There is also a possibility that diodes used like this will cause
IMD when used near a strong RF Field. I agree with Roelof, don't
try to fix a problem that isn't there. I have used the antenna less
than 5 feet away from a 150 watt HF data transmitter without issue.
The U310 is a very good device.
Steve KD2OM/NNN0HSB
On 9/22/2010 4:34 PM, Marco IK1ODO wrote:
Hello Gerhard,
the 100n capacitor will do nothing, it is in series with the input
pad capacitance (a few pF).
The diodes will clamp at 0.6 V, that is too low (every static
"crack" will send the diodes in conduction) and limits the dynamic
range.
More, they will add capacity (2 pF each?) at the very critical
point of the amplifier input, decreasing the gain.
I think I will leave the gate alone, as in the original design.
Possibly the idea of a small reed relay to be closed in TX may be
better; those have very low C. But I will do that only after the
ninth burnt J310 - they are so cheap from Roelof :-) (just
jocking, of course, I could not resist)
73 - Marco IK1ODO
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