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Showing posts from June, 2014

HD-CCTV Cameras: Cheap quality live video for DATV

HD-CCTV Cameras: Cheap quality live video for DATV In my quest for high quality DATV (Digital Amateur Television), I learned a lot experimenting with the HiDes DC-100-B-01 HD-CCTV DVB-T modulator/camera, the subject of an earlier post. With a good lens, it gives an excellent DVB-T signal at up to 1080P. It is a modified HD-CCTV SDI camera with a DVB-T daughter board modulator with a 50 Ohm BNC output that go to cable or to an amplifier then antenna.

Using the BlackMagic Design ATEM TV Studio, I could use SDI cameras. Box-style, HD-CCTV cameras, with inter-changeable "CS" mount lenses and SDI digital and analogue output cost less than $150 on eBay. A bargain! Most use Sony image sensors.

The cameras have a composite output that allows setting up the digital video even H.264 compression.

The catch! The purpose of HD-CCTV video is to allow high definition video to allow clearer inspection of suspicious activity. As such, and perhaps to avoid extra circuitry, they are not inter…

DSLR cameras for live TV: not so simple!

DSLR cameras for live TV: not so simple! In the course of setting up an amateur radio DVB-T transmitter, I have sought high quality video and audio.

The modern DLSR (digital, single lens reflex) cameras seem to be a good candidate as they are capable of recording very high quality video, have a wide range of relatively inexpensive lenses and have some auto-focus capability for use by a one-person camera operator. They are generally better than consumer-grade camcorders.

DSLR cameras are very popular with cinematographers, with an ability to do Full-HD and even up to 4K resolution (4K is used by cinema projectors). See sources such as http://nofilmschool.com/ Digital Filmmaker magazine

For DVB-T the maximum resolution is Full HD 1080i at 24, 25, 30, 50 or 60 fps (frames per second), and more commonly 720p at the same frame rates. The frame rates are related to the frequency of the electricity supply in the country, 50 Hz in Britain and Australia, 60 Hz in Northern America.

However, th…

DATV DVB-T BlackMagic Design ATEM TV Studio: Proof of concept

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DATV DVB-T BlackMagic Design ATEM TV Studio: Proof of concept

An objective has been to get high quality video and audio, as well as TV production studio abilities for my DATV DVB-T system.

Production studio abilities includes the capacity to switch between multiple live TV cameras, recorded media and overlays, such as my call sign.

I originally experimented with software production systems, mainly aimed at network feeds, such as Vidcaster and Open Broadcaster. The commercial Vidcaster software has a virtual camera that can be the input video stream for a HiDes's device, such as the UT-100C via PC2TV. This required a fast PC, a HDMI video capture card from a DSLR camera, the Vidblaster software, the PC2TV software and the UT100C all working properly; a difficult feat many of us have stumbled on.

An alternative is to use a hardware production studio. The BlackMagic Design ATEM TV Studio is very suitable and a reasonable price, about $1000, given its capabilities. It is designed for …

Multi-band squid-pole dipoles and Yagi antenna: Feasibility?

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Multi-band squid-pole dipoles and Yagi antenna: Feasibility? One source of thin fibreglass for use with the loading coils on the TET-Emtron antenna I have been working on is telescopic "squid" poles (used for catching squid). A 7m squid pole is in seven sections, a metre long, from 45mm to 8mm for the heavy-duty version. The poles only cost about $30 each. They are available from http://haverford.com.au/telescopic-poles.html.

Given that I was thinking of the TET Yagi elements using the tricks of vertical antenna to reduce length, I thought, why not go the other way and use telescopic squid-poles as rotatable dipoles or Yagi elements?

Telescopic elements are quite useful for me as my tilting mast tilts to the short end of a trapezoid, with only 3 to 4m for a boom, compared to 10m at the other end. With the mast right down, I can mount the boom and one side of a Yagi horizontally, rotate the boom 90 degrees to its correct orientation, then extend the elements on the other sid…

Computer monitors: Beyond Full HD- 1920x1200, 2K-2560×1440, 4K-3840 x 2160

Computer monitors: Beyond Full HD- 1920x1200, 2K-2560×1440, 4K-3840 x 2160 I have used a series of computer monitors with a resolution above Full High Definition: 1920x1080.

The obvious question is why? The highest resolution for most movies is 1920x1080.

The answer is simple; I don't watch movies on a computer but read a lot; web pages, books and magazines. The higher the resolution the better!

The high resolution gives a better quality display of a PDF document. PDF originally was a printing format and generally has a higher resolution than a computer monitor can display. Printers typically can print at 600 or 1200 dots per inch, about ten times higher than a video monitor.

LCD monitors produce their best display at their native resolution, anything less usually looks bad as there are not enough pixels to give a sharp image. Try lowering the resolution of your own monitor and you will see what I mean.

Ultra high resolution has been picked up by tablet manufacturers, particularl…

Small multiband HF beams- TET-Emtron revisited- 40/20/15/10m 2 element beam

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Small multiband HF beams- TET-Emtron revisited While I haven't posted much recently I have been chasing a few wild ideas.

I bought a few antenna from a deceased estate, including bits of a couple of TET and TET-Emtron HF beams.
TET 2 element 20/15/10 beam TET 2 element 20/15/10 beams are quite innovative, especially considering they were first made pre-1985 with:
capacitive hats to physically shorten the element lengthdual-drive, driving the radiator and reflector, 180 degrees or more out of phase. This doesn't increase the gain much, but does increase the front to back ratio, which is just as good.close-coupling of radiator and reflector to shorten the boom length.

I had just the radiator of a version of the HB-23M, which is enough to use an antenna analyser to see what it does, albeit at ground level (which messes up capacitive hats and low frequencies). I have to make up the rest.

The traps, the rectangles on the elements, are two parallel R/C circuits tuned to 28 and 21m.…