Whilst working in the generator room at WFLY, I found this bit of treasure stashed on an overhead shelf:
That is a very old FM broadcast antenna from 1947-48. It must have been intended as a spare antenna in case the main antenna had a problem. It was never needed, so it remains in its original shipping crate. I would think that these were rather well made since the original main antenna was in service from 1948 until 1970 or so when it was replaced with a Shively 6710.
The entire antenna is intact including the Interbay lines, power divider T’s, and tuning section. Of course, it is of little use to the radio station today, as it is horizontally polarized. Perhaps some museum somewhere? I don’t know, it would be kind of neat to put it all together and use it as an exhibit.
Had a coupe bays of that same antenna stashed at an AM site.
Paul, the picture doesn’t show it clearly, but are there two rings of different diameter pipe on each element— one is a matching section?
Steve Brown
Put it on eBay as “NOS – New Old Stock”! 🙂
Steve, I will have to carefully uncrate one of the elements and look at it more closely. My first thought is that it is for some sort of matching, but it could also be for physical support or to increase bandwidth. I will re-examine and post a picture of the feed arrangement.
Chris, NVOS…
Those are really small bays, physically.
The second, smaller ring is to step up the bay impedance. It connects the two capacitor plates creating a folded dipole of 1/2 wavelength.
Very similar to the ERI sold under Collins and other names. Those you could purchase a power divider and separate vertical bays if you were so inclined.
I stumbled on your blog and was perusing old posts; your comment about the value to the station due to horizontal polarization moved my meter because of something I saw just a couple weeks ago. I was doing ABIP inspections in South Dakota and was taken to a pair of mountaintop sites for stations licensed for 100kW and found they were built with horizontal polarization for the sole reason of keeping the TPO down for the bay count. They are licensed horizontal and there’s really no other good reason that I can tell for them to be so. They bought an Armstrong “package” of 10kW transmitter and 14-bay, half-wave spaced horizontal antenna for two of their sites. These are mountaintops with stubby little towers so RF radiation is a concern. They say it’s modeled and passes muster but it’s weird how there’s an observation platform just a short distance away right in the aperture of some antennas at one site. Wish I’d had a Narda meter with me just so I could know. Anyway, horizontal only isn’t completely unheard-of these days. The 302 for one of the sites was filed in 2007.