AM broadcast interference

Discussion in 'Tips and Tricks' started by WA0DIL, Sep 24, 2021.

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  1. WA0DIL

    WA0DIL Ham Member QRZ Page

    I live about 1 1/2 miles from a 50 kw AM broadcast station. The signal is so strong that it just overwhelms my receiver and I can hear garbage from the station at about S3 on my Yaesu FT-450D. None of the filters do anything ... 50 kw is just too much. I ended up using an external antenna tuner even thought the auto tuner in the 450 works just fine. The external tuner blocks the AM station as it tries to go "backwards" into the 450. Problem solved.
    KQ9J and KA0HCP like this.
  2. W1VT

    W1VT Ham Member QRZ Page

    Yes, the typical transmatch has a T network that works quite effectively as a high pass filter.
    WA1GXC likes this.
  3. K8JD

    K8JD Ham Member QRZ Page

    Only AMBC transmitter near you is WCCO and it's 6.6 miles from your QRZ address ! A bit far for severe interference. Is this an FM station interfering (could affect VHF ham bands) or have you moved >?>?
    The only other 50 KW AM stations, on 1500, 900 and 1030 kHz, are northeast and southeast of St Paul, a lot more distant from you.
    K0UO and W1PEP like this.
  4. N8AFT

    N8AFT Ham Member QRZ Page

    May wanna make sure you have the RF Pre-Amp OFF and rethink the RF Attenuator/RF Gain...
    WQ4G and AC0OB like this.
  5. N2UHC

    N2UHC Ham Member QRZ Page

    I think this is the high pass filter I built to put in front of the upconverter for my SDR dongle. It really cuts down on the AM spurs.

  6. N3EG

    N3EG Ham Member QRZ Page

    I'm 2 blocks from a 1kw station, and the Dunestar high pass filter works for me. We have a radio club station 200 feet from a 1kw AM station, and this filter also works for them.
    K0UO likes this.
  7. K8JD

    K8JD Ham Member QRZ Page

    AM Transmitter Nearby
    N3EG...Yes you sure are close to KBAM on 1400, at 0.29 miles.
    The big station in town, KEDO, on 1270 khz with 5 KW in daytime, and at night only 83 watts, Is 2.42 miles from your house.
    The other 1 KW AM is KLOG on 1490 across town, 5.1 Miles away.

    I am pretty lucky I have two AM transmitters that share antenna toewrs, one 1 kW and one 15 kW at 5.3 miles from here.
    They have not caused me any problems, the next closest is over 20 miles sway.
    K0UO likes this.
  8. KV6O

    KV6O Ham Member QRZ Page

    You can make a notch filter out of a 1/4 wavelength piece of coax (need to adjust for the velocity factor).
    K0UO likes this.
  9. K8JD

    K8JD Ham Member QRZ Page

    That's a LOT of coax ! not so hard to make a LC filter with discreete coil and capacitors.
    KP4SX likes this.
  10. KV6O

    KV6O Ham Member QRZ Page

    Agreed, the principal works on higher frequencies as well. Just a good trick to have up your sleeve. And if you have an surplus of coax (don’t need fancy stuff), it’s useful.

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