Technical Section | | 
Strip cable and fold back copper braid over outer sheath. Loosen saddle clamp screw. Fit 5mm inner copper core into connector, clamp gently with screw. Tighten saddle clamp screw gently so it holds but doesn't crush the cable. Cut off any protruding wire. Ensure that no strand of braid can touch the screw connection. Centre connection is for output cable to receiver. Left and right inputs are for high- and low-band aerials (if used as a combiner). If used as a filter, fit a resistor to the unused aerial input by wrapping the wires under the screw heads and tightening gently. Cut off any protruding wire. Pass filters look similar but have only one aerial input. No resistor is required if you buy a pass filter. As diplexers are not screened, mount away from any source of interference such as mains power cables. If mounted outdoors, apply a generous coat of silicone grease to all connections and cable ends. This will help keep condensation at bay. Slide the cover down and mount the housing vertically so that rainwater can not enter. | Problems with your Diplexer? | | Send this page address - CLICK HERE - to a friend ! |
> Dear Martin: > My name is Alfonso Dastis and I live in Madrid, where I am fortunate
> enough to have a Sky digibox and an installation that enables me to
> see some Sky digital channels, not all those I would like though. I
> am a fan of your websites, I read your mailshot and have bought some
> of your very useful books, "piping tv around the house" among them.
>
> Having read it, I have tried to improve reception of satellite tv in
> my bedroom upstairs. I send the signal trough an RF cable and the
> problem I have is that I do not have any channel free of
> interference from the tv aerial, since more and more local tv's keep
> cropping up and using channels that were so far free.
>
> Following your advice, I have ordered a diplexer with a matching
> resistor in order to filter out some channels to use them for
> satellite and DVD (by the way, impressive speed with the shipment,
> congratulations to your team; I placed the order on friday and got
> it in Madrid yesterday).
>
> Now comes the technical question: I do not know anything about
> electronics and although I have figured out more or less what I have
> to do, I do not know how to connect the resistor. I know I have to
> connect it to the unused aerial input but I wonder if I have to
> connect it in a particular place. The resistor looks to me like a
> wire with a protuberance in the middle, so I do not know if alI I
> have to do is pass one of the sides of the wire trough the loop of
> the unused input and fasten the screw or I have to do something
> special, what position should the protuberance be in?, does the
> resistor need to remain inside the diplexer entirely? can I or
> should I bend it in any way?.
>
> I will try a further question in case you feel benevolent enough to
> answer it. You say in your book that the diplexer needs no power,
> but in the box containing it there was a plastic bag with a screw
> inside and some kind of of instructions that I understood as meaning
> that If I use some kind of electric current I should fasten the
> screw in a free hole in the diplexer next to the input. Did I
> understand correctly? should I disregard the screw and the
> instructions? Please understand that I do not want to make a mess of
> the installation.
>
> I thank you in advance for your answers and I congratulate you for a
> most useful and informing website to those who, like me, are
> interested in satellite, tv, electronics, etc and are no experts.
> PS: please excuse any mistakes in my english, you must have guessed
> that it is not my mother tongue.
> Best regards, > Alfonso. | Firstly, may I say that your English is better than that of most English people! The resistor takes the place of the aerial. You see, if you do not connect the aerial, the aerial input is "open-circuit" and it can pick up interference. The 75 Ohm resistor prevents this by correcting the "impedance mismatch". So you simply connect one resistor wire to the terminal where the aerial cable centre wire would go. And you connect the other resistor wire to the "bridge clamp" or screw that would hold the outer braided copper shield of the coaxial cable. The resistor can go either way round. You may bend and/or cut the wires shorter. The diplexer needs no power. However, some aerials have an amplifier on the mast (a "masthead amplifier"). This needs power so, in this case, you would insert the screw. This will allow electric current to reach the amplifier. So, if there is no amplifier between the diplexer and the aerial, you do not need the screw. | | |
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Copyright ©2003 Martin Pickering
Version 1.0 updated on September 10, 2003
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