NEW UPDATE: WCBN is broadcasting at 1.6 KW as of July 20th!
We have been getting great reports about the improved coverage.============================================================
UPDATE: Successful testing completed on Friday July 13th. Yeah!
Jim Campbell said:"Last Friday night, working with Manos in the Studio, I sat at the new transmitter and ran it over the air for about an hour at half power.
Results were very good with the reflected power so low it barely budged the SWR meter on the FM2000 (1:1.04 at 350 Watts). We are now awaiting the final license from the FCC to commence full power operation. This could take several more months."
So now we wait...again...
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The new transmitter and antenna for WCBN are finally installed on the UM's North Campus microwave tower. It only took....how many years?
The tower is located off Dean Rd., between Hubbard and Baxter, and between Green Rd. and Huron Parkway. Our new transmitter rack here, too. It holds the entire chain of electronics that make our FM transmission possible. It s in located in the small hut at the base of the microwave tower there.
there is also another antenna on that tower, and it is because of that antenna that we need to locate our antenna array a low on the tower as it is. That height does not affect our transmission footprint, so don't worry!
The audio from the studio in the SAB first hits a signal processor that makes sure it is at good level and keeps it from over-modulating our transmitter.
It then goes into the low power exciter that takes our audio signal and modulates a low power FM carrier at 88.3 MHz.
This is about the same power as our current transmitter, and can be used as out transmitter in an emergency, or if we need to do maintenance or repair on the main transmitter. We are also going to keep our current transmitter system located at the top of the Weiser Building on central campus in case we need it to fill in when we have to take the whole new transmitter system off the air for any reason.
Then it goes into the 3000 watt transmitter that actually feeds the new antenna array. While we are allowed to broadcast at up to 3000 watts, the optimal pattern to reach our allowed area ends up having us transmit at 1600 watts.
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| Location of the new antenna and transmitter |
We have 2 parts to the new antenna, and they are designed to be placed just so in order to shape our transmitter "footprint" to accommodate other radio stations around us. And then they are put into protective plastic covers to keep them safe from the elements. The covers have no effect on the RF transmission.
Here is what the antennas look like before they are enclosed.
Half of one of the covers is in the background.
Here is a close-ish view of what they look like on the antenna tower, with the workers on the tower:
Below are 2 sets of before and after shots of the tower. from far away and closer Our new antennas are the lowest objects you see in the second set of photos. They are enclosed in weather proof covers and so look like big black objects.
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| BEFORE, from the UMTRI building. |
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| BEFORE, from the tower parking lot. |
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| AFTER, from the UMTRI building. |
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| AFTER, from the tower parking lot. |
This one is annotated to show what's what. The existing antennas are for other uses, and also determined where ours could be located on the antenna tower. That's why ours are the lowest. But they are just fine for our need.
Here are some photos of the new rack in the tower hut at the base of the microwave tower.
And a movie of going in to the shed:
Note how big the new line is compared to our temporary line.
And a movie of going in to the shed:
Note how big the new line is compared to our temporary line.
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| The big hole in the middle is the connection for the transmission line. |
Here are some photos of how we have to keep the new transmission line (it's no longer just a cable) dry, using nitrogen gas under pressure in the line.
That's all for now. Happy listening!
-t
That's all for now. Happy listening!
-t
