AM Radio

Viewing 15 posts - 16 through 30 (of 91 total)
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  • #2131
    Andy Brown
    Participant

    The most complex is probably the new 910/1080 site. 910 was always a DA-2 with tight nightime nulls. Haven’t spent much time looking at the new engineering paperwork for that one. I think 910 compromised their coverage to make it work based on the last time I looked at it.

    The most mismatched is the 860/1550 site. Towers are way too short for 860. It is also the most poorly engineered both from RFR and good ground perspectives. Running a close second on mismatch is the 620/1190 site. The old Westinghouse 1190 towers are way too short for 620.

    When towers are short you can assume the ground radials are short as well.

    The old 750 site at what is now Clackamas Town Center was a four tower square, not common but what they’ve got in Damascus is simpler. It might have even changed since they moved out there thirty years ago. Don’t know anymore.

    When 1480 had two sites, the night time site had 4 in line towers like the old KISN but they were DA-N with the daytime site remaining at Smith lake. Their night time nulls were bad but not as bad as 910’s old night time nulls. 910 was a few miles to the south which helped cover SE Portland. 1480 had problems there at night.

    1520, despite its 50 kW never had outstanding killer coverage during the day or night. 10 kW at night I think. I forget which adjacent used to give them issues during the day.

    Most bizarre was the old 1410 KPAM shunt fed antenna used for the FM sitting on a pile of rocks up at what is now Stonehenge. Second most bizarre would be a tie between 970 and 1330, both on hill tops where AM’s have a difficult job filling the valley, yet those two did OK. 1410 did not. Horrible coverage.

    #2132
    big89
    Participant

    I’ve noticed lately that 1330’s HD doesn’t seem to be working. All I get is a flashing HD light, but never locks on to the HD signal. I live on mt Scott near Kaiser Hospital. Anyone know what’s going on there? Their towers are only 2 miles from my home.

    #2133
    semoochie
    Participant

    “When 1480 had two sites, the night time site had 4 in line towers like the old KISN but they were DA-N with the daytime site remaining at Smith lake. Their night time nulls were bad but not as bad as 910’s old night time nulls. 910 was a few miles to the south which helped cover SE Portland. 1480 had problems there at night.” I’ll say they had trouble. You couldn’t hear them south of the Columbia River without wavering! For some reason though, you could hear them around Hillsboro.

    #2134
    MarkAndrews
    Participant

    At the end of the newscast “live at :55” they used to give their top of the hour ID as “KISN Vancouver radar weather eye…” and lead right into the weather forecast. The FCC took a dim view of that, too…

    #2135
    Andy Brown
    Participant

    “You couldn’t hear them south of the Columbia River without wavering!”

    Not true at all Semoochie. I did the field survey, and lived back then at SE 23rd & SE Salmon. The signal was great in Gresham and in SE Portland as long as you were not in the null which I have heard you describe with exhuberant inaccuracy.

    The null was at 187º which is approximately the 205 corridor.

    At Marine Dr. it was noticeable but the signal strength was still good enough to be received. Kind of sounded like a big whoosh on a car radio but on the Potomac FIM sounded fine.

    At Fremont it was noisy between about 72nd and 122nd, but still intelligible.

    Burnside it was 55th and about 145th. In the center of that area, no longer listenable, on the edges noisy and Eureka is starting to be detectable depending on the receive antenna orientation. That’s about 10 miles and as far as the survey went.

    In the car, though, at Hawthorne, close to where I lived, I could listen to the signal on the way home after 6AM but before sunrise down I-5 to the off ramp for SE Belmon/Morrison and would lose quality signal at about SE 15th. I could still keep it locked up at SE 23rd but if I shut it off and then back on, it was tough to pick up. Going in to work at 10 PM I could lock onto it at about 12th and Morrison and hear it fine going north on I-5 all the way to work with no co channel issues at all. The signal was good on the west side not only in HIllsboro, but in many areas of Beaverton close to US 26 and on the north side if you were up high enough. Obviously great in N. Portland and St. Helens because that was the major lobe of the pattern. It was better in downtown Portland at night than it was in the day, again depending on buildings and bridges and tunnels. Gresham, Wood Village, Troutdale, etc were all decent coverage.

    In my apartment on my porch where I had a workbench, with a couple of feet of wire hooked up to an old tube table radio, I could tune it in. Weak, but intelligible.

    I also got lots of DX calls after going on at night from the coast range and even the coast. The coverage to the north was a mirror image, so the signal in Battle Ground was weak like in SE Portland but as you swung around to Ridgefield, Scappoose and Sauvie Island it was fantastic. All of Columbia County was in the zone.

    That’s the way it really was.

    Got calls at night from certain areas of Idaho, Montana, South Dakota and Canada. All it takes was the receiving end to be in someone else’s null. Having previously worked at another 5 kW DA-N in Allentown, I knew what to expect in coverage at night and I can tell you that 1480’s was a lot better then you ever describe it as. Maybe you just had a cheap p.o.s. radio in your car.

