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Re: Damage to SMT version bitx40 from nearby transmitter


 


You would have landed up with thyristors!!

At 29/12/2016, you wrote:

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No doubt, Jerry, I was just afraid that someone with less knowledge ( like me :) ) might order the 2n4148s without understanding the difference. 73 and thanks for advising.

Sent from my iPad

On Dec 28, 2016, at 3:10 PM, jgaffke@... [BITX20] <BITX20@... > wrote:

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Yup, 1n4148's, or whatever it was that Raj was suggesting.
Would be very tough to find some 2n4148 diodes ;-)
?

---In BITX20@..., wrote :

Jerry - don't you mean 1n4148 diodes , not 2n4148? Please advise. 73 w4usf

Sent from my iPad

On Dec 28, 2016, at 1:11 AM, jgaffke@... [BITX20] <BITX20@... > wrote:

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Raj's suggestion of two back-to-back 2n4148 diodes between K1 pin 12 and ground puts them only in the receive signal path.? That seems the ideal spot.

K1 pin 14 is in the transmit signal path, a relatively low level signal from the exciter into Q13.
Perhaps you were looking at K2 when you suggested pin 14?
K2 pin 14 is only in the receive path, but does not have the benefit of the impedance of that long trace from K2 to K1, which might keep the diodes from blowing.

Jerry, KE7ER


---In BITX20@..., wrote :
?Looking at the schematic, I would put the diodes between pin 14 and ground.
?This puts them in RX? only.?

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