Jump to content

TV Aerials


RobinJ

Featured Posts

I have been looking at the various omnidirectional aerials available, MaxView, OmniMax, Gazelle etc.

(The cheap and nasty stick is getting a bit bent and doesn't seem to work terribly well in bad reception areas or with digital).

 

What's the views on which one is best?

Do the ones with built in amplification work better?

At least one is available with an optional mag mount or removable fitting (Need to be able to reduce air draught in tunnels!)?

Do they all have to be mounted flat, fitting onto a bulkhead would presumably cause problems (no longer omnidirectional)?

 

Project for the up coming holiday.

Link to comment
Share on other sites

Omnidirectional aerials in my view are a bit of gimmick they seldom live up to the claims receiving analogue and are quite often appalling with terrestrial digital.

 

You are far better with cheap standard aerial and a pole or better still a satellite dish and receiver.

Link to comment
Share on other sites

Omnidirectional aerials in my view are a bit of gimmick they seldom live up to the claims receiving analogue and are quite often appalling with terrestrial digital.

 

You are far better with cheap standard aerial and a pole or better still a satellite dish and receiver.

Thanks Gary, I will consider the satellite and broadband issue when I retire (hope we are still both around then).

At the moment we were just looking to get the news and keep up with the 'to be continued' situation occasionally.

I have up to press resisted the pole too, though I am not convinced the current cheap standard aerial would improve with elevation (put that on my test list)!

Link to comment
Share on other sites

Robin

 

As you will already know, TV signals (wavebands) vary around the country, the best type to cover all areas are 'Log Periodic'.

 

Example here: http://www.maplin.co.uk/Search.aspx?criter...FZ&DOY=29m6, this is not a recommendation. :lol:

 

The blurb on Maplins' web site says: '... Advanced log periodic design rejects unwanted signals making it ideal for strong digital terrestrial UHF TV signals...'

 

What isn't clear to me is whether this means it's for use in areas where there is a strong digital terrestrial UHF signal, or that you will get a strong signal at the TV if you use the aerial. I suspect it's the former, meaning that digital TV reception in weak signal areas will remain rubbish.

 

The canal network goes through some remote rural areas and tends to be low down in the countryside, so TV reception is bound to be patchy.

 

Radio reception is pretty good everywhere, though...

Link to comment
Share on other sites

There is a delay but all Digital Terrestrial signals will be increased when all analogue TV is turned off (2012). (That's what the blurb says)

 

Or you can go wideband

 

A Wideband aerial is optimised to receive TV channels anywhere in the UK TV band. In areas of weak signal, a wideband aerial may not be as effective as a high-gain aerial designed for the specific band you're trying to receive (a mast-head amplifier may be needed to help boost the signal).

 

The best aerial is one that is specific to the local transmitter but that is not always possible unless you wish to carry about six different aerials.

Edited by bottle
Link to comment
Share on other sites

I have been looking at the various omnidirectional aerials available, MaxView, OmniMax, Gazelle etc.

(The cheap and nasty stick is getting a bit bent and doesn't seem to work terribly well in bad reception areas or with digital).

 

What's the views on which one is best?

Do the ones with built in amplification work better?

At least one is available with an optional mag mount or removable fitting (Need to be able to reduce air draught in tunnels!)?

Do they all have to be mounted flat, fitting onto a bulkhead would presumably cause problems (no longer omnidirectional)?

 

Project for the up coming holiday.

 

 

Hi,

 

We forked out loads of dosh - £63.00, for an Omnidirectional aerial but the picture we received using it was awful. We now use a really cheapo directional aerial - £5.00, stuck on the end of a 7' pole - £11.00, and get a very respectable picture indeed.

 

I should have taken the manufacturers claims of what these omnis will do with a BIG pinch of salt!!

 

Regards,

Pav.

Link to comment
Share on other sites

The advice here is exceedingly sound.

 

Any omni-directional "egg-whisk" or "wok" type antenna, for terrestrial TV can never compete with a properly positioned directional aerial, however much amplification the manufacturer introduces.

 

An amplifier can only work with what's coming down the wire, and if that is a weak TV signal mixed up with a lot more weak TV signals and crap, it will always to some degree amplify the crap as well as what you want, (these amplifiers tend to work across a wide spectrum, and often the antennas claim to cover radio frequencies as well as TV).

