Advice Needed UHF aerial spacing of the rods looks odd to me ?

Spiff · Dec 9, 2016

Good evening most knowledgeable gentlemen of the Satellite forum. : )

I have noticed that this is not a satellite aerial as the dustbin lid is missing off the back.

We live in Mullion Cove Cornwall which is located between two cliffs, the transmitter at Redruth perhaps 20 mile away it completely screened.

Out of interest I put up a UHF aerial a couple of years ago on a long pole, with a fully screened preamp, plus low loss coaxial able.

I had to fit another amplifier before the distribution amp in the loft space before it would produce a picture.

It works surprisingly well, but will drop our under certain weather conditions.

The UHF aerial in the images, was given to me when the cottage next door was sold and renovated.

It had been mounted on a pole in the garden, Dorcus the old farmers wife who lived there did not bother much with TV and had trouble with the reception anyway.

If Dorcus should ever read this and see that I referred to her as old I am dead : )

It looks to be a better made aerial than the one we have, so I have been cleaning up the connecting box.

The spacing of the rods which are just clipped on the boom looks odd to me, in that the last three before the dipole are all the same distance apart ?

I have searched online but cannot find a similar one.

Has anyone of you gentlemen a thought on the subject.

God Bless Spiff

jeallen01 · Dec 9, 2016

Spiff

I've got a very similar one in the attic except for the lack of the horizontal elements at the front end (totally overkill here - put it up about 25 years although I'm only about 15 miles from Crystal Palace, but I am glad that I did as I have a large chimney breast in between it and CP and, now, some double Al-foil roof insulation in next door's attic as well after the guy realised that my attic was vastly warmer than his

after installed that insulation in mine. ).

FWIW. I suspect that the front-end elements provide general "tuning" for the specified UHF band (A, B or C/D) and the X-shaped elements behind them provide further gain/selectivity, and also better rejection of opposite (i.e. vertical) polarity signals - given where the previous occupants lived, and now you are, I suspect that anything that improved the signals was beneficial.

OTOH, never seen anything like yours before.

Spiff · Dec 10, 2016

jeallen01 said:
Spiff

I've got a very similar one in the attic except for the lack of the horizontal elements at the front end (totally overkill here - put it up about 25 years although I'm only about 15 miles from Crystal Palace, but I am glad that I did as I have a large chimney breast in between it and CP and, now, some double Al-foil roof insulation in next door's attic as well after the guy realised that my attic was vastly warmer than his after installed that insulation in mine. ).

FWIW. I suspect that the front-end elements provide general "tuning" for the specified UHF band (A, B or C/D) and the X-shaped elements behind them provide further gain/selectivity, and also better rejection of opposite (i.e. vertical) polarity signals - given where the previous occupants lived, and now you are, I suspect that anything that improved the signals was beneficial.

OTOH, never seen anything like yours before.

I find the three closed spaced elements near the dipole strange, it may be just the design ?

When I have finished renovating the connecting box I will measure the signal on the old antenna, then use a spare long pole I have to hold this one near it and compare the signals.

The aerial is guyed so a bit of a hassle to take down, it also has two wind anemometers mounted on it so lots of wires : )

Channel Hopper · Dec 10, 2016

If you can let all know of the distances between the elements near the front end, and any colour of the end caps , somebody will be able to work on the frequencies, though from what I can gauge from the boot sizes , the aerial is a group A, with a high attenuation much beyond 600 MHz.

jeallen01 · Dec 10, 2016

Just had another look at the photos in the cold light of day, and I can see that I was totally wrong about there being horizontal elements at the front end - must have been the effects of it being late at night, and a drink or two, when I posted (think I "misread" the middle photo)! Surprised that no-one picked up on my "deliberate mistakes" :rolleyes:

!

That apart, and that the fact that it is (now obviously!), a vertically polarized antenna, it does look very much like the Band A (albeit with more closely spaced X elements, and so not Band A) one I have in the attic - think I may have the receipt for that somewhere and will take a look for that to see what I bought.

Edited: Sorry, must have binned the receipt in a clearout some years ago - but, IIRC, I put the antenna up in around 1990/91 and so the one in question was probably from around that time.

Channel Hopper · Dec 10, 2016

jeallen01 said:
Just had another look at the photos in the cold light of day, and I can see that I was totally wrong about there being horizontal elements at the front end - must have been the effects of it being late at night, and a drink or two, when I posted (think I "misread" the middle photo)! Surprised that no-one picked up on my "deliberate mistakes"!.

Nobody picks on 'deliberate' mistakes.

(It's upside down by the way)

Spiff · Dec 10, 2016

rolfw said:
Black end caps should mean it's a wideband aerial, have seen a few like that, although it's not a brand I recognise, probably from one of the DIY sheds. The bunched director grouping is used in some makes, like the Triax Unix 52.

