DTV technology obsoleted analog TV? Zoom ?
Submitted by atang1 on Fri, 06/13/2008 - 05:08.
After many years of R&D, DTV came of age. The main technology is not the many more channels(1-6) of digital ipTV for each station, but the ability to present three digital formats. anamorphic, 16:9 preferred and 14:9 formats from digital data to analog TV on channel 3 or 4.
Some DTV converter such as the one sold by Radio Shack still has analog passthru for VCR or DVD recorders. And so it should be. Cheaper unit such as Venturer ATSC converter box sold by Target stores at $49.99 less $40 government coupon is perfectly usable. If you use round UHF antenna with VHF rabbit ears as reflector for the UHF reception; the short rabbit ears had to cover the UHF antenna active area.
Others may leave out analog passthru also, then you need to pass thru from DTV box(some has antenna signal amplifier) to VCR(antenna signal amplifier) to analog TV, or use an antenna signal splitter or amplifier or both if you wish.
After February 19, 2009, We will only have DTV broadcast on UHF antenna. Signal strength has to be over 70% typically. Round UHF omnidirectional antenna set horizontally seemed to be more effective than bowtie UHF antenna which is directional. Rabbit ears for VHF channels are not usable for the current DTV channels. Far away DTV channels are not available at all. So, you maybe forced to use satellite TV or cable and telco TV.
It seem to me, computer browsers are late in adapting zoomed framebuffer pixeled formats for text rendering(adobe reader, pdf files) using well established zoom technology.
DTV Loop UHF waveguide VHF reflector ? theory ? Works ?
Since DTV channels are all UHF frequencies, we use loop antenna for best results. Loop UHF antenna is omnidirectional, because the loop is a waveguide. signal comes thru the loop from all directions. Because high frequencies travel on the surface of metals, your uHF antenna has to be clean on the metal surface for best signal capture by the tens(10-30) of micorvolt intensity.
Waveguided signals can be reflected by rabbit ears placed behind the loop. Just move the rabbit ears in place using the DTV converter signal strength meter. The maximum benefit is 60%(barely sufficient) signal strength without reflector can become 90%(very good) signal strength when the rabbit ears are placed in the critical location, behind the loop. Front of the loop antenna is best facing a window towards the outside of the building; the less reflecting surfaces, the better the signals. Glass does not reflect TV signals, but transmits good signal strength.
Footnote:
Waveguide is use in microwave cooking. The microwave electronic tube has an antenna in the waveguide. The microwave travels thru the waveguide into the oven to heat up the water and oil in the food. Waveguide keeps microwave power within a metal channel for delivery to the target.
If only DTV has more channels to display webpages on net ?
DTV broadcasting stations can have 6 channels per carrier frequency. Except the stations did not have more media to braodcast.
Most broadcasted programs have associated websites today. These websites can show previously recorded programs without using your own Tivo or DVR.
So, we could expect that DTV will expand from 10 channels to sixty channels in the near future continously 24/7 in your local area.
With the government $40 coupon, and minimum convedrter boxes can be paid for with $9.99, and a loop antenna; it is a bargain to look forward to DTV programming. The more channels, the better DTV; someday even interactive with dialup modem to a bbs on the telephone connection to see by pay for view box(sync signal) or similar to satellite TV set-top boxes.
DTV QoE can still have room for improvement ? Time delayed ?
Signal strength from antenna is still a problem. It seems that there is a periodic(signal strength changes in a timed period which may be sinusoidal, like effected by 60 hz powerline noise) loss of signal. this may be helped by using multielements of UHF antenna to multiple signal strength, or have parallel antenna connected to each DTV or add UHF amplifier.
The present DTV converter seemed to have a time delay built in, so that The last picture frame can be repeated to avoid blue screen of death or black blank screen. This is sort of pleasant experience, but not without a sadness in experience.
QoE, which is the latest cable TV technology used rerouting or redundancy of signals to restore data lost.
DTV technology for QoE will use time delay over signal loss which is periodical, storing signals with strength and avoid signals that are weak. This requires signal sampling, and adjust the speed of data transmission and data storage memory size? Some feedback to the station equipment may be necessary?
Until then, antenna(multi or placement) or antenna amplifier may still be your responsibility to get good reception? Or spend subscription money on cable, telco or satellite TV.
Secrets of how to use DTV converters ? direction ? noise ?
At night when others shut down their appliances, it is time to finetune antenna direction. Loop antenna can still be pointed towards any large reflecting surfaces for maximum signal strength. Then adjusting VHF rabbit ears also for maximum signal strength. This may raise 30% signal strength to 70% average across all channels. Because UHF wavelength is minute, antenna position has to be secured. Any slight move will change signal strenth. Any electrical appliance may distroy your signal strength in your house.
DTV boxes are turn on all day all night(make sure in menu, sleep timer and power off timer are clicked off). Which is a way of burning in the silicon IC(integrated circuit). Continuous burning in is a technology to get rid of moisture in the IC package, and burn out contamination under the oxide. This improves noise from transistor leakage current in oxide isolation region.
It also will improve noise level generated by silicon transistor; by low temperature annealing of dislocation in the silicon crystal left during the hundreds of high temperature processing and subsequent errors of cooling process.
So, after a few days of power on, Venturer converter box begin to improve, and worked with over 30% signal strength instead of 70% on the Radio Shack converter box. This can be confirmed by feeling the heat on the converter box. It will be just luke warm.
Everything you ever wanted to know about DTV converter boxes has now been discussed.
Changing antenna on Venturer ? Extra cooling on decoder IC ?
When another cheaper antenna is used with separate wires on both UHF and VHF, Venturer decoder IC got overheated. The pictures were even super imposed on different channels. Apparently cache memory were overloaded with signals. In other words some transistors were saturated.
Fortunately, I just moved the front of the converter 1.5" off the table to get extra cooling on both the top and bottom of the case by free airflow.
The extra cooling got extra benefit of receiving more signals from channel 68. Proving the reason that Target stores had a lot of returns over the many years they had these Venturer converters. Anyway, the extra cooling proved that it is very good converter. We just have to know how to use it.