Is this correct or is that a smelly load as I have suspected. You do have to be carefull what you read and not blindly follow.
I have seen 30 watts come from a 2SC-2029 factory final. That is about the limit. I don't like MOSFETs. It may do 35 watts but for how long? Five watts more peak will not make a difference. The older Uniden PC-76 used to do 35 watts peak and it is the same radio as the original Cobra 29 LTD and the Cobra 29 GTL.
MOSFETs are Hype. They are not better just cheaper to manufacture.
wyatt knight wrote:I have a 29 I've been playing with and have read guides claiming 35 to 40 watts from a single 2030. Is this correct or is that a smelly load as I have suspected. You do have to be carefull what you read and not blindly follow.
I have seen 30 watts come from a 2SC-2029 factory final. That is about the limit. I don't like MOSFETs. It may do 35 watts but for how long? Five watts more peak will not make a difference. The older Uniden PC-76 used to do 35 watts peak and it is the same radio as the original Cobra 29 LTD and the Cobra 29 GTL.
MOSFETs are Hype. They are not better just cheaper to manufacture.
Respectfully,
Rick,
I've seen pc 76 with side mics and front mics, which one do you classify as "older Uniden PC-76?"
9-7-1 Coastal Maine Mobile usually hanging out on 38 LSB
At the home QTH, Uniden Madison/Realistic TRC 457
In the mobile, HR2510/Grant XL
I've seen 29's do 40-50 watts.. We did a mosfet conversion on one and saw that.. I thought it was the mosfet, but then I saw a 29 do the same wattage with the stock final...
I don't get it.. My Tuned 979s do perhaps 25 and my tuned 2000GTL does 17..
A 29 with the same final as the 979 does almost double on the same meter.
Perhaps its all splatter <shrugs>.. Although I can get the same 50w per IRF520 in an RM Italy KL203.. The same box at my friends house does 25w per IRF520.
Primarily antenna differences (good reason to do testing with dummy load).
Splatter or RF being read by the meter coming back to the transmiter? I have a 959 that has an IRF-520 and it shows 3 1/2 swinging+ +to 16-18 on my Para Dynamics PDC-137meter. I put up an old A99, and the same meter, with same radio and coax, and got a reading of 12 1/2 DK, swinging to just over 60. I'm not sure what caused the erronious readings, perhaps a hoseclamp that was halfway up the bottom section, but no matter what caused them, in my case, I know the high readings aren't for real. Perhaps some of those meter readings are some kind of harmonics that has nothing to do with the signal being transmitted. My grand-dad taught me not to believe everything I read, but when it comes to power meter readings, perhaps we shouldn't believe everything we read or see. Especially since meter readings can be easily influenced both intentionaly and unintentionaly.
.
Galaxy 959 mobile 1969 final, with extra channels
Cobra 142 base, with extra channels
Galaxy 959 mosfet final
Nobody can go back and start a new beginning, but anyone can start today and make a new ending.
wyatt knight wrote: I have a 959 that has an IRF-520 and it shows 3 1/2 swinging+ +to 16-18 on my Para Dynamics PDC-137meter. I put up an old A99, and the same meter, with same radio and coax, and got a reading of 12 1/2 DK, swinging to just over 60. I'm not sure what caused the erronious readings.
Whenever checking the wattage output of a transmitter use a dummy load never an antenna if you want an accurate reading.
I have a cobra 29 that was given to me and is going to be my test subject untill i get comfortable with modding radios. I keep reading about swapping out finals and drivers and my question is; is there any step by step guide for this? I know how to solder, i guess my biggest issue is knowing which component to swap out, and also what pots i need to turn once im finished? i read for 5 hours last night and never really found what i was looking for or any information. i read a couple of things about following a guide on cb tricks, but i could not find it for the life of me. I am 23 years old and am trying to learn the ways the the "cb shop" so that i can carry on a profession that seems to going by the wayside in my area. Thanks in advance for any help you all may me able to give me.
