Hello, I am new to this forum and have been reading and learning tons here. My question is this. I have one of the new Uniden 980 ssb radios and loved it till the crappy RD16HHF1 transistor went south. When I was removing the transistor I noticed it was just mounted right on the back of radio with a little heat sink but no insulator like the old transistors are. Is this something new with the Mosfet transistors or what. Can you mount them right up with no insulator ? Thank you for any help on this dilemma...
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New Mosfet transistors
- Thread starter basstracker1970
- Start date
So if i use a mica insulator as you suggest what about the steel screw they used to mount it that would cause it to ground should i use like a plastic screw and nut so it wont ground to the back. Why would uniden just put it in there like that with no mica insulator and a steel screw to bolt it down?
I would mount it as the factory did. Contrary to popular belief they DO know what they are doing. As for whether an insulator is needed depends on the construction of the device. If the element to be grounded is indeed connected to the case then it is best NOT to use any insulator as it creates another mating surface that needs to be thermally bonded as well as means that some form of ground wire must be installed which can create it's own set of problems related to RF feedback etc. Not using an insulator is not new or unique to MOSFETS. Bipolar transistors have been constructed with the emitter connected to the case which allows the device to be grounded directy and others have the collector connected to the case for better thermal transfer. These devices can be connected directly to the heatsink if the heatsink is floated above ground. In short do as the factory did. It will result in fewer thermal junctions which will result in better heat transfer.
Does the IRF520N Mosfet transistor need a mica insulator or can it be mounted directly to the back without?
If you plan on putting in an IRF520 for a replacement, you'll need to observe the pins, as the IRF520 and the RD16HHF1 are NOT the same pinout. Two of the pins are reversed between the two, the Drain and the Source. If you look up the datasheets for each, and reverse the Drain and Source pins, it should work with just a minor retune of the bias voltage. The bias voltage on an IRF520 should be around 3.8V at the Gate.
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Old Thread but here goes I have a v2 of the 980 on the bench with UFZ24NL final in it would there be any benefit in swapping in a 520? Pick up any out put The 880 I have with the irf520 does way better out put than this thing.
mosfet tabs are the same as the drain so running without an insulator would cause a ton of problems
I would venture to say that only someone who has tried it can answer that question.
What will be harder to predict is which one goes "POOF!" quicker when the SWR gets too high.
For my money that would qualify as "out perform". Not sure how you would tell without blowing up a batch of each, keeping careful records of circuit measurements at the moment of death.
73
This whole part number is just new to me never seen one in a radio before couldn't find a reliable data sheet to compare it against a 520.
The data sheet should come up at http://www.alldatasheet.com
But it won't tell you one thing about RF amplifier service. Wasn't built to do that, so all the specs will tell you is how efficient it is switching DC circuits on and off 50,000 times a second, more or less.
The RD16HHF1 is designed to amplify RF, and the specs will spell this out. It will usually tolerate high SWR until someone turns up the gate voltage trimpot and croaks it. This is that part's one weakness. Tweakeritis will kill it.
73
But it won't tell you one thing about RF amplifier service. Wasn't built to do that, so all the specs will tell you is how efficient it is switching DC circuits on and off 50,000 times a second, more or less.
The RD16HHF1 is designed to amplify RF, and the specs will spell this out. It will usually tolerate high SWR until someone turns up the gate voltage trimpot and croaks it. This is that part's one weakness. Tweakeritis will kill it.
73
Went and looked the part up on alldatasheet.com, from the first page of the data sheet:
"The UTC UFZ24N is an N-channel Power MOSFET, it uses UTC’s advanced technology to provide the customers with a minimum on state resistance, high switching speed and low gate charge."
URL: https://pdf1.alldatasheet.com/datasheet-pdf/view/581535/UTC/UFZ24NL-TA3-T.html
If the selling point is high switching speed, it's probably not intended to amplify RF. Obviously it can, but that's a bonus function.
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