Freeview loft aerial?

[T i m]

Whilst playing with a multi-tuner networked recorder solution I've come across all the muxes, frequencies and power levels from Crystal Palace and am not sure if our loft mounted aerial is ok or not?

By that I mean it seems 3 of the Muxes are relatively low power and if I tune to one, (8, London Live, C29 (538.0MHz), 20,000W) it comes though good and error free but only showing a signal strength (as shown by TVHeadend) of around 60%, whereas the main Muxes (200,000W) come though at 85%. So far so good.

However, I don't think I can see the two 'com' Muxes (com7/8) at all but whilst they are roughly twice the power of LW mux (43,000 /

40,000W) I don't seem to see them at all (fails to tune). Should I see them?

The biggest difference on the last two is they are up at around 750Mhz and I wondered if that was outside my current aerials (or distribution amps) bandwidth?

I like understanding this sort of thing a bit better (at a practical / utility level) and follow the 'You can manage what you can measure' thing so wondered what would be the best / cheap solution for measuring this sort of thing? It doesn't have to be absolute in this case because we are well within the range of Crystal Palace and we generally get a very good signal on all TV's (even using the little stick antenna etc).

By that I think I'm talking at relative signal strengths between the known frequencies but also the Bit Error Rate / Quality?

Googling I see you can by 'intelligent testing kit and some of it for a lot of money but I wondered if someone had found something (like a cheap Freeview box?) that served this sort of purpose well? By that I mean you can sometimes go into a sort of Info mode and see things like Signal Strength / BER, on some boxes it's not that easy if available at all.

Cheers, T i m

p. s. I think I bought a newer aerial years go but didn't fit it and it's too hot to go in the loft to look right now. ;-(

[Andrew]

Cough. They're all analogue. It's the TV or STB that extracts the digital signal.

[Max Demian]

Your aerial is probably Group A, which would have been suitable for CP from analogue days. COM7/COM8 will be discontinued in a year or two (I think one already has been), when the top end of the band is sold off to the mobile phone operators. Just use what you can receive.

[T i m]

<snip>

Well I'm pretty sure I was using the same aerial back then so you are probably right.

I read about that in my Goggling and there seems to be some disagreement as to if it's actually been sold off (or when if it will be)?

Ok, that's fair enough, assuming those bands won't be used for more Freeview TV etc?

On this TVHeadend install it seems to map the Freeeview channels to just a contiguous numerical run (1 to 100 odd) so it's not easy to see what's there or not, without going though them one-by-one against another TV.

I am interested to hear how many other Lundners (who live within the range of CP) get the stuff shown against the Com 7/8 muxes here?

If the channel info is sent OTA, why don't all non smart (that can't get the EPG any other way) TV EPG's not all line up, or line up with what they are supposed to be? It seems if I see something is advertised on Chan xyz, there is a good chance that won't be the channel we find when we go to that number? Or maybe it just seems like it?

Cheers, T i m

[Fredxx]

Hmm. The analogue spectrum was actually wider than now used by digital MUXes. The term digital aerial is often used to refer to the differing bands.

[Brian Reay]

If you are willing to ?risk? a few pounds, you could try one of the unbelievably small DT240 type antennas. The numbers vary a bit but they are about 4? tall, the top 2? are perhaps 1/2? in dia, the rest about 1/4?. They come with about 6? of coax.

I bought one as an experiment - not really expecting it to give even half reasonable reasonable results- but I?ve been shocked. Don?t get me wrong, I?m NOT suggesting it is some super design / special technology (it isn?t, in fact it is a simple helical antenna, a few turns in the ?bulge? at the top). Obviously, it relies on a combination of signal strength and the capability of the digital TV system. BUT I?m not in the best of RF spots, pre digital I had problems and in the early days of digital it was marginal.

I?ve tried this little antenna indoors. It will work upstairs. I?m about 5 miles from the nearest transmitter AFAIK, with a poor path.

