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Old 1st Aug 2016, 11:58 am   #21
Scimitar
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Default Re: "Contractor" UHF TV aerials

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So we have the irony that aerial systems are being installed for digital that are the ones that should have been installed for analogue
Absolutely, however the rubbish installations were saved by the graceful degradation of picture quality that analogue gives.

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and those Contractor aerials and cheap downleads of the analogue era would in general just be fine now.
No they wouldn't. No baluns, poor flatness across the band, poor physical quality and relatively unscreened downleads.

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Would I be correct in thinking that digital is most prone to IMPULSIVE interference - hence the foil downleads? The higher the QAM the more prone? Impulsive interferenece hardly affected UHF analogue TV - VHF TV was a different matter.
Yes, impulse interference is a significant issue, which is why the screen and balun is important.
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Old 1st Aug 2016, 4:00 pm   #22
ms660
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Default Re: "Contractor" UHF TV aerials

My old antenna, probably no balun and crap coax, digital reception's ok

https://www.vintage-radio.net/forum/...d.php?t=111523

(Scroll to Post#9)

EDIT: Second thoughts, probably has a balun (folded dipole) It's probably full of water as I type.

Lawrence.

Last edited by ms660; 1st Aug 2016 at 4:07 pm.
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Old 2nd Aug 2016, 12:48 pm   #23
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Default Re: "Contractor" UHF TV aerials

Re the downleads,

Yes, Scimitar, I agree with your point. Having used cheaper cable for quite a few years at home for experiments I moved on to fully screened units, RG57 cable (I know it is lossy but as I always had pre-amps ahead of it I was prepared to accept the losses) and using F-type connectors for a better impedance match compared to Belling & Lee plug/sockets.

Incidently, did you ever deal with any of the Channel 5 blocker filters? The short connecting cable supplied acted as a good aerial. No wonder I read of advice to 'throw it away'!
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Old 2nd Aug 2016, 2:19 pm   #24
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Default Re: "Contractor" UHF TV aerials

Yes we were involved in the C5 Retune fiasco. We just did things our own way and sorted the issue without recourse to them. I had a newspaper article written about the business around that time, in an attempt to educate the public.

One of the issues with lossy cable is tilt. A standard pre-amp can't overcome that of course.
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Old 2nd Aug 2016, 8:00 pm   #25
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Default Re: "Contractor" UHF TV aerials

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One of the issues with lossy cable is tilt. A standard pre-amp can't overcome that of course.
Is this a loss of signal against frequency over the bandwidth of the aerial or over the width of any 8Mhz channel, or perhaps something entirely different?

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Old 3rd Aug 2016, 1:43 am   #26
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Default Re: "Contractor" UHF TV aerials

I have a roof mounted group c/d 13 element contract aerial which was probably fitted nearly 40 years ago when the house was new. It still works well giving good reception on all the available Mendip Freeview channels including the two HD muxes on the lower group A channels. So if it physically holds up it should continue to give good results after they clear the 700Mhz of TV channels in a few years time.
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Old 3rd Aug 2016, 11:13 am   #27
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Default Re: "Contractor" UHF TV aerials

Re lossy cable.

I agree tilt can be a problem if you are wanting really wide-band performance. In my case I was only using a frequency span represented approximately by a TV Group. Finding a good low-noise pre-amp which has good high level handling characteristics (for strong out-of-channel signals) I found to be more of an issue!

Actually I need to correct my earlier post no. 23 where I said I used RG57 cable. I looked again this morning and I actually use both RG 59 /U and URM 70. They may be lossy but they are flexible and RF tight. Whilst I could have used satellite Al foil cable I feel it is not designed for frequent flexing - rather such cables are more appropriate for a fit-once-and-forget satellite dish installation. I still use my collection of non-specified coaxes (both VHF era and earlier UHF era) for less demanding uses, so I'm not hung up on any particular one.
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Old 4th Aug 2016, 8:32 am   #28
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Default Re: "Contractor" UHF TV aerials

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People weren't all that keen on getting one, but if they did, they sure wanted the neighbours to know!
I'm told that this was one of the reasons for the failure of ONDigital/ITV-digital: unlike when you got Sky (or BSB), with ONDigital you didn't have any obvious new aerial with which to advertise the fact!
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