Fake SD1407

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XXL
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Fake SD1407

Post by XXL » Tue Feb 04, 2020 1:06 pm

Got a few SD1407 transistors that I’m struggling to get power out of. I’m driving it with a 30w fet and only seems to output about 40w. Iv spent ages on the amp playing with matching but Iv had no luck.

Iv even had it on one of those classic 150w broadband amps that is posted all over the internet. That’s even worse. Gives me around 5w. And the amp is tuned only .4 MHz away.

Iv tested it using a multimeter and seems to be in working order. Iv used fakes before and seem fine. I’m lost.

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BriansBrain
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Re: Fake SD1407

Post by BriansBrain » Tue Feb 04, 2020 6:58 pm

What make is the SD1407, have you got any pictures ?
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teckniqs
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Re: Fake SD1407

Post by teckniqs » Tue Feb 04, 2020 8:20 pm

I usually drive them with about 15 to 20w, 30w is overdriving them.

....I had some cheap sd1460 once from China and they worked really well instead of the genuine 1407 that ran really hot they gave me about 20w more watts and ran nearly stone cold.

Maybe I was just lucky as I've had other stuff from China that wasn't so good.

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Re: Fake SD1407

Post by radium98 » Wed Feb 05, 2020 7:17 am

sd1407 FT:30mhz ? datasheet

s2000
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Re: Fake SD1407

Post by s2000 » Wed Feb 05, 2020 12:01 pm

The original ones were 30mhz devices, as far as I am aware the only ones that worked well on the fm band were ST ones. Maybe the fake copies you have would be ok on 30mhz but not fm?

I would try Tecknics suggestion and try a fake sd1460, the original was designed for the fm band so the copy would be more likely to work.

In the original 150w broadband design, also the TP9382 and TP9383 work really well with a bit of adjustment on the coils.

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teckniqs
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Re: Fake SD1407

Post by teckniqs » Wed Feb 05, 2020 4:46 pm

Yes the SD1407 was usually found in power amplifers for CB and HAM radio down on the HF bands up to 30MHz but they were found to work well up on the FM bands only they need a lot more drive as they have a lot less gain further up the bands.

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