If,you're going to go to the trouble of a difficult replacement, you may be better looking at some of the modern alternatives like the

Televes DAT HD BOSS 790

Big, but massive gain and a built in intelligent amp.

Thank you for the reply's, : )

From comments the grouping of the three elements after the dipole is correct.

Looking at one of my images it also has odd spacing after the first couple of elements from the transmitter end, there being a large gap instead of a progressive reduction ?

I will measure as requested and post back.

I am sure we are group B will check again, the group did not change with the switch over from analogue to digital.

God Bless Spiff

Spiff · Dec 10, 2016

Spiff said:
Thank you for the reply's, : )

From comments the grouping of the three elements after the dipole is correct.

Looking at one of my images it also has odd spacing after the first couple of elements from the transmitter end, there being a large gap instead of a progressive reduction ?

I will measure as requested and post back.

I am sure we are group B will check again, the group did not change with the switch over from analogue to digital.

God Bless Spiff

Channel Hopper said:
Nobody picks on 'deliberate' mistakes.

(It's upside down by the way)

I have had a look at two other UHF aerials that I have acquired in the past that were in the workshop loft.

Both had similar spacing.

On unclipping the dipole and one of the directors they have a locating pin on the clip that locates into a hole on the boom, so they have to be in the correct position.

Thank you for all your help and suggestions it has helped me a lot to move forward and check the other aerials plus to discover that the plastic clips that hold the elements have a locating pin.

It should be ok to install as soon as I finish cleaning up and varnishing the PCB in the connecting box.

Some images of our location which according to the transmitter coverage charts is a no signal spot : )

Not a good day weather wise today.

God Bless Spiff

jeallen01 · Dec 10, 2016

Spiff.

Where there a "will" then there's often a "way" to get the signals that you want - that's how I managed to get Capital Radio from London in West Oxfordshire in the 70s - even in Burford in quite a deep valley - (the signals were quite weak then), with very careful alignment and also adjusting the polarity to about +/- 10 degrees from the nominal Vertical "optimum". Same sort of thing "might" help where you are?

Terryl · Dec 10, 2016

Spiff said:
Good evening most knowledgeable gentlemen of the Satellite forum. : )

I have noticed that this is not a satellite aerial as the dustbin lid is missing off the back.

We live in Mullion Cove Cornwall which is located between two cliffs, the transmitter at Redruth perhaps 20 mile away it completely screened.

Out of interest I put up a UHF aerial a couple of years ago on a long pole, with a fully screened preamp, plus low loss coaxial able.

I had to fit another amplifier before the distribution amp in the loft space before it would produce a picture.

It works surprisingly well, but will drop our under certain weather conditions.

The UHF aerial in the images, was given to me when the cottage next door was sold and renovated.

It had been mounted on a pole in the garden, Dorcus the old farmers wife who lived there did not bother much with TV and had trouble with the reception anyway.

If Dorcus should ever read this and see that I referred to her as old I am dead : )

It looks to be a better made aerial than the one we have, so I have been cleaning up the connecting box.

The spacing of the rods which are just clipped on the boom looks odd to me, in that the last three before the dipole are all the same distance apart ?

I have searched online but cannot find a similar one.

Has anyone of you gentlemen a thought on the subject.

God Bless Spiff

Looks to be standard channel spacing to me, and the last 3 are the directors, this help tighten up its receive beamwidth, making it more directional to the front, the more of these you add (to a point) the tighter the beam becomes

Terryl · Dec 10, 2016

jeallen01 said:
Spiff.

Where there a "will" then there's often a "way" to get the signals that you want - that's how I managed to get Capital Radio from London in West Oxfordshire in the 70s - even in Burford in quite a deep valley - (the signals were quite weak then), with very careful alignment and also adjusting the polarity to about +/- 10 degrees from the nominal Vertical "optimum". Same sort of thing "might" help where you are?

I managed to get BBC1 on a 6 meter beam when I lived in North Dakota, it was a Polar shot.(and yes I did have a PAL TV set)

jeallen01 · Dec 10, 2016

Terryl said:
I managed to get BBC1 on a 6 meter beam when I lived in North Dakota, it was a Polar shot.(and yes I did have a PAL TV set)

Must have been a long time ago when BBC 1 was in analogue on the low VHF band - now it's on UHF, so "not a chance" nowadays:mad:

Spiff · Dec 10, 2016

Terryl said:
I managed to get BBC1 on a 6 meter beam when I lived in North Dakota, it was a Polar shot.(and yes I did have a PAL TV set)

That is amazing on UHF, was this only when there was a lift on ?

