Magnetic TV roof aerials

Thanks David, I see that’s in a vertical polarity can it be switched when stuck in exactly the same position on your van to horizontal polarity? Just concerned before I buy that essentially it’s just an omni aerial! Not meaning to fuss but I bought a different make and model which promised much but performed pretty poorly where the broadcasted signal was a less than strong.

We used it with our first motorhome which didn't have a built in aerial but we did have a satellite dish but that wasn't always usable if there were trees in the way. I would say that generally the  Avtex worked pretty well if you have a decent signal. Mainly I stuck it on the side of the van as illustrated by the photo but have been known to put it through a hatch onto the roof. In poorer signal areas we would find the BBC channels fine but ITV not so good as they sometimes come from different transmitters. We often had to play around with it depending on what programmes we wanted to watch. Having said that for about £35 its a reasonable bit of kit to have around.

David

 We use the Apple antenna Aligner app (£2.49) this lists the available TV transmitters in order of signal strength plus shows polarisation and when you select a transmitter a compass comes up with an arrow  pointing to the direction of that chosen transmitter. The Avtex  aerial looks like a dipole to me so just swivel vertical and horizontal and course place it on the transmitter side of your outfit  

The two basic factors for getting a good signal from a terrestrial transmitter is that it depends on how much metal one can get into the air, and how far above the surroundings it can be raised.

One then has to consider what signals are being received as well as the wanted one. This has led to all sorts of shapes of bent wire and fantastic assemblies being designed. Whatever recieving aerial one uses needs to have a good response in the polarity of the transmitted signal - in UK at least either vertical or horizontal. It also helps greatly if the aerial has an ability to receive in a particular direction as that will reduce unwanted signals and noise from other directions.

In order to avoid the user who is uninterested in this having to do much, many aerials have been produced that are "omni-directional" and/or "omni-polarity". They will work as such in an area with strong signals but they are far from ideal with weak signals.  A very efficient aerial design is the Yaggi which in plan view looks like an arrowhead which one points at the desired transmitter, either lying flat or on its side. Some makers, such as Status, enclose the metal bits in a shaped plastic housing to protect them.

When the signal is strong, a straightened out wire coathanger stuck in the socket on the back of the television can be as good a some of the cheap "does everything" commercial aerials.

Trouble is we tend to go to far flung remote areas which often have ‘poor’ signal strength delivered to them. I have an expensive omni fitted on my van which is more or less useless in these situations or even in medium strength areas and have searched high and low for an alternative.  Presently I carry a Log Periodic which is on a short pole, it does work slightly better but is a faff to erect and align. 
Just looking at what the locals have on their roofs can be helpful mind. Large complex aerials on display usually means a challenge but these do help with determining direction and polarity.  Many products promise the world but in reality don’t provide and I just thought Avtex is a good make of TV but wanted to know how it really performs in those challenging areas before parting with even more money.

The reason we no longer take the Avtex with us when we go away as on our current motorhome we have a directional aerial which has been pretty good and I doubt the Avtex would perform better. When we can, we always use the site bollard if it has a connection point. I have toyed with the idea of another satellite dish but they are a lot of money and thus far the built in aerial has prove reasonably reliable.

David

The free(ish) application "Freepoint2" gives all the information one may need about direction to transmitters, distance and polarity. It has lists of Caravan Club sites and CLs - as well as the other club and commercials - so one can look at the possibilities before one arrives.

The polarity can be very important when there is more than one transmitter on a similar heading.  Also note that many of the handout site maps are inaccurate in showing the direction of north so a proper map or a compass can be required.

What is not given is the path profile to the transmitter from a selected location. There could be a whopping great hill in the way so again a proper map is your friend. In these situations all is not lost since there can often be a usable reflection of the signal one wants from something like another hill that is in line of sight to the desired transmitter.

One still has to consult the Internet to find out what stations are in the mix being transmitted from any selected site though.