[Lowfer] My Active Loop is apparently dead

[Eric NO3M]

You could homebrew a suitable amplifier:

http://www.home.earthlink.net/~christrask/Wideband%20Loop%20Antenna%20Amplifier.pdf

The Trask design is a bit elaborate, a simpler alternative might be a 
high-impedance input source follower design (J310....) driving a normal 
50 or 75 ohm input preamp (2N5109 single or PP, J310, etc.).

The high impedance part is important for the first stage, so the term 
"peamp" needs to be used carefully, as a typical low-impedance (50 or 75 
ohm input) preamp directly connected to the loop will not work, loading 
down the antenna and diminishing the available signal voltage.  More 
appropriate is referring to it as a "buffer"; in most cases, there is 
actually a net loss, -6dBV being typical.  I don't have any knowledge of 
the Wellbrook design, but it probably includes a low impedance output 
amplifier after the buffer stage to boost the net gain.

Yet another alternative is to scrap the Wellbrook and just homebrew a 
multiturn loop, plenty of designs on the subject on the web (VE7SL, etc.).


73 Eric NO3M





On 11/20/19 9:05 PM, Andy - KU4XR via Lowfer wrote:
>   On Wednesday, November 20, 2019, 8:53:31 PM EST, David L. Wilson via Lowfer <lowfer at mailman.qth.net> wrote:
>
> The pre-amp is in the base of the loop. The separate box only contains
> coupling comonents-a diode, coil, and capacitor. These are likely not
> to fail. I amf n0ot sure how easy one can replace the pre-amp at the
> base of the loop.
>