what are the most effective mods for the time/money?
With that radio, not too many. 29's are made to look pretty and be a convenient size for modern SUVs, but as a radio they are fairly mediocre.
Is the 520 or the 2030 going to do better? Or should I stick with the 1969, even? Is the 2sc2312 same/better?
By that, I'm assuming you want to increase the transmit power. Don't bother.
To double the range of a radio, you need TEN times the transmitter power. To quadruple the range, you are going to need a HUNDRED times the power. A 2SC1969 / 2312 / 2030 will boost your output from 4 watts to 15 or so.
The result? Only your power meter can tell, other users on the channel won't be able to hear ANY difference.
Does the 2SC2999 RX upgrade (less noise?) work on a 29? Is it worth the time/trouble?
In a base station at a quiet location, maybe. In a vehicle, it will just make the noise and static louder.
What about the RX boost of PLL (switched, with variable resistance of 100K-500K between pin PLL P14 and R11?)
Playing with your local oscillator injection levels will just make the RX performance worse with simple transistor mixers like those in the '29.
I see a lot of disagreement about clipping limiting diode D-11... Where would his help/hurt?
Your call. The "swing kit noobs" will always say YES, as your distorted voise will sound "louder" (because overdriven, distorted audio is always "louder")
Experienced users like clear
modulation, so they will buy a decent radio or add a linear amp (or both!), but will never
clip a limiter. It's there for a reason! If "clipping the diode" really made your radio work better, the makers wouldn't have put it there in the first place.
very noisy power when the fan/wipers/heater blower is on What else component setup would be a good filter?
The noise is being generated at the motor, and traveling through the air to the antenna and then into the radio.
Filters in the radio power line / powering the radio from a different source will NOT stop the noise, you have to add a suppressor at the motor itself. Nothing else will work.
However, please don't tell me to go get a better radio
It depends what you want to do. If you are chatting in a convoy situation, the '29 is fine. Just don't expect high performance from a $59 "radio".
You haven't mentioned your antenna system. This can have a huge impact on range.
Hams have known this principle for years - $10 spent improving an antenna will give better results than spending $100 to "improve" a radio.
I won't repeat earlier answers here, read a couple of my old posts if you want to know more about power and modulation. Links:
http://www.radiomods.co.nz/forum/viewtopic.php?f=1&t=2914You'll have to copy and paste these into your browser, as linking no longer seem to be working on this forum.