AM Radio

Viewing 15 posts - 31 through 45 (of 91 total)
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  • #2146
    Scott Young
    Participant

    People often complained about the deep southerly null in the 910 patterns, but their lobe to the west was a monster. As a kid I remember listening to KISN on the car radio all the way into Tillamook. It was good almost all the way to Seaside too, until we got close enough to KSWB for their 930 buckshot to bury 910. Not bad for 5kw at the east end of the metro.

    #2147
    W7PAT
    Participant

    Andy: I’m not nit-picking but KMTT is 3.3 Kw day and 4.3 Kw night.

    #2148
    itsvern
    Participant

    KWBY in Woodburn comes in great n McMinnville day and night with these power levels:

    http://radio-locator.com/info/KWBY-AM

    How do they do it?

    #2149
    Andy Brown
    Participant

    Vern, there is nobody else on that frequency plus McMinnville is only 12 miles away. There are only three stations on that channel within 1000 km of Woodburn (624 miles).

    The closest is KICE, Bend OR at 174 km (108 miles) . KICE 10 kW day and 60 watts at night, it is directional all day with a null coming back this way and all of it’s signal going east, away from here.

    Then there is KDIL in Jerome Idaho. That’s 712 km away (442 miles) and it’s 1 kW day, 250 w at night.

    Finally, CJIB in Vernon B.C. at 632 km (393 miles) which is 10 kW, directional at night with nulls towards the U.S. and all its signal pointed Northwest.

    The nearest first adjacent at 930 is KYAK in Yakima, WA. 10 kW Day, 127 watts Night

    The nearest first adjacent at 950 is KTBR in Roseburg, OR. 3.4 kW Day, 20 watts Night

    That’s why when you are only a dozen miles away from KWBY they come in great. It’s not rocket science.

    http://tinyurl.com/qck755v

    All of the aforementioned are Class D AM’s.

    The only 50 kW flamethrowers in the U.S. on 940 are WCPC in Houston TX, KFIG in Fresno CA and WMAC in Macon GA. In Mexico, there is XEQ in LOS REYES ACAQUILPAN and in IZTAPALAPA at 150 kW Day, 50 kW Night. There’s a whole bunch of 50 kW in Canada, see the next link if you’re curious.

    If you didn’t have a good signal you’d be hearing one of those co channels or first adjacents mentioned or found in this list showing everything on 930, 940, 950 within 4000 km (2485 miles) of Woodburn.

    http://tinyurl.com/plcj4ru

    Pat: “KMTT is 3.3 Kw day and 4.3 Kw night.”

    Thanks, got those reversed. Two towers day, three towers night is correct, though.

    #2150
    semoochie
    Participant

    I thought I remembered 1080 having their construction permit modified for 10KW at night. I wonder what happened to it, if indeed, anything did. I can’t find the authorization for the 302 but here’s the 301: https://licensing.fcc.gov/cgi-bin/ws.exe/prod/cdbs/forms/prod/cdbsmenu.hts?context=25&appn=101328027&formid=301&fac_num=57830

    #2151
    W7PAT
    Participant

    KFXX does pretty well with their 9 kW. Last spring I visited San Fransisco and KFXX comes in very well down there at night. In fact, about an hour before sunset on their 50 kW signal they were booming in.

    #2152
    Andy Brown
    Participant

    Wrong 301, semoochie. The one you linked to was just an addendum for adjusting coordinates to agree with those on file:

    THIS APPLICATION CORRECTS THE COORDINATES OF THE LICENSED KFXX TRANSMITTER SITE TO MATCH THE COORDINATES OF THE ASR FOR THE CENTER TOWER OF THE ARRAY. THIS APPLICATION DOES NOT SEEK TO MODIFY BP-20080717AAW, WHICH AUTHORIZES CONSTRUCTION FOR AN UNBUILT NEW TRANSMITTER SITE. NO OTHER CHANGES ARE PROPOSED.

    Here’s the correct 301 http://tinyurl.com/mldepet which clearly shows 9 kW as the applied for power. Go to the link and scroll down to III A No. 5 and you can see the Nightime Operation parameters. Scroll down to the very bottom for the maps and exhibits and read Exhibit 20 “KFXX Engineering Report” for the full explanation. Exhibit 16 KFXX “Nighttime Allocation Study” shows all the night time maps, too.

    #2153
    Andy Brown
    Participant

    Also, the 301 before the one with the 9 kW night power that I linked to from ten months earlier also has 9 kW. It appears that when they re engineered the site to add 910, their 10 kW night power ended.

