Hillsborough
Sheffield
S6 2LL
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Aerial test site on the moors above Sheffield, at an altitude of around 345m (1140ft).
Now that`s what I call “line of sight”, you can see for miles......
Over the years we have tested dozens different models of antenna on Belmont
(A / Wideband), Waltham (CD / Wideband), Bilsdale (A / K), Crosspool/Sheffield
(A / Wideband), Emley Moor (B), Stocksbridge (CD) Oughtibridge/Wharncliffe (CD).
The results are interesting to put it mildly, we rely on our own data now and more or less ignore manufacturers figures. This is particularly the case where they only give a (peak)
gain reading. Even if the latter is accurate, this figure can be misleading, especially with wideband aerials. What you really want is the gain graph, but many manufacturers won`t release this information, arrogant gits.
On the left is Ferrybridge power station and on the right we have West Burton.
Belmont is situated just to the left of the latter, except it`s a further 26 miles away.....
From the area of the site you can see an incredible 7 (seven ! ) power stations and these are marked with white pins on our TX map. From the NE to the SE they are :
Ferrybridge (24m to the NNE, opened in 1966, 2GW)
Eggborough (26m to the NE, opened in 1968, 2GW)
Drax (32m to the NE, opened in phases 1974 & 1986, 4GW, largest in Europe)
Thorpe Marsh (22m to the ENE, open 1963 to 1994, 1GW)
West Burton (32m to the ESE, opened in 1967, 2GW)
Cottam (34m to the ESE,opened in 1969, 2GW)
High Marnham (36m to the ESE, open 1962 to 2003, 1GW)
Incidentally I`ve been on trips round West Burton and Drax and they were mind blowing !
Also compare to :
The above table is a summary of the results, for the full results click here.
We tested the aerials against each other at the same time, in the same location,
and in actual reception conditions. We have also retested the same antennas and find
the signal reception can vary for no apparent reason (possibly the temperature, the
humidity or even differing -
In summer 2007 we decided to institute a major new test programme and identified a site
on the hills above Sheffield which would enable us to do this as it has good signals off four main transmitters and three repeaters. Between them they cover virtually all the TV band frequencies. Some of the most significant data concerned the response of grouped
antennas above and below the designed for frequency band, this is particularly relevant for some Digital (i.e. Freeview) transmissions. As an example it proves that a B group aerial
(certainly the ones we sell ! ) will work perfectly well on CH55, which is MUX6 off Sutton Coldfield transmitter, see relevant graph.
At least two readings were taken -
every aerial (including many not published on this site), so some idea of the work involved can be imagined. In fact I reckon I took around 8,000 individual readings and whilst it
was very interesting to start with, it soon became a hell of a grind......
The results are arranged in tables / graphs as follows :
Aerial Groups (the same model of aerial but all the different groups)
The C/D group aerials we stock
It should be noted that as antennas leave their designed for band their performance can become erratic and the further out of band you go the more pronounced this becomes.
This can give spurious readings, particularly in a spot where multiple TXs can be received, because the aerials directivity can become very poor and inconsistent. This is the main reason why we have not published some readings (e.g. C/D off an A group) as they are meaningless.
I thought long and hard about how to make the results relevant and comparable with
each other, and have decided to show all readings (in dBuV) relative to a DM Log Periodic aerial. The latter has a pretty flat gain curve and thus is an ideal control aerial.
Quite apart from anything else, wherever possible (i.e. in reasonable signal areas), Logs
should be used as a matter of course, so the table(s) will show how much gain you have to make your decision on antenna choice. Note how the Log performs pretty well (in terms of gain) against small/medium wideband Yagis at the bottom of the band(s) but falls behind
as the frequency rises.
For those who are interested I reckon the gain of a DM log would be about 6dB at the bottom of the band, then rising by about one dB in the middle, before dropping again at
the top end. These are the figures I used when calculating the absolute gain for the graphs. The absolute gain figures are conservative estimates, but I bet they`re not that far out.
One things for sure, they`re all accurate relative to each other !
Note this is dBd, gain compared to a half wave dipole, NOT the (dishonest ? ) dBi....
