I have been in contact with many of the engineers at the local TV stations asking various questions. Some of the info I will directly pass on as it helps with antenna aiming and selection.
ERPs (Effective Radiated Power)
KTTC-DT is 26kW ERP, with plans to add a new transmitter into place that will boost them to 33.7kW, which has been approved by the FCC. This will also allow them to use the older 26kW max transmitter for backup.
KIMT-DT is 800kW, where it will stay. It was increased from 200kW, because KIMT would like to begin sending out mobile DTV signal and a much stronger signal is needed to make mobile DTV work well on small devices with small antennas.
KXLT-DT is 220kW, with no plan on a power increase.
KSMQ-DT is 322kW, they were planning to go to 400kW, but this would have required an additional transmitter cabinet, and their signal testing, showed that they do not believe to need to the extra power. (Which, I agree, their signal is very strong as it is.)
KYIN-DT is 533kW, recently upgraded from 250kW. This one is tough to receive at the authors home, just North of down tower Rochester, even at 533kW, a tight aim for the shared tower with KIMT-DT is required)
As for KAAL, that one is a mess and I wish I knew what the FCC is going to concerning their request to move to the KSMQ-DT/KXLT-DT tower in Grand Meadow and start a translator in Mason City. I have an email out to the engineer, but have not heard back in the last week.
As for our neighbors in La Crosse:
WXOW-DT will be moving from RF channel 14 to channel 48. Also will be increasing power to 371kW, from a brand new top mounted antenna. This signal should be as strong or a but stronger then WHLA-DT currently. The antenna will be installed in the next few weeks (weather permitting) with final move at 9AM on June 12th, 2009.
UPDATE (5-29-09)
I heard back from over at WXOW. They are planning to get the old RF channel 19 antenna pulled off of the tower on Monday or Tuesday (weather permitting)This tower stuff is VERY dangerous and needs very calm weather to work out well. They may be off the air or at 1% power while the tower workers are near the RF channel 14 antenna (the current digital [DT] antenna). (which will affect everyone, cable, DBS, and OTA)If they can stay at 1%, cable and DBS will stay up, but if the radiation levels are too high, they will pull it off the air completely.
7 comments:
Kind of funny how in the current carbon concerned economy that the move from the VHF - low band to UHF band has caused a conversion from lower powered transmitters to real torches (KIMT 800KW for example).
Yes, it has been fun to watch what stations are concerned with. As to the 800kW ERP, this is not the power that leaves the transmitter up the feedline (basically big coax) to the broadcast antenna, but actually the power after the antenna, so with a decent antenna, I doubt they run more then 50kW up the feedline. The newer antennas are often have more gain and are better designed.
I can understand how modern feedlines have less loss than in the past. However, I don't understand how you can get any transmission gain form an omnidirectional antenna. Antennas typically give transmission gain by concentrating the signal on a focused footprint. Are there now omni-directional antenna that provide a gain over a vertical dipole? I suppose an antenna could focus the signal better on a lateral signal limiting the signal going directly in the ground or into space.
EXACTLY right, the signal has very little component going out to outer space or into the ground, most signal leaves the antenna on a flat plain with the earth. Remember these antennas are HUGE, 60-80ft long is very typical for VHF, with 40-80ft common on UHF.
Even in WIFI (2.4GHz), you can get a an omni-direction antenna with decent gain (some up 9 dB), it just has to very long compared to wave length, same thing applies here.
Thanks. I always enjoy learning something new. That makes sense. With UHF's smaller wavelengths, it makes it physically possible to have high multiples of wavelength long antennas.
Wiki has an article about this topic
http://en.wikipedia.org/wiki/Omnidirectional_antenna
Antennas are very interesting. There is a LOT of schooling out there on antenna design. The Wikipedia link is a good for anyone with interest in antennas and RF.
The engineers that build broadcast antennas and receive antennas for that matter, probably pull their hair out to get things right and test designs. The biggest thing with receive tv antennas, is that most are broadband, meaning they are tuned for multiple channels, so compromises are inevitable. (for example, my favorite tv antenna, the Antenna's Direct 91XG, has great gain up in the RF channel 40-50 range, but fairly poor gain in the 14-30 range, which hurts some of the locations in weak areas, KYIN-DT-18, for me is very weak)
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