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I'm looking at offboarding the IRF510 on my 20m ver3b board and attaching to a heatsink outside the cabinet. To do that I'd need to extend the leads by about an inch. Would that be feasible or am I going to run into potential issues with instability and parasitics ? Thaks for your comments, 73 ZS2OE

Should not be a problem,? to reduce gate inductance related parastics etc you can add a ferrite bead or use trifilar wiring.
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AncelB, MIT EE6002

Totally reasonable, totally feasible.
You know, if you were carrying it a little distance, like 3 inches (7.6cm) you? could have Pin 2 travel back via a bit of short, RG174 coax, shield grounded (say, even to pin 3).

But - one inch - meh, don't bother, straight leads, no worries.

Mike Y, KM5Z (Darn! I need to make time for Sunday's net...)
Dallas, Texas

Mike could be right, could work fine at 7mhz with longer IRF510 leads.
But an RF amp like that can be awfully unpredictable.
A bit too much inductance in the gate lead and it might go into oscillation at VHF, for example.?
The source pin of the IRF510 has to be nailed hard to ground.
The drain should be kept clear of anything having to do with the gate.
As Ryan's plots have shown, performance is already falling off a bit at 7mhz on a stock Bitx40v3.

I'd suggest you measure DC power into the IRF510 drain and RF power out to the antenna
before and after the mod for a known signal (perhaps use Allard's CW mode).
If power out and efficiency remain as they are on a stock rig, that's probably good enough.

And take a look at this post from Allison:
? ??/g/BITX20/message/22597

Good luck.
Jerry, KE7ER

Thanks to everyone for the pointers...much appreciated. Will pay close attention to all suggestions.??
73, Paul ZS2OE

I'm still experimenting, but I may reverse my "lead length shouldn't matter much". Let's just say it's a good thing I have spare IRF510's. Although Jerry if my initial experiment was successful, I may have solved the output issue at 14mhz. More testing needs to be done.?
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Ryan Flowers W7RLF

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?<-- Learn how to go digital on the BITX40

Hi,
No problem but: isolate the IRF510 from the heatsink.!!
Rob