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Author Topic: What do the commercial radio stations use for an antenna?  (Read 42302 times)

KM1H

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RE: What do the commercial radio stations use for an antenna?
« Reply #30 on: August 01, 2018, 07:50:15 AM »

Quote
A newer type of antenna is starting to be used by AM broadcasters:

http://www.nab.org/xert/scitech/pdfs/rd020909.pdf

We got the very first one in 2009 in Florence, Oregon.

Anyone aware of any other Kinstar installations?  BTW, they use 5 antennas configured as cage verticals and phased as a single radiator for a claimed 98% efficiency over a 1/4 wave with 128 radials. While still tall for many wanting to use on 630 it appears to be a choice for 160. They still need a full ground radial system or a simpler elevated one to reach that efficiency.

http://www.star-h.com/docs/STAR-H%20KinStar%20NAB%20Presentation.pdf

Has anyone done a NEC 4 study of elevated radials for 630, and what heights and quantities are required?

Carl
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RFRY

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RE: What do the commercial radio stations use for an antenna?
« Reply #31 on: August 25, 2018, 03:54:08 AM »

... Has anyone done a NEC 4 study of elevated radials for 630, and what heights and quantities are required?

Don't know, but I'll do that and post it if a sufficient definition is provided.

In the meantime, below is a NEC4.2 analysis of a 630-meter T antenna system using 16 buried radials:


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KM1H

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RE: What do the commercial radio stations use for an antenna?
« Reply #32 on: August 29, 2018, 06:55:56 PM »

Hmmmm 14' radials equals 33% efficiency which will likely be a lot less in most ham installations with their typical ground conditions.
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RFRY

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RE: What do the commercial radio stations use for an antenna?
« Reply #33 on: August 30, 2018, 12:57:24 AM »

Hmmmm 14' radials equals 33% efficiency which will likely be a lot less in most ham installations with their typical ground conditions.

Earth conductivity as stated in that NEC4.2 study was set at 5 mS/m, which is about typical for the continental US.

Installing that T antenna system in an area of higher Earth conductivity would improve its radiation efficency; lower conductivity of course would reduce it.
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G4ZOW

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RE: What do the commercial radio stations use for an antenna?
« Reply #34 on: November 11, 2018, 05:26:11 AM »

Just my 2c I mean 2p.

Not all AM (MF) broadcast antennas are insulated at the base. you can use a grounded base and shunt feed her at the 50 ohm point.

I believe the vast majority of non-directional stations use a 1/4 wave or 90 electrical degree stick or close to that figure.

Transmitters do indeed have a built-in output network but you still require an antenna matching unit at the base of the mast or tower.

A carefully designed AMU is critical to optimize b/w & efficiency. It is not unheard of for two identical RF chain stations to sound completely different to one another without correct tuning. One can sound as if they have a pillow over the mic and the other, well you get the idea.

In a past life I was part owner of a small town AM in Williamsport, Pa. 1kW day and 38W night. We had a 229ft  ND stick. Protecting a station in NY was the reason for low night power.  I junked the old LPB 'low level mod' night TX in favor of a pulse width modulated solid state transmitter and nearly doubled the signal coverage!

We sold the station to a local girl and I moved back to the UK.

David  G4ZOW



 
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