2x2 switching on UHF/VHF

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KG4OOZ, Dec 13, 2017.

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  1. KG4OOZ

    KG4OOZ XML Subscriber QRZ Page

    I have recently bought on Icom 910H to use in my shack along with my existing Icom 2370. The problem is I only have one antenna for UHF/VHF. Does someone make a product or an easy to build solution that would allow me to switch the two radios between the antenna and allow the other one to be hooked to a dummy load to prevent me from burning it up. I know that MFJ makes a 2x2 switch but it don't appear to be rated for above 50mhz. I plan on adding a set of UHF/VHF beams to qth come spring time but would like to be able to switch the 2 radios between the 2 antennas easily, so that is why I want to tackle this early. I realize that I could just hook and unhook but I want to make this as dummy proof as I can because I tend to get in a hurry and forget things. Any ideas would be greatly appreciated, ideally I'd like to buy something but if it can be built using fairly simple circuits and save money I can do that too. 73s
     
  2. K9STH

    K9STH Ham Member QRZ Page

    Make a patch panel with one connector to ground and another to the antenna.

    Just reverse the connections from the units to switch between being grounded and being connected to the antenna. Additional jacks can be added to connect to additional antennas.

    Glen, K9STH
     
  3. KG4OOZ

    KG4OOZ XML Subscriber QRZ Page

    I had given that some thought and it will most likely be a last resort because I just don't really have a place that I would want to mount one.
     
  4. K9STH

    K9STH Ham Member QRZ Page

    Build the patch panel in an aluminum mini-box using BNC connectors. The box won't take up any more space than a coaxial switch.

    Glen, K9STH
     
  5. W0AAT

    W0AAT XML Subscriber QRZ Page

    Coaxial relay and a switch box, I know of nothing that will auto switch unless you can figure out how to tap the TX out on each radio... 2 relays feeding a T on the output to the antenna, NC closed(no power position) grounds the input to a 50 ohm low power load. T might give a slight SWR bump, a third relay would eliminate that. Use relays with decent isolation, not going to be cheap...
     
  6. AI3V

    AI3V Ham Member QRZ Page

    What you seek is called a "RF baseball switch"

    You might want to be sitting down when you get the price!

    Rege
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Why would the radio with no antenna connected "burn up?"

    A good coaxial switch rated (and characterized/tested) for UHF operation can easily have 40 dB port isolation: If you run 100W from one rig into the antenna, the level at the other port (second rig) will see only 10mW (50 Ohms), or +10 dBm. There isn't any kind of rig anywhere that I've ever seen that would be damaged by a +10 dBm signal.

    A "better" coaxial switch can have 50 dB or more isolation.

    I've tested the Alpha Delta switches (2 positon and 4 position, with N connectors) at 70cm and they all provided >50 dB port isolation. That means with a 100W transmitter on one port, the other port will see less than 1 mW (0 dBm). This is absolutely non-destructive to any kind of receiver.

    http://www.alphadeltacom.com/pdf/Delta 4 Switches4.pdf
     
  8. KG4OOZ

    KG4OOZ XML Subscriber QRZ Page

    I am just concerned with me forgetting which radio I have hooked up and keying it with nothing to key into. That is what I was referring to as burning it up. More preventing me from messing up than anything else. I guess a patch panel may be the only solution I can afford. Thanks for all the replies.
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I avoid doing that by following a firm rule: Listen first, and if no stations are heard, that means there's no antenna connected.

    I've never "transmitted first" without listening before that to confirm everything's connected.

    I find it a very easy rule to follow, even if I'm half asleep.:)
     
  10. KG4OOZ

    KG4OOZ XML Subscriber QRZ Page

    I understand and am a true follower on of that rule on the HF relm but I find myself working to many repeaters and such on VHF/UHF where I am the first to call. In this area I'd listen for days before I heard anything sometimes on the upper bands. But I do see where you are coming from. I think I am going to end up going a patch panel route and hide it under my desk. I will most likely buy a couple of the small barrel shaped Dummy loads that have the PL-259 connector on the end. So I can simply attach them to the panel on the radios that are not on an antenna.
     

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