You need to watch the impedance on RF75,150,300 etc.......If you look closely at it they are not 50ohm which makes the output power suspect. Same thing goes for the RM Stinger board when you cut that big resistors legs to get the power from 50 watts nominal up to 100-150 watts the impedance match goes out the window. No one seems to bother to check impedance on these they just assume it must be 50 ohms.
When people just take an existing circuit design and sub in fet's it is almost never right. You can not treat a mosfet like a bjt in the circuit. the Mosfet's should not even work but they do but almost everyone forgets that we use 50ohm for coax and antenna impedance.
Not only that but at 12V and 27Mhz the gain is almost nothing for these fets and when looking at "am" only radio's and the 50-150hfe gain a lot them had on the driver and final you are losing a lot to gain some watts. In a Cobra 29/Uniden 76/78 a well-tuned stock radio can key all over a mosfet moded radio especially if the fet radio had hifi or broad audio!!!! The fet radio will be loud and proud locally but just will not talk as far as you would expect. When the audio and rf are not linear. It is even more apparent when driving an amp. And lastly, if your SWR is just slightly high poof goes the fet! I have keyed bjt's with less than ideal swr's for hours at a time and never had one fail on a T-hunt. Mosfet's you go over 1.5:1 and poof....LOL They are cheap.
I am sure some of you are aware of this but they do actually make RF specific mosfets that actually have at least as much gain on 27Mhz and the 2SC1969. SSB radio's used bjt's that made more power but they were always low gain compared the the drivers and finals used in "AM" only radio's.
The only reason to use a non-rf specific mosfet in a CB is because they ultra cheap and idiots that chase insignificant watts on a meter are impressed! Did I mention they are ultra cheap?????
I hate lies and subterfuge and it seems like no one on this site ever mentions cheap, low gain, low durability when talking about non-rf fet's it is always about insignificant watts. Worse thing you can do to a radio after super swing mod's is put a fet in the radio in place of a a bjt because you or your customer are too cheap to put the right part back in while we can still get the right part. It is not like we can not still get he right part they are just not dirt cheap. They are however not insanely expensive either. It is not as if you need to put 10 matched 2SC1969 in a radio.
