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antenna tuner help

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD0OCN, Aug 26, 2011.

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  1. KD0OCN

    KD0OCN Ham Member QRZ Page

    I just picked up an MFJ -941D tuner that does 10m-160m, only problem i have is i have never used a tuner before. i have used swr meters to tune the antenna in the area i want to use it for but since i am back and forth from cb to 10 meters my antenna is a bit off to do both.

    a few questions regarding the operation of this tuner:

    is this the correct way to hook it inline:

    radio to antenna tuner input, antenna tuner output to input of SWR meter, swr meter output to antenna?

    the process of matching should it go in this order:

    set unductor setting to closest area of transmit, then tune the transmitter matching knob to lowest swr on other meter, then tune the antenna matching knob to check for lower swr?

    is there any maintenance that ever needs to be done to this antenna tuner?

    i should point out that i am tuning my galaxy saturn turbo 10m radio at 150watts and the swr meter is a SX-200 diamond and the antenna is an IMAX 2000 10/11 meter 5/8 wave omni antenna
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    You've got the SWR meter in the wrong place, it will always read the same no matter where you set the antenna tuner.

    The SWR bridge should be between the transmitter and the antenna tuner -- NOT between the tuner and the antenna.
  3. KD0OCN

    KD0OCN Ham Member QRZ Page

    ok i have that correct.

    do i need to clean the tuner inside? every once in a while as i am turning a knob the swr spikes randomly then goes away almost instantly back to where i left off. dirty?

    how does the swr/ watt meter work on this tuner? set the swr to the end of the red then switch it to reflected power?

    as for the power meter on the tuner, is it average or pep?

    i know my radio does 150+ but the meter on the mfj says 60 and the sx-200 says roughly 150 avg
  4. KD5SPX

    KD5SPX Ham Member QRZ Page

  5. M0GVZ

    M0GVZ Ham Member QRZ Page

    Here is how to use that tuner.

    First of all the SWR meter. There is no need to adjust it. Just select SWR on the SWR/POWER switch. If you want to read power, first of all make sure the 30/300W switch is in the right position and then flick the SWR/POWER switch to POWER and key up.

    How to tune.

    Firstly turn the power down on your radio. If you try to tune it with 100W CW carrier with a large untuned SWR you will fry the SWR sensing diodes due to the thousands of volts that can be present at such a mismatch. 20W is OK.
    Secondly, put both the Antenna and Transmitter knobs to 5. Turn the Inductor selector until you hear the loudest background noise. At this point key up the radio. Adjust the transmitter match first for the lowest dip and then the antenna match to bring that down lower. You may find that a further tweak of the transmitter match will drop it down even further. Wind up the power and then you may find out you need to carry out a bit more fine adjustment. If you find you can't get near a 1:1 SWR, wind on a bit more inductance by turning the inductor knob clockwise one position (A is lowest induction, L is highest) then carry out the tuning procedure again from scratch.

    With mine, because I was using the same antenna at the same location, I noted down all the settings for each band - although on 80m and 160m you'll need to make several. You will find that they won't give you 1:1 every time but will get you close enough.
    Last edited: Aug 26, 2011
  6. KD0OCN

    KD0OCN Ham Member QRZ Page

    thank you. that really helped alot.

    with a 50 watt carrier on AM i adjusted the tuner accordingly, i was only able to get it to a 1:4 swr ratio at lowest on 10 meters.

    I made a map of all the common frequencies i use and tune through.

    28.3000mhz it goes as transmitter matching: 5, inductor: C and antenna matching 1

    28.5000mhz it goes as transmitter matching: 4.5, inductor: B and antenna matching 1

    with the amp off in the radio it has a 7 watt carrier with swing, i tested it at that first then readjusted it with high power and fine tuned it best i could. 1:4 was lowest with high power and 1:1 or 1:2 on low power
  7. KD0OCN

    KD0OCN Ham Member QRZ Page

    i did notice after i had it tuned and when i was talking, my swr would occasionally spike and receive go away. i found that if i move the antenna selector knob a few positions then back again it worked fine after that. i think its dirty? can anyone tell me what to do to it?
  8. K6BIG

    K6BIG Ham Member QRZ Page

    This tuner will wear you out. Go get yourself a good tuner like a cross needle or
    find a used Kenwood At 230 or equiv. If you are seeing the spikes and receive
    troubles you mention, one of the diodes or rollers might be toast already.
    Don't fry a good transceiver with a rotten tuner

    oh and if you still think still think it is only dirty.. a good spray from contact cleaner would not hurt
    internals.. but make certain the contact cleaner does not have a lubricant!!
  9. G0GQK

    G0GQK Ham Member QRZ Page

    When you're adjusting the ATU only use minimum power, 5-10 watts, start whacking out full power before you've checked the SWR properly might become expensive
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