Freeview in Mullingar

mullingar · 08-03-2004 8:12pm #1

I have freeview in mullingar

I recieve from Brougher mountain:

Mux1 90% Always perfect
Mux2 50% Rarely breaks-up
MuxA 20% Cant See
MuxB 20% Cant See
MuxC 70% perfect
MuxD 70% perfect

To see what each mux transmits see: http://www.digitalspy.co.uk/terrestrial/mux/

Mux A&B are suffering interference from Mount Leinster which transmit TV3/TG4 on these frequencies ch23/26. Mullingar sits nearly exactly half-way between these two transmitters, so I will need to spend a lot of money if I wanted to get Mux A & B, and I could not be arsed!

As you can see Mux A is for this new TUTV Pay service on FREEview!, so no loss (except for ch5), and Mux B has a lot of radio on it, no loss either!

My aerial is:

2 x Triax 100 Element Group A
1 x Televes 5006 Active combiner (30dB)
1 x Cheap UHF aerial for Cairn Hill (RTE)
1 x Triax UHF/UHF combiner

Pic: http://f1.pg.photos.yahoo.com/ph/afarrellie/detail?.dir=/65bf&.dnm=ea18.jpg

If anyone has any questions on where I got my stuff, email me.

Andrew

Smeagol · 09-03-2004 2:25am

What interests me, hows the difference in signal strenght between only one triax100 and two of them.
I suffer from similar problems, with Castlebar coming in strong on E26, E29 and E33. Mux1 is the only one I can pick up with my Hirschmann 817 N37 Gr.A + two Triax masthead amps on a 14m (40ft) mast. With an extra 6m to be added next month.:)
TXs: Technisat DigiPal1 (mobile) and Goodmans GDB3

Delboy5 · 09-03-2004 1:31pm

Mullingar,
What make\model digital set top box do you use to receive freeview !? I live in monaghan, bout 3/4 miles from the fermanagh border and am wondering if i could receive freeview using my existing roof aerial ! At the minute i get all the standard irish and uk channels and even get channel 5, its a bit snowy but watchable !
Just wondering if some of the digital set top boxes are better for picking up signals than others.

watty · 09-03-2004 1:58pm

not really.

The most important things in decending order is
1) Height
2) Good Aerial array
3) very low loss good sheild down lead (Perhaps Satellite Cable)
4) Low noise Masthead amp. Small noise figure more important than gain. The gain is just mostly to compensate for downlead loss (18db perhaps). Too much gain simply amplifies noise and co-channel interference.

The gain of the masthead amp easily compensates any variation in sensitivity.

To reduce noise pickup effect in the cable I have approx 6 to 12dB too much gain in masthead amp and then an attenuator at the bottom of cable / tuner end. This reduces any noise injected by the power supply as it is after the PSU for the mast head amp.

Smeagol · 09-03-2004 2:28pm

If you pick up FIVE, it should be the Divis(Belfast) transmitter. From my experience if you can get a snowfree picture on BBC2 and a 100% working teletext, you should get Freeview aswell. (if from a main Tx., not a relay).
I made tests with my two receiver compared to a Triax with Setpal technology, and there was actually none. I've heard somewhere though that the new Echostar (£51at Sainsburys) has an even more sensitive tuner than the setpal boxes.
@Watty
So, could there be an improvement with two high gain aerials instead of one?

Delboy5 · 09-03-2004 2:56pm

Thanks Guys,
I actually dont have a clue bout Aerial arrays or shielded cables or anything very technical in this area.........was just wondering if there was any way of knowing if i could receive freeview without buying a receiver, just have to chance buying one and see what happens i suppose ! I actually live in a block of flats and so the aerial is located quite high, probably explains why im able to get channel 5.
Thanks anyway.

watty · 09-03-2004 3:52pm

A yagi for size has best gain really, and more as you make it longer. Overall boom length is more important than actual number of elements. A so called 52 or 100 element aerial may really be 13 or 25 elements anyway.

Once you get to two wavelengths (At 600MHz UHF, about 50cm x 2 = 1m) the extra gain as you make it longer drops off.

So to get more gain, the answer is multiple aerials about 2.5 or 3 wavelengths long.

