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MRF477
- Thread starter Green Tiger
- Start date
It does not come insulated as a stock 2510 radio but it IS greatly recommended to insulate it if you increase the output power. If the radio is completely stock then don't worry about it to much but if you plan or it already has Rogerbird mods done to it I would insulate it. Once you turn up the power out and the final gets hotter than normal, you'll understand why.
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Emitter = negative or - is on the tab no insulation needed just some heasink compound.
Just my .02 cents. I had a 2510 that was dropping out on xmit. Had some intermittent issues. I sent it to DOCS as he was the man on these...no offense to Rogerbird as he's a guru as well, and he spent some time on it and found that the issue was the 477 being insulated. He fixed that and did all his other mods to it and I never had an issue after that.
The Final has no insulator from the factory, that's how they are built.
There are known cases were they "can" have an issue.
In my experience I have seen one 2510 that exhibited the goofy high SWR with the covers on problem.
That one radio putting an insulator behind the final stopped the issue.
It's an exception not the rule.
The 2510 and Lincoln I have now have no insulator in them and work fine.
The info can be found on Rogers page.
See below.
73
Jeff
There are known cases were they "can" have an issue.
In my experience I have seen one 2510 that exhibited the goofy high SWR with the covers on problem.
That one radio putting an insulator behind the final stopped the issue.
It's an exception not the rule.
The 2510 and Lincoln I have now have no insulator in them and work fine.
The info can be found on Rogers page.
See below.
73
Jeff
thermal grease on both sides of an insulator does not worsen thermal path.
And that is why I said it would need one... if the swr issue arises. That's why I wrote "If the radio is completely stock then don't worry about it "
The heatsink is aluminum and not a great conductor of ground which can cause a higher swr problem as the final gets hotter. Key word...Hotter. The 477 final mounting TAB is a power ground not a chassis ground. Sure the heatsink is soldered to the board in a couple spots as chassis ground but its not enough and it is not a true ground. It can cause RF feedback without an insulator at higher power levels.
It was suggested by Doc(who was a local friend... R.I.P.) and Rogerbird(a pure genius) to run a copper braid from the heatsink to a tuning can for better ground so that the higher swr, if any, can be controlled.
These are all things I have dealt with working on my fair share of 2510's that have been modified away from stock that put out higher watts. Even worse, is if you do the MRF455 mod which needs 2 fans to keep it cooler. Without the fans it turns into shit show.
The following is right from Rogerbirds website.
Cure for High SWR with covers off or on
Usually this problem is caused by the fact that Uniden did not install an insulator between the MRF477 Final and the heatsink.
The mounting tab of the MRF477 (and MRF497) is 'Power' Ground and the heatsink is 'Chassi' Ground.
Meeting through the final can cause a 'RF ground loop effect' which tends to cause the High SWR issue.
The cure is to add an insulator between the Final and heatsink. Be sure to add a thin coat of Thermal Grease to both sides of the insulator.
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