Tag: LPTV

A little bit of catching up…

I regret not having enough time for writing these days. There are a number of reasons for this. Firstly, much of what I do running my business is mundane and not worth noting. For example; today I am going over work reports and reconciling the bank account. Necessary, but about as exciting as watching the grass grow or reading about drying paint.

However, the rest of the time I have been working on various projects around the northeast, to wit:

In Boston, I took part in converting an LPTV station to ATSC 3.0. That was interesting and I am enjoying the TV work.

WCRN-LD exciter GUI
Boris Johnson resigns, also one of the first ATSC 3.0 images transmitted OTA in Boston, MA

In Syracuse, we had to lower a TV transmitter from the 23rd floor to the 22nd floor on the outside of the building. The transmitter itself became marooned because an electrical conduit for an alarm system was installed restricting the size of the stairwell.

Carefully lowering a 2KW UHF TV transmitter, State Tower Building, Syracuse, NY
Transmitter re-assembled and on the air

Fortunately, we hired a moving company to do this. I am pretty sure that our insurance does not cover damages from transmitters falling 22 stories.

In NYC, I installed two FLX-40 transmitters for GatesAir.

WXBK FLX-40 transmitters, Rutherford, NJ
FLX-40 Heat Exchangers
“Do you see over yonder, friend Sancho, thirty or forty hulking giants? I intend to do battle with them and slay them.” “Take care, sir, those over there are not giants but buildings on the island of Manhattan.”

In Kingston, NY a used BE AM1A (along with a coax switch and dummy load) was installed at WKNY.

Slightly used BE AM1A installed as backup at WKNY, Kingston, NY
7/8 inch coax switch and 2.5 KW oil cooled test load suspended from the ceiling

It is nice that this station has a decent backup transmitter to buttress the aging, yet very reliable Nautel ND-1.

Even though it is a short drive away, I had never visited the 1969 Woodstock Music and Art Fair site in Bethel, NY. It was interesting and being sort of an audiophile, I enjoyed this exhibit in particular:

Your author, standing in front of a “Woodstock Bin.”
Back of high-frequency horns

From the display:

This speaker stack sat on scaffolding high in the air… festival sound engineer Bill Hanley custom-built eight speaker cabinets for Woodstock, amplifying music and stage announcements across the large festival site… Afterward, the design would be known in the industry as the “Woodstock Bin.”

Bethal Woods Performing Arts center Museum, August 10, 2022

The high-frequency horns used Electrovoice diaphragm S/A compression drivers. I don’t know which driver was used for the bins.

Site of Woodstock ’69 stage, looking up into the field
Looking down from the field to the stage area. Person(s) for scale.

I am also writing articles for Radio Guide, I hope that you are enjoying them!

Doing it with sound AND pictures

AKA: Television!

I am talking about the type of TV you need an antenna for. I have been installing a few of these low-power digital TV transmitters at various places and it is good work.

Anywave MPTV 2.2 KW digital TV transmitter, WCRN Boston
Anywave MPTV 2.2 KW digital TV transmitter, WCRN Boston
LPTV antenna side mounted on tower in Quincy, MA ERP is 15 KW.
LPTV antenna side mounted on tower in Quincy, MA ERP is 15 KW.

Anywave MPTV unpacking, rolling into the building, Ellenville, NY

This transmitter’s dry weight is about 500 pounds, which was a little bit too much for our appliance hand truck, so we built a ramp. They have a nice set of wheels on the bottom, so they roll into place.

Carrier power after pre-correction files updated

There are a few differences in the way things are done. First of all, there is a different set of acronyms:

  • ASI- Asynchronous Serial Interface, format for MPEG transport stream, max speed 270 Mbps.
  • SDI – Serial Digital Interface – Similar to ASI but can run much faster, up to 12 Gbps.
  • TS – Transport Stream, Encoded video and audio streams into the exciter. Same idea as composite audio input on an FM exciter.
  • TSID – Transport Stream ID, a unique number assigned to each DTV station and encoded with the transport stream.
  • PSIP – Program System Information Protocol, carries program and system data about the transport stream.
  • ATSC 3.0 – recently updated ATSC standard that allows TV stations to do more with their transport streams than before. Will also change the modulation from 8VSB to COFDM.

Then, some things that look familiar are called by different names, BNC cable vs ASI cable… I am a neophyte in the TV world, so there are still many things to learn.

EAS is still EAS, but now there is a locally generated video to go along with the audio.

A while back, some fool wrote their congressman because THE COMMERCIALS ON THE TEE-VEE WERE TOO LOUD, so there is something called CALM Act compliance.

However, at the output connector on the exciter, through the amplifier, filters, directional coupler, etc; it is RF and behaves like RF. Even more interesting; Mr. Doherty’s name is used to describe the RF amp. Doherty amplifier or Doherty modulation was designed by William Doherty for Western Electric in 1936. It was not until Continental Electronics began using it in their AM (317B) and Shortwave (420A) transmitters that it became known broadly. Old things are new again:

Continental Electronics 420A 500 KW Shortwave transmitter, Greenville site B

That picture is from my visit to Greenville, NC in 2017. This is the control console, the transmitter is behind the glass and takes up half the building. It was installed when the site was built in the early 1960s. The new Doherty UHF amplifiers use LDMOS devices, notably the BLF888E in the Anywave units.

Antenna sweep, channel 30 UHF slot antenna, WCRN Boston
Antenna with channel band pass filter, Channel 30 WCRN Boston

The Channel Band Pass Filter is required by the FCC, basically, it ensures that the TV transmitter is staying in its allotted 6 MHz channel. They add phase rotation, as noted above. This is why pre-correction is needed to keep the ATSC signal linear across the entire 6 MHz bandwidth. RF is RF and we like RF.