But they have to be identical.

The signals need combined in a very accurate combiner (Hybrid) with IDENTICAL lengths of coax.

The aerials must be identically affected by the mast and brackets and indentical disitance and angle to transmitter or signals cancel instead of adding.

Two aerials isn't too hard to match.

Four (A quad array) isn't impossible.

For various reasons, doubling the amount of aerials each time to get more is the best system. (2, 4, 8 , 16).

For very large gain a Dish is better. There is a catch. Dishes work worse at lower frequency (UHF TV) than high (MMDS, /WiFi, then C Band Satellite then KuBand).

A dish with 40dB gain at satellite frequency may only be 14dB gain at UHF.

The gain of a dish increases with area, or square of diameter "for ever" essentially.

The highest realistic gain of a Quad Array (four big Yagi) might be 26dB when real life losses are considered.

A Dish can use wider mesh as the frequency is lower, hence Sky dish is very fine mesh, MMDS dish (22dB gain typically) like rabbit cage wire and UHF can use fence mesh wire on wooden or metal frame.

A 2m size dish will be slightly better than the best quad yagi. Much better than a poor one.

A 4m size dish is like FOUR x quad arrays of Triax 100! (Which would be impossible to match).

The aerial at the focus of the dish (instead of MMDs aerial or Satellite LNB) can be a simple set-top dipole with one reflector and one or two director (see if removing one makes it better) pointing into dish, i.e. the back of aerial faces the transmitter.

There are other kinds of aerials. The RSGB VHF/UHF handbook has a representative selection of designs.

The other problem with a Yagi, is as it gets longer it is narrower band. A quad array of high gain Yagi may only cover 3 channels in a group.

A dish is essentially wide band, getting better as frequency rises. A Dish with a suitable low gain / wide band aerial at focus can cover entire UHF band.

Also yagi has "lobes" of high sensitivity even at points to rear. In a quad array the vertical and horizontal spacing (and even deliberate forward offset) can reduce or move sidelobes or reverse direction gain.

A large dish (2m) has almost no gain in reverse direction and if a perfect parabolic curve with aerial at focus, no side lobes at all.

As aerial gain is higher the accuracy of pointing it is more important. A 40dB gain aerial system will pick up NOTHING at all, with a 2 degree pointing error! (Horizontal or vertical)

Accuracy of the shape of a dish needs to be better than 1/10th wavelengh, i.e. about 1.5 to 2mm at Satellite TV and only 50mm (5cm) at UHF TV. C Band Satellite is about 1/2 way in frequency between UHF TV and Sky Satellite TV (Ku band), which is why a home made Sky Dish will likely not work (not accurate enough) and a 10m C Band dish might.

Smeagol · 09-03-2004 6:37pm

e.g. Dish
But is it possible to put up a dish like that without sight to the Tx (in my case Brougher or Divis), because I have plenty of trees blocking, thats why I had to put up such a high mast.
And finally, do you know where I can find some input on how to make such a monster dish? I have a 180cm channel master dish and will have my first field tests next week.

mullingar · 09-03-2004 10:21pm

I have a Triax Setpal & philips 1500 , setpals are known to be one of the best tuners out there, well as of 6 months ago. The setpal IS more sensitive that the philips (in my case)

Here is a very good site that tell you a lot about stacking aerials :

http://www.atechfabrication.com

It was done in the USA, but give a good clue about DTT transmissions and stacking aerials

Here is a site that has good info on aerials & cable etc:

http://www.geocities.com/toddemslie/UHF-TV-DX.html

I got my setpal & triax gear from Burns Aerials in Templogue, and the Televes stuff from a crowd called Agency Trading in Blackrock.

watty · 10-03-2004 9:30am

TO compare like with like, the dish needs to be at same height.

The Line of Sight issue is no more critical with dish vs Yagi aerial. It is as you move to higher frequency that LOS is more important. I got 6km through trees with video senders (10mW at 2400MHz) using MMDS style / size mesh dish.

There is a REALLY big mast and mesh dish on Nenagh / Portliose rd (N7), I forget where, on Left as you head toward Dublin.

