Multiple Antennas through amp

Discussion in 'Amateur Radio Amplifiers' started by K4NUC, Feb 10, 2019 at 3:58 PM.

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  1. K4NUC

    K4NUC Ham Member QRZ Page

    I am curious how others have hooked up multiple antennas to an amp with one input/output.
    I have an ftdx3000d with has 3 antenna outputs. Ant 1 is to a hex that is through the amertitron 606 and works great (auto band changing connected). My next antenna is a double bazooka for 40M and the third a double bazooka for 80m. What's the best way to get the 40 and 80 through the amp? 3 way antenna switches before and after the amp? I don't particularly want to manually switch every time an antenna is changed. What is everyone else doing? 73
     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    When you use an amplifier in line the amplifier has to be looking at the antenna when in use and not the radio. You may have 3 antenna ports on your radio but it doesn't do any good when the amp is on line because the amp has to see the antenna and not the radio. Unless you have an antenna switch that can follow the radio selection the only other method would be using a manual switch after the amp.
     
    WG7X likes this.
  3. K4NUC

    K4NUC Ham Member QRZ Page

    Wouldn't I also need an antenna switch before the amp also? Split from the radio (3 antenna inputs- I am using all 3 at the radio) into the amp and split out of the amp into the antennas.
    What your saying is pretty much eliminate Ant 2 and Ant 3 at the radio and just everything out of Ant 1 into the amp.
     
    Last edited: Feb 10, 2019 at 4:49 PM
  4. WG7X

    WG7X Premium Subscriber QRZ Page

    No. Antenna switch after the amp, or after the tuner if you use one.

    Think about the linear flow, maybe draw a box diagram. Radio > Amp> tuner (if used)> antenna(s) switch. That way the amp always sees the final load.

    Does that help? A switch before the amp would do nothing. Think about it; the amp is the bottleneck.
     
  5. KD2ACO

    KD2ACO Platinum Subscriber Life Member Platinum Subscriber QRZ Page

    I can't speak for everyone else, but I'm manually switching every time I change which antenna or radio is hooked up to the amp with 2 mechanical switches. You could make a box with relays and electrically do that. I like my Alpha Delta switches better than the idea of a box full of relays doing the same job.
     
  6. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Yes, forget about the 3 antenna ports on the radio, it doesn't matter.

    Connect three antenna feedlines to a coax switch, with the common terminal of that switch to the output of the amp, and a single coax connection (like ANT 1) from radio to amp.

    I manually select which antenna I want to use, with a coax switch on the side of my operating table directly below the amplifier. I can reach it easily while sitting and never have to look at it, since I know which antenna is connected just by feeling the position of the switch knob. Takes one whole second to do this. I can spare the second.

    Plus, this allows the opportunity to see which antenna works best for any given situation. It isn't always the one you installed for a specific band. You may find while on 40m you're getting out great with the double bazooka but having difficulty hearing someone; click the switch over to the Hexbeam and the noise level may drop down sufficiently to hear that station, even though the signal level is much weaker. Just remember to flip the switch back to the 40m antenna before you transmit.

    Transmitting is all about e.r.p., but receiving is all about signal-to-noise ratio and a single antenna often does not provide both at the same time.
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    Steve is right. I found at times that I had better results receiving on my 160m Beverage than on the beam on 20 meters.
     
  8. PA1ZP

    PA1ZP Ham Member QRZ Page

    Hi

    I have an antenna switch after the amp.
    So my antenna switch is between the amp and tha antennas, each antenna has its own homebrew tuner if needed.
    Its homebrew relay switched.
    Its for 3 antennas now but I can build it for 5 antennas also, but I got only 2 antennas now for 10 yrs so its OK for me.
    And it automaticly switches to recieve or TX antenna, its steared with the PTT ground like the amplifier is.
    Its working for 13 yrs now like the amplifier.

    73 Jos
     
  9. N5WVR

    N5WVR Ham Member QRZ Page

    Well, yes.

    I only use the Ant 2 jack on my radio for 6 meters, which doesn't use the HF amp and is on a separate antenna.

    I use the ATR-30, which is on the antenna side of the amp, to switch between antennas. If you aren't using a tuner, you could put a plain, hi-power coax switch between the amp and the antennas.
     
  10. WB5WPA

    WB5WPA Ham Member QRZ Page

    Curve ball - This configuration beats swapping coax I/O between amps.

    One radio, one antenna tuner/antenna switch, two amps.

    One amp series connected with another as shown:

    Radio --> input SB-220 output --> input LK-500ZA output --> Tuner/switch

    All that needs swapping between the two now is AC power and the keying line.

    LK-500Za doesn't complain about 800 W of RF passing through it.
     

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