 

An "omni" antenna has little or no "gain" itself, whereas even a basic "beam" roof-top type antenna will magnify signals very strongly from the direction it is pointed, and, equally important, attenuate those coming from other directions.

 

The rub, as has been said, is stowage when not in use, and also you have to know which way to point it at each mooring, and whether to have the elements horizontal, (used by long distance main transmitters) or vertical (used by lower power localised in-fill transmitters). The trick is to look at other boats, or better still housing, and mimic what they are doing.

 

If anybody says they get good reception with an omni antenna like the Gazelle pr Omnimax, then they are almost certainly in a strong signal area. Around where I live, you haven't got a prayer.

 

Putting any antenna up a 10, or even 6 foot pole, rather than near the boat roof, will almost certainly make it perform better.

Link to comment
Share on other sites

The advice here is exceedingly sound.

 

An amplifier can only work with what's coming down the wire, and if that is a weak TV signal mixed up with a lot more weak TV signals and crap, it will always to some degree amplify the crap as well as what you want, (these amplifiers tend to work across a wide spectrum, and often the antennas claim to cover radio frequencies as well as TV).

 

Putting any antenna up a 10, or even 6 foot pole, rather than near the boat roof, will almost certainly make it perform better.

 

Aye Alan, I agree... I've an Omnimax somewhere around, which has seen service in odd locations over the years, whilst running a TV off an small inverter in the car whilst camping, for catching the F1! I had it on a very long run of nasty co-ax, and about 30ft up a tree in the lakes and managed a watchable picture, but not to a level I'd like to watch every day. As you say, with intentionally poor rejection, they collect all the reflections and rubbish bouncing around.

 

On the boat, we've got a temporary setup of a £9 Screwfix antenna, zip-tied to a mushroom vent. I know I was preaching a bit on a similar thread recently, about using decent quality downlead, but I've run out of PF100 and so this is on some really nasty white coax - and when in our marina points straight at an embankment. Despite that, we get enough signal to drive the Freeview receiver, although the analogue isn't perfectly clean. This contrasts with other long-term boats in the marina with 20ft masts. I suspect since we're very close to the biggest (?, or at least second-biggest) transmitter in the country [sutton Coldfield], a decent signal should be easy to achieve...

 

It's worth noting that [like in the old analogue satellite days], analogue receivers are useful for getting antenna alignment right, as you can see the 'problems' directly in the picture - do that first, and then check the Freeview box afterwards...

 

IMG00417.jpg

 

As you say, amplifiers only have one use. They're there to increase drive over long cable runs and reduce cable losses - and should be mast-head mounted. At the house, we've a mast-head amp driving some long runs of PF100 down to the garage, where there's a set of decent splitters to drive the DVB-T cards in the IPTV server.

 

There's a website somewhere which will show line-of-sight path between any two locations, and shows a view of the height of land between the points on a graph. I'll dig it out. I use it for surveying wireless installations for point-to-point links, but it's useful for TV antennas too.

 

PC

Link to comment
Share on other sites

It really does depend on where you are. If you are in a good signal area, the Omnimax is simply ideal; if you are in a weak signal area, it won't do anything for you.

 

As Pav says for example, around Stourport/Kidderminster an Omnimax gets nothing at all. Even a directional aerial gets virtually nothing unless (as he has done) you mount it in a pole. On the other hand, around here (Milton Keynes) and around most of the East Midlands the Ominmax does a perfectly good job on both analogue and digital signals. Apart from the obvious advantage of not having to point it in the right direction (which can be difficult if you are moored away from other boats and so cannot see anybody else's aerial) is that if your crew want to watch TV while you are moving, an Omnimax will let you do that even on a digital signal.

