This explains why they yanked the mod request to drop night power...the boat wouldn't be needed to conduct community ascertainments. How else could they interview at all those schools (of fish)?
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WBBM AM to diplex with WSCR
- Thread starter radioman148
- Start date
This explains why they yanked the mod request to drop night power...the boat wouldn't be needed to conduct community ascertainments. How else could they interview at all those schools (of fish)?
Maybe they're just waiting for the inevitable earthquake tsunami to bring the fish to them.
Looking forward to more diplexing of AM sites as some plots become more valuable due to their location. It's only a few years since KHJ became the triplex with KBLA in Los Angeles. I couldn't believe that the WBBM site is on the future junction of Future I-390 and I-290; no wonder they want to sell the land!
Similarly, a subdivision popped up across the street from KBME's transmitter in north Houston. The site was once a remote area and now is on a future major intersection with two major thoroughfares that just need their various segments connected together. Hurricane Harvey flooded the KPRC site in NE Houston, so it might be more likely that KPRC might be diplexed instead with one of the other two iHeart Houston AMs.
Similarly, a subdivision popped up across the street from KBME's transmitter in north Houston. The site was once a remote area and now is on a future major intersection with two major thoroughfares that just need their various segments connected together. Hurricane Harvey flooded the KPRC site in NE Houston, so it might be more likely that KPRC might be diplexed instead with one of the other two iHeart Houston AMs.
The only significant challenge with WSCR and WBBM is the 110 kHz separation. That requires some rather sharp tuning, making preserving bandwith for each station a bit more difficult. But with computer design, the tuning and rejection networks can be fairly well optimized.
I'd be curious to know why the engineering exhibits for the proposed facilities show protection vis-a-vis CKLW over U.S. soil?
From what I understand, CKLW is not entitled to any sort of contour protection over U.S. territory.
Is CKLW the only station prompting the reduction in power, or does that station at 750 kHz in NW Indiana factor into the equation (insofar as daytime specs are concerned) as well?
FCC has granted WBBM a CP to move their transmitter site to Bloomingdale, IL where it will share the facilities with WSCR:
http://licensing.fcc.gov/cgi-bin/prod/cdbs/forms/prod/getimportletter_exh.cgi?import_letter_id=83014
http://licensing.fcc.gov/cgi-bin/prod/cdbs/forms/prod/getimportletter_exh.cgi?import_letter_id=83014
WBBM Will take a hit
The taller tower will create problems for WBBM at about 50-90 miles out. With the taller radiator, a 2nd minor radiation lobe increases at about 60 deg. and eventually reflects back to the surface as skywave to "self interfere" with the groundwave. Even during the day. And eventually the efficiency curve starts to fall back once above 270 deg. I don't think the non-technical types at CBS/Entercom fully assessed this issue.
Most tall radiators have (and always had) this problem. WBBM runs into the problem at about 60 miles on their current stick. WGN at about 80 miles. This is well known in the engineering side of the business. That being said, the non-technical management of these high power stations don't care as it's outside of their core service area. That same business opinion prevails here as well. The prevailing consensus is the optimum radiator is around 185 deg. balancing pattern bandwidth, transmission line match challenges, efficiency, and the impact effect of the increasing minor lobe with height. It is very much a science to find the best efficiency/height for a given location.
OTOH the smaller 1KW "graveyard" stations do this on purpose to extend their coverage. A lot of those stations run 225 deg. radiators. At about 15 miles, their groundwave runs out of gas...depending on ground conductivity. The skywave augments that, though with a very inconsistent signal.
Now...I heard from someone earlier in the week who intensely monitors transmissions for specific technical purposes that WBBM might already be on the air at the new site. Their HD signal is absent, their operating frequency shifted by a subtle amount...like 1Hz (Which in today's world of GPS locked systems is a huge shift), and their signal field dropped measurably.
I would not be surprised to learn WBBM and/or WSCR kills HD permanently due to practical filter limitations. It's not an simple matter to design a hyper flat filter system with a separation of only 80Khz. Now I know they're 110Khz apart. The 80 Khz comes from the HD sidebands and necessary added allowances compressing that spacing. BTDT...and spent the money on a grand experiment for stations spaced much farther apart.
