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The Televes DAT aerials and MRD
| DAT45 |
Black version includes MRD
Yellow does not.
| DAT75 |
Does NOT include the MRD.
Requires a 2" diameter pole and substantial bracket if mounted outdoors.
The DAT45 aerial has a maximum gain of around 16 dB which is quite high if you consider that an increase of 3 dB represents a DOUBLING of signal. An "ordinary" TV aerial has a gain of about 12 dB so the DAT45 can be considered to be around 200% better. The DAT75 has a gain of 18 dB max. which is "only" 2 dB higher (in fact about 60% more gain!)
However, this gain is concentrated in the upper part of the UHF band so this type of aerial is NOT suitable for use with transmitters where most or all of the channels are at the low end ("group A"), such as Crystal Palace and Rowridge. See notes. If your transmitter uses channels below number 30 you might like to consider a different aerial.
What it does is to reduce problems of interference from "impulse noise" (such as you'd get from passing traffic, thermostats etc.) In other words, it does the job of a "balun" (balanced to unbalanced transformer). The "MRD" is a 13 dB amplifier as well.
There is an "amplifier" available. It's actually a 5050 "margin raising device (MRD)".
You must add a power supply unit* for the MRD to work. If the MRD is not powered then the aerial works normally, without amplification and without the "balun" effect to reduce impulse noise. The power supply connects anywhere in the aerial coax cable but usually near to the Freeview box)
If you are unsure, you can order the aerial with the 5050 MRD alone. Install the aerial and, if the signal isn't strong enough, order the power supply.
How can I tell whether my existing DAT aerial has an MRD fitted?
The standard DAT aerial comes with an H shaped dipole which has exactly the same moulding and "F" connector as the version that has the MRD electronics inside. Unfortunately, the only way to tell is to borrow a telescope and look for the letters "MRD" or the number "5050" on the label on the dipole box.
*The 2 output 5020 was superseded by the 5487 power supply. That is also now obsolete. If the Televes 8203 is unavailable we will supply a Fringe amplifier or other equivalent.
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The Televes 8203 100mA 12V PSU has 2 TV "F" connector outputs.
This is handy if you share an aerial with a neighbour or if you need to feed the signal direct to a second TV set.
The Fringe P1290/2 90 mA 12V PSU has 2 TV IEC output sockets.
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The power supply can be fitted anywhere in the cable from the MRD. There must be NOTHING else between the power supply and the aerial MRD!
The power supply can feed one or two rooms* with the TV signal. Connect the PSU signal output to your satellite receiver aerial input or to your Freeview box.
For more information on connecting up equipment see our eBook "Piping TV Around the House".
For more information about Freeview installation see our eBook "The Freeview Bible".
*Be sure to order the correct PSU.
The DAT75 aerials has a MASSIVE gain and should never be used when a transmitter is close by. They are for use in areas of very weak signal - i.e. where the nearest transmitter is no closer than 20 miles. They should be used only with double-shielded WC100 cable or better. Aerials of such high gain also have a very narrow "focus" so alignment is super-critical. They will not work well if you guess the direction of the transmitter or if you leave them flapping around on top of a long pole.
Although it is possible to mount these aerials for vertical polarisation (with extra parts - see data sheet*) it is extremely unlikely that you would need to do so. In the UK, vertical polarisation of terrestrial signals is used only by local repeater stations. If the station is local, then you are unlikely to need a high gain aerial!
The DAT75 requires a 2" diameter pole and substantial bracket if mounted outdoors.
*Data sheets are available for download, after purchase.
Thanks for your very prompt reply to my enquiry. I ordered the 5020 PSU, which I have now installed, with the result that I can now receive ALL the Freeview channels in an area (S35 0JG) that theoretically is not yet fully covered. See this page.
I have also looked on the box in which the aerial arrived and found the interesting sticker saying that it was "ESPECIAL Black antenna "Active Aerial"". for your information this is black plastic where the one on your website is Yellow and includes the 5050 preamp, which if used without the PSU just passes the signal through, but amplifies the signal by an extra 13 dB when used with the PSU.
For some reason the analogue signal from ITV is good here but that from the BBC and Channel 5 is much poorer, ghosting and grainy. This resulted in my Nokia (one of the original On-Digital boxes) giving excellent pictures for ITV and channel 4, but not even tuning in any of the BBC channels. The PSU has now boosted the signal properly so that I can now see pixel-perfect BBC1 and Channel 5 for the first time since moving here from Manchester.
The PSU also has two aerial outputs so that it could feed another part of the house if required.
We are 25 miles or so from Emley moor, but due to Sheffield being very green and hilly, well out of line of site. The "proper" transmitter for this area is an infill one and requires the aerials on their side thus no Freeview unless people have gone to the lengths that I have had to. I have only gone to such lengths as I object to giving Mr Murdoch any of my hard earned cash!
The local transmitter is also in the middle of a forest and the trees have grown up round it, so local reception is totally rubbish and most of the neighbours have Sky.
Thank you once again for your excellent and rapid service.
Ed Send this page address - CLICK HERE - to a friend !