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Travel Back In Time To Buy A Good TV Antenna

The technical side of broadcasting. Think IBOC is a sham? Talk about it here! How about HDTV? Post DX reports here as well.
k8jd
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Re: Travel Back In Time To Buy A Good TV Antenna

Post by k8jd » Fri Dec 04, 2015 1:48 pm

Hi Art Thermo Meter, do U think much of the "FMfool" and "TVfool" website estimations. A lot of info pops up there. I have used them for various camping sites around the state, to find what can be heard and seen there.
Arthur Mometer wrote:Here's a site that you can find the elevation for a location. You can touch the location and get the AMSL in meters. For example, put in Fenton, MI and then touch just north of US 23 and Center Rd. in Tyrone Twp., and you get 325 meters, about 1056 feet.

http://www.mapcoordinates.net/en



Arthur Mometer
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Re: Travel Back In Time To Buy A Good TV Antennalivicio

Post by Arthur Mometer » Fri Dec 04, 2015 10:40 pm

TVFool and FMFool seem to be based on some model that is very similar to or identical to Longley Rice. Since terrain and point to point terrain profile is a very important factor in signal prediction, one that was not used fully in FCC coverage estimations, I'd rate the site Good to Excellent. Obviously a DXer can get signals further, all the time or occasionally, but as far as easy reception, the lists generated are very accurate.

The gain quotes I recall for the UHF Parabolic Reflector were 17 dBd at Channel 14 to 21 dBd for Channel 83. The combination of wave and particle theory and frequency/wavelength are the only thing that separates "radio" waves from optics. Optical Telescopes are essentially antennas for visible light. Antennas just change in design from VLF and below to visible light and above.

Reflection calculations at optical surfaces are similar to VSWR calculations. I was told that it all had to do with the wave equation, but the Physicist I asked never showed me exactly how. One thing we couldn't immediately reconcile is how Glass has a refractive index of about 1.5, and Water 1.33, but refractive index is supposed to be close to the square root of dielectric constant, and it works fairly well for Glass and Transparent Plastics, with dielectric constants averaging 2-2.5, but not Water, which has a dielectric constant of 78. It has to do with relative permittivity and permeability, related to electric and magnetic properties, capacitive and inductive properties at the atomic or molecular level, and is actually the square root of the product of those. Those properties determine the speed of light and the inverse index of refraction, in a substance. In a transmission line, the dielectric (but it would have to also have to be related to the magnetic properties, not just electric) determines this.


"I'm meteorologist Arthur Mometer."

"Those of you who think you know everything are very annoying to those of us who do."

"Lies have to be repeated and repeated to be believed. Truth stands on its own merit."

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WOHO
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Re: Travel Back In Time To Buy A Good TV Antenna

Post by WOHO » Tue Dec 08, 2015 9:43 am

Yeah, if only the FCC would have used TVFool to realize that they needed to give VHF stations a bucket load more ERP to reach their old analog contours, but instead they used FCC-FOOL.



Arthur Mometer
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Re: Travel Back In Time To Buy A Good TV Antenna

Post by Arthur Mometer » Sun Jan 17, 2016 12:04 pm

If you can page through and find the Index, you can find images of TV and FM Antennas used since the beginning of such Antennas.

One thing that surprised me, is the large number of designs in the early History, and many were designed for VHF-UHF. There are even VHF-UHF Antennas using Rhombic designs for UHF. It looks like a single wavelength per side of the rhombus, so I don't know how well these would work. Most designs I have seen in books specified three to five wavelengths per side of the rhombus. I would also think the bandwidth would be limited. Back when these designed, shortly after they opened up Channels 14-83, UHF stations were mostly designed to serve a small local area, like 10-20 miles, so they probably worked OK for that.

I have always heard people say they were going to build a rhombic antenna to get some difficult to receive channel. Due to the difficulty of designing, building, space requirements, and orientation, I never talked to anyone who followed through building a rhombic antenna. Has anyone here built a rhombic for TV or FM?

http://www.americanradiohistory.com/Ele ... talogs.htm


"I'm meteorologist Arthur Mometer."

