Welcome to the FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
The latest SmartSDR Software:
SmartSDR v4.2.20 | SmartSDR v4.2.20 Release Notes
SmartSDR v3.10.15 | SmartSDR v3.10.15 Release Notes

The latest 4O3A Genius Product Software:
The latest 4O3A Genius Product Software and Firmware
How to Receive Technical Support::
If you are needing assistance with FlexRadio products, please refer to the product documentation or check the Help Center for known solutions. Need technical support from FlexRadio? It's as simple as creating a HelpDesk ticket.

Flex 6400M SWR Bridge accuracy

N7CXI
N7CXI Member ✭✭
in FLEX-6000 Signature Series

My 6400M’s SWR meter shows roughly 1.3:1 when directly connected to two different Bird Termaline loads that don’t cause any visible meter deflection on my other rigs. The 6400M does have the internal ATU, which is obviously not engaged when testing.

What should the nominal accuracy of the meter be?

Thanks,

Jim N7CXI

Comments

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    The SWR Bridge is calibrated during its build cycle and it should be the same as your Bird watt meter. You might want to try a lower power slug on the reflected power on the Bird.

    Also, try measuring into a 25 ohm resistive load (2 dummy loads in parallel) and see what you get for a reading on both meters.

    If you feel your SWR meter on the radio is not correct and the radio is under warranty, you may wish to open a support ticket.

    This is good article on SWR readings.

    https://www.arrl.org/files/file/Technology/tis/info/pdf/q1106037.pdf


  • N7CXI
    N7CXI Member ✭✭

    Thanks, Mike.

    There’s no question the meter isn’t accurate, I was just looking for the normal variance.

    The rig is not in warranty, so I’ll probably just ignore it for now. If it gets worse to the degree that it affects operation, I’ll send it in for repair.

    Your comment about putting two loads in parallel is interesting, and might help me hazard a guess whether the error in the coupler is resistive or reactive. I’ll bet three macaroni on resistive.

    FWIW, the Bird loads I mentioned don’t have integrated meters. I connected each load to the 6400M ANT1 port with a 6” piece of known good RG142, and observed the meter on the 6400M only. The 6400M reads 1.3:1 , while 7000DLE MKII, a TS890S and a FT-710 all read “flat” when connected in the same manner and tested with each of the two loads independently.

    73,

    Jim N7CXI

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    Keep in mind Bird Watt meter accuracy.

    It is 5% of the full scale reading of the slug.

    That means that a 100 watt slug can be off as much at 5 watts at all areas of the scale. It means that a 20 watt RF level could be considered accurate 15 and 25 watts.

    Welcome to the challenge of having 2 pieces of test equipment. Which one is correct? :)

    73

  • N7CXI
    N7CXI Member ✭✭

    Ok, thanks for the reply.

    I tried to point out that I didn't use any Bird meters, just the Bird loads and the internal meter on the 6400M.

    The internal meter shows 1.3:1 when the internal meters of other rigs attached to the same loads show "flat". I'll just ignore it unless it gets worse or gets in my way for some other reason.

    73 Jim N7CXI

  • JohnT
    JohnT Member ✭
    Hello Mike,

    I agree with Jim! The swr meter on the Flex radios are not accurate! I can place a 50ohm load right on the antenna port of my 8600M, transmit, and it will show an swr deflection! It of course shouldn't! I never had a rig yet (and there have been many) where placing a 50ohm load on the antenna port showed a swr deflection during transmit! Is Flex Radio not calibrating the trimmer capacitor on the swr bridge? What is going on? I wish they would fix this issue!

    73 John N2KBE
  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi John, you say a deflection. How much? My LP200 dummy load tends to show about 1.1 or 1.2 to 1 on my Flex 8600. My old hamfest special MFJ shows close to 1.4 to 1. Two loads, two different results.

    I chalk it up to less than well calibrated loads in my shack.

    If your SWR is radically off and you have a known good dummy load, then you should submit a help desk ticket.

Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.

Comment As ...

Categories