Two aerials into one?

SirEcho

Standard Member
We have an aerial feeding a booster/distribution box linked to aerials in 1) lounge (Panasonic 3D TV - maybe 10 years old?!!), 2) bedroom (even older Toshiba) and 3) kitchen.

We had a MkII Linsar 24" in the kitchen (brilliant sound and picture; slow tuner) which started showing 'no signal' and/or freezing. I dropped this carrying it through to try on the lounge aerial, and bought another Linsar MkIII. This too intermittently displayed the same issues; it was sent for repair and the old Toshiba used - without issue - instead. I even replaced the cable back to the booster. The three cables are all about the same length, and I tried swapping them round between different outlets on the booster.

Eventually got refund and now have a Sharp 24" Smart TV. Sadly, this too stutters and freezes a little, although not as badly as the Linsar, and we can watch BBC over WiFi., but its still a pain. Sometimes even the radio channels go off with ‘no signal’ – even though the weather is dry and calm, there’s no bird sat on the aerial or any other apparent reason.

Our aerial is oriented to Crystal Palace, which is about 27 miles away and signal strenght apparently 10. Our nearest transmitter is Guildford – perhaps 3 miles away, but lacking many channels. About 65% of local TV aerials are oriented towards CP. Is it possible to feed two differently-oriented aerials into the booster, and hope that the TVs will auto-select the strongest signals for each channel?
 

Rodders53

Distinguished Member
Previous thread: similar subject. Not had answers of S/Q the sets report.


No idea if Guildford serves your location - nor CP for that matter. Would need a very nearby postcode to use the prediction tools.

Guildford is a 6 multiplex '81 main transmitter site'. The same as CP.

CP has the London local multiplex vs Guildford local mux : not sure of which TV channels each carries.

The temporary COM 7 HD mux on ch 55 from CP closes end of next month so you can forget that one. ;)

Not possible to combine the two aerials into one: their frequencies overlap so they will combine unpredictably and usually for the worse.

Wideband combiner would lose over half the signal anyway.

IF Guildford is better/stronger at your location use it rather than CP. Aerial prongs vertical rather than horizontal for CP.
 

SirEcho

Standard Member
Thanks for that.

We deleted our chimney stack (i.e. mast!!) a while ago, so I switched from Guildford to CP; also to get more channels and more HD. Ch4 promptly dropped HD on all except their main channel anyway. I think I'll try a separate aerial aimed at Guildford for the TV in the kitchen.
 

SirEcho

Standard Member
Thanks again.
Transmitter info gives signal strength for all channels as 'good' - I've seen another similar site which indicates the strength of various signals from 200kw to 43kw - so realistically, some are going to be better than others. We also have hills on the estate - although we're higher than most ...but in a bungalow. We're 26 miles from CP, and -again, somewhere else- its limits are supposed to be about 30 miles. What beats me is why sometimes we get 'No Signal' and other times all is well. Unless Putin's goons are jamming.....
Would an extra booster next to the TV do any good, do you think?
 

Rodders53

Distinguished Member
NO Freeview checker: Good = no significant interference IT IS NOT a signal strength indication.

Wolfbane gives field strength numbers in dBuV/m - from that one can add aerial gain, amplifier gain, cable and termination losses, passive split losses to work out what is at the TVs.
The standard is to get 45-65 dBuV at the TVs for reliable working.

CP is 200kW erp on the 6 main. Guildford only 2kW.

Don't go on hearsay - give a postcode nearby (school/shop/pub/church) - ideally within 100 metres of your home and I'll run the numbers.

Use the TVs' built in signal metering to post the numbers you get on all 6/7/8 mux frequencies. Signal strength S and signal quality Q. Use it again if/when you get the 'no signal' message.
That metering may show a pattern or obvious issue.

Boosters (amplifiers) need to be as near the aerial as possible to get the full benefit. Cascading one amplifier after another is deprecated (causes more problems than they are worth in almost all cases). So that's an emphatic NO from me ;)


I was employed to give advice like this professionally to the Trade and Public before I retired...
 

SirEcho

Standard Member
Something that intrigues me is that the older TVs - running off the same aerial, via the same booster are fine, whereas the new one, albeit SMART and capable of all sorts of WiFi tricks, struggles. Are today's tuners less sensitive or something? My sister says aerials are irrelevant, as she gets all she wants via the internet - although I don't share that view.
I'm at GU3 3NH, 14 Envis Way. Its a bungalow.
Amp proximity may have opportunities. Aerial is towards the rear of the property; cable runs 4~5M forwards to the amp in the centre of the loft; boosted signal returns to same place in the lounge; similar distance to kitchen & c.15M to bedroom (all plus 1 ~ 2 M drops to TVs) Would moving the amp c.3M closer to aerial, and reducing the feed to kitchen by 2~3M make an appreciable difference? Feed to bedroom would then be c.20M.
Again, many thanks for all your time, trouble & expertise!
 

