WPBY antenna toast

[philo]

Antenna and transmission line toast.

Running 500W from WOWK ch47 antenna.

[lastone]

Interesting.

Last summer I would see what looked like a VSWR trip when it would get hot out. It would start slow and speed up over time. Each time I would notice it, I would e-mail them about it in hopes they would shut it down before tube damage. But they let it go until complete shutdown each time. Pulsing the tubes at full power every half second couldn't have been good on any thing.

Makes one go Hummmmmm.

[Big Media]

Why do these newfangled DTV antenners seem to be so susceptible to VSWR problems?

[Hoosier Daddy]

Why do these newfangled DTV antenners seem to be so susceptible to VSWR problems?

Well ... Ten movies streaming across that, that DTV antenna, and what happens to your own personal antenna? I just the other day got ... a DTV signal was sent by my staff at 10 o'clock in the morning on Friday. I got it yesterday. Why? Because it got tangled up with all these things going on the DTV antenna commercially. They want to deliver vast amounts of information over DTV. And again, DTV is not something that you just dump something on. It's not a big truck. It's a series of tubes. And if you don't understand, those tubes can be filled and if they are filled, when you put your message in, it gets in line and it's going to be delayed by anyone that puts into that tube enormous amounts of material, enormous amounts of material.

Got it?

[Big Media]

I give up.

[genlock]

Unlike the old ntsc transmissions, the DTV signal fully occupies the entire bandpass of the 6mhz tv channel.
Any anomaly in the transmission characteristics of the antenna will impair the picture.
You might still see a perfect picture, but the work would be done by the active equalizers
and other distortion software in your tv. Multipath or some other disturbance would
then find it easier to exceed the bit error rate maximum and give you the blue screen.
Also, peak power on analog transmitters occurred at tip of sync, on dtv transmitters,
average power is peak power. There is more power delivered to the antenna on a continuous
basis than in NTSC or old analog transmission. 19.something megabits per second, trellis coded on 8 levels.
There can be maybe 6 or 8 standard def streams of video running along with their audio, captioning, psip, other overhead
and data and software update services at the same time. KET is doing 6 streams.

[Hoosier Daddy]

What HE said.

[Big Media]

Thanks, Gen, that was actually very informative. Are the problem antennas only Dielectric or are all makes, models, and sizes failing like this?

[genlock]

The antenna at WPBY is a TCI. TCI was purchased by Dielectric just before the delivery of the antenna to WPBY.
Tjere were stories of antenna failures in this design before we got it. Complicated end fed cavity backed resonator things.
(for the record: I did not choose this antenna) I will be interested seeing the antenna on the ground. Possibly lightening
had a part in the failure, if it did, then losses would be covered by insurance. I have not heard what WPBY
is going to do. Whatever is done will be expensive.

[Cameron]

Mike Blair requests that every last-one of his tax-dollars go directly to the WPBY project.

[Hoosier Daddy]

Mike Blair requests that every last-one of his tax-dollars go directly to the WPBY project.

Nope. Won't happen. Mike's lifetime tax dollars have already been allocated to a broadcast-related project in the works. NPR will installing at least five IBOC-capable transmitters in every Arbitron market. NPR will be on the main channel. Air America, National Socialist Radio, and Radio Cuba will be on the "in between" channels. Gotta get the word out, comrades.