It is MUCH harder to stack 8 aerials properly than have a dish with same gain.

But a Dish has more wind loading (even fence mesh!).

Build a heap of rocks / rubble / stones, with vertical pole through . Cover with sand.

Cut piece of wood in parabola shape (F/d I'll look up).

Push it around the mound to get the shape.

Cut triangles of mesh and lace / tie all the edges using mound for shape.

Cut more bits of wood like first from marine plywood and mount on a marine plywood "hub". About 8 pieces arranged in octagon.

Staple / nail mesh on.

Mount on a 4" pole in about 4ft cube of concrete base with steel cable guys to top of pole etc....

90ft is a good height :-) (if you have a lattice tower mast!)

(20 ft is more achievable)

mullingar · 11-03-2004 6:37pm

The F**KING WIND bend my aerial, F**king bastard.

Smeagol · 11-03-2004 8:15pm

Sorry to see that, I've been lucky so far. Have to clean my sat-dishes though every 3h, heavy snowstorm all day.

Galway · 11-03-2004 11:37pm

hi mullingar.

Sorry to see what wind did to your fine array – triax unix 100s I notice.

I have a unix 100 gr B with 26db gr B fringe masthead pre-amp on 16 foot pole.

Receive irish terrrestrials on UHF (Maghera messy with rte 1 and net 2 on VHF bIII).

Signal good on ch 40, 43 and 50 but get diagonal patterning on TV 3 ch 46 – but signal level seems fine. Tends to disappear in very frosty still weather but not always. Cairn hill about 100km away but on 800kw power of course.

Do you get this patterning too as you are in the service area?

I have noticed it in Limerick (woodcock hill) on ch 45. But Tv 3 is always very clean on ch 66 from maghera and 63 from truskmore.

I have a unix 100 gr A which receives UK channels from Balla deflector in mayo (variable quality) and RTE 1 Net 2 and TG4 come through from castlebar (no tv3 from there though)

I cant seem to get rid of it. Any thoughts? I need clean Tv 3 signal but don’t want to combine grps A B and C/D. Cant understand why Cairn Hill not giving clean TV 3 signal on ch 46.

mullingar · 12-03-2004 12:00am

Galway,

which side of galway are you??

Am I correct in saying triax GpA for a deflector, and triax Gp B for Cairn Hill??

Have a look at:

http://www.geocities.com/Broadway/7225/tvch.html

It tell you all the local 'fill-in' transmitters

Mullingar

Galway · 12-03-2004 12:04am

yes spot on the deflector is largan hill at balla co mayo chans 21, 27, 31 and 35 cbar comes in on 23, 29,33.

so what about cairn hill tv 3? u have the patterning? its not the masthead amp

Galway · 12-03-2004 12:06am

oh yes am on the galway side of tuamland quite high, tuam in a dip we can look down into it

mullingar · 12-03-2004 12:07am

TV3 was always perfect, even NOW for some strange reason as none of those aerials are pointing at a transmitter (in pic its due right for cairn hill)

Galway · 12-03-2004 12:12am

maybe then as it is the strongest the 26 db gr B amp is over amplifying it hence the patterning.if i unlplug the power supply, TV 3 still can be seen but the others dissolve in to snow,suggesting that its the strongest of the 3 from there? what is weakest ur way?

mullingar · 12-03-2004 12:16am

With that array I had all 8 stations perfect, no snow/haze or anything like that.

Is there no a local relay in your area for ch1-4 on UHF???

Here is another site to try:

http://www.wolfbane.com/articles/eitv.htm

Galway · 12-03-2004 12:20am

nope main tx is maghera co clare.only tv and tg4 on uhf ch 666 and 68 (very clean sigs) but ch 68 drops off rapidly elsewhere.

Cbar on uhf bu tno tv 3. truskmore only tv and tg4 on uhf like maghera.

