There is no external antenna input on the PL-380. The DSP chip needs an inductor for AM/LW and a whip/wire for SW. The details are in the documentation at Silicone Labs website.
---In ultralightdx@..., <kugellager@...> wrote:
I don't think he is talking about directly soldering wires to the PL-380 antenna inputs. I think he is trying to match his 50 ohm coax to the input impedence of the antenna input using a torid matching transformer.
For example, I have a Rycom 1307A-GR which I use for my non-ultralight LW DX. Its RF input impedence is not the typical 50 ohm input but is a 3000+ ohm input. To match my 75 ohm RG6 Quad shield coax to the 3000 ohm input of the radio I need a matching transformer that gives me aobout a 40:1 RF ratio. For this I use a FT140 type J toroid with 38T:6T giving me about a 40:1 RF ratio.
This isolates the coax from the radio but still matches the two different impedences allowing for maximum signal transfer from the coax to the radio.
I think this is what Hans wants to do.
So the question is: What is the input impedence of the PL-380 antenna input? It seems like since it is a variable matching circuit there must be some ideal middle value impedence he can use to match the coax to the radio.
I would actually like to do this as well so that I do not have to lug around a fragile ferrite rod loopstick to inductively couple an external antenna as I do now. Internal antenna has been removed..