[Milsurplus] [Army-Radios] TCS Antenna Matching, Again.

Wed Jan 27 10:20:19 EST 2021

Hi Dave – 

I have mentioned this previously several times. My preferred method was to use a 4 to one RF transformer. A UNUN where the 1 goes to the set and the 4 goes to the resonant antenna. This has worked for me just fine on the TCS, the BC-474 and the WS-19. I am sure it will work with a lot of others as well. 73 – Mike

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

848-245-9115

-----Original Message-----
From: main at Army-Radios.groups.io <main at Army-Radios.groups.io> On Behalf Of David Stinson
Sent: Wednesday, January 27, 2021 9:50 AM
To: milsurplus at mailman <milsurplus at mailman.qth.net>; Boatanchors at mailman <boatanchors at mailman.qth.net>
Subject: [Army-Radios] TCS Antenna Matching, Again.

Good Morning.

I'm de-bugging TCS-13 RX/TX  to prepare them for trade.  Was discussing this with a friend who says he's going to "get around to getting mine on the air."  He said he needed to gather a bunch of parts to "build a matching box for the antenna" and/or add turns to the link output.   We've talked about this before, but perhaps it is time to take this old horse out for another ride.

Each to his own, of course.  But if your goal is to match the output of your TCS to a 50-ohm, resonant, coax-fed antenna, you need exactly *one* part per band:

A good-quality, RF capable capacitor

like these 100pFd from Ebay:

 <https://www.ebay.com/itm/264384761640> https://www.ebay.com/itm/264384761640

 <https://www.ebay.com/itm/192780283722> https://www.ebay.com/itm/192780283722

Shop around, because some suppliers think they are made of gold.  The ones from Ukraine and Russia are usually good, but there are exceptions. These from Russia are also garbage.  Threw them all in the trash:

 <https://www.ebay.com/itm/274483321049> https://www.ebay.com/itm/274483321049

Do NOT buy the blue or red dipped ceramics.

These are Chinese garbage and useless at RF.

Here's the one I prefer.  They show-up on Ebay from time to time.  You should grab some.

 <https://photos.app.goo.gl/giUwmLB9uDmDEEPq8> https://photos.app.goo.gl/giUwmLB9uDmDEEPq8

For 75-80 Meters, use 100 pFd.  It connects in series with your coax center conductor and Antenna connector, NOT to ground.

For 40-30 Meters, just switch the lower-left control to "SERIES."  This places an internal 50 pFd cap in the circuit and the rig will tune right up on those bands into your 50-ohm load.

I don't remember what I used for 160M,

but it was somewhere between 750 pFd and

1000 pFd, a good USA- or UK-made high voltage disc ceramic.

In this video, the transmitter ANT post

is connected to a coax jumper.  That runs to the Wattmeter (not using the tuner- using the dummy load).  The coax jumper center conductor goes to the cap and the other end of the cap goes to the

SO-238 center pin connection.  Coax

shield to ground, of course.  Here is the result of this configuration on 75M:

 <https://photos.app.goo.gl/cWKT5nhQbKuhWJaT9> https://photos.app.goo.gl/cWKT5nhQbKuhWJaT9

Everyone do what they think best, of course.

As for me, "simpler is better."

GL OM ES 73 DE Dave AB5S

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