[Milsurplus] TCS matching

[Rob Flory]

Dear Roger, copied to the group,

How are you?

I think maybe you were the one who commented on my youtube video, and then I saw your post on milsurplus about antenna matching with the TCS.  As others have pointed out the TCS (like so many other military radios) is made to tune into an electrically short antenna, meaning a low resistive with capacitive reactance.  The step down(looking from transmitter side) balun with a series capacitance serves well.  I have done well with hundreds of picofarads series cap.   

One way to implement the impedance transformation is to use 2 quarter wave sections(electrical, meaning take velocity factor into account) of 50-ohm coax paralleled up from the 50ish ohm resistive antenna to the series capacitor, and then the capacitor to the TCS antenna input.

Transmission line transformers a la Jerry Sevick W2FMI do a nice and elegant job on multiple bands, but if no cores in hand and an antenna that needs feeding on one band, the coax setup does nicely.  I did this with a full quarter wavelength on 80m and it fed well on 160 and 80 with a 400pF cap in series.

73, RF
K2WI