NEW transmitter for KBAM 1270

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  • #26596
    johnmackey
    Participant

    KBAM 1270 KHz is testing a NEW Gates DAX-5 transmitter running 5000 watts day power from Longview. (nite power is 83 watts)

    Some audio adjustments (processing & level) still need to finalized before testing ends.

    I was listening to it this morning while driving around in Beaverton & listener reports would be great to hear.

    #26603
    mwdxer1
    Participant

    K-BAM has always had a good signal on the Northern Oregon Coast (Seaside-Astoria) for years dating back to the 60’s & 70’s. The FM 93.5 is good here too.

    #26606
    jr_tech
    Participant

    Was the power of the old transmitter diminished by age? On 4/29/15 the S meter on my Icom indicated “S-9” on the station, today I am reading 5-8 dB above S-9 on the tiny meter below the dx cat’s right paw.
    <<<<<<<<<
    Same antenna, same Icom, morning reception from Hillsboro in both cases.

    #26609
    johnmackey
    Participant

    Regarding the increase in signal strength for Hillsboro, I suspect there are 2 things helping for increased signal:

    1. I completely rebuilt (re-wired/re-plumbed) the RF output switching and the how it was feeding power to the ATU. The way it was done prior to this was not as good IMO.

    2. I suspect the audio was not modulating very well before, I have it running at 100% now during this phase of testing. Next week I will re-adjust it for 125% on the positive peaks & re-evaluate.

    Special thanks to Randy Pugsley for helping with the KBAM audio processing – which is still a work in progress.

    #26611
    Andy Brown
    Participant

    “Next week I will re-adjust it for 125% on the positive peaks & re-evaluate.”

    IMO OK for voice but not music. It rounds off the peaks and valleys.

    Lower trace: RF envelope
    Upper trace: audio (note the loss of sinusoidal shape)
    125% modulation

    #26618
    Andy Brown
    Participant

    Way back when (before I was yielding an Xcelite R3322), 125% modulation was used to make a station sound a little louder but that was an era when the only processing out there was a Volumax and Audimax. As processing blossomed in the late 60’s and 70’s (Dorrough, e.g.), balanced modulation was preferred by the music stations and the generation of engineers using the new processing since 125% modulation is not symmetrical (even at 125% positive, the negative peaks are still limited to 100%). The way it distorts the sinusoidal peaks and troughs as in the above post results in increased IM, increased THD and in some legacy receivers noticeable peak clipping. I’ve tried it with rock music and it is awful. Just my experience. It’s possible that newer gear can support this asymmetric method but I’ve not read much about it. In fact, you don’t see many articles about anything AM anymore. YMMV

    #26619
    Alfredo_T
    Participant

    I wonder whether it is possible that changing propagation conditions are the main reason for the changing signal strengths on KBAM. A 5-8 dB change in transmitter output power, is pretty significant, and if their old transmitter had been running at reduced power due to failure, they would have filed an STA.

    I think that this could be just like my experience listening to 840 about two weeks ago. First, KSWB had a surprisingly strong signal. About 45 minutes later, it faded under KKNX. A few minutes later, it came back, but not to where it had been before.

    #26620
    jr_tech
    Participant

    Definitely, I need more data points, but 1260 strength matched the older readings, so I am thinking that there has not been an increase in background noise in that area of the band. Loosing the station right now in grey line signals.

    #26622
    semoochie
    Participant

    I am a little surprised that there is still a significant market for new AM transmitters. You would think that it would be hard to recoup your investment at this point.

    #26624
    Andy Brown
    Participant

    “they would have filed an STA.”

    Should have but probably didn’t since they knew they were going to replace it. There is a grace period AND they can notify the FCC by letter. I forget what the grace period is.

    #26625
    johnmackey
    Participant

    To bad I couldn’t convince them to make it an HD system!

    #26626
    Andy Brown
    Participant

    Alfredo, it is also allowable during the day to run at night or PSA parameters without needing an STA or notification of the FCC unless it drags on. Again I don’t remember how long you can go that way but it’s OK to do it.

    #27158
    Master of Disaster
    Participant

    Dunno if this is helpful at this point, however I received 1270 KBAM at a location off of 72nd and King Rd. in Milwaukie today. Not as strong as the local stations but still listenable. Believe it or not I remembered the name of the person voicing the “Community Calendar” from the old 105.5 KLYK over two decades ago! 😮

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