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Log aerials tuned to reject 4G


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Old 07-05-2013, 10:49
Winston_1
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These look interesting. Scroll to page 9.

http://issuu.com/solutionsgroupplc/d...rs?mode=window
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Old 07-05-2013, 10:55
chrisjr
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More details here

http://www.vision-products.co.uk/cat...roduct/V10-28L

And it seems they are doing a range of channel 21 to 60 aerials

http://www.vision-products.co.uk/cat...-radio-aerials
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Old 07-05-2013, 15:24
reslfj
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More details here

http://www.vision-products.co.uk/cat...roduct/V10-28L

And it seems they are doing a range of channel 21 to 60 aerials

http://www.vision-products.co.uk/cat...-radio-aerials
The more energy you can reject before the first amplifier the better.

The lower part of the spectrum i.e. 791-821 MHz is however not filtered much. This is where the 4G/LTE800 base stations will transmit. You will need an additional 4G/LTE filter if you are close to a 4G/LTE800 mast in about the same direction as your TV mast (or just very close to the LTE800 mast.)
These aerials will attenuate the upload signal (832-862 MHz) from a 4G mobile device being close to the aerial. This is potentially a much bigger problem for indoor amplified aerials - as mobiled devices can get very close to such an aerial.

In addition these aerials should eliminate problems when GSM900 is converted to 4G/LTE800 in a few years.

Lars
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Old 07-05-2013, 16:06
lotrjw
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The more energy you can reject before the first amplifier the better.

The lower part of the spectrum i.e. 791-821 MHz is however not filtered much. This is where the 4G/LTE800 base stations will transmit. You will need an additional 4G/LTE filter if you are close to a 4G/LTE800 mast in about the same direction as your TV mast (or just very close to the LTE800 mast.)
These aerials will attenuate the upload signal (832-862 MHz) from a 4G mobile device being close to the aerial. This is potentially a much bigger problem for indoor amplified aerials - as mobiled devices can get very close to such an aerial.

In addition these aerials should eliminate problems when GSM900 is converted to 4G/LTE800 in a few years.

Lars
it seems strange that OFCOM didnt mandate that the upload frequencies for 4G were at the 800-830MHz and that the signal from the 4G transmitters down to the phones, in the 840-870MHz range. I believe its the other way round to what I just said! if it was the way round I have just mentioned, there would be less interference as it would only be the limited power aerials in phones broadcasting close to the TV signals.
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Old 07-05-2013, 18:06
technologist
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if it was the way round I have just mentioned, there would be less interference as it would only be the limited power aerials in phones broadcasting close to the TV signals.
But it would be a lot less predictable ....
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Old 07-05-2013, 20:58
Winston_1
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it seems strange that OFCOM didnt mandate that the upload frequencies for 4G were at the 800-830MHz and that the signal from the 4G transmitters down to the phones, in the 840-870MHz range. I believe its the other way round to what I just said! if it was the way round I have just mentioned, there would be less interference as it would only be the limited power aerials in phones broadcasting close to the TV signals.
Wouldn't work if the phones were not designed that way. This 4G thing is an international arrangement, Ofcom have no say about the uplink and downlink bands.
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Old 07-05-2013, 21:05
iangrad
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Whilst allowing 4g broadcasting is poor planning , I would wait until transmission actualy start before any aerial / filter changes with a tv with selective and well designed tuner you probably will not have any problems
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Old 07-05-2013, 21:46
reslfj
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it seems strange that OFCOM .....
But it would be a lot less predictable .... ( yes, an impossible arrangement /reslfj )
.... This 4G thing is an international arrangement, Ofcom have no say about the uplink and downlink bands.
Indeed - just the idea that the UK is large enough for anything significant by itself - is not of this world.

Ofcom can within limits have a say, by being a team player.

Ofcom was e.g. forced to change its ch31-40 + ch 63-68 plans for digital dividend into the ITU region 1 agreed ch 61-69 (now 800 MHz band) mobile band The UK government could legally decide whatever, but mobile devices were unlikely to be produced for special UK bands.
Get real - the UK has less than 1% of the worlds population.

Lars
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Old 07-05-2013, 22:04
Fly4440
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In what way could an antenna affect 4G signals, or would the 4G signal affect the DTT signal coming in?
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Old 07-05-2013, 23:38
reslfj
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In what way could an antenna affect 4G signals, or would the 4G signal affect the DTT signal coming in?
?

