Hello,
I wonder if (shock horror ) any forumites have any experience of onboard TV aerials and west coast reception (including Croabh marina). I am considering fitting a Glowmex omnidirectional aerial, probably at the masthead, but would prefer the pushpit to save more clutter at the masthead.
Angus
have masthead 'nargus' into hauppage dongle on laptop. Works well but I think height matters in borderline cases.
Looking through the log, I didn't list Tv availablility, although I remember intending to. Sorry.
It's got better with digital I think. There will be a coverage map on here somewhere I'm sure.
http://trooncruisingclub.org/ 20' - 30' Berths available, Clyde.
Cruising, racing, maintenance facilities. Go take a look, you know you want to.
I have have a removable TV aerial which I mount on a telescopic pole on the Pushpit which I connect to a cable already run from the cockpit locker to the TV. It takes about 2 mins to set it up. It works surprisingly well all over the Clyde and west coast. as long as you know where to point it and whether it is in a vertical or horizontal orientation. I downloaded a map of transmitter sites here. http://stakeholders.ofcom.org.uk/binari ... alv2.2.pdf
I went down this road after hearing poor reports about masthead omnidirectional aerials.
Remember you need to retune each time you connect to a different transmitter.
Many thanks for your responses, I certainly did expect the "why do you want to watch TV when sailing", I agree that creature comforts do detract and can be antisocial. I trust that you do not interweb when sailing Anyway the Nargus looks like a good option, just need to find a vendor now, might try Jeff Rutherford who has supplied these in the past.
All the best
I think DDZ fitted the one I have (previous owner did it) and it also does a great job "Teed" into the Car VHF radio.
To clarify to those looking down their noses at us poor "addicts", the peace of cruising can sometimes only be achieved if others in the vicinity are not deprived of their Wimbledon/Royal wedding or whatever... My soup-dragon watched the Spanish rw while I enjoyed a super sail from Alicante to the Mar menor in 2004 - everybody happy = ship happy.
http://trooncruisingclub.org/ 20' - 30' Berths available, Clyde.
Cruising, racing, maintenance facilities. Go take a look, you know you want to.
I don't have TV aboard, but some knowledge of how these antennas work makes it clear why a masthead installation of some types would be a retrograde step.
1. An antenna works similarly as a receiving antenna as when a transmitting antenna.
2. A similar analogy is to think of light from a light source.
3. May TV antennas are quite directional. If you use the "Yagi" type, (a boom with multiple elements at right angles, similar to what a house uses). This type have "gain". The Yagi has higher gain the more elements it has, (and so longer it is) .
4. Gain is a concentration of the signal in one direction.
5. Imagine your masthead anchor light. It's an omnidirectional source - shines equally brightly in all directions. But if you installed a spotlight there, with a beam of light, it would not work in the out of beam directions.
6. Not only would it cease to be omnidirectional, but that spotlight would wave about as the mast moves. The length of mast amplifies the movement of the boat.
7. So a receiving antenna with any gain will do the same. Signal strength of the received signal will vary enormously.
8. Mount same antenna at boat height and the problem is reduced.
9. With TV, some gain is usually required, unless you can see the transmitter mast with your eyes.
10. A low gain omnidirectional antenna will work best if in a strong signal area.
11. Omnidirectionality works in both the horizontal and vertical plane. A typical masthead VHF Marineband antenna has a little gain, so that with a mast at an angle, (boat on heel) the direction of strongest signal is now into the water on one side of the boat, and up into the sky the other. With pitch same applies forward and aft.
12. Probably the simplest TV antenna will work best all round for these reasons, while at home, mounted on a chimney that doesn't wave about, a high gain permanently pointed to transmitter will work best.
Geoff.
"Contender" Rival 32: Roseneath in winter, Mooring off Gourock in summer.