    #2136
    semoochie
    Participant

    That’s the first time I’ve heard their pattern described in such detail. What probably happened was that they were having problems when I listened. I believe I was describing reception directly south of the towers. They must not have been too happy about it, having claimed “volcano interference” soon after.

    #2137
    W7PAT
    Participant

    I don’t know if it’s still this way but 1480 used to have a better nighttime signal on Vancouver Island than in Portland.

    #2138
    Steve Naganuma
    Participant

    Here is a short MP3 of a jock on 10Q/Los Angeles (late 70s) doing an on-air bit about the directional antenna change. People without a AM broadcast background were probably wondering what he was talking about.

    http://www.divshare.com/download/12507-56d

    #2139
    Andy Brown
    Participant

    “I’ve noticed lately that 1330’s HD doesn’t seem to be working. All I get is a flashing HD light, but never locks on to the HD signal. I live on mt Scott near Kaiser Hospital. Anyone know what’s going on there? Their towers are only 2 miles from my home.”

    KKPZ 1330 is DA-1 (directional all the time with the same pattern).

    If you draw a line from their site on Mt. Scott to Kaiser Hospital, it’s very close to 200º which is the heart of one of the nulls.

    This would make HD reception difficult even though you are close in. See the pattern below:

    http://transition.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/312608-18679.pdf

    #2140
    Andy Brown
    Participant

    “Here is a short MP3 of a jock on 10Q/Los Angeles (late 70s) doing an on-air bit about the directional antenna change”

    They (KTNQ) were celebrating getting on the air 24/7 with a new night time directional antennae when that recording was made.

    The Real Don Steele worked there but I think that was much later on.

    They are currently 50 kW DA-2 using 5 towers daytime and 4 towers at night, from the same site. I do not know if that was the case back when they first added night time service.

    https://www.youtube.com/watch?v=Q_IuzWvGw9g

    #2141
    Broadway
    Participant
    #2142
    Scott Young
    Participant

    I often wonder about the real estate value of AM transmitter sites, especially multi tower arrays. I’m thinking specifically about the 1190/620 site in Clackamas. The improvements to Lawnfield Road (which runs right in front of the site) will surely cause the surrounding property to appreciate substantially. At what point does it make more sense to sell the property than to use it for two failing AM stations. Maybe I’m overly pessimistic about AM broadcasting but I can’t help it.

    #2143
    big89
    Participant

    I’m surprised that the directional stations didn’t put their towers in the Gresham area. Would have given better coverage to the Portland Metro area, and probably would have allowed for some to run more power since they would be shooting their signal to the coast. It would definitely improve KKOV’s nighttime coverage, as well as KBMS.

    #2144
    semoochie
    Participant

    When I was a kid, Gresham had about 4,000 people and was completely separated from Portland. It didn’t really start to grow until the advent of Mount Hood Community College. Beaverton and Hillsboro weren’t much larger. A station like 970 had plenty of signal, not only for what existed of the metro area but down the valley as well. Stations used to be required to cover the main business district of their community of license with 25mv/m. For some stations, this wasn’t possible, if they located farther out. In addition, stations that are 30KHz away from another, must not cross 25mv/m contours. KKOV just barely clears that of 1520.

    #2145
    Andy Brown
    Participant

    With respect to the suggestion that e.g. 910/1080 move further east, that would not be possible. Both of those stations are DA2 so as an update to my above post, they are definitely the most complicated DA.

    1080 Day is 50 kW using two towers:

    You can see from the pattern: http://transition.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/1482201-117177.pdf that they are protecting eastward from 40º to 140º and moving any further eastward would require a pattern like they have at night which would mean less power and hurt them going towards the west and south where Portland proper is.

    1080 Night is 9 kW using three towers:

    http://transition.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/1482201-117176.pdf

    910 by already moving east a few miles still has to be DA-2 as well as losing power from their old site.

    910 Day is 4.3 kW using two towers

    http://transition.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/1456872-116607.pdf

    You can see that they now have more power going east then west during the day. Moving further east would only mean less coverage towards Vancouver/Portland and they probably barely cover Vancouver with required signal as it is.

    910 Night is 3.3 kW using three towers. Oh how the mighty 91 has fallen. They used to be 5 kW day and night, so as you can see moving eastward just a few miles has compromised them in more than one way. You can see from the night pattern that moving further east would not be possible without going down even further in power and that’s probably not possible due to the distance and coverage needed over Vancouver.

    http://transition.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/1456872-116608.pdf

    Here’s the site:

    https://maps.google.com/maps?q=Portland,+OR&ll=45.558468,-122.487334&spn=0.004202,0.00581&sll=45.5234515,-122.6762071&sspn=5.9317309,11.3003009&client=safari&oe=UTF-8&fb=1&gl=us&hnear=Portland,+Multnomah+County,+Oregon&t=h&z=18

    Note the Google maps aberration on the right most tower, making it almost look like a fourth tower.

    It appears these towers are 1/4 wave for 910 and slightly over that for 1080 (3/10 wave).

Viewing 15 posts - 16 through 30 (of 91 total)
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