Aw, I thought you were going to tell me about something new I could explore.
-
Get involved.
We want your input!
Apply for Membership and join the conversations about everything related to broadcasting.
After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
If you use a disposable or false email address, your registration will be rejected.
After your membership is approved, please take a minute to tell us a little bit about yourself.
https://www.radiodiscussions.com/forums/introduce-yourself.1088/
Thanks in advance and have fun!
RadioDiscussions Administrators
KOST 103.5
- Thread starter 30james
- Start date
Sorry, dude. You've cornered the market.
I'm still looking for things... like 60's Gavin Reports!
(I did just get two big boxes of Hard Report issues... looking for FMQB issues, too)
60s and 70s Gavins and the remaining missing R&Rs would be wonderful. I saw that you got more issues of Fred and was delighted to see the "Spectrum III" editor mentioned having listened to me (on KOLO, Reno) during a long drive and that he enjoyed it. Rare to get positive feedback 42 years after the fact.
For the safety of personnel the FCC has prohibited single bay FM antennas for many years. It's noteworthy to say that in ancient times after KGIL-FM (x-KVFM) 94.3 ceased operations from the Panorama Towers office Bldg in Panorama City, they moved the xmitter (3 kW) to the AM site in Mission Hills and attached a single CP antenna to their original 1/4 wave AM antenna. Their were/are residences within feet of that installation-talk about blanketing interference. The facility has since been relocated to a relatively isolated area in the North Valley, the hilltop at the old Odyssey in Grenada Hills.
Many stations used extremely high ERP and quite low RCAGL on AM towers in the early days of FM. WEAW-FM 105.1 Evanston, IL, now WOJO, comes to mind, with 180 kW with 8 Bays on a circa 300 foot WEAW 1330 tower. Our Chicago Area DXers may recall more details.
Another case is WITL-FM 100.7 Lansing, MI. They first used 6 Bays H only on top of the legacy Ransom E. Olds Tower building in central Lansing, MI with 82 kW ERP. Recently, what is now WLMI 92.9 Grand Ledge, MI had to do all kinds of fancy footwork to get just 5.4 kW ERP with 5 Bays with 1/2 wave spacing at the same spot at the top of the same building, now known as the Boji Tower.
You can get any number of Bays N to have a null straight down with (N-1)/N wavelength spacing. It requires extra work to get proper power division and phasing to the Bays though. You would probably have to prove it to the FCC, but spacing on the order of 0.8 to 0.9 wavelength spacing maximizes gain. So a 5 Bay antenna with 0.8 wavelength spacing would have near maximum gain and a null straight down.
http://licensing.fcc.gov/cgi-bin/prod/cdbs/forms/prod/getimportletter_exh.cgi?import_letter_id=82282
Another case is WITL-FM 100.7 Lansing, MI. They first used 6 Bays H only on top of the legacy Ransom E. Olds Tower building in central Lansing, MI with 82 kW ERP. Recently, what is now WLMI 92.9 Grand Ledge, MI had to do all kinds of fancy footwork to get just 5.4 kW ERP with 5 Bays with 1/2 wave spacing at the same spot at the top of the same building, now known as the Boji Tower.
http://licensing.fcc.gov/cgi-bin/prod/cdbs/forms/prod/getimportletter_exh.cgi?import_letter_id=81451
You can get any number of Bays N to have a null straight down with (N-1)/N wavelength spacing. It requires extra work to get proper power division and phasing to the Bays though. You would probably have to prove it to the FCC, but spacing on the order of 0.8 to 0.9 wavelength spacing maximizes gain. So a 5 Bay antenna with 0.8 wavelength spacing would have near maximum gain and a null straight down.
Last edited:
I just did some calculations, and if a newfangled 1 CP Bay with 0.1 a relative field straight down, with a 6 kW ERP in the Horizontal Plane, at 200 feet directly below the COR, it would be on the order 1 Volt/meter field strength, or 120 dBu. This wouldn't even allow a McIntosh MR-80 to tune in a first adjacent less than 60 dBu/1 mV/m. You might do better at 25 degrees from straight down with a multi bay antenna.
Without an extremely directional outside FM receiving antenna, the MR-78 (55 dB rejection at 200 kHz) and the MR-80 (60 dB rejection at 200 kHz) are both quite compromised in areas with a lot of IBOC sideband interference.
The original Class As, with 1 kW/250 feet, could be about 45 miles apart and still meet the rules at the time, no overlap between the 1 mV/m F(50,50) to the 0.1 mV/m F(50,10) for two cochannel Class As at maximum reference facilities. In circa 1962, that became 3 kW/300 feet, and two cochannel Class As had to be 65 miles apart. In larger cities and metropolitan areas, those rules were not applicable to many stations which were grandfathered under old rules. That situation, addressed by an ever changing CFR 47 Part 73 Section 73.213, has made it extremely difficult to relocate stations if a tower site has been lost or sold because of rising property values. Many formerly full facility Class Bs with 50 kW/500 feet that were short spaced under the older Section 73.213 rules, cannot relocate without going to ridiculously directional antennas which force wide arcs, even in the major lobes, to have measured licensed patterns with ERP well below the maximum permitted in those directions. You can find some of those measuried patterns on the license to cover applications. The FCC pattern, the horizontal polarization pattern, the vertical polarization pattern, and the composite pattern (the greater of the H POL and V POL relative field values) are shown on those license to cover applications.
Because of the way the rules are written, it is often almost useless for a 3 kW Class A to upgrade to 6 kW Class A directional. You are often better off to be 4 kW or 5 kW nondirectional, or even maximizing HAAT to 100 meters at 3 kW nondirectional, than to be 6 kW directional.
The original Class As, with 1 kW/250 feet, could be about 45 miles apart and still meet the rules at the time, no overlap between the 1 mV/m F(50,50) to the 0.1 mV/m F(50,10) for two cochannel Class As at maximum reference facilities. In circa 1962, that became 3 kW/300 feet, and two cochannel Class As had to be 65 miles apart. In larger cities and metropolitan areas, those rules were not applicable to many stations which were grandfathered under old rules. That situation, addressed by an ever changing CFR 47 Part 73 Section 73.213, has made it extremely difficult to relocate stations if a tower site has been lost or sold because of rising property values. Many formerly full facility Class Bs with 50 kW/500 feet that were short spaced under the older Section 73.213 rules, cannot relocate without going to ridiculously directional antennas which force wide arcs, even in the major lobes, to have measured licensed patterns with ERP well below the maximum permitted in those directions. You can find some of those measuried patterns on the license to cover applications. The FCC pattern, the horizontal polarization pattern, the vertical polarization pattern, and the composite pattern (the greater of the H POL and V POL relative field values) are shown on those license to cover applications.
Because of the way the rules are written, it is often almost useless for a 3 kW Class A to upgrade to 6 kW Class A directional. You are often better off to be 4 kW or 5 kW nondirectional, or even maximizing HAAT to 100 meters at 3 kW nondirectional, than to be 6 kW directional.
Last edited:
- Status