May 2018
M T W T F S S
« Mar   Jun »
 123456
78910111213
14151617181920
21222324252627
28293031  

Archives

Categories

AM station downgrade

I have been working on another formerly direction class B AM station, this one is in Rutland, VT.  WSYB has been on the air since 1931 with the same call letters serving the east central part of Vermont.  In 1931, it was operating on 1500 kc with 100 watts of power.  In March 1941 it moved to 1490 kc with 250 watts before settling, a few months later, on 1380 with 1,000 watts, directional night time protecting CKPC in Brantford, Ontario, Canada.

The transmitter site was first located at 80 West Street (now known as BUS US 4), in Rutland.  It was moved to its current Dorr Drive (Formerly Creek Road) location in 1938, when the station was requesting a power upgrade to 250 watts.  Whilst cleaning out the old transmitter building, a copy of an operating log, dated December 7, 1945 was discovered in the attic above the transmitter room:

WSYB transmitter log, 1945

Back from the time when readings were required every 30 minutes.

In 1956, WSYB was allowed 5,000 watts daytime non-directional with 1,000 watts night time directional.

At some point in the early 1990’s, the original towers were replaced with solid leg Pirod towers, each 195 feet tall.

After that, things went the way things do; AM steadily declined in favor of FM, local programming was mostly replaced by syndicated satellite stuff, there were several transfers of ownership, etc.

A translator on 100.1 MHz was added in 2016; the two bay Shively antenna was installed at the top of the South West tower.   There is local programming on the station from 6am to noon on weekdays.  There may also be some gardening shows and other such programming on weekends.

The current owner has decided, like they have done in other markets, that AM directional antenna systems are a maintenance nightmare, the risk of FCC sanctions are high for an out of tolerance antenna array, the ratings and income from the station do not justify the risk/cost.  Thus, non-directional night time operation was applied for and granted.  The station is now a Class D with 25 ass kickin’ night time watts.

WSYB had a two tower night time antenna system.  The tower closest to the building (SW) was also the daytime, non-directional tower and it now holds the FM translator antenna and STL antenna.  Thus, it was decided to ground that tower and keep those antennas in service.  The far tower (NE), which was the second tower of the night time array would become the AM antenna.  The night time ATU was built for less than 1,000 watts input power, so several components needed to be upgraded for 5,000 watt operation.

WSYB rebuilt ATU

WSYB rebuilt ATU

I had available these nice vacuum capacitors that came out of another decommissioned antenna system.  The vacuum capacitors are great because the voltage/current ratings are much higher than the mica capacitors that were in the circuit before.  You can see black goop where one of the Sangamo mica capacitors on the input leg failed several years ago.  These vacuum capacitors are rated at 15 KV and the current rating at 1.38 MHz is probably in the 70-80 amp range.  I had to move the base current meter from the former daytime (SW) tower out to the NE tower.  The day night switch was taken out of the circuit.  The transmission line to the far tower was replace with 7/8 inch foam dielectric cable.  A slight touch up of the coil on the input leg of the T network was all that was required to bring it into tune.

The electric lines to the tower have been temporarily disconnected.  As soon as they are reconnected, I will vacuum out all the mouse crap and other debris.  The ATU building also needs some work sealing in up against the elements.

The tower base impedance is 75 ohms, +j95 making the base current 8.6 amps daytime and 0.58 amps night time.

WSYB radiating element

WSYB radiating element

For me, the magic of radio exists at that boundary between the real objects (towers and antennas) and the ether.  The transference of electrical voltages and currents into the magnetosphere is something that still fascinates me to this day.  Coupling a 5,000 watt medium wave transmitter to a tower and watching it work is something that I will never grow tired of.

Be Sociable, Share!

3 comments to AM station downgrade

  • Good looking work Paul. Now if only the programmed content were worthy of the magic medium that sends it forth into the aether.

    p.s. I wish I could have 25 watts, any time of day.

  • AW

    I love seeing old log sheets/books. It harkens back to a day when radio was serious business. Professionalism was the word of the day then.

  • Lee Rust

    Aside from the fact that every digital wireless device interacts with the magnetosphere in similar fashion, I agree that there is a difference with the older broadcast technologies, especially AM. The tuning house components are so large and physical, it’s easy to visualize the electrons zipping around doing their thing. Then you can step outside, lean back, and imagine the radio waves rippling off the tower. That’s when the real fun begins.

    Old AM radio shows I did back in the 1970’s have already passed by the nearby star Arcturus and are well on their way to nobody knows. Anyone who has ever been heard on broadcast radio is a deep-time space traveler. Not so much with the internet, with its weak little Wi-Fi signals and data archiving which will only last as long as server farms can be maintained by our fragile little civilization.

Leave a Reply

 

 

 

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

Axiom


A pessimist sees the glass as half empty. An optimist sees the glass as half full. The engineer sees the glass as twice the size it needs to be.

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
~1st amendment to the United States Constitution

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.
~Benjamin Franklin

The individual has always had to struggle to keep from being overwhelmed by the tribe. To be your own man is hard business. If you try it, you will be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself.
~Rudyard Kipling

Everyone has the right to freedom of opinion and expression; this right includes the freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers
~Universal Declaration Of Human Rights, Article 19

...radio was discovered, and not invented, and that these frequencies and principles were always in existence long before man was aware of them. Therefore, no one owns them. They are there as free as sunlight, which is a higher frequency form of the same energy.
~Alan Weiner

Free counters!