[Lowfer] active whip - continued

[Eric Smith]

On Sun, 13 Jul 2003, Mark Phillips wrote:

> Whose active whip was it?  I'd like to try a similar trick myself.

Hi, gang,

Well, it is based on the AMRAD active whip.  If you want to build the 
full-blown original design (which I did not) or if you just want to see 
what this is all about, check http://www.amrad.org/lf/actant/ ... this 
appeared in a September, 2001 QST article.

The version I built is based on a suggestion in the AMRAD FAQ (that FAQ is 
also available at the above URL) and has (what are in my mind) several 
advantages:

 - Uses the cheap J310 JFET instead of the $15 ($20 by the time you get it 
to your house) JFET of the original version.

 - Runs on a 12V supply instead of 24.  I don't need to tell you why THIS 
is an advantage :)

 - Does not require the special power supply (and expensive transformer).

 - No alignment.

 - Simpler circuit -- easier to build!

 - No heat sink -- easier to build!

All these advantages do not come without some compromise, as noted in the 
AMRAD FAQ.  They mention that the J310 is not quite as linear, for 
example.  For me, as a newbie, I don't know if I'm an experienced RX-er 
enough to tell the difference, though, and this version is much easier and 
cheaper to build.  I have not made any real measurements, but I am way 
impressed with how well it works.  Definitely rivals my 30' LowFER 
vertical for reception, and this is only a 1 meter whip.

They publish a response curve that is nearly flat from 10 kHz to 30 MHz.  
That's not a type-o: 10 kc to 30 Mc.  Amazing, huh?  Of course, that 
published curve is of the original version.  Check that URL.

If you'd like the schematics for the one I built ask me off the reflector 
and I'll send them to you directly. 

73
Eric, KD5UWL