Cobra 29 wx st mod

[Dark Star]

Wow there certainly is more to this Mosfet mod than I first thought. Thank you for explaining this all to me. I bought this 29 used and full of mods that I didn't understand and you have definitely helped shed some light on them for me. I just found the the way the Mosfet mod was done was much different than any I've seen before and it stoked my curiosity to dig a little deeper as to precisely how these components were interacting with each other. I will say that it looks surprisingly clean on my scope and very loud. I think that whoever mounted the component part on the solder side of the board did so because there is also an adjustable dead key mod done and the large cap for the dead key mod did not allow room to mount the companion part on the component side. It appears that whoever modded it did their homework and "fiddled" with the values to achieve some pretty good results. Thanks again for all your help Andy.
73's

 

[Handy Andy]

Hmmm...sorry then, to have taken up your time...

IF it works well for you, then the job is done, I can only go over finer details but...

Hey, life is short- get out there and enjoy that gift of radio you got. While it's still working!

All the best!

 

[Dark Star]

Not at all friend...time well taken. Great info for sure. Much thanks.

 

[Low_Boy]

I sure would like to see a picture of how clean it looks on a scope. I have yet to see a conversion that put out any power and had a clean pattern.

 

[Dark Star]

Low Boy this is what it looks like on my cheapie scope. Not great but not too dirty. That's a 400hz and a 1k signal outputting around 35 watts peak on a Palstar and around 120% mod on my Boonton meter. So take that with a grain of salt considering the measurement equipment, plus I'm not very knowledgeable with a scope as well...still trying to learn. It is a good lil am skip talker though, that's for sure. 73's

 

[Low_Boy]

OK my opinion is a wave like that that is a bit over modulated will not sound bad. And usually some that look worse than that will not cross channel on my spectrum analyzer. So I would say whoever did that did not do such a bad job. Anyone else please chime in.

 

[Dark Star]

I haven't had any complaints from the locals on splashing over channels but then again I live in the middle of nowhere so there aren't too many talking locally anyhow. That little bit of extra obnoxious loudness goes a long way on blasting through the mayhem when talking DX...even if it's somewhat over modulated...but that's just the CB'er in me lol.

 

[Shadetree Mechanic]

Before I got a scope, I would tune the modulation by ear with another radio on the bench with no antenna and headphones. Now when I use the scope, I still listen to it and there is a little bit of leeway there where you can see it on the scope but still sound good. Even pinching the carrier on voice peaks doesn't sound too bad and will make it loud for sure. Where it goes down hill is when the positive peaks start to flatten out. I would run your radio right where it is at and not worry too much about it.

The one thing to do though is to make sure your MIC level is set correctly. Listen to it on another radio and turn it up until it starts to sound scratchy while talking into it and then back it off a little. Also pay attention to how close you hold the MIC, this will affect the audio level in a big way when you are at the limit of what the radio can do. I usually set mine up so that I can hold it about 4 inches away and turn the MIC sideways and talk across the front of it to reduce "popping" on the "P" sounds.

Chris

 

[Dark Star]

I kind of got it where I thought it sounded nice and loud but no obvious distortion, at least by my ear. At that point I threw it on the scope and took those screenshots. I'm happy with it right about there. I can push it a little more without the positive peaks flattening out but no need to go to far. I prefer for my transmission to sound somewhat pleasing to the ear and not too obnoxiously loud lol. My thanks to all of you guys for all this great info!!! I'd be lost with most of this stuff if it wasn't for the help given on this forum, so a real hats off to everyone who spends the time to help us newbies and educate us with facts and not all the silly myths that I've heard over the years. 73's