The unit itself probably works well, but there are 3 different outside influences which could spoil the results from your easyDVBT:A) Cable quality and length The DVBT frequencies are received by a regular VHF antenna, but not in a sufficient quality to watch TV. What our unit is doing is to amplify the signal strength so that the digital receiver box can interpret the signals. But amplification only works, if there is a base level of signals at our easyDVBT. If the cable which is used or the transitions between the cable and the inside of the cabin is no good quality, we do not get any “amplifiable level of signal” into the easyDVBT. Proposal for a solution: Use of a good quality cable e.g. RG 213 or ecoflex 10. Attenuation of RG213 or Ecoflex 10 at 1000 MHz is around -2dB/10m which is an acceptable value. RG58 is very bad for TV frequencies: Attenuation of RG58 at 1000 MHz is -6,4dB/10m which is an enormous attenuation. Another important factor of the quality is the connector: The TV high frequencies lose signal strength if the transition into the cockpit is soldered too easy and not “by plugs and sockets”. You easy loose -3 to -4 dB if only soldered not in a very exact coaxial way.
B) Self oscillating of the amplifier In a very seldom, but possible case, the amplifier starts self oscillating in consequence of a critical impedance of the existing cable and the VHF antenna, which is very bad. To find a remedy, you can extend the cable by 1-2 meters. If this does not help, please ask us for a little electronic system which eliminates the oscillating, material No. B041.
C) Polarization of the TV transmitter from the TV stations VHF antennas are made to receive vertical polarized HF waves very good. This transmission of DVBT is the norm, for that reason everything should work fine. But we found out that some TV transmitters in the Baltic Sea stilldo work with horizontal polarization (as in the former years) and then the polarization might course technical difficulties. If you want to receive per horizontal polarized TV transmitter, please notice our self-developed “horizontal wave catcher” unit for the regular bar antenna (except of fibre glass antenna).
Let us explain what influences good reception.
- How does the unit work: Normally a VHF antenna do not receive well the UHF frequencies of the television transmitters. But there is still a reception signal, even with the regular VHF antenna. What the easyDVBT does is, that it amplifies the UHF television signal so that the digital receiver can work with the signals. But to do so, it is necessary to get an “even small” UHF signal to the unit, to amplify it there.
- UHF attenuation of cables. The regular used VHF cables are of the type RG58. These cables do have a normal attenuation at the VHF frequencies of app. 140-160Mhz. But at the UHF frequencies for TV, up to 900 MHz the attenuation of these regular cables is very high, which means very poor signal transmission of these frequencies. Just to give you an idea: RG58 at 144MHz for 10 m cable: attenuation app. -1.9 dB RG58 at 900MHz for 10 m cable: attenuation app. -6,5 dB
- Poor transmission power of TV stations In some areas the coverage and the transmission power is not very good. This means that almost no signal is received.
Summary: To recveive a good TV signal out of the easyDVBT you need a good cabling, e.g. RG213 or Aircell 7 or Ecoflex 15 and good cable connections from the cable to the unit. Also the area where you are sailing is important, that there is enough “signal strength” to reveive TV signals.
FAQ: easyDVBT >>>
This effect is not wrong, it is just the logic consequence of the unit.
Reason for that is the following. Imagine, that a VHF would “over the easyDVBT” directly transmit with 20W. The TV or the receiver would immediately be broken. Therefore the easyDVBT unit needs to disconnect all other connected units, (except the VHF Radio) in the moment when the VHF Radio is transmitting.
In order to operate your DVB-T receiver with the easyDVBT mostly perfect at your VHF-antenna, please attend the following:
- Because of the higher frequented DVBT-channels (500 bis 860 MHz) have in the coax-cable a higher decay compared with the navy-radio-signal, it can be necessary to use a high quality, low-loss coax cable at higher cable lengths. Types of good coax cables are e.g. RG 213/U, AIRCELL 7, ECOFLEX 10. 2..
- Also a preferably uninterrupted transmission of the receiving signals from the antenna to the easyDVBT is only possible when you use the installed coaxialcable with together fitting coax plugs and jacks (.e.g coaxial deck-disconnection point)..
- In the easyDVBT the TV-Receiver-Signals will be separated (filtered), heightened and routed to the TV-receiver. This will be only successful, when an adequate high signal level is at the easyDVBT input. That means that the decay of the signals from the mast-top to the input of the easyDVBT has to kept small.
FAQ: easyDVBT >>>
For receiving DVBT on board you need the following hardware: your already available VHF-antenna, an „easyDVBT“ – a DVBT receiver (commercial) and a TV. Later you can complete the easyDVBT with an easySPLIT and easyAIS.