I assume it was UHF as you mentioned a PAL TV set which would refer to colour.

I had heard of the old VHF 45mc/s 404 line BBC1 transmitter being received in Australia many years ago when a lift was on, but not UHF.

I recall installing the first UHF aerial on the roof of the TV shop I worked at when BBC2 started transitions.

This was in Eastcote Middx, the building was three stories high, so no problem with the signal. : )

We lived for a while in Little Hullton Nr Manchester, it was a high spot.

As well as Winter Hill the local transmitter, we used a rotator to receive HTV from Wales ,Yorkshire TV Emley Moor I think and Midlands TV.

Spiff

Spiff · Dec 10, 2016

jeallen01 said:
Must have been a long time ago when BBC 1 was in analogue on the low VHF band - now it's on UHF, so "not a chance" nowadays:mad:

PAL TV would mean UHF colour ?

jeallen01 · Dec 10, 2016

Spiff said:
That is amazing on UHF, was this only when there was a lift on ?

I assume it was UHF as you mentioned a PAL TV set which would refer to colour.

I had heard of the old VHF 45mc/s 404 line BBC1 transmitter being received in Australia many years ago when a lift was on, but not UHF.

I recall installing the first UHF aerial on the roof of the TV shop I worked at when BBC2 started transitions.

This was in Eastcote Middx, the building was three stories high, so no problem with the signal. : )

We lived for a while in Little Hullton Nr Manchester, it was a high spot.

As well as Winter Hill the local transmitter, we used a rotator to receive HTV from Wales ,Yorkshire TV Emley Moor I think and Midlands TV.

Spiff

I stand corrected (and, PaulR, don't say "You may sit down!" - I know

)

Llew · Dec 10, 2016

jeallen01 said:
Spiff.

Where there a "will" then there's often a "way" to get the signals that you want - that's how I managed to get Capital Radio from London in West Oxfordshire in the 70s - even in Burford in quite a deep valley - (the signals were quite weak then), with very careful alignment and also adjusting the polarity to about +/- 10 degrees from the nominal Vertical "optimum". Same sort of thing "might" help where you are?

When London's Jazz FM actually broadcast on FM, I needed a 5-element VHF aerial high up on the roof to be able to receive it well enough in Cambridgeshire. Alas, Lincs FM started on the same frequency, 102.2, shortly afterwards, and even though being 180° to the north of my location, the excellent directivity of the aerial still picked up this unwanted local rubbishy station.

Solved by leaving the aerial for BBC London stations, and making a small twin whip aerial/LNA combo for Jazz FM and putting it in the garage window pointing to London, blocking Lincs FM by the reinforced concrete garage walls

A single BFG65 MOSFET saved the day...;)

Channel Hopper · Dec 11, 2016

jeallen01 said:
Spiff.

Where there a "will" then there's often a "way" to get the signals that you want - that's how I managed to get Capital Radio from London in West Oxfordshire in the 70s - even in Burford in quite a deep valley - (the signals were quite weak then), with very careful alignment and also adjusting the polarity to about +/- 10 degrees from the nominal Vertical "optimum". Same sort of thing "might" help where you are?

You didn't know about their AM service ? 539 metres originally

jeallen01 · Dec 11, 2016

Channel Hopper said:
You didn't know about their AM service ? 539 metres originally

CH, I knew about the AM service - which was actually pretty poor that far from the transmitter anyway - but I wanted the FM "HiFi" version!

FWIW, the receiver (in fact at least 2, might have been 3, of them in different locations - the other 1/2 being with friends) was an Amstrad 3000 - dirt cheap but actually a very capable FM unit in its day - so nothing exotic or expensive, although I did have to stub-tune the 4-element FM antennas for the best reception.

aceb · Dec 11, 2016

Terryl said:
I managed to get BBC1 on a 6 meter beam when I lived in North Dakota, it was a Polar shot.(and yes I did have a PAL TV set)

Winter 81? Cycle 21 was pretty good with quite a bit of transatlantic F2 upto 55MHz or your A2. Cycle 20 was a bit before my time ;)

aceb · Dec 11, 2016

Looks group A to me, the directors are all of a similar length rather than decreasing in size as I'd expect for a wideband version. Unusual spacing isn't uncommon if someone has spent some time modelling the design to optimise both gain and directivity, the narrow spaced elements near the driven are probably there to help matching as is the small parasitic element in front of the driven, think it's variant of something Antiference used back in the B1 days. A lot of the shed products no longer use coloured end caps even for grouped designs.

I've built a couple of 19 element FM beams which have been optimised for a sharp pattern and flat response, the element lengths vary as you move forward along the boom even becoming longer at some points.

Advice Needed UHF aerial spacing of the rods looks odd to me ?

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