Even if you use it as a way of just getting a dish installed it probably not a bad deal.
Having said that, the attraction of a DIY dish install is the choice to have it somewhere other than the sky installers mandated "two drunks high" on the front of the building option.
that to sky.
You are totally missing the point I was trying to make.
If any of the CAI approved antennas are log periodics, then the statement that all CAI approved antennas have baluns is erroneous.
I made no implication as to the value of something being CAI approved.
OK by whose standards? >>And anyway, some of the log period antennas are "better" quality than >>many cheap and nasty Yagi-Uda antennas. > > And vicey verser;)..
Indeed that is possible but since log periodics are a rather specialist item, I would be interested in your providing an example of a particular brand of log periodic antenna being of inferior quality to some of the poor quality Yagi-Uda design antennas which are sold.
Perhaps the log periodic model sold in Maplins?
On Wed, 04 Mar 2009 16:49:52 +0000, charles wrote: > The one the BBC designed for use at transmitters was very much larger > than any of the ones sold for domestic use. I do know that the BBC one > worked as designed.
When the currently non digital relay sites go digital, will they be removing the fourth log periodic receiving antenna (I think they use one for each network do they not?) and then selling them all off?
Or will they be left in place as a spare backup?
Well spotted; I'd never noticed that- FSFS has approx. 20 less TV stations, but 5 more radio stations, than POWF.
Even though it is obvious from the photograph that the Log 40 has more elements than the DM Log Periodic?
On Wed, 04 Mar 2009 16:51:54 +0000, John Rumm wrote: > Anyone have any comments on what is out there for people who buy generic > non sky and non freesat boxes?
Much better quality programs on Arte and the German PSB stations than the ratings chasing junk with which the BBC fill most of the schedules of BBC-1, BBC-2, and BBC-3.
Where there are multiple logs, the combined output of all four transmitters is normally fed to all of them. The radiation pattern, and therefore service area of the relay station is shaped by the manner in which the RF is applied to the logs within the array, and their relative proximity to each other.
Further reading:-
It's interesting that both Martin at Satcure and Justin at ATV claim higher forward gain figures for the Vision 40 over a standard Log. I know Justin carries out his own testing and I wonder whether the extra gain of the Log
40 exceeds the 1dB figure that's being bandied about?
I didn't think it was a simple as that. Most relays do not have 4 receiving aerials. Only those with reduced incoming feeds use more than one, and for really marginal sites some use ruggedised Yagi multi element arrays built to optimise the channels of the parent station. In some cases installed as phased arrays.
Whilst many relays that use transmitting Logs seem to use 4, many do not. Some only have one, up to 8 or so. Again it will depend on conditions, ERP and target area. See this gem for example
Do they have standards?. Having seen the "work" of one of their members perhaps they do have -standards- but these can be rather variable;!..
A log is just another lump of plastic, screws and Ally formed differently..to a Yagi..
Can't really see the argument. We can by a Yagi from Maxview or from Jaybeam .. same materials but fashioned rather differently and different prices and end product;?..
Justin has a good website but he seems to think logs are new. "The Log Periodic is a fairly recent development"
no, most relays used a single log. Occasionally there were two, to get a narrow angle of accepatance; very rarely there were four to get an even narrower angle and at one site there were 24 (guess where).
All four services shared the receiving aerial.
I wouldn't recommend one for normal Astra 2 reception because there would be no EPG Incidentally, I bought 5 faulty Grundig GDS200 Digiboxen for 99pence* on Ebay All had PSU capacitor problems and I had all 5 working in one evening.
*Pity about the £17.50 postage, but they were still a bargin
Just out of interest, can you remember where you first heard the expression 'the man on the Clapham bendybus' ?
Bill
Yes I agree.
Bill
Should gluing be encouraged?
Bill
I believe that the number of elements for a given bandwidth can be varied because the scaling factor can be varied. You could actually have a narrowband log with a large number of elements if you so desired. However, the scaling factor and thus the number of elements to achieve the required bandwidth has little or no effect on gain. In effect, any sensible combination of scaling factor, boom length, and bandwidth will give the same theoretical gain. Antiference used to sell a Group E log, the TS15, but the gain was only the same as the wideband one. See
I have little or no evidence of this but I would think that very short logs would be less directional than those of normal length. Certainly the log-periodic set top aerials, when used outside, are less directional than a normal log.
I'd guess that the scaling factor and subsequent boom length would have an effect on the characteristic impedance, and it could be that dictates many designs.
The design of logs is full of pitfalls. The feedpoint in particular seems to be a difficult issue. Almost all logs have the maximum forward gain for the top 4% or so of bandwidth slightly 'off centre', and I'm guessing that this is a feedpoint issue. One log sold many years ago performed very well up to channel 60. From 61 to 64 the polar resonse was starfish shaped. From 65 to
68 the aerial had a slight but significant negative value of f/b ratio!There's one thing that puzzles me greatly about the log arrays used for RBL and transmission. Often they are 'toed in', meaning that the outer ones point inwards a bit. I've read the BBC research paper that explains that this improves the directional properties. However, I can see no difference between having the outer pair toed in or toed out. When you add together the response patterns of the arrays the result is the same. Toeing in or toeing out can only broaden the forward lobe. This even applies if non-equal splitting or combining is used, as long as the array remains symetrical.
Bill
Alderney, for reception of Stockland Hill (until the BBC started using the IBA's SABRE array there).
In article , Bill Wright scribeth thus
Dunno .. might have invented it meself ...
Still round these parts we'll have the man on the misguided bus soon;(...
I have one of the cheapo Labgear ones and it has Now and Next on each channel on Astra 2 (& Eurobird1?). That is no more or less than the old Freeview boxes (non-PVR, that is) have.
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