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Ok, I been super busy but I found this very old thread, it is littered with bantering back and forth but contains some really deep digging into the 2n2999 / diode mods. If you can stand digging through it to find the nuggets. It started with how to do the mod them progressed...

I noticed that the OP is in Germany, I have no idea what the legality is running low power FM. 73 Jeff

It's a violation if you are blocking a licensed FM broadcast station, we can run 100 watts ERP on a LPFM station here in the us but it still requires a license, and at the moment they are not accepting new applications. 73 Jeff

Here's the NB thread https://www.worldwidedx.com/threads/cobra-29-ltd-classic-schottky-diode-mod.228657/ The subject radio was a 29 but the info is useful. There's another one about the low noise transistor used to enhance RX a 2n2999 or something I can't remember right now. If I find that one...

There's a thread about NB diodes here somewhere that has some information.... Let me look 73 Jeff

Buttermilk biscuits, ya I remember The Big man just dropped this hammer on the northwest tip And I'm reading the mail 4-10 4-10 I been waiting to key this duck pluckin Johnson. Put it on you later, I got to go to the mine The Man in the cold lakes with this big Johnson is 10-7 73 Jeff

The parts come in a kit from RF Parts, NFB2 is for a two transistor amp, I don't know the current cost. Keep the leads as short as possible. Adding negative feedback will help with this but it's no substitute for a properly biased amp. 73 Jeff

SRF 3749 are Motorola MRF transistors that have been tested and matched for high gain. Then they would remark them for RF Parts as Select RF parts, hence the SRF prefix. The answer is yes, they were good and no longer available. 73 Jeff

They were biased hard as built I think @bob85 quoted almost 10 times the required bias current as built. Making for a clean signal, the trade off is more heat and more current draw. 73 Jeff

Yes, they were biased when built, however many units were modified to reduce the bias current in the wild. 73 Jeff

There really isn't a "fix", the 15 meter band was really not a feature of the Pro, it's a extra, or as Pez says a gift band. It's kinda stretching the limits of the hardware in the radio moving that far out of band. 73 Jeff

Welcome to the forum. I assume you are talking about SSB The reason that some users report that your signal is "crunchy" is in part caused by a amp with no bias. Many of these little amps were built like that, just a fact of economics. The variable resistor you are referring to is actually a...

Check this out, I watch Mr Carlson on YouTube and this was in my feed yesterday. Shows how unstable the wrong cap can be in the wrong place. 73 Jeff

Nice, old school Messanger. 73 Jeff

It's a common practice for removing money from the radio owners wallets........ 73 Jeff

I looked through my books last night, I thought I had a Lou Franklin service manual that had the radio in it. No luck. I will keep looking 73 Jeff

Copy I will look more when I get home. 73 Jeff

Try here https://www.eserviceinfo.com/downloadsm/242900/ranger_RCI-6900%20F25.html I am on my phone so I can't extract the file but I think this is the service manual. 73 Jeff

I "think?" The Connex 4800 DXL is the same board. I think, it's been a long time since I had that radio, it's was the f 25. Let me dig around..... 73 Jeff