RoadKing RKCB Radio tuneup

[Pizzaman247]

Factory IFR520 mosfet - Turn the amc full on - adjust L204 for dead key - I got about 4.5 watts with swing to about 18 watts - Which is about typical for a stock Cobra 29 LTD - - Not bad , but not anything special either - so I decided to play around with the output some - So, I added a 100pf ( 101 ) ceramic cap from the chassis ground point to the rear leg of L 202 - Then fold two coils of L202 flat towards the rear of the radio - Now re-tune L 204 an it will adjust to a maximum of 8-9 watts - I set mine at 6 watts an the radio swings to 25 watts with the modulation limiter still active - Local reports confirmed that it is loud an clean

6 Watt key an Swing 25 watts is a conservative setting - with a 68pf the radio will swing just over 30 watts - but even an IFR520 has its limits

[MDYoungblood]

Thanks for the info. When I would tune a radio with mosfets, I never went over 4wDK (@13.8vdc), tuning them to the max usually resulted in failure in a short period of time mainly from SWR changes (antenna swaying, etc.) or overheating. Those couple of extra watts will never be seen by the receiving radio. When spreading the coils, the radio starts to show signs of harmonics throughout the frequency multiples. Have you ever put it on a scope to see this?

3's

Greg

[Pizzaman247]

That coil was already factory spread about 1/4 on an inch - Im suggesting laying those two coils flat towards the rear of the radio just for aesthetics - But it did swing about 5% extra - Not that anyone would notice .

[MDYoungblood]

3's

Greg