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#31
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In article ,
Jeff Layman wrote: On 28/09/18 04:21, Bill Wright wrote: On 27/09/2018 23:40, Woody wrote: On Thu 27/09/2018 22:32, tony sayer wrote: https://cpc.farnell.com/antiference/...og-periodic-f- conn/dp/AP01931 I'm sorry to have to disagree in part Tony but there are two things in the CPC advert that rancour. It says 'highly directional' which we know a LP isn't (per BW's contribution earlier) Logs have a reputation for being highly directional because the front-to-back and front-to-side ratios are very high. However the main front lobe is actually very wide, so the aerial offers little protection against interference coming from a quite a few degrees either side of the tx direction. The reputation for good directivity comes largely from the analogue days, because it's unusual for a reflected signal (the cause of ghosting) to come from the front quadrant. (It can happen though, especially in cities with high rise flat-sided buildings. It was for instance a major problem at a lot of the sites I worked at in central London.) The wide forward lobe shouldn't put anyone off using a log periodic. To generalise wildly, transmission stations are often on high ground, which means that co-channel interference from further away in the same direction is unlikely to make the trip over the hill. If the directivity of a log periodic isn't enough it helps a lot to mount two side by side and combine the outputs. and in this country what is the point of any aerial that can only be mounted horizontally in its basic format? It's odd that you have to pay extra for a VP clamp. Most logs are designed so they can be installed both ways. I can only think someone was unaware the the UK uses VP! What main transmitters other than Rowridge use HP? I could look it up but it's quicker to use this newsgroup! They don't. However some 1500 relays do. And Rowridge is mainly HP. -- from KT24 in Surrey, England "I'd rather die of exhaustion than die of boredom" Thomas Carlyle |
#32
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On Thu, 27 Sep 2018 23:40:32 +0100, Woody
wrote: On Thu 27/09/2018 22:32, tony sayer wrote: https://cpc.farnell.com/antiference/...og-periodic-f- conn/dp/AP01931 I'm sorry to have to disagree in part Tony but there are two things in the CPC advert that rancour. It says 'highly directional' which we know a LP isn't (per BW's contribution earlier) and in this country what is the point of any aerial that can only be mounted horizontally in its basic format? Normally CPC are pretty good at what they sell but I think they've slipped up with this one! If it does the job, it does the job, and he says that it does, so I guess it does. Most TV coverage will be from main stations, which I understand are all horizontally polarised, so that will be the most frequent requirement. It makes sense not to include an accessory with every aerial that only a few purchasers will need. For what it's worth, I bought a LP aerial long ago when I lived in a top floor London flat. I had it ceiling mounted in a bay window and could swivel it through quite a wide angle, while watching the picture, so a good opportunity to examine the directional properties. The window faced away from CP so the best reception was from Hannington, although it was further away. There was a very small range of angles with perfect reception, and lots of ghosties outside this, so it did appear to be very directional, just as the textbook (or perhaps it was a Wireless World article) said. Rod. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#33
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On 28/09/18 08:25, charles wrote:
In article , Jeff Layman wrote: On 28/09/18 04:21, Bill Wright wrote: On 27/09/2018 23:40, Woody wrote: On Thu 27/09/2018 22:32, tony sayer wrote: https://cpc.farnell.com/antiference/...og-periodic-f- conn/dp/AP01931 I'm sorry to have to disagree in part Tony but there are two things in the CPC advert that rancour. It says 'highly directional' which we know a LP isn't (per BW's contribution earlier) Logs have a reputation for being highly directional because the front-to-back and front-to-side ratios are very high. However the main front lobe is actually very wide, so the aerial offers little protection against interference coming from a quite a few degrees either side of the tx direction. The reputation for good directivity comes largely from the analogue days, because it's unusual for a reflected signal (the cause of ghosting) to come from the front quadrant. (It can happen though, especially in cities with high rise flat-sided buildings. It was for instance a major problem at a lot of the sites I worked at in central London.) The wide forward lobe shouldn't put anyone off using a log periodic. To generalise wildly, transmission stations are often on high ground, which means that co-channel interference from further away in the same direction is unlikely to make the trip over the hill. If the directivity of a log periodic isn't enough it helps a lot to mount two side by side and combine the outputs. and in this country what is the point of any aerial that can only be mounted horizontally in its basic format? It's odd that you have to pay extra for a VP clamp. Most logs are designed so they can be installed both ways. I can only think someone was unaware the the UK uses VP! What main transmitters other than Rowridge use HP? I could look it up but it's quicker to use this newsgroup! They don't. However some 1500 relays do. And Rowridge is mainly HP. I have always used HP, as with VP Com7/8 aren't transmitted. But they disappeared on my HP group A yagi with the frequency changes a few months ago, which is why I am looking at a new log periodic (mainly for BBC4 HD). -- Jeff |
#34
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On 28/09/2018 08:25, charles wrote:
What main transmitters other than Rowridge use HP? You mean VP I could look it up but it's quicker to use this newsgroup! They don't. However some 1500 relays do. And Rowridge is mainly HP. Bill |
#35
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On 28/09/2018 13:56, Bill Wright wrote:
On 28/09/2018 08:25, charles wrote: What main transmitters other than Rowridge use HP? You mean VP I could look it up but it's quicker to use this newsgroup! They don't. However some 1500 relays do.Â* And Rowridge is mainly HP. Bill Glad you posted that, I was getting confused. I thought that Rowridge also used VP because the sea can have an influence on the HP signal under some freak weather conditions ?. |
#36
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On 27/09/2018 18:44, Bill Wright wrote:
On 27/09/2018 17:26, wrote: Wow - many thanks for the variety of helpful responses. Following Bill's recommendation I’ve been in touch with ATV today - I've photographed the entire installation and sent the images along with questions for Justin tomorrow with a commitment to buy any equipment they suggest to solve the immediate problem and bring the installation to the best possible situation. The knowledge that ATV (and companies like them) provide is essential for people like me, I’m keen to support them even though B&Q etc may be cheaper. Martin B & Q aerials are ****e. Bill Are they more ****e than Labgear though ? |
#37
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On 28/09/18 19:58, Andrew wrote:
On 28/09/2018 13:56, Bill Wright wrote: On 28/09/2018 08:25, charles wrote: What main transmitters other than Rowridge use HP? You mean VP I could look it up but it's quicker to use this newsgroup! They don't. However some 1500 relays do.Â* And Rowridge is mainly HP. Bill Glad you posted that, I was getting confused. I thought that Rowridge also used VP because the sea can have an influence on the HP signal under some freak weather conditions ?. It's because of possible interference from French transmitters. Much more information at http://www.aerialsandtv.com/rowridgetx.html -- Jeff |
#38
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On 28/09/2018 19:58, Andrew wrote:
Glad you posted that, I was getting confused. I thought that Rowridge also used VP because the sea can have an influence on the HP signal under some freak weather conditions ?. It's because there's some Froggie HP stations on the same channels. The idea is to protect against interference. But who's going to put up a VP aerial when two muxes are HP only? Bill |
#39
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On 28/09/2018 19:59, Andrew wrote:
B & Q aerials are ****e. Bill Are they more ****e than Labgear though ? It's a different type of ****e. Bill |
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