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RX ANT A Specs

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Lew
Lew Member ✭
in FLEX-6000 Signature Series
I can't seem to find the HW specs for the RX ANT input (6500).
1. Is it 50 or 75 Ohm input.
2. Is it open or grounded during transmit to protect the input.
3. Min/Max Signal levels.
I plan to connect a Beverage to this input but don't want to "toast" it when I transmit. There are external boxes that disconnect and terminate the Beverage but I don't want to add another box if I don't need it.
Thanks in advance for any information
Lew

Answers

  • Butch
    Butch Member ✭✭✭
    Options

    The answers to some of your questions are in the Flex-6000 Hardware Reference Manual: https://www.flexradio.com/documentation/flex-6000-hardware-reference-manual-pdf/

    Page 40 shows the wiring diagram for the RxAnt A circuit.

    Butch, KF4HR

  • Lew
    Lew Member ✭
    Options
    Thank you for taking the time Butch!
    That is a different HW Ref Manual than I had.
    It seems to show that the RxAnt A is switched, it doesn't say that it is disconnected on Transmit but I will assume (ouch) that the SW guys did drive it to open on transmit.
    I expect to hook up the Beverage next weekend so I will find out for certain!
    Lew
    K6LEW
  • Butch
    Butch Member ✭✭✭
    Options

    Lew it's a safe bet that the receive paths are (normally) disconnected during transmit. If it wasn't the transmitter would smoke the receiver. You should be fine connecting your Beverage antennas to the RxA input.

    The exception might be if you turn on the FDX (full duplex) mode, in which case FRS has provided a spreadsheet to help keep the dbm T/R separation at a safe level (see FRS documentation), but under normal T/R operation, no need to engage FDX.

    KF4HR

  • Stan VA7NF
    Stan VA7NF Member ✭✭✭
    Options

    The safe thing to do is place a front-end protector box on the RxA fed by the beverage. I also have a broadcast band filter in series to keep those high power nasties out of the RX path. With the 6700 I make extensive use of "LoopA", especially when down on 160/80 as a 160 dipole does a very good job of picking up BC band signals, to the extent of over driving the front-end, and also protects against going "wide" with all those receivers.

  • k3Tim
    k3Tim Member ✭✭✭
    Options

    This worksheet:

    https://www.flexradio.com/documentation/flex-6000-fdx-power-calculation-worksheet/

    that details the FDX power/isolation may be of interest.

    A 250' BoG is used at this 6500 station (FDX mode) with vertical antenna. No problems after several years. The BoG is very low noise and used for all bands 10-160 meters.

    _..--

    Tim

  • k3Tim
    k3Tim Member ✭✭✭
    Options

    This worksheet:

    https://www.flexradio.com/documentation/flex-6000-fdx-power-calculation-worksheet/

    that details the FDX power/isolation may be of interest.

    A 250' BoG is used at this 6500 station (FDX mode) with vertical antenna. No problems after several years. The BoG is very low noise and used for all bands 10-160 meters.

    _..--

    Tim

  • Lew
    Lew Member ✭
    Options
    Thanks to both Butch and Tim,
    Tim do you know if the RxANT A input is 50, 75 or some other impedance?
    I know the difference isn't big but Franklin said if you count the decibels the Bels will take care of themselves, or something like that :)
  • KD0RC
    KD0RC Member, Super Elmer Moderator
    edited February 2021
    Options

    Hi Lew, All the antenna and XVTR impedances are 50 ohm.

  • Ron K2RAS
    Ron K2RAS Member ✭✭
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    If the RxANT input is 50 ohms will my DXEngineering (Pixel) amplified receive loop antenna with a 75 ohm output perform better with a 75 to 50 ohm converter?

    Thanks, Ron K2RAS

  • KD0RC
    KD0RC Member, Super Elmer Moderator
    Options

    I don't know for sure, but I doubt it. The mismatch is only 1.5:1 and the amplifier should be more than able to make up that small loss. The 6000 series radios typically have more than enough RF amplification, so more signal can be dialed in that way as well. If you are setting this up for 160 meters, you may need to go the other way by reducing gain. Any small loss due to impedance mismatch will actually help in that case.

  • WX7Y
    WX7Y Member ✭✭✭✭
    Options

    75 Ohm's on a 50 Ohm BNC antenna port is as Len said and will work just fine, Remember the basic flat top Dipole is 75 Ohms at the feed point and there are many many thousands of these Antenna's in use being used with great success, even the UHF (PL-259) antenna connectors on your radio are close to 75 / 100 Ohm's impedance.

    Make sure you build a cable to go between the 75 Ohm connecter and the 50 Ohm BNC on the radio with the proper ends or you will break the 75 Ohm connector and the 75 Ohm BNC wont make contact on the 50 Ohm socket on the radio.

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