This Saturday I held the annual entry-level D-ATV training for TV operators for BCARES, including some hands-on time with the new prtable ATV packsets I donated.
Thanks to Jim KH6HTV for his presentation on the Boulder ATV repeater.
Fairly soon I will add an upper-level class covering the portable repeater, quad box, and streaming ATV onto a network. We’ll also get into how to plan and run an event involving ATV. Stay tuned!
This year I put up another antenna in the attic, an end-fed 10/20/40-meter Horizon tri-band from down under (Bushcomm).
It’s just over 50 feet in length and just fits the attic running east-west down the centerline of the house. The 50-foot coax feedline acts as a counterpoise, then runs through an isolator in the attic and down a wall into the shack.
The antenna’s bandwidth is a little tight at 40m, but good at the frequencies I need for Winlink HF packet (SWR under 1:1.4 around 7.1 MHz), and reasonably flat at 20m (under 1:2) and 10m (under 1:1.5):
Today I made contacts on 40 and 20 meters to two different Winlink stations.
So now I have a total of four working antennas under one roof, including two X50s for VHF / UHF and one 70cm yagi for digital ATV. They all come down through one wall to my office on the main floor.
On top is a two-radio go box with an Icom 880H and a Yaesu 857D; below it is the portable D-ATV repeater which can also be used as a TV transceiver (note the video camera set up on top for input).
Once again BCARES is running a couple of D-ATV cameras at each CU home game. This year there haven’t been any new technical challenges. At events like this, we always station two operators with each camera for safety — one can be looking around if the other is focused on an incident. Here Jack K3UGR and Eric AIØJ keep an eye on the departing traffic after the game (OK, it’s pretty much all departed by now!).
Generally we’ve used Sony cameras in the field for digital ATV, with an HDMI cable running from the camera to the TV modulator.
Last year I got a small, inexpensive CX405 model. I recently tried using it for the Boulder-area weekly ATV net, and no one could hear me. A little digging with the DVB-T test tool revealed that the audio stream was simply absent — no sound was being transmitted at all.
It turns out that newer Sony cameras don’t put out any audio through the HDMI cable (except during playback from a recording). Sony says (as of 2015), “There are no Sony Handycam models that can pass the audio through while recording the video. Again, both video and audio passthrough is only possible when the camera is on playback mode [actually, the issue wasn’t recording, but just live output out the HDMI jack, recording or not].”
This has not been an issue for older models such as the Sony CX430V and AX33.
Also note that the behavior of the Hi-Des modulators is to omit the audio elementary stream from the output transport stream (TS) when no audio is present on the HDMI input. The PID is still listed in the PMT, so the test tool can easily identify it as missing.
Last night I gave a presentation on digital ATV to the Adams County ARES (R1 D1) team including a live demo of a portable transmitter and my quad receiver box. It was the 90th anniversary of the first modern TV transmission (7 Sept 1927).
I also talked about streaming TV signals over a network using several different hardware devices and technical approaches. This week YouTube introduced ultra-low latency for live streams. I tested it at home over my wired network, and found that end-to-end latency from camera through RF and conversion to an IP stream, out to YouTube, and back to my browser, all happened within about 2 seconds. That’s fantastic!
In this case I was streaming through a Matrox Monarch HD. I’ve also tested an Epiphan Webcaster X2 but it kept changing the stream latency back to “normal” (15–30 seconds!). I have confirmed with Epiphan that this is an issue that will need to be addressed by a firmware revision.
YouTube live streaming gives us an option when RF alone can’t deliver the picture to a distant command post — provided that we have a suitable internet connection where we operate the ATV receiver. (One catch, however, is that only folks with some type of Google or YouTube account can be invited to watch a private stream, while an “unlisted” stream is accessible to anyone who has the URL.)
See the slides from my presentation: DATV for ARES Sept 2017
Another year’s gone by, and football season is coming soon. We use the CU home games (planned events) to prepare our members to run TV for emergencies. Here I am explaining how DVB-T works. At far right I have some equipment to demo; I usually leave a transmitter up during the class (it’s off to the left of the picture, watching the attendees :-).
Thanks to the Boulder Office of Emergency Management for the use of their facility. See the BCARES web site for more information on how we serve the community.
This Wednesday the Denver International Airport ran its mass-casualty drill at the DIA fire training center. BCARES members ran four digital ATV cameras to provide real-time situational awareness as well as record the event for after-action analysis. Three of the cameras were in the “infield” around a mock airplane and near where the casualties were placed; the fourth was a half-mile or so away covering the fire/medical staging area. We covered the fire response to the burning airplane as well as medical and “fatality management” (!) handing the casualties (nearly a planeload of volunteers with moulage).
This was another opportunity to run my portable quad receiver/processor. Thanks to the University of Colorado for the loan of their cameras and portable transmitters.
Thanks to George KAØBSA, Don NØYE, George NØRUX, Dosha KBØNAS, Starr NØAES, Tom KDØUOI, and Ron K2RAS.
This past Wednesday CU hosted the controversialist Milo Yiannopoulos, a week after his visit to the University of Washington produced violent protests. We had about 150 protesters show up, but the excellent security team kept things safe and running.
BCARES provided two camera teams around the Math building, one on the roof and one on the ground. Given our location on the southeast corner of the building, the ground transmitter had to run on high power (3 watts) to bounce a signal off the nearby buildings and west towards the stadium antennas. Thanks to the new 20 Ah LFP batteries we got last fall, that was not a problem.
Last week I gave a presentation and demo to the Boulder Emergency Squad (BES). They operate drones (“unmanned aerial vehicles” or UAVs) for county emergencies, such as swift-water search and rescue efforts. One issue they have is downlinking the video from the drone. We discussed how digital ATV could be used to backhaul video from the drone pilot/controller to a command post some distance away. This is needed because the drone pilot must have a line of sight to the drone, and so may have to move some distance away from a command post.
The presentation was largely the same as the one I gave last fall to the Arapahoe County ARES group.
Last night I gave a presentation on digital ATV and the DVB-T standard to about twenty members of the Arapahoe County ARES group, followed by a live demo of a backpack transmitter sending to the quad receiver box, which then streamed the picture over IP to a laptop.