Cairn hill is the only option, I have good aerialand high pole so should be perfect no? wonder waht tv 3 prob is all others are fine.

mullingar · 12-03-2004 12:27am

If you look at the above link and do a CTRL+F search for 46, you will see all the transmitters that could intefere with this frequency,

apart from that I would say that you are over-killing the signal, 800kW is a HUGE power output from cairn hill

Galway · 12-03-2004 12:37am

there is nothing nr enoughpor with enough power to interfere with ch46 achilllisted as 20km but tv not provided from that site. It cant be presely in wales at this distance and in all weathers. must be cross mod as tv3 is the strongest of the 3 from cairn hill.

remember im outside the service area and the cairn hill transmission drop off rapidly onnce u are - its terrible in tuam and claremorris forexample but is strong in mountbellew and moylough and athenry further east from me. my aerial faces north east, maybe that beam isnt as strong as one your side and tx aerial config is different? also cairn hill is on a low site 900 ft compared to maghera, mt leinster and truskmore

mullingar · 12-03-2004 12:42am

Cairn Hill transmit every channel @ 800kw.

I was looking up www.irish-tv.com for a solution and I came across a link that said WAGON, curious as we all are, its the music,cast and end credit film of Wonderly Wagon!!!! memories!!

Alas you problem, right, what electronics are on your mast? inc gain/combiners etc...

mullingar · 12-03-2004 12:51am

here is another link for you (Galway) to look at:

http://www.wolfbane.com/articles/eiacmap2.htm

Galway · 12-03-2004 12:53am

theres a 26 db group B "super" fringe masthead amp the triax 100 gr B is combined with the unic 100 grA using a fringe a-e combined with power thru on both legs - the grp a is ampified separately using televes 31 db masthead amp. tv 3 prob still there BEFORe aerials are combined.i think im overloading tv 3 sig or it could be breakthrough from the nearby galway bay fm tx 5 miles away - can be seen from house at ground level?

mullingar · 12-03-2004 1:07am

It could be the gain of your system, try removing the Grp B amp from the system and take out the screw that sends through power to it too from your combiner.

You say that castlebar doesn't transmit TV3??

i found this:

Castlebar 29 33 26 23 A H 20k A=Gp A, H=Hor

(this info might be wrong)

Booms · 12-03-2004 9:26am

HI Galway,

It's probably a silly question, but have you tried switching off any modulators you might have on your VCR/Satellite boxes to see if the interference disappears?

Delboy5 · 12-03-2004 10:27am

I tried getting freeview last night, live in county monaghan close to the fermanagh border. Using a Digifusion STB but only temporarily as i seen a number of complaints bout these on the web, thinking of picking up an Echostar STB as ive heard that these are supposedly one of the most sensitive !?
From Mullingars weblink earlier im receiving Mux 1, Mux B and Mux D but thats all, the reception was ok but not great, last night was quite windy\cold outside..............would this affect it !!??
According to the STB it says im picking up my signal from Divis, anyone know why im not picking up any of the other Muxes !? Is it cos the STB isnt sensitive enough or cos im so far away from Divis !?
As im a lot closer to Brougher mountain than Divis, would it be a fact that if i pointed the aerial towards there id receive many more channels !!??

Galway · 12-03-2004 10:42am

tv 3 is not transmitted from any relays except collins barracks cork and woodcock hill limerick. the cairn hill signals need amplification but maybe by less than 26 db. so just using any aerial is not sufficient. i have fed the signal direct to the tv and it makes no difference. bloody wind seems to have knocked motorised dish off arc too. i think it was worst we have had this year? south easterly blowing right onto dishes

mullingar · 12-03-2004 12:31pm

Galway,

Maybe just get a VHF aerial (a cheap one) and a VHF/UHF combiner at the lower end of your mast, and point it to you 'local' main transmitter.

I am out of ideas as it has to be one of these faults:

1. Too much gain/ too big aerial
2. Co-channel inteference, either from another transmitter or from inside your house
3. Mulitpathing
4. Water in down-cable
5. Pray for inspiration

Good luck

Mullingar

Delboy,

The signal from Brougher ORIGINATES from divis and is more or less a relay foir divis

Galway · 12-03-2004 3:04pm

by multipathing do u mean ghosting? anyway there's no problem with the rte 1 and 2 so no need for vhf at all. btw if i use an wideband unix 100 in loft with amp the picture is grainier but no patterning!

Freeview in Mullingar

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