On Jul 27, 12:53*am, "~ RHF" wrote:
On Jul 25, 6:23*pm, Ross Archer wrote:



I'd like to try building an *untuned* loop amplifier covering HF and
wonder if anyone has seen links on this.

The thinking so far is using a pair of 2n2219a bipolar transistors
running a few hundred milliamps, with their collectors driving
opposite ends of an RF output transformer, and a reasonably large loop
(say 1 meter square or more).

I'd like the output to be "hot" enough to compensate for a losses from
a nice long run of cheap cable-TV type coax cable (through which power
will be fed up to the amp). *But not so "hot" as to create distortion..

Anyone here have experience with this sort of project? *If so, is the
2n2219a a stupid choice? *Would I be better with JFETs, and would a
single-ended amplifier work almost as well as a balanced amp? *(My
thinking is the balanced amp would potentially be quieter.)

It would be fun to try this, and my junk box is overflowing with
parts, so why not?

-- ross

Add-On Loop Antenna Amplifier -by- Bruce Carterhttp://www.hard-core-dx.com/nordicdx/antenna/loop/amamp2.html

Balanced Loop Amplifierhttp://jlkolb.cts.com/site/dif_fet.pdf

Loop Antenna with Balanced Amplifierhttp://www.qrss.thersgb.net/active-loop-receiving-antenna.html

Thanks for the links.

The first one is not balanced, but I suppose it might come in handy
someday. AM DX fun.
The second one is tuned - but there's nothing in the circuit to
suggest it couldn't work with an untuned loop. Looks good!
The third one looks super-promising. Untuned input and transformer-
coupled output. I may just build this or something along these
lines.

Thanks a bunch.

-- ross