"Those of you who think you know everything are very annoying to those of us who do."

"Lies have to be repeated and repeated to be believed. Truth stands on its own merit."

k8jd
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Re: Travel Back In Time To Buy A Good TV Antenna

Post by k8jd » Mon Jan 18, 2016 7:01 pm

A long Yagi can get nearly the gain of a Rhombic and you can rotate it a lot more ealily if you want to look elsewhere. Rhombics are great for point to point HF work.



Arthur Mometer
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Re: Travel Back In Time To Buy A Good TV Antenna

Post by Arthur Mometer » Sat Jan 30, 2016 10:16 pm

It's amazing the variety of antennas that were in use in the late 1950s and early 1960s. I walked to school and remember many of the antennas along the way. Some were brought back by the Allied Catalog pictures. I didn't know who the manufacturers were at the time. Our next door neighbor had a 2 Bay Inline High Low Amphenol with an Alliance Tenna Rotor. It was on a guyed mast, probably 20 feet high above the Cape Cod roof. One windy day, I came home from school to see it sprawled over the front porch. They had it fixed that time. I remember that they had the kits or parts on the truck I peered into. We were the first on our block to have a tower. I think that was because of the rusting stains and multiple guyed antennas falling in the neighborhood. Ours was a Par 5, a 2 Bay Inline High Low with two High Band Directors on each bay, plus a 5 Element Channel 6 Yagi. There was a knife switch to change antennas. Some people had 4 separate 5 Element Yagis for Channels 2, 4, 6, and 7, and a 4 Antenna switch. After there were 8 VHF channels you could see, people would try all kinds of combinations of the 4 antennas to optimize the performance on a particular channel. In our area, reception of some channels was very area dependent. I didn't know at the time that small terrain ridges on the order of 100 feet a couple miles from and parallel to rivers and streams were the reason for this, and the inexplicable areas where the UHF stations came in well all the time 45-50 miles away.


"I'm meteorologist Arthur Mometer."

"Those of you who think you know everything are very annoying to those of us who do."

"Lies have to be repeated and repeated to be believed. Truth stands on its own merit."

Arthur Mometer
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Re: Travel Back In Time To Buy A Good TV Antenna

Post by Arthur Mometer » Tue Oct 30, 2018 3:52 am

This thread had a huqe number of views, so I'm going to repost this recent link.

http://www.kvhf.com/flyers.htm
Last edited by Arthur Mometer on Tue Oct 30, 2018 3:53 am, edited 1 time in total.


"I'm meteorologist Arthur Mometer."

"Those of you who think you know everything are very annoying to those of us who do."

"Lies have to be repeated and repeated to be believed. Truth stands on its own merit."

Rich
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Re: Travel Back In Time To Buy A Good TV Antenna

Post by Rich » Tue Oct 30, 2018 6:14 am

A day or so ago, Arthur Mometer posted that a high power broadcast station might be able to be received on the Moon. Here is a short response I had put together and tried to post but couldn't, as the site was having some issues at that time:

A UHF signal of one million watts ERP at the peak of its major lobe produces a field intensity of about 1 V/m at a horizontal distance of 3 miles. The distance from Earth to the Moon is about 240,000 miles, so, by inverse-distance attenuation the field at the Moon would be about 12.5 µV/m. But that would occur only for very brief intervals each day as the Earth rotates, when the Moon was fully "illuminated" by the main lobe portion of the UHF transmit antenna radiation pattern.



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Re: Travel Back In Time To Buy A Good TV Antenna

Post by Arthur Mometer » Thu Nov 01, 2018 4:31 pm

I was about to post a reply also when the message board disappeared. When the article I read was published long ago, WJFM was still 500000 watts. It also alluded to all the "stars" having to be in alignment and proper rotation for this to work.


"I'm meteorologist Arthur Mometer."

"Those of you who think you know everything are very annoying to those of us who do."

"Lies have to be repeated and repeated to be believed. Truth stands on its own merit."

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