Bonner Martin
13-05-2008, 09:29 PM
I originally sent the below report to a few people in the trade and have been requested to enter it into the forum for discussion. It was written over three days hence the add on at the end.
I have been installing the Zinwell DTT STB’s in a poor signal area for the last month and have been delighted with there ability to work even in a high multi path area like Katikati when we have to work off the Te Aroha transmission when Kopukairua signal is too weak
With analogue UHF the average signal level from either Kopukairua of Te Aroha is around the 46 db microvolts and with the digital signal, even in spite of the lower transmitter power it’s about 49db at the antenna.
By the time the signal gets to the TV through triplexers, splitters and RG6 cable you loose on average about 15 to 16 db. Which means in most cases a mast head amplifier is required for analogue viewing.
I have had no trouble getting the Zinwell to work even in cases of high multi pathing. On prime analogue the news reader looks like an army of news readers and there can be as much as 12db difference in signal strength between the different channels. The Zinwell will still work for HD reception.
I find that where one would not advise a customer to proceed with analogue uhf because the signal level is too low. 35 db of digital signal and a Matchmaster masthead amp will still give a perfect digital picture. With analogue at that level you can still get a picture but there is lots of video noise in the amplified signal. Where as with digital is still perfect with no break up.
Using our motor home with it’s Winegard crank-up antenna as a test vehicle I have been amassed how far away from Te Aroha one can receive digital signals. We were in Rotorua recently and found areas where Digital would work. Lake Rotoiti where we spent the weekend analogue was nearly unwatchable but digital still worked. Even out beyond Opotiki at Opape and digital was still working. Prime on UHF was a black and white picture full of snow was just visible. My meter showed 25db for prime at the TV and 28db for the digital signals. The antenna is only 3.5 meters off the ground on the motorhome so a bit more height would have helped greatly.
There is one fault with the Zinwell and that is on the channels we have in our area running an analogue signal through the Zinwell STB to a TV causes interference on the TV in the form of squiggle lines over the screen. I find it is best to fit a splitter before the Zinwell and feed the 2 separately.
Stacking 2 matched UHF antennas with matched lengths of 75 ohm cable into a “T” “f” connector with the right spacing will give you just under 3db of gain. I have stacked antennas in the past to increase gain and reduce ghosting on analogue.
Latest information;
My lowest signal strength install to date was at a place with only 26db microvolts at the antenna. A Matchmaster Johansson 10-J35 was used to boost the signal to get it down to the HD receiver. Needless to say I and my customer are delighted that it worked.
I have found that some of the older amplifiers that were popular a few years ago are not satisfactory to amplify the digital signal and they have had to be replaced
The thing I like about digital is; “It runs on the sniff of an oily rag”
May 13
Today I had a job where on my standard Strongway TX26 (53 elements) would only receive 23db of signal strength on the digital channels. I considered that I was pushing my luck at this low level so tried a TX 48 which has 97 elements and I raised the antenna height from 2.2 meters to 3.1 meters this increased the signal level to 29db which over come the low signal level nicely and again a perfect picture distance from Kopukairua 48 km as the crow flies. Amplifier used; Matchmaster Johansson 10-J35
I have been installing the Zinwell DTT STB’s in a poor signal area for the last month and have been delighted with there ability to work even in a high multi path area like Katikati when we have to work off the Te Aroha transmission when Kopukairua signal is too weak
With analogue UHF the average signal level from either Kopukairua of Te Aroha is around the 46 db microvolts and with the digital signal, even in spite of the lower transmitter power it’s about 49db at the antenna.
By the time the signal gets to the TV through triplexers, splitters and RG6 cable you loose on average about 15 to 16 db. Which means in most cases a mast head amplifier is required for analogue viewing.
I have had no trouble getting the Zinwell to work even in cases of high multi pathing. On prime analogue the news reader looks like an army of news readers and there can be as much as 12db difference in signal strength between the different channels. The Zinwell will still work for HD reception.
I find that where one would not advise a customer to proceed with analogue uhf because the signal level is too low. 35 db of digital signal and a Matchmaster masthead amp will still give a perfect digital picture. With analogue at that level you can still get a picture but there is lots of video noise in the amplified signal. Where as with digital is still perfect with no break up.
Using our motor home with it’s Winegard crank-up antenna as a test vehicle I have been amassed how far away from Te Aroha one can receive digital signals. We were in Rotorua recently and found areas where Digital would work. Lake Rotoiti where we spent the weekend analogue was nearly unwatchable but digital still worked. Even out beyond Opotiki at Opape and digital was still working. Prime on UHF was a black and white picture full of snow was just visible. My meter showed 25db for prime at the TV and 28db for the digital signals. The antenna is only 3.5 meters off the ground on the motorhome so a bit more height would have helped greatly.
There is one fault with the Zinwell and that is on the channels we have in our area running an analogue signal through the Zinwell STB to a TV causes interference on the TV in the form of squiggle lines over the screen. I find it is best to fit a splitter before the Zinwell and feed the 2 separately.
Stacking 2 matched UHF antennas with matched lengths of 75 ohm cable into a “T” “f” connector with the right spacing will give you just under 3db of gain. I have stacked antennas in the past to increase gain and reduce ghosting on analogue.
Latest information;
My lowest signal strength install to date was at a place with only 26db microvolts at the antenna. A Matchmaster Johansson 10-J35 was used to boost the signal to get it down to the HD receiver. Needless to say I and my customer are delighted that it worked.
I have found that some of the older amplifiers that were popular a few years ago are not satisfactory to amplify the digital signal and they have had to be replaced
The thing I like about digital is; “It runs on the sniff of an oily rag”
May 13
Today I had a job where on my standard Strongway TX26 (53 elements) would only receive 23db of signal strength on the digital channels. I considered that I was pushing my luck at this low level so tried a TX 48 which has 97 elements and I raised the antenna height from 2.2 meters to 3.1 meters this increased the signal level to 29db which over come the low signal level nicely and again a perfect picture distance from Kopukairua 48 km as the crow flies. Amplifier used; Matchmaster Johansson 10-J35