Re: On the subject of fake IRF510

Mvs Sarma <mvs_sarma@...>

 You also need to check the possibility of getting a genuine RD16HHF1.
 while selecting RD device,  I recollect some one using RD16(15)HVF1 and their feeling was it improves gain at 21 and 28MHz, though the device is not meant for HF.

All the best

On Sunday, 16 July 2017 11:42 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

I considered moving from the IRF510 to the RD16HHF1.
In a TO-220, better heat dissipation, tab is tied to source pin.
Designed specifically for RF service at Bitx40 power levels.
Only 10x the price of an IRF510.

Pins are swapped around a bit from the IRF510, though that's easy enough to accommodate.
Vds max of 50v, vs 100v for the IRF510.
Threshold voltage might be higher than the IRF510, though probably within range for the Bitx40's RV1.

The low Vds max means it's not a good idea to feed an RD16HHF1 PA  with
more than 12v, whereas the IRF510 does well at 24v.
If I need better than the Bitx40's single IRF510,
will go to a push-pull IRF510 pair like the uBitx or WA2EBY amp.
Beyond that, multiple IRF510's in parallel on each leg of a push-pull amp as Allison is doing.

If swapping in random NFET's for the IRF510, you need to look hard at Vds-max and Vth.
Also the inter-electrode capacitances, this is typically what prevents the use of other switching FET's
meant for use at sub-MHz frequencies, our 2n2219a driver stage simply can't deal with the low impedance load
it sees at RF.  The IRF510 has an unusually low Qg (the total gate charge).

The IRF510 works fine if it has enough heatsink to keep it cool.
Maybe invest a few pennies in TO-220 insulators and heat paste.
Ideal for experimenters, cheap enough to have a dozen of them on hand in case you have a learning experience.

But as this thread has shown, buy from a reputable distributor, avoid those awesome deals on ebay.
Hard to imagine why anybody bothers to counterfeit the IRF510, as it's under $0.50 in quantity. 

Jerry, KE7ER

On Sat, Jul 15, 2017 at 03:25 pm, Andrew Krause wrote:
Is there an alternative in a TO-220 package? 
. . .

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