Antenna/Radio Crossover Switching

Discussion in 'Ham Radio Discussions' started by KC3KWA, Aug 16, 2019.

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  1. KC3KWA

    KC3KWA Ham Member QRZ Page

    Looking for some advice..

    Assume that I only have a dipole antenna and an 80M loop installed at my QTH. At all times I want to use one of them for transmitting and the other as my RX-only antenna. However, I want to be able to easily switch between the two. Antenna 1 to RX, Antenna 2 to TX >>or>> Antenna 1 to TX, Antenna 2 to RX.

    I would have to add two-way switches to each antenna, and then on the RX and TX ports on my radio, plus four additional coax jumpers, and then remember to switch all four switches to make the adjustment. Alternatively I found an MFJ-1703 online, and it seems to be able to do exactly that. But I'm hearing the warnings about switches, let alone MFJ crossover switches.

    Is there an easier way that I'm overlooking, or other products out there that I'm not finding? Obviously swapping the feedlines is an option, but I'm lazy and it's kind of inconvenient with how my desk is set up. Aside from adding the 20 steps to my fitbit, what are some other options?

    Thanks and 73s


    KC3KWA, Luke
     
  2. SA4MDN

    SA4MDN Ham Member QRZ Page

    I have one of those, been in the basement for the past 2 years, switch went a bit finicky and swr was jumping all over the place, in my opinion the switch is the weak point, bit naff.
     
  3. KQ0J

    KQ0J XML Subscriber QRZ Page

    "Is there an easier way that I'm overlooking, or other products out there that I'm not finding? "

    I used to use a MFJ-1025 noise cancelling signal enhancer for that. Hook the receive antenna to where the noise antenna plugs. Turn the main
    antenna gain to zero and use the gain on the Aux antenna so you receive on the other antenna only instead of phasing them - of course you
    can always phase them to add the signal from both antennas together to either peak or null the station you are hearing.

    The input is sensitive to high RF levels though - they have a poor indicator of high RF which is a grain of wheat
    bulb inside the unit that will light when the aux antenna is picking up too much signal when you are transmitting. I fixed this by adding a
    T connector that added 2 oppositely connected diodes ( 1N914 ) in parallel to limit the signal in to the box on the receive antenna.
    If you dont do this you burn out the light which is used as a fuse and it will no longer work.




    73
     
  4. KC3KWA

    KC3KWA Ham Member QRZ Page

    I have one too and intend on using it in conjunction with this. While it lets me phase between the two antennas for RX, there’s no switching between the two for TX.
     
  5. KC3KWA

    KC3KWA Ham Member QRZ Page

    Perhaps this is the right answer. Thanks for chiming in.
     
  6. K4AGO

    K4AGO Ham Member QRZ Page

    The manual switching method you described is by far the easiest and most mechanically and electronically sound method to accomplish your goal.

    If you forget to switch antennas when you need to switch antennas, no harm done. Of course you must REMEMBER to switch. There are many things you MUST remember in ham radio. What you are trying to accomplish here is probably the most simple and straight forward thing you will ever have to remember. It's no more complicated than remembering to turn on the powersupply BEFORE you switch on the radio or tuning BEFORE you transmit with full power.

    Mechanical switches are very reliable. MFJ, unfortunately, not so reliable. I have not ever had a problem with MFJ products; i have had with their service department. Other will tell you horror stories about poor quality MFJ construction and loose parts rattling around inside MFJ products.

    Manual switches are cheap, reliable and last a very long time. As another very knowledgable ham with a great deal of common sense (frequents the Zed) always says... Your Milage may vary.

    I would like for you to follow up and tell us what you decided to do and how it is working out for you. Thanks for asking this question.

    John
    K4AGO
     
  7. KC3KWA

    KC3KWA Ham Member QRZ Page

    Thanks for the response. I think that this is the answer I'll run with. In my head I'm telling myself that I would switch them back and forth frequently, but I doubt that will be true most of the time. Access to the back of my rig is available through a door on the wall behind my desk, but I have to go to a different room to get there.... KC3KWA DON'T BE LAZY.

    Thanks John.
     
  8. K4PIH

    K4PIH Ham Member QRZ Page

    Having experience with just such a setup, I would advise you to use a patch panel instead of switches. It's too easy to get it wrong and poof!
     
    KC3KWA likes this.
  9. KL7AJ

    KL7AJ Ham Member QRZ Page

    I think you already have the minimum possible arrangement.
     
  10. N3PM

    N3PM Ham Member QRZ Page

    Can't this be done with a DPDT switch or relay and 4 connectors?
    Mike N3PM
     

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