Advice Needed UHF antenna coupling

[Terryl]

One other small problem, at 251 kM from the transmitter you have the curve of the Earth to worry about, also if I read the elevation graph right there is some tall stuff in the way.

Remeber TV signals are line of sight, (mostly) and what I see is mostly a secondary knife edge signal, or tropospheric signals, that's a problem.

 

[Adam792]

One other small problem, at 251 kM from the transmitter you have the curve of the Earth to worry about, also if I read the elevation graph right there is some tall stuff in the way.

Remeber TV signals are line of sight, (mostly) and what I see is mostly a secondary knife edge signal, or tropospheric signals, that's a problem.

I would say the best possible result in the end will be for @zorrin to be able to get the Belgian UHF signal fairly regularly via tropospheric ducting, rather than permanently.

North-eastern France between Paris and the Belgian border is largely quite flat, which might help with that too. I tend to get fairly frequent reception from south east Ireland on FM here in the West of England, at around 330km (205mi) distance. The first third of the path has nothing in the way. Unfortunately the heavy frequency re-use within the UK and Ireland in UHF makes TV much more difficult.

 

[zorrin]

I think that you need a better antenna like that one:

View attachment 145555

I bought it from castorama.fr ( in France )

This is what I received Belgium with in September...
It's really low-end, mounted back to back and without targeting Belgium ...
I know that the two new antennas are not the best but for 20 euros I will already do the test with them.
It's the price and the idea of coupling them that made me decide to use them.

 

[zorrin]

For the coupler, do you have any links for me?
Amazon, eBay...
Or an example to understand the type of product?

 

[Adam792]

For the coupler, do you have any links for me?
Amazon, eBay...
Or an example to understand the type of product?

You can use a splitter in reverse as a combiner (so the two outputs become the inputs for the antennas, and the single input is the output). Then just make sure there is identical cable length between the splitter/combiner and each antenna.

Something well screened is going to be best (full metal casing).

For example -

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www.cdiscount.com

(which looks like it’s for indoor use so may not be suitable unless you can put it in a plastic box - you want to combine the signal from the antennas as close to the antennas as possible).

Or one designed for exterior use -

https://www.bricoman.fr/sedea-repartiteur-ext-sat-ter-2-sorties-1476755.html

 

[ozumo]

DAB discussion moved to a new thread:

Advice Needed - DAB in France

So,DTT airwaves travel in a similar way as TV analogue signals,including occasional tropospheric phenomenons? isthat also valid for digital radio? how can I set a wavelength for digital radio?

www.satellites.co.uk

 

[Terryl]

The problems I have run into in the past, is that some of the cheap 2 way signal splitters are not too well balanced for combining two antennas, one side may have less/more signal loss then the other, this can cause phase problems with the two signals, is one antenna input is slightly out of phase with the other it will degrade the signal, by how much is anyone's guess.

We used adjustable couplers for joining two or more antennas, watching the signal on a spectrum analyzer we adjusted things till all was matched up.

 

[Fisty McB]

IIRC using a splitter "in reverse" to combine two identical aerials fed exactly in phase still won't give you a purely 3db gain due to the power losses inherent in the splitter, especially resistive splitters as opposed to inductive splitters. Having used Fringe UHF-UHF diplexers in the past their insertion loss for the passband was usually given at 1db.

In the days prior to easily receiving BBC TV broadcasts via satellite in non-cabled areas, some of the terrestrial TV aerial setups in many parts of the Republic of Ireland to receive terrestrial stations from NI or Wales were a near art form. I remember when going to the likes of Dublin the size, height & even combos of UHF aerials installed in places grew bigger the further south you went (and west to a certain extent). It went from having a standard 18 element Group A in Cavan town (to pick up Brougher Mountain) to seeing some monster setups in north & west Co. Dublin often involving four very high gain UHF aerials phased together and even spotting a parabolic UHF reflector on the roof of a pub (the sort of aerial Channel Master in the USA used to have as its top "fringe" UHF aerial) - in both cases a decent masthead amp was also being put to use. In one case in Co. Meath I recall a house close to the roadside whose northern-facing aerial was on top of a tower that was at least 15 metres tall - the next time I went past it there were GSM aerials placed below it!

 

[dmaavrigdo]

IIRC using a splitter "in reverse" to combine two identical aerials fed exactly in phase still won't give you a purely 3db gain due to the power losses inherent in the splitter, especially resistive splitters as opposed to inductive splitters. Having used Fringe UHF-UHF diplexers in the past their insertion loss for the passband was usually given at 1db.

