All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
Tim:
Agreed if the log-periodic is not large enough. If, however, one of sufficient elements is used then no amplification is needed. That is the better solution as an amplified will not on;y increase the wanted signal strength but also any unwanted signals as well! So iis, and always has been, better to use an aerial of sufficient inherent gain. Log-periodics are available with many elements, I know of 36 element types (see http://www.trade-works.co…625) and there may well be some available with up to 72 elements. Most seem to be 20, 22 or 28 element which may not give sufficient inherent gain, but rather than adding noise with an amplifier it is always better top swap the aerial for a higher gain design.
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Ed Henderson:
Engineering work has been going on at Emley Moor simnce at least last Thursday, with it being noted that there are likeluy to be some service interruptions. The works being noted above your posting.
By retuning you have lost several of the signals that were available, you would have been better off waiting until the engineering works have been completed.
That is still the case and you should only retune once that work has finished. Check back here to determine if the work has finished, indicated by the engineering works notice not being posted afresh again.
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Tim:
Using a higher gain log-periodic obviates the need for any amplification. That has been my professional experience over 50 years in the TV industry!
Amplifiers amplify everything - wanted signal as well as noise.
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David and MikeB:
Bath is approximately North West of Mendip and only about 14 miles away, so signals shlould not need any amplification.
As MikeB states, a signal strength of 100% is too strong and will oberload the tuner, causing picture and/or sound breakup or even apparent loss of signal. Fo most equipment a strength between 60% and 80% is ideal.
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David:
One thing you might try, but no quarantees it will resolve the issue, is to add an attenuator *after* your first amplifier. That will reduce the signal level (and that of any 'noise') entering the distribution amplifier. The overall effect should be to reduce the excessive signal level arriving at the receivers. Coaxial attenuators are inexpensive and available in various strengths (typically 3 dB, 6 dB, 12 dB and 18 dB), so try a 6 dB one first. If that is still allowing too much signal (over 80%) then you can add another in series. If it is too much reduction (signal strength drops below 50%) then try a 3 dB type instead. You can combine attenuators of different strengths until you get the required result.
The 'local' transmitter for Bath is a Freeview Lite intended to serve mainly those areas shielded from Mendip by the hills.
Though I am on Mendip and have no problems, there could possibly be some temperature inversion effects perhaps. Do any or your immediate neighbours have the same problem?
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Ruby:
It is not unusual for a few strands of the shielding braid to appear outside the connector body. The cable has an inner core surrounded by an insulating sheath. That is wrapped in a braiding of silver wire and often has a sheath of silver metal ribbon inside that. The inner conductor shows as the central pin at the end of the connector and the braid is in contact with the outer body of that connector. In fitting the cable into the connector the technician strips back the outer plastic covering a short way, folds back the braiding (and the ribbon is present) and then carefully removes part of the inner insulation so the core is exposed. That is then fed into the 'F' connector so the inner core and outer metal braiding do not touch each other. If the amount of outer insulation removed is longer than the depth of the connector then some of the braid will appear outside. That is not a problem at all.
The silver appearance is because the copper wires have been plated, which is not a bad thing at all. 90 is not expensive to have a dish, LNB and cabling installed for reception of Freesat. If the work was done by a professional installer it should be reliable and be covered by a work guarantee.
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M Griffith:
COM7 is an HD multiplex and many TV sets are somewhat sensitive to the signal strength on such multiplexes. Can you please check what the signal strength reported by you TV set is on this multiplex. It should not be below 50% and not above 80%. Any strength less than 50% will cause the problems you report, as will any signal strength above about 80% (it does vary slightly dependent on make of TV). Having too much signal is well known to cause these type of problems. If that is the case for your reception, search this website for 'too much of a good thing' and take the advice to reduce the signal strength by fitting attenuators in the aerial lead at the back of the TV or removing any amplifiers you may have.
If you give us a full post code for where you live (or that of a very nearby shop or post office) we could examine the signal path and advise if there are any other possible causes.
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Richard Baguley:
It is possible that temperature inversion atmospheric effects are causing many of the reported loss of signal problems.
The Freeview signals are digitally encoded data modulated onto a UHF carrier signal, so the term digital is appropriate when discussing the data multiplexes carried on the several different carriers.
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Alexei Romanov:
The problem you are reporting is characteristic of too much signal on the HD multiplexes - as you have been previously advised.
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Sunday 15 May 2016 4:15PM
Trowbridge
Bill Martin:
It is essential that you provide a full post code so that we contributors can determine where you are in relation to the transmitter and hence find out if there are any particular problems that can affect your reception. Without that, useful assistance is impossible.