 

Our set-up gives us achoice of 3 methods: an Omnimax, a very small directional aerial (it's a Labgear set-top Yagi which plugs in on the roof in place of the Omnimax), and a satellite dish. Having recently bought a Freeview digital TV I was keen to make some comparisons on our recent trip. We travelled from Milton Keynes via Fradley, Great Haywood and Autherley Junction to Llangollen then back to Autherley, down to Kidderminster and Gloucester, then back to Stourport and up to Birmingham before heading home. Every night I tried the Omnimax (on both analogue and digital) and for the first part of the trip I got a good signal on one or the other about 60% of the time. Using the technique of scanning with the TV to find a signal (any signal) with the Omnimax and then changing to the directional aerial and pointing it for the best signal on that station before re-scanning with the TV, increased that to nearer 80% of the time. Then once I got past Autherley junction heading south, the Omnimax rarely got anything and even the directional aerial only got a good signal 20% of the time so we used the satellite dish instead. Then once we had climbed back up to the Birmingham level we were back to using the Omnimax with an occasional change to the directional aerial (and just a couple of nights where we had to use the satellite dish).

 

My personal preference is to use the Omnimax, since for well over half the cruising that I do I can use it without the inconvenience of having to point the aerial the right way. As with any aerial, mounting it on a pole would help, but their design isn't ideal for that (note, poly waste-pipe is a perfect fit over the fixed base part). Surprisingly there seemed to be some sort of resonance due to its distance above the roof, which meant that it struggled to get Freeview ITV from the Sutton Coldfield transmitter, although BBC was fine; raising it just a half-inch completely cured that issue so I now have a poly-pipe spacer in there.

 

 

Edited for typing errors - yet again!

Edited by Keeping Up
Link to comment
Share on other sites

This is the site I was thinking of - a bit fiddly to use, but instructions are there...

 

http://www.wolfbane.com/cgi-bin/tvd.exe?MAP=661,936

 

It outputs Postscript, and I know there's a slightly different site somewhere which will output something more useful, but if you've got Acrobat Distiller installed, or Ghostscript/GSView - you can get to a decent format...

 

Here's what it reckons for the marina at Alvecote, to Sutton Coldfield transmitter...

 

sutton-los.JPG

 

So we should be okay! :-)

 

PC

Link to comment
Share on other sites

It's worth noting that [like in the old analogue satellite days], analogue receivers are useful for getting antenna alignment right, as you can see the 'problems' directly in the picture - do that first, and then check the Freeview box afterwards...

So what do we do after 2010 then?

Link to comment
Share on other sites

So what do we do after 2010 then?

I've asked that question in numerous places, including digital TV forums, and NOBODY has been able to give me a good answer.

 

However I've been pleasantly surprised at the effectiveness of the technique that I mentioned in my post above (scan with an Omnimax until you get something, anything, with even the poorest signal, then change to to directional aerial and point it for a better signal and re-scan).

 

Also it should get easier after 2010 because the digital signals will all be a lot stronger, as they will turn up the power after switching off the analogue service.

Link to comment
Share on other sites

Seeing the comments would add our experience -

 

We purchased a Gazelle (seeing that quite a few folks in the marina have them and only one states he dosnt get a good signal.)

 

Plugged in the system last weekend and we have 40 plus channels immediately -

 

Would agree that your location is probably equally if not more important and would do what we did - check with others in the same on how their reception is and make your descion based on that.

 

FYI we are on the souther GU at Aplsey marine - surrounded by 4 story flats...

 

Happy viewing - :lol:

Link to comment
Share on other sites

I get the distinct impression (without staying longer when I get a good signal) that I am looking for a more robust (log) standard directional (possibly attached to something telesopic that doesn't have to lay on the roof when not in use) that can swivel, tilt or twist and send the crew out with a walkie talkie!

Link to comment
Share on other sites

I get the distinct impression (without staying longer when I get a good signal) that I am looking for a more robust (log) standard directional (possibly attached to something telesopic that doesn't have to lay on the roof when not in use) that can swivel, tilt or twist and send the crew out with a walkie talkie!

 

Yes, got it in one. :lol:

Link to comment
Share on other sites

I get the distinct impression (without staying longer when I get a good signal) that I am looking for a more robust (log) standard directional (possibly attached to something telesopic that doesn't have to lay on the roof when not in use) that can swivel, tilt or twist and send the crew out with a walkie talkie!

Either that or a periscope system that lets you look at the TV of the next boat through the curtains - maybe using a rubber sucker to attach the final mirror quietly to the outside of their boat. Of course they might get a bit upset when you point your remote-control at the mirror and change channels though!