I tried it outdoors just inside the M25, near were it crosses the M23 (there is a campsite there). It was brilliant.

The one I have is the simple antenna. Some, I assume, have preamps in them as they have a USB lead for power.

[John Rumm]

Loft mounts can be a variable feast - but will work well in some locations.

Assuming the aerial is group A, then they will be well out of band. So not surprising really.

Indeed - I was in a similar boat 12 years ago trying to sort out what was going on round here part way through digital switchover. Having some capability to meter what is actually there is often required to make sense of more "difficult" installations.

In the end I went for a proper test meter on the recommendation of Mr Wade, formally of this parish... I posted a review of it at the time:

Alas I don't think Swires are trading any more, so you would need a different brand. However Amazon etc will probably be able to source a range of similar toys.

I feel similarly about the pile of fencing materials I had delivered today - too hot to bother looking at!

[T i m]

<snip>

<Googles>, interesting. (August also do the USB tuners I was looking at).

Ok.

Also to *my* surprise I got a good clean signal with one of the little magnetic base 'stick' antenna you get with the USB tuners, but only really when it was stuck on a ground plane (unsurprisingly, considering the design etc).

Cool.

Makes sense.

The thing is, I'm not sure if one like that could ever be 'better' that a proper directional aerial, with it's ability to reject signal from behind and even interference from mobile phones etc. Also, I get how the DT240 would be *very* handy when used in a RV (specifically it's lack of directionality (plonk it down somewhere and not worry where it's facing), assuming a reasonable signal etc) because of how compact it is.

The other part of my question was how one measures / compares the signal strength and BER of an aerial solution without having to buy the specialised kit.

If any tuner is actually 'tuned' to the particular mux, rather than it being a real wide band transmission and the various muxes / channels decoded from that then in theory any mux with the same radiated power should be seen as such by any receiver that covers the whole band equally?

I tried re-tuning my big / older Panasonic TV the other day and it seems to 'rate' each channel within a mux (out of 10) and wheat you got was say a batch of 10's, then a gap (as it was scanning to the next mux), then another batch of 10's, etc etc until it came to the lower output mux when it gave them 8 (so still pretty good etc).

So it was really the higher frequency (700Mhz+) muxes that may be in question but if they are going in the near future ...

It wasn't really about specifically wanting the content they carry, more of 'should I be able to get them', given everything else ... is my new muti-tuner (7) test rig working properly etc [1].

Cheers, T i m

[1] It's interesting to setup several clients to the tuner and either, get all the client watching channels from the same mux (when they can all share the same tuner) then getting each client to specifically select a channel from a different mux and seeing all the tuners kicking in one by one. ;-)

[T i m]

I was thinking further on that and I can't think of an instance (no matter how bad the weather, roof covered in snow etc) where we have suffered a depreciated picture quality ... so I'm guessing this instance must be one of the good ones. Slate roof, fairly clear view towards CP, may all help. ;-)

When I got the roofers in to do a bit of work here (but mainly on next doors, he's a good guy so we look after him), I got them to cut off his aerial that has been hanging down the back of our shared stack for the last 10 years. ;-)

<snip>

Quite, hence why I was checking. I was just wondering how many people here get the 700+Mhz channels and not realise how lucky they might be (given the recommendation for CP FV is a Group A)?

I think the really basic devices are just wideband signal strength meters but that might actually be enough for aligning the right aerial to the right transmitter (once you know it is)?

I think I read that with interest at the time John. ;-)

The thing is, with so many clones of this sort of kit about, it's only the price that's a big clue to the likelihood of it working as it should.

Quite.

