Did I buy the wrong aerial

lonewolf2010

I bought a televes dat 75 aerial to try and receive freeview from enniskillen. The only thing I can get is utv very badly. Is it the wrong aerial. Its mounted on a pole 4 meters high above the gable on the house.

lucernarian

We'll all need a bit more info. Whereabouts are you located roughly? Do you have a separate aerial for the Irish channels? Are you familiar with the various dos and don'ts of installing an aerial (e.g. inner and outer conductors must be separate, use properly-wired joiners, don't use cheap "low loss" coaxial cable)?

Does your DAT75 have a built in amp which needs a 12V psu?

Are you picking up UTV on UHF Ch. 25? Are you even getting black and white BBC2 on Ch. 28?

lonewolf2010

Hi

I am five miles east of Tubbercurry Co Sligo. Its a Dat 75 HD Boss. I am using a 12v 100mA power supply with this. The cable is black Coax "RG6 high performance 2.25ghz digital cable, and all connections are f type. I have a saorview box for RTE which work perfect from the same aerial. I have the aerial pointed at 045 degrees which should be bang on as iv checked a few in my area. Utv is on channel 25 not geting bbc at all now.To be honest the picture is so bad its hard to tell.

Sponge Bob

Brougher is Group A channels 2x in the main.

http://www.ukfree.tv/txdetail.php?a=IH350527

Truskmore Digital Group C/D on Channel 54

Wideband Aerials are notorious for working as Groups BCD but not well in Group A too. Brougher Freeview is veeeery low power at present. Analogue a lot more powerful and Freeview will be 20x more powerful after UK ASO

Importantly Brougher has Horizontal Polarisation same as Truskmore DTT but the Curlew Mountains are between Brougher and Tobercurry IIRC or else Arigna mountain in Leitrim

Unless the aerial works pointed straight at Brougher I would personally wait for switchover and Brougher power increase in late 2012 early 2013 or else get a second Group A aerial pointed at it. I doubt Truskmore requires any amplification TBH and certainly won't in 2 years. A variable amp where you can separately up and down amps in certain bands independent of each other sounds better than a wideband amp to me.

Even then you may have to turns amps down in less than 2 years if you amplify either of them.

If you lived somewhere like Easkey you could point a single wideband at BOTH Truskmore and Brougher cos they are lined up....but Tobercurry ( bar up above Tourlestrane or up high out the Boyle end) seems too low to me TBH.

If I was in Coolaney ( high) I might try an all group A solution with the aerial pointed at Brougher and in the hope that I could pick up Castebar Group A off the back of the aerial as a side effect because I am right between those transmitters ...but that is the chancer in me

My 2c FWIW!

lucernarian

There has to be something wrong with the aerial setup. I know I'm on a bit of a height but it's hardly a mountain and I can just about get a black and white picture from Brougher with rabbit ears facing out a window at ground level. In south Louth! Even with the mountains of north Leitrim there should be some sort of analogue picture on all 4 channels in that part of the world. As it stands that installation won't receive Freeview even after the power is turned up fully! Plenty of people can get watchable Divis in Drogheda and even the odd Freeview multiplex despite the Cooley Mountains being a significant obstacle in the path.

Here, how does analogue TV3 look from Truskmore on UHF ch. 60? Is it absolutely perfect or a little fuzzy/grainy? How good is teletext on TV3?

lonewolf2010

Tv3 on channel 60 is perfect ,picture and teletext. Can any one recommend a good group A aerial bearing in mind Brougher is 60 miles away

lucernarian

The problem is that a DAT75 will not offer the best group A performance out there but it will still be hard to beat. 2 or 3 dB at best. That will make the difference between picking up the trace of BBC2 and getting nothing. A big massive Antiference XB16 will not produce watchable pictures assuming all else is equal.