Such are the signals available at 1140ft that even the Log was giving low/mid 70s dBμV
on analogue channels off Waltham (55 miles away and 250kW power), Belmont (59 miles
& 500kW) and Bilsdale (65 miles & 500kW).
Emley Moor is only 13 miles away and pumping out 870kW so it was giving mid/high 80s. The Yagi18s were giving up to 7 dBμV more than that and the XB16s up to 9 more than a Log, that`s NINE ! Just to put it in perspective, one should be aiming for 60 to 80 dBμV,
and not more than that or cross modulation interference can result.
Differences of dBμV on any individual frequency should be disregarded, manufacturing tolerances or a truck going over a hill somewhere between the test site and the TX could easily account for those ! Furthermore the response of any aerial is not linear, it`s gain
curve will have bumps and dips in it. That said, a 1dB difference across the whole band is significant, and an increase (or decrease) of two or three dB is very significant.
It should be remembered that 3dB is a 50% higher signal level, and such an increase at
the aerial (as opposed to through an amplifier) is very difficult to achieve.
Obviously if you live in a decent signal area these amounts of signal variation are not important, but if that`s the case, you should just use a Log Periodic anyway !
In order to give some idea of the gain of the aerials we also included a Tri Boom yagi,
e.g. DAT 45, on the tables. We do not stock Tri Booms, but for those who know of them, the figures could be illuminating, over rated.........
I didn`t test the DAT 75 because it was too unwieldy, but Televes report it as being about
the same as a DAT 45 at CH21, rising to +1dB at CH45 and peaking at +2dB by CH62.
Incidentally this trend for extra directors to add gain at the top end of a widebands gain
curve (and less so at the bottom) was reflected in our own tests of other antennas.
It should be borne in mind that gain is not everything, which is why Logs are still one
of the best aerials despite being having relatively low gain figures.
Impulse noise rejection, directivity, out of band rejection, cross polar rejection and
front to back ratio and can all have significant effects on the quality of the received signal.
Having said that, gain is often a function of the others as it usually demonstrates that the antenna is performing efficiently.
All of this is before you even start talking about wind loading considerations and/or
build quality. Fortunately, we definitely know what we`re talking about when it comes
to the latter, there are no “Bacofoil” aerials here......
This table compares six Yagi 18s of the same model, but of all five groups plus
Wideband. Note, we don`t actually sell the Yagi 18 wideband (because our preferred
model of XB10WB outperformed it) but the gain plot is included because it directly
compares aerials of the same model. Interestingly these grouped Yagi 18s performed
just as well as grouped XB10s, and since they are cheaper, have lower wind loading
and are (arguably) more robust in construction, we do stock those.
The test methodology, and points to bear in mind when interpreting the results, are explained above. The figures are obviously for this particular model of antenna.
Other models varied in performance and this was particularly the case for gain outside the designed for band. As an example, the point above which significant gain fall off occurred,
for A group aerials this varied from CH40 to CH42, and for B groups from CH56 to CH59.
For gain within band, other tested 18 element A groups (which we don`t stock) gave
around 3dB (av) more than a DM Log, the other B groups gave 4 to 4.5dB and other
C/D groups gave 4 to 4.8dB.
I must confess to some surprise that the Yagi18 K performs as well as it does up to CH62,
but this was consistent over three sets of tests on three different days. It will be noted that the B group “beats” the K (on average) over the K band. However this is primarily due to its excellent performance in the B group, note how the B trounces the Tri Boom (e.g. DAT45), which is a larger and more expensive aerial don`t forget. The K is superior to everything bar an A group at the bottom of the band, and this is the area that is the weakest by far for all wideband (or semi wideband) aerials.
Note that the A group antenna is a huge 3.8dB up on the wideband (of the same size) for
the A group frequencies, it`s also a massive 3.2dB up on the (larger) Tri Boom antenna.
In fact such is the widebands inferiority that there is no such thing as a “High Gain” wideband aerial for the A group frequencies, or if there is I`ve yet to come across it.
The C/D`s performance was inconsistent, it was sometimes only on a par with the E and
the W/B, but sometimes it was in front ! It would have been easy to “massage” the results
to say what they should, but being supremely honest, I decided not to........