Hi there

Recently I changed the position of my setup (got a motor stand for the mx and hung the ouverture on the wall), and hence, I needed some new cables. I took the chance and bought some semi expensive double shielded antenna cables, put the best one between the video and the tv, and WOW what a difference! much more crisp picture, more detail and hence dept. I can only recommend this to anyone using old antenna cables, don't upgrade your tv, just upgrade the cables.

I’ll post some pictures of the setup when I get all the cables sorted in some sort of duct or the like.

Best regards

Christian

Christian,

Aerial (antenna) cable is so important for a quality picture and you have clearly found this out. I normally use the double screened thicker CT100 cable, but it is important that cables do NOT have sharp bends and the termination at the "F" connector or aerial plug is made correctly to ensure a perfect impedance match.

There is further information about aerial cable on the RF Link Amplifier FAQ HERE

Nice factsheet, Keith. Thanks.

Can only second the sentiment. Believe I've mentioned my experience before. I had the internal cabling revised by the cable company, and had them set up a dedicated path with shielded cable (without distribution points into other rooms) to the main viewing room from their point of entry.
Just as with your experience, Christian, I got a much better signal - and it was measurable. The installer said I had a 40% boost in signal strength and  that the previous signal cabling had reduced the level to a point below where I could get a good digital feed.
And all by changing a cable - total cost, including the manpower about € 200!

I think a lot of the complaints we see about inferior images on the modern upscaling flatscreens is due to a bad signal being fed to these screens. My BV8 is two completely different animals, depending on whether it's getting an RGB-signal or the composite out from my STB, for instance. And my 50" Kuro would have glitches before the cabling to the main viewing room was changed.

The BV8's image became crystal with a menu change to RGB in the STB; and the Kuro got to shine as it should when new cable was in place.

soundproof:

I think a lot of the complaints we see about inferior images on the modern upscaling flatscreens is due to a bad signal being fed to these screens.

I agree. I work for a cable tv provider, and most of the complaints (from customers) regarding picture quality when viewing analogue tv on flatscreen tvs are solved by replacing their cables.

(disclaimer: RF technology ios not my field of expertise, btw)

Often it's mechanical fault. The cable's been there for ages, it can have gotten damaged, a nail may have been hammered into it, when someone was placing another run of wire next to it ...

It's really worth it to have the signal strength checked, and to replace them if there's a drop that can't be accounted for. 

I talked about "Impedance Mismatch" previously in other threads, but I thought I should explain exactly what it means. I was surprised that no one asked me, so either everyone knows the answer, or you thought I won't ask that question because ??? 

So, let me explain how this effects your aerial and RF link and why the cable and its termination are so important:-

The typical B&O installation with the RF link or main aerial have a fixed LOAD impedance with an impedance of 75 ohms resistive. To minimise interference we have to use coaxial cable to connect the aerial to a "transmitter" or "receiver".or Beovision RF link output or Aerial Link input.

Coaxial cable behaves as a transmission line at radio frequencies, and as a result it has its own characteristic impedance. This simply means that because of the inductance to capacitance ratio of the cable, RF energy tends to move along it with a particular ratio between the electric and magnetic fields. All cables have both inductance measured in "Henry's and capacitance measured in Farads or more usually sub-divisions of them like 10 nano farads
When the energy reaches the end of the cable, we want as much as possible to transfer into our load of the aerial, in the case of a transmitter (Master Beovision), or the input RF stage in the case of a receiver (Link Beovision). For a transmitter this gives the highest power efficiency, while for a receiver it gives the best noise performance.

To ensure this optimum energy transfer, it is important to match the characteristic impedance of the cable to the impedance/resistance of the load. So for a 75 ohm aerial input, we need to use 75 ohm coaxial cable. This, then, is an area where impedance matching is very important. Because what happens if the cable and aerial (or receiver) impedances are NOT matched is that some of the RF energy reaching the end of the cable is not transferred into the load, but is REFLECTED back along the cable, towards the source. This reflection can set up standing waves in the cable. In a receiver (Link Aerial), this mismatch degrades the effective receiver gain and noise figure normally provding poor picture quality and ghosting or reflections to the right of an image like someones face on the Link Beovision screen.

In the commercial world of cable TV the installer would normally use a "Time Domain Reflectometer" to ensure as near perfect impedance match as possible, but in our world we need to use high quality double screened 75 ohm cable such as CT100 or FT100 and wherever possible use "F" connectors rather than the normal 75 ohm aerial connectors. There should be no sharp bends in the cable and no bend greater then 90 degrees. The cable should not be allowed to be flatten or distored as this changes the inpedance of the cable.

So, the bottomline is:-

With "Aerial" and "link" TV distribution spend a lot of time making sure your coax cable and its termination are perfect in every way to ensure a crisp sharp picture.