So the issue could boil down to just the question of 'should I be able to see the two 700+Mhz muxes' or not, and if I should, is there any point getting to that position if they are going to be shut down in the near future (ignoring the issue of is there anything on there I'd want to watch etc). ;-)

Cheers, T i m

p.s. Re our previous conversations around networked DTV-T2 PVR's I have TVHeadend running on a RPi3B with the T2 TV_Hat and a T USB stick from Amazon (£10 inc). Like my OMV RPi it seems pretty durable and even though it's still just tacked together in a 'testing' form, I'm fining myself setting up recordings, series links and instant recording (all from a Web browser) and (currently) typically watching it back with the TVHeadend PVR client in Kodi (on Windows, Linux and an Android TV box/Kodi).

Apparently you can install a proxy that allows Plex to interact with the TVH servers but that seems to require a reasonable spec PC (for the client), as does SchiboPVR (that also has a TVH client option built in).

I also now have an i3 box running Ubuntu 18.04 desktop on a small SSD (+3TB drive for storage) with TVH and Kodi that also seems to work pretty well and may be the nearest I have to an all-in-one replacement for our Toppy+ solution so far. I am using a wodge of XBox One single T2 USB tuners (£5.95 on Amazon) and apart from the clutter (I'll probably 3D print a frame to hold them all to keep them out the way and cool) testing them is part of this question / stage.

Thanks for all your previous help that got me into trying all this different stuff. ;-)

[Paul]

Sadly, very few commercial twigs are that carefully optimized. They still have significant gain in bands that are no longer used for television.

You can see this sample antenna, has no trouble at channel 60. It might be a tiny bit feeble at the bottom end, but usually the high end is "limitless". Even if you *wanted* to stop gain on channel 40, you couldn't. You can probably, with some effort, de-tune or invert the receiving direction and plonk it into the reflector or something. But without outright negligence, there's a tendency for a wide band of UHF to come in anyway.

When I built my own antenna, the designer claimed it was optimized for the new TV limit and "cut off" the non-TV area that had been auctioned. While analog TV was still running (I only had one day to do this testing before the transmitter was shut off!), the (finished) antenna had

*plenty* of gain above the expected limit. As a result of this little experience, I would not assume that magically, someone has managed a sharp cutoff skirt on a TV antenna top end.

One way of losing usable signal is via multipath. That's where there is actually too much signal, it bounces off two office towers, arrives at a slightly different point in time, and ruins the signal recovery. Sometimes, a more directional twig might help, if you could, say, prevent the second signal from being in the "viewing angle".

Paul

[Brian Reay]

I?m not suggesting these mini things are some wonder antenna but they do give better results than (I) expected and certainly, if you have a reasonable signal in you area, may be an alternative based on what I?ve observed. I was expecting to see nothing, at least in my home location.

What they do save, assuming they work in your area, is climbing on the roof etc, plus they are cheap- I think I paid about £6 for mine.

Tuning to the signal you want isn?t just about maximising signal strength- or more exactly tweaking your system so it amplifies the signal you want the most, it is also about rejecting unwanted signals. (?Spread from adjacent channels, general RF clutter etc.....)

Re Bit Error Rate etc, I?ve got a cheapish handheld beast to set up sat dishes. Basically, a mini TV with a sat rx built in and the size of a large multimeter, say 5x3x2?, with a small TV screen and keyboard- all for about £60. From memory it is called a Satlink. One of the ?pages? includes a BER display, although I tend to rely on signal strength as it is quicker when setting up the portable dish. I would think someone makes a similar beast for terrestrial TV.

[Paul]

There's some tech out there suitable for signal level measurements.

The tuner in your computer could likely do it, if someone wrote the software for it.

At least you can see how filled the 6MHz slots are, when a TV station is present on the band. The envelope of that signal looks a bit different than what the old analog TV used.

The RTL-SDR is an example of a cheap toy for SDR purposes. One of its limitations, is the tuner range. It should work just fine for UHF work. But if you wanted to do any verification of Wifi signals, the front end on the SDR has to span a wider range to cover 2.4GHz or 5GHz Wifi. Like an RPi, the amazing part is someone making these things at a price you can afford.