...which it may not be. I found one of those Televes DAT BOSS aerials online, it seems they have an automatic power adjustment feature to pick the best level of output. That may be inadvertently notching down the power on the brougher mountain channels to a level where they're non-existent. (This assumes this BOSS feature has no channel equalisation which is a safe assumption). Truskmore TV3 would be roaring in by comparison, and the aerial could have 3dB gain on ch. 60 compared to ch. 25 which would exacerbate this possible issue.

Blake do some good aerials. Generally aerials will perform better if they're bigger but if you can handle a DAT75 it shouldn't be too much of an issue. A DMX10A could be good or the JBX14WB. Can you get a swap or a credit note on that DAT75 aerial you have?

You could also join two DMX10As or any aerial in a phased array. This of course means using two aerials, the poles to support them and they need some extra attention in setting them up first time. They need to be mounted on a bar and spaced about 5 ft apart from each other.

Sponge Bob

If that theory is correct then maybe pointing NE or ENE ( ie a bit east of Brougher) may reduce the Truskmore signal to a level where Brougher and Truskmore power 'appears the same....and risking Castlebar coming in 'from behind' on channel 22 H instead ....might be worth a punt out of curiosity??

lucernarian

That would help SB if my theory is correct, most aerials have a disproportionate drop in gain as the angle of the incoming signal increases but that ignores side lobes etc. Also, the disporportionate drop in gain wouldn't be "disproportionate" enough to make a big difference I feel.

Sponge Bob

But we are sending him up a ladder out of interest and lets be clear about that , I reckon Brougher is a waste of time till they boost the Brougher ( and Truskmore) signals in late 2012 or early 2013 and thereby allowing a proper fine tuning.

A contract c/d aerial ( meaning bog standard) pointing at Truskmore and a better quality band a pointing at Brougher with a variable gain amplifier like so may be best.

lucernarian

If only there were variable gain grouped amplifiers out there. A group A will still pull in okay Truskmore, such would be the strength of Truskmore in that part of the world. That will end up being boosted on the brougher mtn aerial along with the wanted signal, and the grouped combiners will have out-of-band rejection of only 20 or 25 dB in a worst case scenario, from the specs I've seen. When that's combined with a C/D contract, that could lead to a ghosting problem but it won't be relevant for saorview receivers, working on DVB-T as they are.

And yes, the turning of the aerial would be a shot to nothing. This problem won't be easy to fix without a pro on site and perhaps it would be worth a €100 to get the aerial setup right or at least be told what the exact problem is.

Sponge Bob

It will be worth hiring the pro installer if it can't be sorted in 2012 or 2013, for now they should install a Freesat rig instead of Brougher seing as there will be no extra channels over Freesat till then.

lonewolf2010

Thanks for the help.
Iv ordered a dx10 so I will have another go next weekend when it comes. I have freesat all ready, am only doing this out of interest.

Galway

To_be_confirmed wrote: »

If only there were variable gain grouped amplifiers out there. A group A will still pull in okay Truskmore, such would be the strength of Truskmore in that part of the world. That will end up being boosted on the brougher mtn aerial along with the wanted signal, and the grouped combiners will have out-of-band rejection of only 20 or 25 dB in a worst case scenario, from the specs I've seen. When that's combined with a C/D contract, that could lead to a ghosting problem but it won't be relevant for saorview receivers, working on DVB-T as they are.

And yes, the turning of the aerial would be a shot to nothing. This problem won't be easy to fix without a pro on site and perhaps it would be worth a €100 to get the aerial setup right or at least be told what the exact problem is.

There ARE variable gain grouped amps - Johannson have some - the 7421 or the 7451. The 7451 has 4 inputs- UHF 21-23/UHF 42-69/Band 3/Band 2 (FM). The gain on the UHF inputs is variable 25-40 db, on Band 3 its 10-30 db and FM is fixed at 12 db. . The 7421 has 3 inputs - 21-38 and 42-60 on UHF with variable gain, 20-25db and Band 3 - 8-28db You could also use a variable attenuator to lower the gain below 20 db. It seems that the Truskmore signal wont require amplification as you dont want to end up with too much signal.

