FM Broadcasting (great way to be heard)

[Max-Paul]

PMC,

Well I went looking for the 4CX1200A7 and could not find it. So, maybe my memory of the tube is slipping. But it looks alot like a 4CS1500A. See them little interrupted fingers for the grid and screen and filaments.

[PMC]

tubes are getting hard to find, even online as a reference. I am getting quotes for backup trasnmitters and 3 of my 4 quotes are for solid states

When I was working for WWVA back in the late 80's and 8 years of the 90's I had a 317-C2 from Continental that transmitter had 2-4CX25000 tubes, 1-Carrier and 1 for Modulation, I should mention for those who are reading this you need two tubes to generate a AM signal. and the 4CX25000 was a 200lb tube and every 6 months I used to swap these tubes with each other so they would dissipate evenly

And talk about aligning the tube so you don't destroy the finger stocks or socket. I don't miss that transmitter at all, and lets not even talk about the step down transformer that started at 18,000 volts. since I was there 1 replaced that twice

I don't miss high power AM....okay a little, and as a side note for those that never worked in High Power AM you can radiate a florescent light tube fully energized which looks likes its turned on just holding the tube in front of the phaser cabinet

I used to hang these tubes for the ceiling of the dog houses under each tower and they would be on all night long, and it was fun walking through the antenna field at night holding a 8ft florescent tube in your hand and it looks like you got a light saber, the cars that would drive by would just slow up and stare, it was very funny

Now onto FM HD, I implemented HD broadcasting for WLTJ back in 2005, the attached pic shows the whole broadcast system, in 1 rack I have a 500 watt HD transmitter (solid state) and the signal coverage on that transmitter equals what the analog generates (transmitter is in the top of the rack)

Now below the transmitter is the Exporter, that box generates the HD signal which came from the importer, (not pictured)

and below that is the exciter, that is the box that tells the transmitter what frequency and it puts out 14watts to generate the 500 watts on the HD transmitter

that picture is from 2005 when i got the system up and running for the first time

As you can see I can talk about this as much as synchronizing lights






Attached files

[Max-Paul]

Never worked with AM per say. It was either FM or DSB. You say tubes are going bye bye. Dang! I suppose then for solid state, they must have near hundred transistors in a 20KW transmitter. Have any examples of how many transistors in a high power transmitter. Gee look what I have missed by going into another career. Just for giggles, do you have a ham ticket? KF0OX here.

[Greg]

PMC,

Cool, wasn't sure, actually it was one of our engineers at the station I work at that told me, he is a transmitter buff!

Thought you'd find this interesting, this is a short video of the aftermath of our transmitter and tower a few years ago, fortunatly we were only off the air for a few hours since our digital transmitter and new tower were already installed and ready to go. During the ice storm the pbs tower also came down (I believe their tower took our guides out)

greg

[Max-Paul]

Seen a few stories over the years about towers coming down. I have been up on smaller towers (190' Rohn 55? 18" face). Nothing I hate more than working with a ground crew that let the antenna bounce off of the tower. But back to the stories. I heard of one that had a two climbers on it, when it buckled. I think it was out near KC. Greg, was anyone at the site when it happened? Hope no one got hurt.

[Greg]

As strange as it sounds fortunatly the transmitter engineer was laid off a few weeks prior to the collapse. No one was injured.

[PMC]

That's good the building was unoccupied...and bad he lost his job
in the past 4 years more and more of my engineer friends are unemployed.

back in 2009 WWVA lost its 3 towers due to a very strong micro-burst. and there was a few hours I sat in my chair at home watching the news looking at the towers laying on the ground thinking..... did I report all the faults with those towers in my logs?

even though I know I did report it, I couldn't help thinking it was due to a ceramic insulator that was cracked and gave under pressure. when I saw the picture from the helicopter and the towers where sliced in half I knew it wasn't the insulators, they were still doing their jobs

the only things that saved me from being laid off is,

1) I work for a single family that owns the 2 radio stations and paper that I am the
engineer for

2) I went to school for computers and networking back when I realized that's where radio stations were going

And today alone. I fixed 3 computers and took a set of transmitter readings I'm a full time IT guy and a part time engineer, I'd rather be a full time engineer.

The company I work for I am the only electronics engineer and only I.T. guy. and I handle the networking, company owned email server + security/filtering, web + security/filtering, CCTV, studios, building and maintenance of those studios, the air chain which is microwave, all satellite installations, software management, and I build my own computers... this is the least but it takes more time to download the updates than it does to build the damn things.

and I have a plunger in my office to take all the other sh*t they throw at me

I would have answered earlier, but I'm playing Betsy Ross at the moment and trying to build the synchronized American Flag for my 4th of July display, God I love RGB. RBG, and any other way you want to assign that

[Greg]

and I have a plunger in my office to take all the other sh*t they throw at me

I think that is how most of us that are in the broadcast communications business feels!!!