Category Archives: Transmitter Site log

Harris Sigma DTV Transmitter fiber cables.

The Problem:

“The Harris Sigma IPA has shut down a few times with no faults on transmitter or in logs. The green lights go out for power and IPA, sometimes the IPA voltage light is finicky, though its on now.
If I goto standby and back. It resets to normal.
I replaced an IPA power supply recently. I am not sure that is related. As this happen once before causing me to replace power supply. I reduced power to 60% for now.”

I started thinking about this overnight as I remember the frustration I had with unknown fault problems on the Analog Harris sigma transmitter. Setting up a camera to watch the fault lights.  Days it dragged out, it may have been weeks.  But what was the solution?Then it dawned on me, I recalled the fix, PTL, the fibers optics! On the old transmitter I had to replace the fibers, the light became weak over time. Also it was related to power and heat, but only faintly related. Weak Light in the fiber! (or weak trip point on PCB).

On the the current problem I waited till it was muted into standby again, pulled and replaced fibers one at a time, and it came back on.

Now it could also be the fiber reciever, or transmitter, or a real drop out for a moment.  but in the old unit it was not.

I isolated the fiber to H13 Ion pump voltage, (the meter on pump shows a normal reading) that is the only fiber I must pull and insert to bring unit out of standby.

So if any green light fades for a moment it can cause the unit to goto standby, and stay there. The fibers are some of the green lights but not all.

looking for a green light out, or moment out, or monitor voltage at trip point. This happens at random is that is rather hard.

At this point, it looks like fiber (or related) or a moment drop out of signal.

Fibers in on A/D PCB Board
Fibers traveling through “the toaster or oven” cabinet (:






I shut down and reseated cables and fibers, though not cables on interface board in toaster box, its interesting to note that the two fibers I “suspect” are off the ion pump board that is open to the back air chamber and bend sideways ( I fixed that) and covered with light dust really that hole through cabinet should have been closed there, we shall see how it behaves after this. I replaced the blower air filter a fram tga3916 while in there it was a very tight fit so I left the shroud or cover off and out of unit on that filter, its not going anywhere.

Ion Pump and Low heat (filament) fibers
Ion Pump and Low heat (filament) fibers







Harris Sigma DTV Transmitter GUI computer – Build your own.

The GUI is a transmitter monitoring computer inside the Sigma transmitter. The touch screen failed (the video) so I built another computer for the job.

Items needed.

Windows 2000 computer with LPT port and 2 com ports – com 2 and com 3- all setup and tested in advance before installing GUI software the ports. Also a lan card setup on your network. I also install Tight VNC remote control software. And software to make a backup image of drive to boot to cd and restore.

Emails and notes on Install (pdf file): ReplacementcomputerSigmaGUI



touchbase V2.45


Silence Alarm

Silence Alarm.


With station automation so prevalent a good silence alarm is about mandatory. Broadcast tools VAD-2 fits the bill and its cheap. It is rather a pain to program but beyond that it dials a call list when silence is detected, ours is now set at 30seconds we had it at 1:30 but time is needed for corrective action.

In addition it has some status and relay commands that can be tripped by a cell phone. So if your remote does not have a cell phone call in… it would work… or for a very basic remote On/Off Power +/- and power normal.

There is an obscure FCC rule that you may have to shut the transmitter off within 3 min. (some say this for AM only?) The relay could go to beam off and in theory a person could do it from a cell phone in that time.

I hook the audio to our STL microwave as our Moseley 1620 will page if we are off the air, but it could be hooked to a cheap DTV converter box or FM radio to also tell you, off air. But normally in our case it indicates a programing error or satellite down.

Harris uni-coder

Harris uni-coder-
Lucent wavestar model ws2-ac
With EVA-162 and NIM100a cards smpte 310 output
with Logic innovations tsm-2800 mux only one smpte 310 input others sdi. smpte 310 output to exciter.

