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Transmission problems were encountered using the Flex 6500 on field day. Looking for fixes.

John
John Member ✭
in FLEX-6000 Signature Series
When transmitting SSB same time as the Yeasu ft-710 transmitted CW output power of the Flex went to zero and the radio swr meter display would max. This happened every time the Yeasu radio was keyed with CW. When the Yeasu key dropped transmission power returned. The CW radio was operating on 20 meters at 100W. Reducing power on the CW radio did not improve the condition. Both radios were physically located next to each other and connected to horizontally polarized wire antennas. The Flex radio was located about 75 ft from the CW antenna. A ground wire was connected from the case of the Flex radio to a short ground stake with no improvement observed. Harmonics were present at significant level on all bands of the Flex radio when the Yeasu transmitted CW.

Looking for suggestions for fixes from Hams who have had similar issues.

73!

Best Answer

  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭✭
    Answer ✓

    Sounds like the Yaesu + system was radiating enough rf to overload the scu's (spectral capture units) on the Flex. Especially since both are close together and using the same polarized antennae. I believe there is protection circuitry in the front end of the Flex to protect these units. You were probably seeing this in action.

    When we run multiple bands on field day, we make sure the rigs and the antennae are well separated (across the field, if possible) . Bandpass filters on each of the rigs specific to the operating band also help tremendously. Also using different polarizations (dipole vs vertical) helps.

Answers

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    bandpass filters are a must at Field Day. and for operation within the same band, physical separation of antennas is necessary.
    We had an old Icom 756 Pro III at Field Day and a 6400m (my 8600 and DuneStar filters were in use so I could not bring them to Field Day. The Pro III was pretty dirty on transmit.

    The contest club I belong to has a nice discussion going on various bandpass filters and not all filters are created equal. The members have been doing tests on original ICE, newer design ICE, Chinese cheap filters, and others. Pretty interesting results.

    Jim, K9YC did a nice write up a while back comparing different filters.
    http://audiosystemsgroup.com/BandpassFilterSurvey.pdf


    73Dave wo2x

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

    This is an RF overload issue, especially if the radios are on the same band at the same time. It would help if the antennas where not parallel to each other. It might even be an common mode RF issue, so chokes on both feedlines would certainly help a lot. Try Mix 43. A ground wire will not eliminate common mode issues.

    If on the same band, bandpass filters won't really help as it is all inband RF.

    I am not sure how clean the FT-710 transmitter is, but it might be worth looking into or trying another radio.

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