"Antenna Tuner" vs. "Transmatch" terminology

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N2EY, Apr 7, 2021.

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  1. N2EY

    N2EY XML Subscriber QRZ Page

    In Amateur Radio, the terms "Antenna Tuner" and "ATU" (for "Antenna Tuning Unit") have become pretty standard.

    I say a better term is "Transmatch". Here's why:

    In most applications, the "Antenna Tuner" or "ATU" is in the shack. In some cases it's actually part of the radio. Nothing wrong with that.

    But such a device doesn't "tune the antenna" at all. What it does is to match the transmission line impedance to what the transmitter/transceiver wants to see (typically 50 ohms pure resistance).

    So, the term "Transmatch", derived from "Transmission line matcher" is much more descriptive and accurate, because it describes what's actually being done.

    The earliest use of the term "Transmatch" that I could find is in QST for July, 1961, in an article by W1ICP ("The 50-Ohmer Transmatch"). It appears again in November of that year in another W1ICP article ("A Wide Range Transmatch") and many times since.

    Shouldn't we use the most-descriptive term?

    73 de Jim, N2EY
    N8ZL, WA8FOZ, KF4NU and 6 others like this.
  2. N2EY

    N2EY XML Subscriber QRZ Page

    To add to the above: Even before the term "Transmatch", EF Johnson had their "Matchboxes".

    73 de Jim, N2EY
    N8ZL, WA8FOZ, K0UO and 1 other person like this.
  3. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    I have to say "Transmatch" is by far the most descriptive to me. I've always disliked "antenna tuner" unless it's me on a ladder with an SWR meter and some hand tools, adjusting the length of a dipole :)

    WD4ELG, N0YPD, K2CAJ and 5 others like this.
  4. N2EY

    N2EY XML Subscriber QRZ Page


    Opinions differ, of course, and we don't always use the most-accurate term.

    (TNX for the title fix)

    73 de Jim, N2EY
    W7UUU likes this.
  5. K1APJ

    K1APJ XML Subscriber QRZ Page

    Of course, some boatanchors had "antenna trimmers", but no matter how hard I tried, turning that knob left my antenna at its original length...
    N8ZL, WA8FOZ, AK5B and 2 others like this.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I made a transmatch once.

    Started out with a small, thin wooden stick. Dipped in potassium chlorate paste and baked until hardened, then same end dipped again in phosphorus paste and baked again until hardened.

    A safety match from a small stick of wood! Clearly a trans-match.:)
  7. N2EY

    N2EY XML Subscriber QRZ Page

    The "50-Ohmer Transmatch" uses the same circuit as "The Ultimate Transmatch" of almost a decade later (July 1970). However the "50 Ohmer" version used tapped Miniductor and did not include a balun, while the "Ultimate" used a roller inductor, had a toroid-core balun, and used larger value variable capacitors to get wider matching range.

    The "Wide Range Transmatch" also appeared in several editions of the ARRL Handbook. It is a version of the classic link-coupled balanced circuit, with additional capacitors to increase the matching range, and bandswitching (no plug-in coils). The version shown is good for up to 500 watts CW or SSB. Capacitors of lesser plate spacing can be used for lower power applications.

    73 de Jim, N2EY
  8. W2SGM

    W2SGM Ham Member QRZ Page

    Aw, you changed the title. I clicked because Subject: "What" was just so plaintive, and stayed because I could relate to the confusion over why the misnomer is still around. :) I personally like the term "matchbox" because it's catchier.

    Proof that the terms manufacturers use make a difference: even Motorola's army of lawyers couldn't get "PL/Private Line" out of general usage during the peak of its business importance, and to this day we still see confusion about tones stemming from that misnomer.

    Maybe it's a matter of perspective. From the finals' standpoint, the ATU certainly tuned something.
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    Take a slightly off-resonance dipole. Feed it with an arbitrary length of 50 Ohm coax. The impedance looking into the coax at the transmitter is not a perfect 50 + j0 Ohms, but is close enough that the transmitter delivers at least some RF to that load.

    Measure the magnitude and phase of the voltage V right across the antenna feedpoint terminals. Measure the magnitude and phase of the current I in the antenna wire an inch or so on either side of the feedpoint.

    Now, add a LC matching network at the transmitter end of the coax, and adjust L and C until the impedance looking into the network is exactly 50 + j0 Ohms. Connect the transmitter to the network and go back and measure V and I at the antenna feedpoint.

    Guess what? Obvioulsly, the magnitudes of V and I are higher (why else use the matching network?).

    BUT... the Phase angle between V and I has been changed by the matching network, too. That means that adding and adjusting the LC network effected the feedpoint impedance (ratio of V to I) of the antenna.

    Is this not "tuning" the antenna???????
    AJ4WC, KJ7RDV and WA9UAA like this.
  10. AK5B

    AK5B Ham Member QRZ Page

    In the UK "antenna matching unit" or AMU is and has been quite the norm for a long time. Rightly so, I might add.;)


    W1BR, KI4IO and PU2OZT like this.

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