Tuner vs no tuner in EndFed40 qrp

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD2RON, Mar 12, 2018.

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  1. KD2RON

    KD2RON Ham Member QRZ Page

    Just ordered a MTR qrp rig puts out only 3 W. Using LNR EndFed 40 M and active on aprox 7.050 and around 7.114 . Is their any way to judge if I would be better office using a tuner and getting the SWR to show 0 on the meter or should I trim the endfed to one freq and live with a modest SWR on the others. Any tips on trimming endfeds. I've trimmed my dipole but does a endfed have special considerations? Thanks for any input.
  2. AI3V

    AI3V Ham Member QRZ Page

  3. WN1MB

    WN1MB Ham Member QRZ Page

    Or...if the lowest band you plan on operating is 40 meters, you could just use a nondescript hunk of wire approximately 5% shorter than a half wave - say 60' - and tune it with a basic L-network antenna tuner. A 30' counterpoise wire is suggested. This combo should tune on higher bands, too.
  4. KM4DYX

    KM4DYX XML Subscriber QRZ Page

    I've always favored trimming the antenna to using a tuner when QRP figuring that I couldn't afford any loss whatsoever. I've used the LNR Trail Friendly 40/20/10 end fed antenna. My unscientific backyard testing indicated that it was a bit more sensitive (SWR wise) than a dipole to height above ground. So don't be too quick to trim too much unless you're going to always be putting it up at about the same height. Another trick is to fit the end with a connector (power pole, spade, etc) and have some various lengths of wire with matching connectors handy to add length to the antenna as required. Good luck.

  5. KU3X

    KU3X Ham Member QRZ Page

    If the SWR is above 1.5 to 1, most solid state radios cut back on power. If the SWR is in the range of what the finals in your radio is designed handle, using a tuner
    will not help your ERP.
    This is the EFHW40 that I use and I never use a tuner since none is ever needed.


    The AA-600 shows the SWR of the antenna with the feed point at 26 feet in the air and the other end of the antenna about 15 feet in the air. My radio is a KX2 and
    I put the tuner in bypass all of the time.

    Barry, KU3X

  6. AI3V

    AI3V Ham Member QRZ Page

    How exactly are you getting the rf to the "end" of your wire?

    You wouldn't possibly be using another wire, connected to your "end fed" ?

    What you ment to post was something like: I installed 1/2 of an antenna. Due to luck it happened to have a sufficient counterpoise, and, coupled with the vswr reducing properties of a lossy impedance matching network and coax operated with high vswr, the impedance seen by my rig doesn't seem to cause issues with output power.

    Since my final is a fixed tuned circuit, of course power changes with load impedance, but due to modern methods of transistor manufacturing the devices sustain no damage.

  7. KU3X

    KU3X Ham Member QRZ Page

    NO ! I did not mean to post what you said ! Everything you said is totally wrong.
    Luck has nothing to do with. It may for you!.....but not for me. I know exactly what I designed and I know exactly what the losses are and they are very low. Maybe when you design antennas they are lossy, but mine aren't.

    Barry, KU3X
  8. W4KJG

    W4KJG Subscriber QRZ Page

    We sure have had a lot of questions recently about end-fed antennas.

    Over the last century there have been countless studies, articles, and books written about end-fed wire antennas. Thousands of the writeups are available by just asking your friend Google to find some of them.

    Not much has changed over these last 100 years, except maybe the very early introduction of coaxial cable and the use powdered-iron/ferrite toroidal core inductors.

    You can choose to put up a non-resonant wire that is generally non-quarterwave and non-halfwave on the bands where you wish to operate. There are many good charts and tables that show approximate lengths to use, and not to use.

    There are several easy, inexpensive, and low loss choices on how you can feed it.

    One of the simplest and most inexpensive methods is put a 1:9 transformer between where the wire connects to your coax. This was really popularized starting about 10 years ago by the Emergency Amateur Radio Club of Hawaii (EARCHI). Plans are described in this PDF: http://www.earchi.org/92011endfedfiles/Endfed6_40.pdf

    They recommend a tuner between the transmitter and coax, but I've found that I can have less than a 3:1 VSWR, usually less than 2.5:1, everywhere I plan to operate by trimming the radiating element. With a tuner at the transmitter, it is easy to tune a 1.1:1 VSWR. The transformer, plus the coax, plus a simple L-network is minimal enough that no one on the receiving end will notice.

    The other alternative is to buy or build a very simple tuner for use between the wire and the coax. A simple L-Network tuner is extremely easy to build and will match nearly any wire you have in the sky, with below 1 dB of insertion loss for a 1.1:1 VSWR.

    The key to all of this is to have a counterpoise. It doesn't have to be fancy. The radiating element just needs to have a complete circuit with the earth. Think of it like a battery and a flashlight bulb. One wire from the battery to the bulb will not light the bulb. You need the counterpoise to be the other half of the cicuit, just like you need the second wire connected between the bulb and battery.
    KU3X and W8IXI like this.

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