Link to comment
Share on other sites

FYI we are on the souther GU at Aplsey marine - surrounded by 4 story flats...

 

Happy viewing - :lol:

Assume you mean Apsley ?

 

You are probably in that lucky position of being so close to the Bedmond transmitter, that you could get a fair picture on a length of damp string.

 

When I lived in Hemel, and had a proper TV antenna installed, it was initially a disaster as it totally overloaded my TVs front end. It took not one, but two in-line attenuators to bring the signal down to the point where the TV could cope.

 

Head up to Tring summit, and try again - you may find it works a whole lot less well.

Link to comment
Share on other sites

I've asked that question in numerous places, including digital TV forums, and NOBODY has been able to give me a good answer.

 

However I've been pleasantly surprised at the effectiveness of the technique that I mentioned in my post above (scan with an Omnimax until you get something, anything, with even the poorest signal, then change to to directional aerial and point it for a better signal and re-scan).

 

Also it should get easier after 2010 because the digital signals will all be a lot stronger, as they will turn up the power after switching off the analogue service.

 

 

Bought one of these little gizmo's from Maplins and it's saved loads of "Left a bit, no, right a bit etc" from SWMBO

 

http://www.maplin.co.uk/Module.aspx?Module...al&doy=24m7

 

 

 

Geoff

Link to comment
Share on other sites

Where do I start with this?? Well here goes.

 

The Omnimax probably has the same gain as a full quarter wave "rubber duck" ground plane - similar to a basic car radio aerial but for UHF TV. These are omnidirectional but only suitable for vertically polarised transmissions. The Omnimax achieves this for both vertical and horizontal signals and may have a little gain - 3dB max I suggest. The most common TV aerial is the Yagi. For a fixed installation a Group A, Group C or Group C aerial is best because of their higher gain characteristic. So, why you may ask are there different groups? Because narrower bandwidth aerials of a given size can achieve a higher gain relative to broadband aerials. Thus, for example, a group A aerial for use in channels 21 to 39 will perform poorly when receiving a signal on group B channel 52. For cruising around type boating a group W wideband aerial covering channels 21 to 68 is required because at sometime or other reception on any channel will be required! A shortcoming of Yagi aerials is their non linear gain across their design range. Typically a group A Yagi will have 3dB more gain towards the mid channels than at channels 21 and 36 - likewise re a group W aerial with a peak around channel 40ish. A log periodic for TV has a flat response the whole UHF TV band but lower gain than a Yagi. I am not aware of any non commercial aerials sufficiently robust for use on narrowboats. Yagis generally have fragile elements and large fragile director arrays all of which are easily damaged. Log periodics removed from the support pole can be laid flat on a roof and are probably the easiest to care for. A low noise - less than 2dB - amplified with moderate gain - around 15dB - preamplifier mounted close to the aerial will give a useful input to a digital tuner however when close to a transmitter the higher power analogue signals may overload the amplifier - just to show unexpected problems may occur!

 

Ok, aerial sorted - maybe. Further info here: http://www.wolfbane.com/articles/tvr.htm

 

Examples of log periodics:

 

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...n%3D4%26ps%3D42

 

http://www.maplin.co.uk/Module.aspx?TabID=...22&doy=24m7

 

however, if running on 12 volts then a DC1 in-line DC inserter or decoupler on this page http://www.satcure.com/accs/page3.htm will be needed but anything above 12 volts may damage the amplifier thus a regulated power adaptor http://www.maplin.co.uk/Search.aspx?criter...rce=15&SD=Y may also be required

 

and

 

http://www.roadpro.co.uk/retail/product_de...BLE&id=1084

 

I hope this helps

Link to comment
Share on other sites

Personally I have found the omni directional aerials on a boat to be near useless.

 

What we have found to be effective is a Log Periodic aerial as can be found here

 

http://www.roadpro.co.uk/retail/product_de...BLE&id=1084

 

We get good analogue and freeview pics most places once you get it pointing in the right direction.

Link to comment
Share on other sites

  • 2 years later...

What is the power consumption of these gazelle aerials with the signal boosters , is the wiring used to supply the power going to be any good for a different bit of kit , radio or extra roof light for instance.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.