[Lowfer] more on preamplifiers

[Jay Rusgrove]

Just a further note...

The preamplifier referenced in John's loop antenna article is much more robust in terms of 2nd and 3rd order IM distortion than the JFET preamplifier you are using. This means that his preamplifier might not overload itself, but it's possible the additional gain from the preamplifier could cause overload in the receiver. If it turns out to be receiver overload rather than preamplifier overload then a filter between the preamplifier and the receiver could work.

You can determine if overload is coming from the preamplifier or the receiver by temporarily inserting a 50 ohm attenuator ( 6 dB for example) between the preamplifier and the receiver. If the interference drops by an amount equal to the amount of attenuation the problem is in the preamplifier. If the interference drops by more than the amount of the attenuation (2 or 3 times the amount of the attenuation) the problem is in the receiver.

The aliens have descended.

Jay W1VD / WD2XNS