RR
The taller tower will create problems for WBBM at about 50-90 miles out. With the taller radiator, a 2nd minor radiation lobe increases at about 60 deg. and eventually reflects back to the surface as skywave to "self interfere" with the groundwave. Even during the day. And eventually the efficiency curve starts to fall back once above 270 deg. I don't think the non-technical types at CBS/Entercom fully assessed this issue.
Most tall radiators have (and always had) this problem. WBBM runs into the problem at about 60 miles on their current stick. WGN at about 80 miles. This is well known in the engineering side of the business. That being said, the non-technical management of these high power stations don't care as it's outside of their core service area. That same business opinion prevails here as well. The prevailing consensus is the optimum radiator is around 185 deg. balancing pattern bandwidth, transmission line match challenges, efficiency, and the impact effect of the increasing minor lobe with height. It is very much a science to find the best efficiency/height for a given location.
OTOH the smaller 1KW "graveyard" stations do this on purpose to extend their coverage. A lot of those stations run 225 deg. radiators. At about 15 miles, their groundwave runs out of gas...depending on ground conductivity. The skywave augments that, though with a very inconsistent signal.
Now...I heard from someone earlier in the week who intensely monitors transmissions for specific technical purposes that WBBM might already be on the air at the new site. Their HD signal is absent, their operating frequency shifted by a subtle amount...like 1Hz (Which in today's world of GPS locked systems is a huge shift), and their signal field dropped measurably.
I would not be surprised to learn WBBM and/or WSCR kills HD permanently due to practical filter limitations. It's not an simple matter to design a hyper flat filter system with a separation of only 80Khz. Now I know they're 110Khz apart. The 80 Khz comes from the HD sidebands and necessary added allowances compressing that spacing. BTDT...and spent the money on a grand experiment for stations spaced much farther apart.
RR
Didn't WMAL Washington move from their old transmitter location a few years ago to diplex with another AM?
Last year when I was in Washington they were having real problems (on day pattern) about an hour before they'd have had to switch to night pattern just North of Silver Spring. There should have been no problem with the day signal there but it was really getting knocked around, maybe 10-15 miles from the transmitter site.
Last year when I was in Washington they were having real problems (on day pattern) about an hour before they'd have had to switch to night pattern just North of Silver Spring. There should have been no problem with the day signal there but it was really getting knocked around, maybe 10-15 miles from the transmitter site.
I believe you are right. They are simply looking at the dollar signs. I've just moved to Plymouth, Indiana area. For probably the 2nd time in my life, I've preset 780 (versus 105.9). It comes in ok in the Plymouth area so far and as long as I am not near
the big power line towers. Today, the HD 780 did come in but as I was moving in the car, it was not stable. I'll post back if I notice any changes....I do intend to listen so I hope that it continues to come in.
the big power line towers. Today, the HD 780 did come in but as I was moving in the car, it was not stable. I'll post back if I notice any changes....I do intend to listen so I hope that it continues to come in.
Checked in Kenosha. Signal seems the same but the HD is indeed off. No hash on first adjacents and no showing on an HD Radio. They don’t really need it to begin with.
Did 670 & 780 really turn off the HD?
Good time to log WSGW 790, even in the Daytime, in SE WI. Before IBOC, I had no difficulty logging it when I was there briefly. Like CFOS 560, and CFCO 630, it turns up in widely diverse locations.
Before HD I heard WSGW during the day a few times driving on Lake Shore Drive. The wall of buildings would null WBBM just a little and WSGW could be heard on a good car radio.
... as do you!
We have been missing you. Welcome back to the board.
Of course, there are considerable economies to be had by diplexing. But there is also the possibility that the "old" WBBM location had grown so much in tax valuation that it was paying onerous annual amounts. And that is beyond the probability that they will make a good amount on the sale of the old site to developers.
Recently a 50 kw AM in Miami found that its site was worth about 10 times what the station itself was worth. They moved to a combined site in the Everglades, but had to cut both day and night power considerably. But they could not sustain the costs of keeping the old site based on current Miami AM radio usage.
The first time I heard about WSGW coming in in Chicago was around 1967. A friend of my relatives was taking us on a tour of the Chicago Circle Campus and talking about listening to Minor League PBP on a Saginaw station. It took a while to figure out it was WSGW. The lobe to the SW is equivalent to about 17 kW Daytime based on minimum Class III/Class B efficiency of 282 mV/m @ 1 km for 1 kW.
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Thanks for noticing and the welcome back.
It is good to have you back SC!
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