222-8200 or 217-221-7529 harris- mark schlinkmen

Closed captions for unit.
TE500A DTV Line 21 Transcoder
— ——————————————————————————

The EEG DTV Line 21 Transcoder is designed to upconvert existing EIA-608 Closed Captions into EIA-708 Closed Caption format. EIA-608 caption data is recovered from an NTSC encoded video input, upconverted into EIA-708 captions and output via RS232 or RS422 data port to a DTV Encoder.The Model TE500A DTV Line 21 Transcoder extracts the Line 21 data from a previously encoded NTSC video source and upconverts the 608 data into a serial 708 data stream.
7760CCM-HD HD-SDI/SD-SDI Closed Caption CEA-608/CEA-708 Translator, Decoder & Analyzer
8083XDS-AD Analog & SD-SDI XDS Encoder
8084 SD-SDI Closed Caption Encoder
8084AD Analog & SD-SDI Closed Caption Encoder
8085 DTV Closed Caption Encoder
HD9084 HD DTV Caption Encoder

Studio caption options:
closed caption encoder
laptop and software
caption mic software
encoder link analog 845

Sigma arc detector E2v

Hello,Suspecting the arc detector to be bad on the primary cavity I replaced it with a new one from Harris broadcasting. part#378-0180-000 $485.

When I tested it the arc detector fault did not come on so I tested in a black box and it worked when examining the new and the old detector … the old detector has brighter and bigger bulb.

We have a old circuit assembly so the metal is tarnished. The new detector bulb is not bright enough… the old detector bulb was.

The new detector works… put the bulb is not bright enough.

I called Harris tech support at 217-222-8200 and talked to Ray Dearing in Harris field service.

He said he experienced the same problem with old tube assemblies and I discussed the issue with him… the idea being I disassemble tube cavity and clean and polish inside like a mirror then arc detector may or may not work with test bulb. It seems like the bulb was changed… or tests done on a new cavity and not a older one that has a dark metal color…. Please call Ray Deering if you feel my case may be a isolated one.

The part cost us almost $500… so you can see where I am concerned with its performance.

Thank you for your after hour support BTW….. its been very helpful.

I will clean and polish cavity and let you know the results.

Jim Wilson

Engineering WTJR TV

WTJR Tower site Report June 7 2007

Wednesday night around 2030 pm the WTJR analog Transmitter shut off with a secondary cavity ARC fault. It returned it to air during Richard Roberts Program.

This is the 4th time recently I have seen this fault. It is a terminal fault requiring a trip to the transmitter site to reset. It appears to happen at random and intermittent times.
What this fault is arc in the output cavity or near it.
I detuned the output coupler in the hopes it will give us more head room.
The transmitter needs to be retuned.
We do not have the equipment to do this so I am working on a Harris broadcasting visit this may help eliminate sources of problems.

The tube trolley was removed and the output cavity examined a while back to look for the source, with minor dust and dirt found and no obvious arcing going on.
A cracked air hose was replaced at this time.
Yesterday I tested the arc sensors they are working but this sensor shows a very slow recovery time (2 min)… indicating aging ( most likely it needs replaced ) not a easy job as this is the old design and requires the entire tube and trolley to be rolled out and the output cavity to be disassembled. This may or may not help the situation.

The common causes for this problem are,
1.Lack of air flow
2.Arc across dust or dirt near tube.
3.Problems with the load (transmission line antenna)
4.Faulty Sensor
5.Powerout spike (transmitter power high)

As can be seen by above these conditions still exist here especially #2,3.

In regards to #5. The analog television exciter is acting up with light streaks appearing in the picture from left to right. There is a problem with this unit and it needs to be repaired. I am working on a solution with Harris broadcasting as we have no backup at all for this unit. The frustrating thing here is again its random and intermittent. It is possible that this unit may be emitting high power spikes.

Also the antenna inspection is still pending with the tower crew.. it could be any day now.
We are at 40% power on channel 16 till all this is worked out.

Please Print this out and insert in station log #4

Jim Wilson
Engineering WTJR TV
Quincy, IL

Sigma Analog Exciter

The Harris analog has a Glitch in the video. It appears like light specks moving from left to right. It is?intermittent.

The suspect is the video module in Exciter at this time.

The other possibility is the flywheel sync circuit tipping the vertical interval there is a pot to adjust this.

The contact at Harris is Robert Spawn for these exciters.

A test setup on wheels needs to be installed as the exciter is across the room from the test rack.

Also a new video cable (or re-crimp ends) for video input.