AM Radio

Viewing 15 posts - 46 through 60 (of 91 total)
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  • #2161
    semoochie
    Participant

    I usually hear good things about 5/8 wave.

    #2162
    Andy Brown
    Participant

    It’s true that 5/8 wave has the best ground propagation, but it also a very high angle lobe that tends to come back down locally and interfere with the ground wave mostly at night and at critical medium distance, and at morning and afternoon drive can have negative impact. Not to mention the impracticality from a cost perspective.

    There are no 5/8 wave sticks around here and very few 1/2 wavers left (970 and 1190).

    http://feedback.pdxradio.com/topic/khj-radio-tower-demolished#post-153944

    #2163
    semoochie
    Participant

    So, optimally, the thing to do is run 5/8 wave during the day and 1/2 at night. 🙂

    #2164
    Andy Brown
    Participant

    It would be risky. With the wrong atmospherics you can still get that skywave self interference during the day. Optimum would still be 1/2 wave all the time if you can afford the steel and acreage for a proper ground field.

    #2165
    semoochie
    Participant

    Great Andy, we can go halfsies on it or is that half-wavesies? 🙂

    #2166
    Andy Brown
    Participant

    It got me thinking about two things:

    1. 1330 When I was CE at 106.7 back when it was on Mt. Scott I used to stop and see Byron Swanson at the 1330 installation all the time as he was CE there at the time, and I recall those towers being pretty big. Because the towers are on the rear downslope of Mt. Scott, from a distance they don’t look all that big but up close they are pretty tall, especially the center tower that had the 98.5 antenna for so many years. I just looked them up and towers 1 & 3 are 146º and the center is 212º (4/10 wave and 6/10 wave). 5/8 wave is 225º so that center tower is pretty close, but the array’s effective wavelength is reduced by the first and third towers. I do not know how one would calculate the effective wavelength when the towers are different electrical lengths.

    2. The dismantled KGW 620 towers on N. Denver Ave were (not counting the appurtenances) 190.8 and 190.7 meters (about 627 feet) but at that frequency, a full wavelength is 484 meters (1587 feet). So using 191 you get just a skosh less than 4/10 wavelength. As huge as they were, they were less than a 1/2 wave.

    http://wireless2.fcc.gov/UlsApp/AsrSearch/asrRegistration.jsp?regKey=607973

    http://wireless2.fcc.gov/UlsApp/AsrSearch/asrRegistration.jsp?regKey=607974

    #2167
    Andy Brown
    Participant

    The ASR’s say the dismantled KGW towers went up in ’78, so I’m wondering how much the previous pair of towers that were there differed in height if at all? Does anyone remember?

    #2168
    Alfredo_T
    Participant

    I calculate that the shorter towers in the KKPZ/KDZR antenna array are 0.493 wavelength at 1640 kHz. I assume that KDZR uses just one of the short towers.

    #2169
    Andy Brown
    Participant

    The calculator I used just now shows that 1/2 wave at 1640 is 91.46 meters.

    The listed height above ground (for tower #1, the one they use for 1640) in the FCC records is 94.6 meters

    and shows an electrical length of 181.9º or .505 wave.

    .505 times a full wave length of 182.9 is 92.4.

    So allowing for conversion and rounding errors, it appears to be slightly over a half wave.

    Don’t know what numbers you used. There are no appurtenances on the short towers, so the mechanical length is all radiating.

    http://transition.fcc.gov/fcc-bin/amq?list=0&facid=86618

    http://wireless2.fcc.gov/UlsApp/AsrSearch/asrRegistration.jsp?regKey=121094

    #2170
    Alfredo_T
    Participant

    I just took 4/10 and multiplied it by the ratio 1640:1330. I made a novice mistake in using three decimal places in my result.

    #2171
    Kent.Randles
    Participant

    That KTNQ aircheck got edited.

    A friend of mine helped build and proof the night-time array.

    Coincidently Entercom DofE Gary Hilliard built and proofed the 6-tower night array for the 1020 in Roswell, NM that got modified so that KTNQ could go full time.

    What got edited out was what happened when the cart with the sound effects wasn’t cued up!

    On the original aircheck you hear silence, and then way in the background “Oh f***!” Then when the cart cues up they restarted it.

    #2172
    jr_tech
    Participant

    “The dismantled KGW 620 towers on N. Denver Ave were (not counting the appurtenances) 190.8 and 190.7 meters (about 627 feet)”

    “The ASR’s say the dismantled KGW towers went up in ’78, so I’m wondering how much the previous pair of towers that were there differed in height if at all? Does anyone remember?”

    Were they both built in ’78, or was the 1937 tower used?

    “1937 KGW inaugurated its 625 foot Truscon tower at Faloma”

    http://feedback.pdxradio.com/topic/this-day-in-portland-radio-history-august-4#post-169051

    #2173
    Andy Brown
    Participant

    I had been in town for two years and I vaguely remember that they were old and worn and needed to be replaced. I think that’s what (the late) Lee (Grid Leak) McCormick told me. He was CE there before moving over to KINK as CE.

    #2174
    jr_tech
    Participant

    The second 625 ft tower for 620 kgw was added in 1941.

    “Dec 25, 1941 added additional 625 foot tower and increased night power to 5,000 watts”

    One tower was lost in the Vanport flood in 1948 (don’t know which one) to be replaced in 1949. So in 1978 the old towers that were replaced could have been built in either 1937 or 1941 *and* 1949. I’m guessing the 1949 replacement tower was 625 feet also.

    http://feedback.pdxradio.com/topic/happy-birthday-kgw-the-radio-station-timeline

    #2175
    semoochie
    Participant

    How did they replace the towers? I don’t remember a period where there were additional towers and I drove by there everyday in 1978. (I can’t imagine them taking down two towers in the middle of the night, moving them out of the way and replacing them with two more!) Of course, I might just not remember. It seems vaguely familiar.

Viewing 15 posts - 46 through 60 (of 91 total)
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