I have to disagree. 6db will make a difference. I was hoping you made a typo in post #9. Why would 6db make a difference on the receiving end when we are using over 100 watts but no difference under 100 watts? Using a mode with a carrier makes it easier to see.
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Cobra 29 ltd chrome with mosfet super tune
- Thread starter 805 california
- Start date
I have to disagree. 6db will make a difference. I was hoping you made a typo in post #9. Why would 6db make a difference on the receiving end when we are using over 100 watts but no difference under 100 watts? Using a mode with a carrier makes it easier to see.
You are taking what I said way to literal, all I was pointing out is going from 6 to 20 watts is not worth the effort and expense. The money would be better spent on an amp. I don't care about the math..
Thanks for the reply. Yeah I'm just doing these mods for my own amusement and trying to learn a thing or two in the process. What did you mean by companion part? Thanks
http://www.wearecb.com/ekl-en1230-companion-part-erf2030.html
You will need the ekl en1230 companion part for the mosfet conversion or just build one with a 1N4148 diode, and two resistors 3.3k ohm & 470 ohm.
Install it in place of R56 just like the CbTricks PDF states...
http://www.cbtricks.com/miscellaneous/fet_papers/mosfet_experiment.htm
This explains what is found inside the en1230, you cannot just install the mosfet without the additional component as it will fry like some McDonald's chicken tenders!
When you have that done, you need to realign the TX stage, and possibly add some capacitance to increase the dead key. I set the bias voltage at the gate of the IRF520N @ around 2.8 volts and it runs happy (not too warm). I accomplished this by using a resistor and a trimmer potentiometer on the solder side of the board, it's ugly but it works!
Taken from: http://www.cbtricks.com/Amp/powerband/rfx_75/graphics/rfx75_cobra_29_carrier_increase.pdf
I used a 68pf silver mica in parallel with C62 on the solder side of the PCB and it worked out great to increase the carrier ("dead key"), also i removed one turn from the coil of l14 (& put the ferrite slug back in, careful not to crack it) for the best results on my 1995 China made Cobra 29 LTD Classic.
When I was done It had a 3 watt carrier "swinging" to 5 watts average under a loud AAAUDIOO modulation using my voice into an Astatic 636L.
( I don't own a true peak reading meter (other than the 'scope haha), and did not use an audio frequency signal generator to create modulation for the test. & as always between different radios even the same make/model radio the results will vary due to manufacturing tolerances of the individual components. All this was done before I ever got the oscilloscope so this "tune" should not be hard to reproduce without one )
All The Best.
-Sam
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Yeah 10-4. In r56 I got a 470 ohm and a switching diode. I also added compacitence in different areas. I got bias at r88 I believe at 2.8. I got a 3 watt key swinging 13 will vr4 wide open. Thanks for your time
Yeah, no problem 805 California!
What about the 3.3k ohm resistor where is that placed is it at r88 and rated at 2.8k ohms?
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You mean 13 PEP watts not AVG right!?
Because if it is 13 watts average then you just built yourself what some would call a "comp-tuned keydown rig"!!
The most "constant wattage" i've seen from an irf520n was in a converted Galaxy 66v in FM mode and it did 13 watts on my average reading meter into a dummy load.
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I agree. The gain is not worth the effort of changing finals and definitely not worth paying a shop to do it.
You made your point but posted some misleading info in post #9.
I prefer the term misleading hogwash.
10W to 100W is 1.5/2 S points on a properly calibrated S meter.
100W to 500W is 1 S point on a properly calibrated S meter.
Biggest gains are going from 10W or less to 100W. 100W is pretty much the sweet spot.
So after buying an irf520 converted 29 i like it for driving amps. Best $75 radio ive bought in a long time. It has variable so i can set it to 1/2w - 1w dk and will it swing 20+ watts which equates to a 20w dk swinging 200+ bird or 600+ pep with my 300a. I get about the same 20w dk swinging about 450 pep with the 4x2879 amp. It reminds me of when i ran my 2950 years ago with a 300a but louder lol. I know my locals know the difference when im on the 148 or the 29. All in all considering the 29 has been reduced to a mediocre pile of Chinese junk i dont see a problem with modifying it, anything is an improvement now. I have 2 more im going to have set up the same way and put on the shelf for future use, sale or trade as they seem to be quite popular and the parts are cheap.
Lmao.
Took a peep at a doa from a pile i picked up for next to nothing and wow, just wow.
I swear if i ever try my hand at modifying one my radios it will never look like this.
Took a peep at a doa from a pile i picked up for next to nothing and wow, just wow.
I swear if i ever try my hand at modifying one my radios it will never look like this.
The capacitor in the "overmod" kit is backwards, the Negative stripe goes to the back.