Lars
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Old 08-05-2013, 21:39
kev
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In what way could an antenna affect 4G signals, or would the 4G signal affect the DTT signal coming in?
4G affecting DTT is the problem.

e.g. imagine your DTTV transmitter being a torch flashing more code on a hill a mile away - you can see this clearly (assume it's dark for this analogy ) - however if someone turns a flood light on in your back garden you won't be able to see it any more as it overloads your vision / receiver.

The filters / optimised aerials are therefore designed to see as much of the wanted signal as possible, while at the same time being able to ignore as much of the unwanted signal as possible.

At the bottom end of the band we've had TETRA doing this for years, but this was in a band TV aerials weren't designed to pick up, now at the top end of the band we'll have 4G transmitters sat where analogue telly used to be (or where digital TV still is in my case!).

Found my old Tetra filter the other day - forgot I used to need that, but it did take BBC ONE analogue from unwatchable to just a bit of pattering and fixed Carlton completely (not that we really needed it as the Nottingham TX carried all the post-ITV Digital collapse channels anyway and we could get them okay)
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Old 09-05-2013, 18:27
Fly4440
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4G affecting DTT is the problem.

e.g. imagine your DTTV transmitter being a torch flashing more code on a hill a mile away - you can see this clearly (assume it's dark for this analogy ) - however if someone turns a flood light on in your back garden you won't be able to see it any more as it overloads your vision / receiver.

The filters / optimised aerials are therefore designed to see as much of the wanted signal as possible, while at the same time being able to ignore as much of the unwanted signal as possible.

At the bottom end of the band we've had TETRA doing this for years, but this was in a band TV aerials weren't designed to pick up, now at the top end of the band we'll have 4G transmitters sat where analogue telly used to be (or where digital TV still is in my case!).

Found my old Tetra filter the other day - forgot I used to need that, but it did take BBC ONE analogue from unwatchable to just a bit of pattering and fixed Carlton completely (not that we really needed it as the Nottingham TX carried all the post-ITV Digital collapse channels anyway and we could get them okay)
Cheers mate,
That makes sense to us ordinary folk!
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Old 10-05-2013, 15:25
Justin Aerial
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Hello Winston.
Funnily enough I`ve just tested one of those, the full results are here at Log40 v Log36 aerial test results. And here are the simplified aerial gain curves.
I could only test it up to CH61 (from Waltham) because that`s the highest CH available from the test site. Even that will go at the end of May, then it`ll only be up to CH60 (which is off Belmont). It`ll be interesting to see if I can use any of the 4G TXs once they start up !
Anyway, back to the Log36, which is (or will be) the Log40 mark 2, I tested the Log36 back to back against the Log40. The gain curves are very little different in the A group, the Log36 is slightly in front for most of the B group but falls behind in the C/D group, even up to CH60. At CH61 (which is technically in the 4G band) it was only about 3dB down on the Log40 so that`s very far from negative gain. Obviously I can`t comment on what happens above CH61, it may well keep reducing in gain as the frequency keeps rising, I`ve no idea.
I`d say that if you want maximum rejection of 4G you should use an A or B group aerial if your TX gives you that option, though the A group will reject the 4G rather better than the B group, obviously. Having said all of this I can`t help thinking that a filter would work rather better particularly if your TX broadcasts all its output below CH56 so the filter has room to get its attenuation going before the 4G signals start. I have tested a load of inline filters and the results are very interesting, when I finally get round to putting them on the site I`ll put a thread on here with the link.
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Old 11-05-2013, 16:39
MartinPickering
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Good work, Justin. Have you also tested the Vision V10-28L aerial? It seems likely that it should have a similar gain curve to the V10-040 but with an even sharper fall off around channel 60. That being the case, it will be a direct replacement but a useful 190mm shorter*. However, "the proof of the pudding is in the testing".

*Less likely to be "realigned" by strong wind and less "sag" towards the ground.
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Old 14-05-2013, 09:24
Justin Aerial
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Good work, Justin. Have you also tested the Vision V10-28L aerial? It seems likely that it should have a similar gain curve to the V10-040 but with an even sharper fall off around channel 60. That being the case, it will be a direct replacement but a useful 190mm shorter*. However, "the proof of the pudding is in the testing".

*Less likely to be "realigned" by strong wind and less "sag" towards the ground.
Hello Martin.
I haven`t tested the 28 element version because I`ve decided not to stock those. The Log40 as was (now the Log36) had a bit more gain than the 28 element version, and if gain isn`t so important I`d recommend the DM Log anyway because it`s better made and, most importantly, it can be tilted up easily. My own experience and that of one or two of our customers is that Log Periodic aerials should be tilted up slightly at the front end.
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