Using a VHF / UHF SWR meter on HF

Discussion in 'General Technical Questions and Answers' started by VK4JJ, Jul 25, 2021.

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  1. VK4JJ

    VK4JJ Ham Member QRZ Page

    Picked up a Daiwa Cn-103 140-525MHz SWR and power meter from an estate sale.

    Is it possible to use this meter on the HF bands too?
  2. N1EBC

    N1EBC Ham Member QRZ Page

    No, it is only for the frequencies of 140-520MHz .

  3. W4HWD

    W4HWD Premium Subscriber QRZ Page

    Try it. Tell us how it goes.
  4. N1EBC

    N1EBC Ham Member QRZ Page

    That could prove detrimental to his equipment if he has an issue. Not a great idea.
  5. W4HWD

    W4HWD Premium Subscriber QRZ Page

    That was the point. If you need a meter that measures below 30MHz, get one that's good below 30MHz.
  6. NQ4T

    NQ4T XML Subscriber QRZ Page

    The thing is most are calibrated to a given frequency range due to the diodes not being entirely linear. Most of them actually become more sensitive with higher frequencies. The length of the pickup lines can also play a role. So while it may function "out of range" just won't function very well. You may need a lot more power to get a reading on HF with a VHF meter, which can cause problems with your radio.
    VK4JJ and N3PM like this.
  7. G8FXC

    G8FXC XML Subscriber QRZ Page

    I've used SWR bridges outside their specified frequency range when I did not have the correct model available - no damage done, but both sensitivity and accuracy can suffer.

    Martin (G8FXC)
  8. WS9K

    WS9K Ham Member QRZ Page

    As always, . . . . use the correct tool for the job.
  9. KM3F

    KM3F Ham Member QRZ Page

    Three main differences between HF and higher frequency on design is the sensitivity, power handling and type of pickup.
    All that is being done is read a Ratio of forward to reverse signal off the line.
    On Hf for example, is the signal high enough for the meter circuit to work with.
    That is usually based on electrical portion of wave lengths considered in the design.
    On strip line types, the length and spacing determine sensitivity and power handling as well as termination resistance of each strip line.
    Diode detector type, meter sensitivity etc.
    Such that the meters tend to be a bit more optimized and for meter face calibrations for the narrower frequency ranges.
    A Bird 43 for example takes care of all these parameters in the design of each complete detector insert (slug) and one meter readout.
    The sample line remains the same and capable of vey high power and low power levels.
    The slug power level is set by how close the Slug is set to the line center conductor.
  10. K8JD

    K8JD Ham Member QRZ Page

    Sure ! It could explode and set fire to his radio shack !!

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