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Shunt Around And Find Out...

T

theantennaguy

KSEV files to move to a single grounded tower with a 400 watt SHUNT feed. Same set up as 850. Predicted coverage map is just slightly less area than it currently covers. I posted pics from the jobsite, but had to edit and take down for security reasons.

Adobe Acrobat

acrobat.adobe.com acrobat.adobe.com
 
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Another shunt fed tower. XEB 1220, 100,000 watts in 1963.

1738931855060.png

Note that there is no base insulator. The tower was fed by open line at the "tuning point" part way up the tower. A shunt fed tower has a point along its height where the impedance matches with the line.
 
DavidEduardo said:
Another shunt fed tower. XEB 1220, 100,000 watts in 1963.

View attachment 8542

Note that there is no base insulator. The tower was fed by open line at the "tuning point" part way up the tower. A shunt fed tower has a point along its height where the impedance matches with the line.
Click to expand...

Your description is absolutely correct. Shunting is an "old school" way of doing it. May not be quite as efficient as a non-grounded stick with radials, but it works and is in fact "type accepted." You're gonna see shunting making a big come back as struggling AM stations cash in on their real estate. Most AMs don't need massive tower farms or a huge power bill to cover the communities where they're selling ads
 
I can see them getting away with this for a STA, but the FCC won't approve new shunt fed AM systems for permanent use. The high angle radiation from the shunt wire is unpredictable especially for night time use.
 
Shunt fed AM's also don't have to have "isolators" for tenants, and the lighting is a lot simpler with out the "Austin ring transformer", there is no glass insulator issues on the tower base or the guy wires. There is an old AM tower that generates enough from the cell companies to pay the electric bill, insurance, and property taxes.
 
rfburns said:
I can see them getting away with this for a STA, but the FCC won't approve new shunt fed AM systems for permanent use. The high angle radiation from the shunt wire is unpredictable especially for night time use.
Click to expand...
Please provide a reference or example where the FCC has disapproved a shunt in recent history.
 
rfburns said:
I can see them getting away with this for a STA, but the FCC won't approve new shunt fed AM systems for permanent use. The high angle radiation from the shunt wire is unpredictable especially for night time use.
Click to expand...

You forget a huge percentage of the AM's are only on to "feed" a FM translator. Is "skywave" even figured or factor on a daytimer? If you have a translator why even run flea power? I realized there are certain places with really good ground conductivity that allow a class A or B AM to have a translator's 60 db outside of the 25 rule but a class D AM with 50 KW daytime only would get the same treatment.

Unfortunately, with the exception of a few stations, AM night service economically is a waste of electricity if you have a decent FM translator

It still is cool to try to DX distant AM stations at night. I don't know how long this will continue.
 
They will save on the electric bill, and the extra cost of directional maintenance. There might be a sweet land deal involved too.
 
secondchoice said:
They will save on the electric bill, and the extra cost of directional maintenance. There might be a sweet land deal involved too.
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I suspect KSEV is up for sale, and they are cashing in on the land value of the existing transmitter site. It’s likely the station itself is of little worth.

Outside of NW Harris County the 210 watt night signal will be shredded by WLW. The 400 watt day signal at least has the advantage of being in the lower end of the AM band, so coverage similar to the 250 watt KIKK 650.
 
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