Geoff,
Many thanks for that. Your light analogy explains directivity well. I would probably only only use the TV when using the boat in the Marina, primarily Croabh. It would not be in use when heeled, since it would be very sad to be watching TV while sailing. The nearest transmitter is Easdale, not line of sight, but quite close and the land is relatively low lying. Speaking to a neighbour in Kip yesterday, they have a Nargus and get good reception in Kip and Puilldobhrain (and Crinan). Bad reception in Tobermory, and in Croabh, it depends on where Jim puts you (hot spots perhaps), perhaps due to reflections from other masts?
An option may be to have a Yagi with gain and last it to the pushpit when moored, what effect does height have, the higher the better
Angus
On land, height of antenna is very important. But that's where the antenna stays still, so always points in the same place.
I'd say that on a mast top though a high gain antenna would be rather useless. Even the movement of walking from one side of the boat to the other would put it off beam. (unless QE2).
For that reason, the pushpit probably better, and a moderate gain ant, (say if a yagi, one with only 4-6 elements).
In a marina, an omnidirectional ant might work at masthead. But then it probably has to stay there.
At UHF (where TV works) the polarisation is very important. They're either horizontal or vertical. Getting that wrong is almost as bad as a missing antenna!
If its horizontal (and that's set by the transmitter antenna), then even a simple dipole is directional - best reception when the length of the active element is at 90 deg to the transmitter.
Geoff.
"Contender" Rival 32: Roseneath in winter, Mooring off Gourock in summer.
mm5aho wrote:On land, height of antenna is very important. But that's where the antenna stays still, so always points in the same place.
I'd say that on a mast top though a high gain antenna would be rather useless. Even the movement of walking from one side of the boat to the other would put it off beam. (unless QE2).
For that reason, the pushpit probably better, and a moderate gain ant, (say if a yagi, one with only 4-6 elements).
In a marina, an omnidirectional ant might work at masthead. But then it probably has to stay there.
At UHF (where TV works) the polarisation is very important. They're either horizontal or vertical. Getting that wrong is almost as bad as a missing antenna!
If its horizontal (and that's set by the transmitter antenna), then even a simple dipole is directional - best reception when the length of the active element is at 90 deg to the transmitter.
Not looking for an argument, but are you sure about the mast top disadvantage? If someone steps on to the side deck making the boat heel by say 5 degrees then the mast will also heel by 5 degrees, as will anything firmly attached to it such as an aerial. That being the case I can see no advantage in deck level mounting other than ease of adjustment. This does, however, ignore vibration which might be an issue at the mast top in strong wind, particularly with a fractional rig.
Well, we've got one (a masthead telly aerial {nargus}) and it works - because it isn't a yagi to get gain - it's omni directional, but amplified.
You're right Geoff , the narrower the beam (because of sensitivity) the more accurate it must be and therefore the more easily it is to lose signal if movement occurs. I've had a look inside Nargus and some of the soup plate types and the signal element is quite simple, usually a horizontal loop, the masthead amplifier being the differentiator. Trust me even if I'm not a doctor, they work, and as I said in an earlier post, VHF radio can benefit from a connection as well.
It does help to wire the amplifier power supply to something that is switched off when you go to bed/leave, as it can be forgotten about.
http://trooncruisingclub.org/ 20' - 30' Berths available, Clyde.
Cruising, racing, maintenance facilities. Go take a look, you know you want to.
Many thanks for your posts, I was keen on the Nargus, but apparently it has been discontinued. I tried suppliers in Germany and the US also but to no avail. I was recommended a Banten by Boat Electrics at Kip. Force 4 seem to do two varieties, one is a similar low profile shape to the Nargus ( Banten 335) and also this whip type which is 25 cm long, I guess that I shall settle for one of these.
) any forumites have any experience of onboard TV aerials and west coast reception (including Croabh marina). I am considering fitting a Glowmex omnidirectional aerial, probably at the masthead, but would prefer the pushpit to save more clutter at the masthead.
Anyway the Nargus looks like a good option, just need to find a vendor now, might try Jeff Rutherford who has supplied these in the past.
