Transatlantic / Transpacific MW Logs

[Tincap]

I love it when WWKB goes to dead air (which happens quite a bit), as it just did. Unfortunately...no sign of Saudi in the breach.

~BG

Satellite-fed programming? How long does this 50kW station have dead air? 1 minute, 5 minutes? Very un-professional! Possibly a windstorm causing the dish antenna to mis-align from the satellite momentarily resulting in loss of audio? In Chicago, sometimes we can hear the audio dropouts on WLS and WIND. One would think engineering for these stations would either use a larger dish to gather more signal or brace the dish so the wind wouldn't cause the dish to move out of alignment with the satellite...

Very unprofessional indeed, but to tell you the truth, I'd be pretty happy with the dead air. It lasted about 3-4 minutes, between the end of a show segment and the news at the top of the hour. There probably should have been a big block of commercials in there, but not to be heard. It happens surprisingly often with KB. I'm used to audio drop outs with the low-buck FM talker, just south of the St. Lawrence from me, but not a big clear channel like WWKB.

~BG

 

[davideduardo]

I'm used to audio drop outs with the low-buck FM talker, just south of the St. Lawrence from me, but not a big clear channel like WWKB.

The two county Buffalo metro is 1.1 million; the daytime 10 mv/m of WWKB covers about 800 thousand. At night, it is worse. This is a station that is simply not viable in any format today... great top of the dial night skywave outside the market, but inadequate inside the market.

 

[stormy01]

I'm used to audio drop outs with the low-buck FM talker, just south of the St. Lawrence from me, but not a big clear channel like WWKB.

The two county Buffalo metro is 1.1 million; the daytime 10 mv/m of WWKB covers about 800 thousand. At night, it is worse. This is a station that is simply not viable in any format today... great top of the dial night skywave outside the market, but inadequate inside the market.

If I recall correctly, aren't the 1520 Buffalo towers electrical greater than 180° (half-wave)? So that would favor skywave. But no AM station is going to shorten their towers just to favor a stronger groundwave. But one would think that long distance listening is so nearly non-existent (except for truckers and DXers, of course!), that AM stations would do all they can to improve their local groundwave coverage even if it is at the expense of skywave coverage...but they want to keep their established coverage patterns too..what a dilemma...hmm...

 

[rfry]

... But no AM station is going to shorten their towers just to favor a stronger groundwave.

Actually it is the other way around. Other things equal, increasing the height of a monopole increases its groundwave field, until the monopole height exceeds 225° -- then the groundwave field starts dropping.

Exceeding 180° height starts to generate a high-angle lobe that can interfere with the nighttime groundwave in some situations, but probably not significantly for the higher AM broadcast frequencies, because the useful groundwave field doesn't extend to the radius where the nighttime skywave from the high-angle lobe returns to the earth.

 

[pianoplayer88key]

What about a segmented or top-loaded antenna?  For segmented antennas, a few examples would be those from WHO, KSTP and KFBK.  As for top-loaded antennas the only one I can think of was KFI, but that was built that way because they were unable to put a standard half-wave antenna in due to flight path problems, IIRC.  Also what about combining the two - segmented (like a Franklin) AND top-loaded (with a capacitance top hat) - what happens then?  Or what about triple-segmented or more, or however it is that FM and TV stations narrow their beam width? If an AM antenna was built on the same principle as a typical multi-element FM broadcast antenna, what might the efficiency be, in mV/m @ 1 km for 1 kW of power?

 

[rfry]

What about a segmented or top-loaded antenna? For segmented antennas, a few examples would be those from WHO, KSTP and KFBK.

Other things about equal, a segmented ("Franklin") antenna can produce a higher groundwave field than a simple monopole. But it needs more height than a monopole, and a complex feed system in order to do that.

For example, the overall height of the WHO sectionalized antenna is 277 meters, and its 1 km IDF is 3343 mV/m. KNX using a frequency 30 kHz higher than WHO and a 150-meter, non-sectionalized monopole has a 1 km IDF of 2828 mV/m.

The distance to the 5 mV/m groundwave contour over 8 mS/m earth is 50 miles for WHO and 43.8 miles for KNX.

As for top-loaded antennas the only one I can think of was KFI, but that was built that way because they were unable to put a standard half-wave antenna in due to flight path problems, IIRC.

Top loading is useful (within limits) to modify the current distribution along a tower or tower section, which can improve the groundwave field compared to not using top loading on that same structure. Essentially it makes the groundwave performance of the radiator about the same as that of a taller structure (other things equal).

Also what about combining the two - segmented (like a Franklin) AND top-loaded (with a capacitance top hat) - what happens then?

A segmented radiator can use loading in either or both sections, and will contribute to the final performance of the system.

Or what about triple-segmented or more, or however it is that FM and TV stations narrow their beam width?

FM and TV broadcast antennas typically use arrays of discrete, identical radiators at spacings of 0.5 to 1 wavelength apart in the vertical plane, each fed with equal power and phase. This arrangement results in maximizing the net far-field from all the radiators in the horizontal plane, and reducing it at higher and lower elevation angles.

If an AM antenna was built on the same principle as a typical multi-element FM broadcast antenna, what might the efficiency be, in mV/m @ 1 km for 1 kW of power?

This is physically and economically impractical for the frequencies used in AM broadcasting. But an h-plane field gain of 6 X and greater is practical for UHF transmit antennas, compared to the peak field of a 1/2-wave dipole.

 

[kilokat7]

Longwave doing good tonight with some good audio from the usual suspects on 162, 171, 183 and 189 khz. TA's also doing well tonight on medium wave, most notable are Saudi Arabia on 1521 (earlier), Spain on 684 and Canary Islands on 621 (when phasing 620 WTMJ directly to the west of me).