A1944

Well-known Member
Looking at Wolfbane, suggests Guildford transmitter as the best bet, but it really needs a vertically polarised aerial pointing just east of south. However, having said that, it also suggests that Crystal Palace should be OK (Horizontal pointing ENE).

Probably safer for you to delete your exact address.

Your problem could be too much signal from Guildford, overloading your equipment
 

SirEcho

Standard Member
Looking at Wolfbane, suggests Guildford transmitter as the best bet, but it really needs a vertically polarised aerial pointing just east of south. However, having said that, it also suggests that Crystal Palace should be OK (Horizontal pointing ENE).

Probably safer for you to delete your exact address.

Your problem could be too much signal from Guildford, overloading your equipment
I'm orientated towards CP
 

Rodders53

Distinguished Member
Aerial type (make/model or a pic) to estimate gain.
Inside loft space or outside on a pole? (-10dB cf outside).

Amp make and model for the gain it has.

Wolfbane guesstimates 77dBuV/m at 6m agl (bungalow ht?) 4km/2miles for Guildford.
CP is only 59 dBuV/m 42km/26 miles.

59dB CP {or 77dB G'd} + 8 dB (low gain aerial) - 3 to 4dB for cable/termination losses + 8dB (low gain distribution amp =
71 dB for CP or 61dB if in a loft. {45-65 being ideal).
So higher gain amplifier would be a likely problem imo; especially coupled with a 'high gain' aerial.

Guildford (99dB :eek:) would need passive splitting (-8db 3/4 ways) and no amplifier to give 75dB which is possibly too high (or 65dB if loft aerial, perhaps). A vertically polarised room aka set top amplifier would likely work for one TV if not blocked by multiple walls between it and the transmitter. Use a directional, non amplified one though.

The Hp aerial - even though pointing at CP - may still be adding signals from G that get amplified and overload the tuner(s) from 'side lobes' of it. Which is why I keep asking for the numbers from their built in metering.

Guildford will be slightly more likely to suffer from interference from the Continent cf Crystal Palace from the numbers ex Freeview. But not all that often.
 

SirEcho

Standard Member
Again, thank you.
Sorry, no details on the aerial other than that it is high gain (I didn't take this pic sideways on!!)
Aerial (2).JPG

You can just see neighbour's behind the foliage at 90 degrees aimed at Guildford.
Aerial (1).JPG

Further down the road: 50/50 aimed at CP or local. Everyone round here seems to have external aerials, unlike our previous house where most had them in the loft.
Amplifier is a Philex SLx6 with following spec:
Spec.jpg

When Panasonic is auto tuning it gives relevant signal strength as 10 ...I don't recall what the Q score is. I don't know where to look for numbers on the Sharp. In any case it programmes in the channels ...which then might go off ('No Signal') even though other TVs are working.
NB There's no correlation with the use of any particular kitchen appliance, weather, birds or anything I can think of. I even replaced the cable at one point as we'd had mice up there in case they'd chewed some inaccessible part!

I'm now considering trying a separate loft aerial for the kitchen.
 

Rodders53

Distinguished Member
So another 4dB of gain due to that amp. 18 element yagi will be perhaps +4, too. 79dB? When 65 is target max?

The +1 port MUST have a 75 ohm termination fitted - and one is usually supplied. Best practice is to fit terminator to the unused ports as well.

I'd suggest trying an attenuator on that TV's port.. or it alone direct to aerial to see if it is happier then?
Aerial alone will be circa 65 to 67 dB to one TV!

Panny TVs with a scale of 10 are post auto gain and error correction. Mine reported 10 both before and after DSO when power increased tenfold. Makes the meter less useful than many other makes.
I have an old Sharp TV without a signal meter, too!

Unlucky.
 
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SirEcho

Standard Member
Thanks again. So when its telling me 'No Signal' it might actually be getting too much signal?!! I might tried the 'straight through' aerial connection on the amp (labelled 'full') just to see what happened. On the Panasonic it didn't work. I connected aerial directly and signal was poor - that definitely needs the amp. I take your point about the terminators - I had some in our last house, and I'll get some for this amp's unused outputs.
HOWEVER I did get a £5 aerial, put it in the loft, point it at Guildford, connect that directly to the TV in the kitchen ....and it has never faltered since!
Many thanks for all your insights.
 

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