VK4ZXI

Testing a cheap Chinese duplexer as a 70cm DATV DVB-T 7 MHz TX filter- Wow! Introduction In my last post I described a cheap Chinese duplexer re-tuned as 70 cm DATV DVB-T 7 MHz TX filter. The duplexer uses notch cavity filters, six in all. The notch filters have a much sharper edge, compared to a band-pass filter. The sharp notch seems suited to the vertical edges of a DVB-T signal. I initially check the signal source, a HiDes camera with direct DVB-T output at 1080P. I was a little surprised at the spread, but the filter cleaned it up well. This would indicate the need for a filter before the main power amplifier. I pressed on with just one filter and tried it at the output of the amplifier, a 10 W device, from Darko OE7DBH, using a RA60H4047M1 60 W module. Even with the indifferent input, the filter was able to reduce the spread to -60 dB and give a clean 10 W output. The notch duplexer/filter seems to overcome some of the major hurdles with DVB-T amplifiers and warrants ...

BlackMagic Design ATEM TV Studio problems with 1080p; a hardware limitation? In this post, I think I have discovered the problem of the ATEM TV Studio not accepting 1080p input, a hardware limitation. Alternatives are then considered. BlackMagic Design ATEM TV Studio As noted in earlier posts, I use BlackMagic Design ATEM TV Studio as the main component of my DATV studio to connect multiple cameras and other video sources. Overall it performs brilliantly well allowing for most features needed in a professional TV switcher, and with nothing else even remotely in the price range; $1000. http://vk4zxi.blogspot.com.au/2014/06/datv-dvb-t-blackmagic-designs-atem-tv.html     No 1080p input, despite being common format for cameras However, it has one very annoying problem, it will only accept 1080i input, not 1080p, which to a point is reasonable as 1080i is the highest resolution for broadcast TV. The big problem is that almost all cameras...

HiDes CCHDTV camera and DVB-T modulator DC-100 (preliminary) I received a HiDes DC-100 (US$250 for camera, $100 for lens) last week but did not have much time to set it up, other than to verify it works. With a bit more time tonight I have a very nice Full HD image from it. The lighting was bad, but a still a good clear image. The DC-100 transmits both a SD and HD channels as can be seen in the channel list. The camera is running on its default setting of 177 MHz, 6 MHz bandwidth, but over a cable with an attenuator. The image is 1080P 30 FPS. As a result there is some flicker from the 50 Hz lights. I will put up some photos of the device and its internals later. CCHDTV is an emerging standard of DVB-T cameras designed to run on existing coaxial systems in buildings and institutions. The devices all seem to be based on the ITE modulator chips. Google CCHDTV for more information. The DC-100 uses a standard CCTV SDI camera, either 2 or 5 Megapixel, the converts the raw S...