In the second link there, you can see a few of the items are really priced well out of reach.

Paul

[alan_m]

Often signal strength and quality figures are somewhat meaningless on many boxes. I've had boxes where a signal strength above 50% (50% of what I don't know) has been OK but unless the "quality" was 97% or above the picture breakup could be unacceptable. On other boxes a quality of

80% has resulted in reliable reception.

[The Natural Philosopher]

Think multipath. Two strong signals one delayed in time is a disaster. One weak signal is way better.

Tune for best signal quality - that may mean tweaking the aerial off target so as to place the other signal in a null point of the radiation pattern...

[Chris Green]

Com8 is due to be turned off in the next few days so there's no point in configuring for that.

There has been a long discussion about this recently in the uk.tech.digital-tv usenet group.

That's why both com8 and com7 are due to be turned off, they're freeing up that part of the spectrum.

[T i m]

<loads of un referenced stuff snipped>

Now, I'm not sure if it's the drugs you are on that means you (and your kind) never bother to snip, or that you are accessing Usenet with a Speak-n-spell that doesn't have a delete key or that you are just lazy, but how about giving it a go?

I mean, it's not like you are doing much other than posting here so 'most people' would look to improve their skills in that time?

Go on, give it a go. You a slowly getting there with your OT (and so you should, given most of what you post is OT:), so now to try the snipping.

Cheers, T i m

[T i m]

<snip>

OK.

In this case it would be in the loft anyway.

I wonder what you would see if you compared that with just a plain magnetic stick aerial?

As mentioned elsewhere, I can get a good signal here with said stick stuck on the top of a PC in our bedroom. What I don't know is how good that might be in poor conditions or how it might reject noise from directions other than the desired transmitter? I'm guessing, 'not very well'?

<snip>

Quite. Hence why directional aerials are generally used in those circumstances.

<snip>

Ok.

It looks like they do, the SatLink WS 6905 DVB-T

Can be found cheaper elsewhere (~£80). I'll check it out.

Cheers, T i m

[T i m]

50% of what it would like to see 'ideally'. ;-)

Sure, that's why I asked if anyone had found a box of some sort (like a basic FV receiver) that gave easy access to signal strength and BER / Quality in a way that actually reflected some useful real world conditions.

Cheers, T i m

[T i m]

<snip>

Ok ...

Yes, I've read some about it but it ranges from 'it / they are going off soon' to 'There have been no firm dates set' etc.

Ok, and that's fine, if it's actually the case (not suggesting it isn't etc) and assuming there was anything on them that I might be interested to watch.

Had I asked this question a couple of years ago I guess it would have been more pertinent (see above), but now, if they are going *anyway*, it's sorta mute.

Have you read anything that suggests if the com7/8 channels will be re-located on the remaining muxes ooi? Maybe they will go live-streaming over the interwebs?

Cheers, T i m

[T i m]

<snip>

<snip>

Well, they have indirectly as most of these soft PVR solutions have to tune the signals and often give the strength of that signal in their advanced options (and often when installing scan/tuning etc).

Handy, ta.

I actually have a 'Wi_Spy' WiFi scanner dongle for that and it has worked very well, diagnosing a Sky signal repeater, a car alarm and a Surround Sound system with remote rear speakers that had failed and was swamping the basic WiFi band like a signal jammer. ;-)

That was the path I was interested in Paul. Something that I might be able to cobble together that actually does *just* what I want cheaply, rather than loads of things I'll never need.

Yeah! I's say most are more that I'd like to spend in this case, especially if there is a Freeview box out there that shows such things (easily) already.

I think I've had a DVB or Sat box that did. You put it in an 'Extra details' mode and use it as normal but it superimposed all the tech data for that tuned stream on screen for you ... and importantly, didn't drop out when you went up/down the channels etc.

There could be a TAP for the Topfield PVRs but none of mine are T2 so would already be limited etc.

Cheers, T i m