In the days prior to easily receiving BBC TV broadcasts via satellite in non-cabled areas, some of the terrestrial TV aerial setups in many parts of the Republic of Ireland to receive terrestrial stations from NI or Wales were a near art form. I remember when going to the likes of Dublin the size, height & even combos of UHF aerials installed in places grew bigger the further south you went (and west to a certain extent). It went from having a standard 18 element Group A in Cavan town (to pick up Brougher Mountain) to seeing some monster setups in north & west Co. Dublin often involving four very high gain UHF aerials phased together and even spotting a parabolic UHF reflector on the roof of a pub (the sort of aerial Channel Master in the USA used to have as its top "fringe" UHF aerial) - in both cases a decent masthead amp was also being put to use. In one case in Co. Meath I recall a house close to the roadside whose northern-facing aerial was on top of a tower that was at least 15 metres tall - the next time I went past it there were GSM aerials placed below it!

Many of these large installations re-transmitted to the local area.

 

[Fisty McB]

Many of these large installations re-transmitted to the local area.

A few were, being used to feed cable distributions systems or "deflectors" - a misleading name to simply describe unauthorised relay stations (though some were leaglised later on). However the vast majority were for private/residential use.

I remember reading about how when cable TV was introduced to Limerick city that there was a system set up on a mountain in northern Tipperary with a 16 aerial arrangement aimed at the Brougher Mountain transmitter site, with a 24 aerial backup aimed at Divis transmitting station that was fed all the way back to the headend via coax cable. Later on the used a link via a microwave distribution system that originated in Cavan where it was a heck of a lot easier to receiver Brougher Mountain TV & FM radio - this microwave system served quite a lot of cable & MMDS providers.

 

[zorrin]

The central Bruxelles/Tour des Finances transmitter looks like it’s only a few kW in power from the info I found, and is V polarisation like Tournai rather than H like Wavre. All are using channel 56.

On the other hand, once the switch to channel 42 happens next year, V pol may be better for you as it would give you better rejection of the H pol transmission on E42 from the Eiffel Tower transmitter.

the planned change from channel 53H to channel 42H and other factors such as my HDMI modulators pushed me to review my installation.
I found this Multi Channel Programmable Filter-Amplifier.
Already it will replace the preamp power supplies.
I now have an adjustable input for the modulators.
I succeeded in blocking channel 42H from the Eiffel Tower.
I have a special entry for Belgium.
and yet another entry for something else.

 

[zorrin]

Hi everyone
small update on my project.
I followed @ozumo advice and the antennas will be one above the other.


I preferred to change the attachment point of the antennas to have a balanced weight between the front and the back to avoid forcing on the rotor.

 

[Terryl]

Be sure to get the right stacking distance from each other, if those antennas are for UHF then about 1/2 to 1/4 wavelength of the lowest UHF channel your looking at, or about 2-1/2 feet from centre to centre. Otherwise they will interact with each other.

 

[zorrin]

View attachment 146296View attachment 146297Hi everyone

Be sure to get the right stacking distance from each other, if those antennas are for UHF then about 1/2 to 1/4 wavelength of the lowest UHF channel your looking at, or about 2-1/2 feet from centre to centre. Otherwise they will interact with each other.

Hi @Terryl,
I was going to ask the exact question
as it is a model called "trinappe" I was not sure.
I planned 80 to 100cm between the bindings.

 

[Terryl]

What is the lowest channel frequency your looking at?

 

[Terryl]

Example:

Using TV channel 30 as the lowest one, it's frequency would be around 566 MHz, so using the calculator below it's full wave length would be 52.96 centimetres, divide that by two or four to get a half or quarter wavelength.

That would be the spacing from the bottom element of the top antenna to the top element of the bottom one.

Frequency To Wavelength Calculator

Find out how frequency and wavelength are connected to each other with our frequency to wavelength calculator.

www.omnicalculator.com

 

[zorrin]

Example:

Using TV channel 30 as the lowest one, it's frequency would be around 566 MHz, so using the calculator below it's full wave length would be 52.96 centimeters, divide that by two or four to get a half or quarter wavelength.

That would be the spacing from the bottom element of the top antenna to the top element of the bottom one.

Frequency To Wavelength Calculator

Find out how frequency and wavelength are connected to each other with our frequency to wavelength calculator.

www.omnicalculator.com

I'm going to put the deflectors of the antennas back to see if it's possible.

 

[Terryl]

Ahh you should as they might not work as good without them, their there for a reason, to reflect the signals back to the driven elements, and improve the front to back ratio.

 

[Channel Hopper]

I'm going to put the deflectors of the antennas back to see if it's possible.

I know you already have the kit, but for a specific range of frequencies you could do worse than try a band dedicated yagi

Triax - Yagi 18 Channel 35-38 (108257) Frequency Range 582-614 MHz Channels 35-38 Elements 18 Gain 15.5 dBi Front To Back Ratio >25 dB Beam Width Hor +/- 17 Degrees Windload 64 N Weight 0.92 kg Dimensions LxWxH 1800x350 mm EAN-number 5702661082573

 

[zorrin]

Ahh you should as they might not work as good without them, their there for a reason, to reflect the signals back to the driven elements, and improve the front to back ratio.

You thought I had removed the deflector permanently.
No, it was to avoid damaging them during the modifications.
It is also to limit the waves coming from the back, very important in my case.