    #2154
    semoochie
    Participant

    Thank you! It was the timing of it that made me leap to conclusions, just before the 302. I thought it was a last minute modification and didn’t bother to read the rest. I didn’t think they would correct outgoing coordinates. Is that a requirement?

    #2155
    Andy Brown
    Participant

    Unaware of “requirement” but it is good engineering practice. Many long ago registered towers had coordinates determined by older less accurate methods using actual topographic maps and polar planimeters or decimal rulers. More accurate coordinates are available to us today with GPS, but because of the way the FCC works, it is often necessary to continue to use older coordinates even though they are less accurate when a registered tower is involved or you have to involve the FAA, the arch nemesis of the FCC and enemy of any new proposal for a new tower or service on an existing registered tower.

    In other words, it’s just easier and way less hassle to use the existing coordinates for the tower and redo your engineering then deal with the interagency war that has been going on for 50 years. Trying to change a tower’s coordinates means allowing the FAA to review everything that’s going on and it only leads to problems of all kinds.

    #2156
    Alfredo_T
    Participant

    When I moved to this area, I, too, was impressed with the excellent coverage that KWBY has, considering its low power. Radio-Locator’s map predicts a field strength of about 500 uV/m in Hillsboro, but the signal sounds too good to be that weak. At night, the reception is spotty. As I write this, one of the co-channel ESPN radio affiliates is clobbering them.

    A really unfortunate casualty these days is KXPD. When 1040 was KLVP, it was quite listenable at night in Hillsboro, suffering from only moderate amounts of co-channel interference. Today, they are nearly unlistenable because an adjacent channel station’s IBOC sidebands wipe out 1040.

    #2157
    RadioRon
    Participant

    I used to engineer KWBY and I too was always impressed with its coverage for 250 Watts. The TX site has good soil conductivity and usually has standing water around the tower during Fall and Winter which gives it a good launch point. The tower is short at 155′, I forget what the wavelength is. Before they had a night time power level KFRE (now KFIG) would slam into Woodburn like a local station. I read an article recently in one of the trades that said a good launch point was more important than good soil conductivity in the coverage area and KWBY has that.

    #2158
    Andy Brown
    Participant

    A full wavelength at 940 kHz is 319 meters (1047 feet). That makes the tower height of 155 feet significantly short of a quarter wavelength (262 feet). Assuming it is top loaded or has bonded guy wires to increase its electrical length, it can have some great bandwidth but it doesn’t help propagation when the ground radials get old and rusted or stolen. You can lose a lot of efficiency in that case.

    #2159
    RadioBuggie
    Participant

    Let’s say that you are trying to build a radio tower for radio station 680 AM. It is transmitting a sine wave with a frequency of 680,000 hertz. In one cycle of the sine wave, the transmitter is going to move electrons in the antenna in one direction, switch and pull them back, switch and push them out and switch and move them back again. In other words, the electrons will change direction four times during one cycle of the sine wave. If the transmitter is running at 680,000 hertz, that means that every cycle completes in (1/680,000) 0.00000147 seconds. One quarter of that is 0.0000003675 seconds. At the speed of light, electrons can travel 0.0684 miles (0.11 km) in 0.0000003675 seconds. That means the optimal antenna size for the transmitter at 680,000 hertz is about 361 feet (110 meters). So AM radio stations need very tall towers. For a cell phone working at 900,000,000 (900 MHz), on the other hand, the optimum antenna size is about 8.3 cm or 3 inches. This is why cell phones can have such short antennas.

    #2160
    Andy Brown
    Participant

    Not exactly. Although electron motion is present, the photon is the quantum of the electromagnetic interaction, and is the basic constituent of all forms of EMR (electromagnetic radiation). The electrons move only tiny distances in the antenna, it’s the photons that carry the EMR away from the antenna.

    Also, the optimum antenna for a 680 kHz is one that is half wave length (a Hertz antenna), not full wave length. The top half of the wavelength radiates from the actual tower and the bottom half radiated from the ground field. Because achieving a half wave tower at many broadcast frequencies is not possible due to the extreme length, quarter wave length (a Marconi antenna) is often implemented where the first 1/4 radiates from the tower and the second 1/4 radiates from the ground field.

    http://en.wikipedia.org/wiki/Electromagnetic_radiation

    http://en.wikipedia.org/wiki/Photon

    http://www.hnsa.org/doc/radio/chap20.htm

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