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My apologies guys for posting this to the list, but I'm trying to get in touch with John Crabtree and my mail to his aol address has bounced. If this gets to you, John, can you please get in touch

That's not at all unlikely. It would be very useful to do a bench comparison to see how various devices compare. I've gone to great lengths in the past to select bipolar transistors for linearity by

stage. and Trying to get positive gain out of similar circuits is proving to be a real challenge, and it's interesting to see how the 10pF whip modeling capacitor makes significant changes in the

My active whip used a U-310, not a J-309. Intercepts of my active whip in the MW band were typically +43 dBm OIP3 and +83 dBm OIP2. They might be slightly lower at the frequencies Steve used, but

Hi Patrick, For the optimum intercepts for an active whipamp, one should optimize it for the actual whip length that will be used. But for a circuit such as mine that has such high intercepts to begin

Hi Chris, Thanks for your detailed comments. It's clear you've put some thought into this problem of a high dynamic range untuned high impedance amplifier, for use as an active whipamp. I've been

for source MHz circuit. pF Yes, I'm beginning to see why there is such a substantial difference between the two. I've spent the entire efternoon with my PSpice models trying to locate the source of

Hi Steve, so basically, there is no difference in the IMD performance with a different antenna capacitance. This is a good thing, since I observed a dependancy on the typical common-source jFET +

Just for completeness, I should mention that I use 3 and 4 MHz tones for all my IMD testing, and for these circuits, set for -10 dBm each tone at the output, as seen on the spectrum analyzer. Steve

Hi Chris, Reconfiguring with a 1 uF monolithic input cap, resetting jfet gate bias for minimum 2IMD: +25 dBm OIP3, +48 dBm OIP2. Vcc 12.87 volts, 26 mA. Drain 4.51 volts, source 1.80 volts, emitter

Prior to breadboarding this, I went back and forth with the PSpice models to determine where the discrepancies. I went so far as to remove the 2N2907 emitter bypass capacitor, but that resulted in a

I'm going to build and test this later. The gain should have improved to about -0.5dB.

Hi Chris, Your revised circuit is just built and tested. Same testing configuration as before (10 pF series input cap with 51 ohm termination at input, to generator; 1 uF output cap; jfet gate bias

get Okay, I see what I did here that made a mess of things. I had hurredly adapted a two bipolar transistor circuit used for low power applications by substituting a JFET for the NPN device and then

The 1/2 size G5RV-style antenna is a simply the full size antenna with the dimensions halved. two 25.5 foot wires connected to 15.5 feet of twin-lead and feed with a length (probably 35-foot) of coax.

In a message dated 09/06/2007 04:13:38 GMT Daylight Time, frtglz@... writes: I would like to request a complete design of a half size G5RV that covers 7-28mhz (not sure) My space between

I would like to request a complete design of a half size G5RV that covers 7-28mhz (not sure) My space between supports is 55feet. I will also try it as a loop antenna.

Hi Chris, OK, I'll be around, ready to try a new configuration/bias, etc. Hope you get it figured out eventually. Have a good trip. 73, Steve

Hi Rob, The gate voltage/pot bias method is a nice way to vary the bias; I've used that method for many years on the various active whips I've built, both for hobby and at the company before I