Eugene Radio Happenings

Viewing 15 posts - 421 through 435 (of 1,086 total)
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  • #767
    Andy Brown
    Participant

    Normally referred to as 2A-B IMD.

    This is the second most common form of third order intermodulation distortion.

    http://www3.alcatel-lucent.com/bstj/vol32-1953/articles/bstj32-1-63.pdf (second page down)

    Receiver intermodulation occurs as the results of two or more high-level off-channel signals overloading the receiver’s RF amplifier causing it to operate in it’s nonlinear region thus acting as a mixer. Older radios may not employ an RF amp and go straight into the first mixer.

    It may be difficult to determine where intermodulation is occurring because the new frequencies being generated are precisely the same whether they are generated in the receiver front end, transmitter PA or some other non-linearity. Inserting a 6 db. attenuator in the receiver front-end will attenuate “transmitter” intermod by 6 db. “Receiver” intermod will be attenuated more rapidly because both signals A & B are simultaneously reduced by 6 db each.

    http://www.midians.com/intermod-explained

    Are the 103.7 and 102.3 transmitters close to each other? See:

    http://www.procom.dk/procomlab/intermodulation-concepts/intermodulation-between-closely-spaced-transmitters

    #768
    jr_tech
    Participant

    KNRQ (103.7):

    http://transition.fcc.gov/fcc-bin/fmq?list=0&facid=61987

    KEHK (102.3):

    http://transition.fcc.gov/fcc-bin/fmq?list=0&facid=7989

    Both appear to be on the same tower, about 22 meters apart.

    #769
    Randy_in_Eugene
    Participant

    Both are listed at the same coordinates on Blanton Heights in south Eugene. I am located just over 3 miles away, with small nearby hill to attenuate the signals a bit, but it’s still a great place for front-end overload.

    However, the 103.7 (KNRQ) license to cover the move from Lebanon to Harrisburg was granted on 9-4-13, yet I have not noted this particular problem until now. My receivers are a Yamaha T-85 and a Sony XDR-F1HD, which have both served me fairly well in this hot RF environment. If it had just popped up on only one receiver I would first suspect that to be a possible culprit, but appearing on two receivers at the same time…I dunno.

    Perhaps a little attenuation would do me good anyway.

    I also have a Pioneer SX-850 and a Pioneer TX-980, which have always been totally hammered with overload at my location.

    #770
    silverdollar
    Participant

    In a failed effort to bring in Portland and Seattle stations, I installed an expensive FM signal booster. The Fail part is KZEL and 1 or 2 other strong locals started popping up at other frequencies. Sony XDR-F1HD with directional antenna aimed north.

    #771
    Randy_in_Eugene
    Participant

    I’ve never known a signal booster to work satisfactorily except in deep fringe to ALL received signals. Boosters built into tiny, undersized antennas are universally garbage.

    #772
    silverdollar
    Participant

    Cumulus Eugene doings… KZEL HD is on again. KUJZ was dead air at least part of Labor Day. And today KNRQ’s audio level is about half what it normally is. Very low.

    Meanwhile, anyone notice that KRVM FM sounds like they’re using more aggressive (read: obnoxious) audio processing lately? More compressed, less dynamic range. Or am I imagining it? More aggressive Optimod settings? I could be wrong but everything suddenly sounds “dirtier” to me.

    #774
    the_radio_guy
    Participant

    KRVM-FM uses an Omnia.

    The harmonic which is now very strong over 105.1, is illegal interference caused by an issue with 102.3 and 103.7. The engineer needs to work on this!

    #775
    Andy Brown
    Participant

    Finding where the spur is being generated is not an easy task, and may not be in the HPA’s of the A or B transmitters.

    We had a spur once in Portland when 103.3 came on the air, caused by an A+B-C where none of the transmitters were co located, being 2 to 10 miles apart. (106.7 + 103.3 – 97.1 = 112.9) Modulation detected was 106.7’s but the mixing was taking place in the 97.1 HPA. 103.3 had to pay for a filter on 97.1. It took engineers from all three stations and some guys at PDX airport to pin it down.

    #776
    silverdollar
    Participant

    103.7 KNRQ has been intermittently up and down numerous times today.

    Edit: 105.1 is indeed a mixing 103.7 and 102.3

    #777
    jr_tech
    Participant

    Do you hear the same mix products on 100.9 as well?

    #778
    silverdollar
    Participant

    No, only getting 100.9 K265DF K-Love translator in Eugene

    #779
    silverdollar
    Participant

    Turns out Cumulus *is* aware of the 105.1 issue. Dead passband filter on 103.7. New one coming.

    #780
    W7PAT
    Participant

    840 KKNX was sure coming in strong in the Portland area last night. Normally we don’t hear much on 840, other than a mix of garbage.

    #781
    silverdollar
    Participant

    What happened to Justin Myers at KNRQ & KUJZ? Seems like he’s suddenly just gone. One of my favorite Eugene air personalities.

    Edit, maybe moved to ESPN Seattle?

    #782
    Alan Craig
    Participant
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