Re: Matching transformer for PL-380

Richard Jones

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.. 




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