As stated, a good high gain group A is essential for Brougher, I suggest the Hirschmann FESA 817-37, though I am not sure if these are still available. Also, note that DTT from Castlebar is on channel 22, co-channel with BBC1 NI analogue from Brougher. As was already mentioned, don't expect much from DTT from there until UK and IRL ASO. The current DTT power from Brougher is very low and is not even presently receivable in parts of the actual service area.

lucernarian

I should have clarified, I have no reason to think there were no grouped amplifiers anymore other than a lack of them on some supplier websites, the ones that deal with more than trade at least. In any case, the OP will probably not have any access to the likes of vanjak.

But a variable amp between 25dB and 40dB? Even 25dB can often be too much for some setups.

lonewolf, can you pick up anything from Saorview on Ch. 22?

Those hirschmanns have a great reputation but they seem very hard to come by.

Sponge Bob

I vaguely remembered a wise piece by Galway on variable gain but I could not find it...think it was about somewhere in the Ballyhaunis Tuam area where a strong Band C/D Maghera and a weaker Castlebar and/or Tonabrocky ( both Band A) were an issue. Thank God they showed up again to post the same information!

After we go fully digital in early 2013 latest Brougher will be group compatible with a number of western Transmitters. Castlebar Ch22 Dooncarton Ch27 and Tonabrocky Ch26.

A high gain directional aerial on a mission to pick up Brougher Freeview HD could well pick up one or other of those transmitters depending.

When RTE activate their second mux then things will become more complex because Band A wil become rather cluttered at that point in much of Connacht. However the main transmitters in Connacht, ie Cairn Hil, l Maghera and Truskmore will always be C/D and should not be much of a problem.

lonewolf2010

No I dont seem to be picking up anything on ch22.

Ok my new plan is take down dat 75 and put up old Triax hg10 and point towards Truskmore for Soarview as this was the original setup which worked fine and its a lot smaller.

Im also going to mount the dx10a on the same pole and point towards Brougher and hopfully at least pick up analogue for now.

I have an old proception 27db low noise uhf preamplifier, and a 12v power supply. Will this be ok to use with the dx10a.

What sort of diplexer would you recommend.

Ps Dat 75 hd for sale

Galway

To_be_confirmed wrote: »

But a variable amp between 25dB and 40dB? Even 25dB can often be too much for some setups.

.

As I said: the Johansson masthead amp model 7421 has 3 inputs - 21-38 and 42-60 on UHF with variable gain, 20-25db and Band 3 - 8-28db You could also use a variable attenuator to lower the gain below 20 db.

Also ALCAD manufacture a masthead amp (AM-113) which has variable gain adjustment 9-24db, with two UHF inputs. Unfortunately these inputs are not groupised so you may well need a group A filter connected between the aerial and the amp to block all but group A signals. Alternatively, you can diplex the two aerials after amplification of the group A channels. PM me for suitable group diplexers for these channels. Truskmore should not require any amplification for DTT at your location, doing so may produce too much signal which can be as bad as not enough!

Tonabrucky is very unlikely to cause any problems with DTT from Brougher Mt. Although it is broadcasts on channel 26, its a low power transmitter designed to serve Galway City and the polarisation is vertical. Analogue signals from Brougher don't make it in to Galway City although they can be receivable at a few high locations in the east and north east of the county, such as Kilconnel nr. Ballinasloe. However, I can get a very good signal from Tonabrucky some 32 km north of this relay, using an Antiference XG9 group A aerial (without any amplification). Only Castlebar on channel 22 is at present likely to cause any problem at Brougher and that only on analogue BBC 1 NI.The Brougher DTT allocated channels are : 23, 26. 30, 33, 34. Note that use of channel 22 is to be discontinued after ASO in NI.