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Call Sign : 26-CT-4013/M7DVQ Posts : 236 Times Thanked : 12 Join date : 2021-02-24 QTH or Location : Brighton, East Sussex Equipment Used : Yaesu 991a - Imax 2000 - CRT Electro - Sharman X50 Age : 77
Subject: PMR446 antenna near freeview aerial question Mon Jul 11, 2022 10:37 am
I'm trying to find a solution to my dilemma which others seem to have on CTDX regarding happiness on the marital front. 'Er indoors is unhappy about me adding another mast to accomodate a PMR antenna, I wonder if it would be ok to mount it above the freeview aerial a few feet above it on the same pole?
Any advise or warning would be appreciated.
keithgriffin1962 likes this post
Victor CT Directors
Call Sign : 26-CT-3228 / M7VIC Posts : 6277 Times Thanked : 389 Join date : 2019-11-10 QTH or Location : Bedford Equipment Used : Various
Subject: Re: PMR446 antenna near freeview aerial question Mon Jul 11, 2022 11:52 am
Hi Tony,
It shouldn't cause a problem mounted above the freeview antenna, but.....
When I first set up my 2m/70cm antenna in the loft I found that 70cm transmissions would cause freeview TVI even at low powers much to the annoyance of the missus.
The cure was a simple 1/4 wave coaxial stub connected to the TV antenna.
PMR frequencies are just above the 70cm band so this should work just as well.
You want to cut about 11.5cm or 4.5 inches of coax, (75 ohm TV coax or even a bit of RG58 50 ohm), plus extra for the connection to the TV antenna. Simply connect it to the same connectors as the TV antenna coax, (usually some screw in affair for the TV coax), leaving the other end cut as in open circuit. (You may want to weatherproof the open end if outdoors with a bit of silicone seal or something.)
This will now appear as a short circuit to your transmissions as far as the TV antenna is concerned and work as a simple notch filter.
Dirt cheap and simple 'TVI' filter.
......or you could persuade the missus to 'upgrade' to cable TV, (we have Virgin), so that the freeview antenna is no longer in use and therefore you aren't creating any problems. Worked for me!
(Luckily I was originally only affecting our TV and not any of the neighbours but most are on cable TV nowadays so I don't need to worry unnecessarily.)
Anyway, that was my fix but someone's bound to suggest a commercial TVI filter, (money), or maybe even argue about velocity factor with my 1/4 wave calculation.
Hope that helps.
All the best, Victor
Razz229 and keithgriffin1962 like this post
Alan Pilot Major contributor
Call Sign : 163-CT-220... Posts : 2637 Times Thanked : 70 Join date : 2019-11-19 QTH or Location : Anglesey North Wales Equipment Used : Yaesu FT-991A,,Yaesu FTDX-10,,Icom ic-7610,,Anytone AT-D878UV PLUS",,LINCOLN II+. Age : 16
I fitted my TV aerial in the loft. The mrs was crying out we needed a digital aerial even though I pointed out we were receiving digital and analogue at the time on the old H aerial
The only reason I fitted a new one was because it finally gave up the ghost. Or so i thought. After climbing on the roof and removing it from the chimney I found the coax had severed at the gutter through years of rubbing
I can't wait to put a silver rod and PMR antenna up now. Then key up with a burner when love island is on
keithgriffin1962 and Tonyvic like this post
Tonyvic Major contributor
Call Sign : 26-CT-4013/M7DVQ Posts : 236 Times Thanked : 12 Join date : 2021-02-24 QTH or Location : Brighton, East Sussex Equipment Used : Yaesu 991a - Imax 2000 - CRT Electro - Sharman X50 Age : 77
It shouldn't cause a problem mounted above the freeview antenna, but.....
When I first set up my 2m/70cm antenna in the loft I found that 70cm transmissions would cause freeview TVI even at low powers much to the annoyance of the missus.
The cure was a simple 1/4 wave coaxial stub connected to the TV antenna.
PMR frequencies are just above the 70cm band so this should work just as well.
You want to cut about 11.5cm or 4.5 inches of coax, (75 ohm TV coax or even a bit of RG58 50 ohm), plus extra for the connection to the TV antenna. Simply connect it to the same connectors as the TV antenna coax, (usually some screw in affair for the TV coax), leaving the other end cut as in open circuit. (You may want to weatherproof the open end if outdoors with a bit of silicone seal or something.)
This will now appear as a short circuit to your transmissions as far as the TV antenna is concerned and work as a simple notch filter.
Dirt cheap and simple 'TVI' filter.
......or you could persuade the missus to 'upgrade' to cable TV, (we have Virgin), so that the freeview antenna is no longer in use and therefore you aren't creating any problems. Worked for me!
(Luckily I was originally only affecting our TV and not any of the neighbours but most are on cable TV nowadays so I don't need to worry unnecessarily.)
Anyway, that was my fix but someone's bound to suggest a commercial TVI filter, (money), or maybe even argue about velocity factor with my 1/4 wave calculation.
Hope that helps.
All the best, Victor
Hi Victor, Many thanks for your comprehensive response to my question, the stub idea I will certainly try if rfi is a problem but was a new one to me. We do have Virgin Media which is mainly for the wife as I'm happy enough with freeview but I originally had the aerial installed in preperation for the battle with virgins customer retention team fully expecting to cancel when some issues were not resolved by the offshore faults team. We were lucky to finally get through to a great guy and it was sorted, as well as £15 per month off for 18 months.
Many thanks for your help, Cheers & 73 Tony
Victor and keithgriffin1962 like this post
Tonyvic Major contributor
Call Sign : 26-CT-4013/M7DVQ Posts : 236 Times Thanked : 12 Join date : 2021-02-24 QTH or Location : Brighton, East Sussex Equipment Used : Yaesu 991a - Imax 2000 - CRT Electro - Sharman X50 Age : 77
Subject: Re: PMR446 antenna near freeview aerial question Tue Jul 12, 2022 11:47 am
Sharpshooter wrote:
I fitted my TV aerial in the loft. The mrs was crying out we needed a digital aerial even though I pointed out we were receiving digital and analogue at the time on the old H aerial
The only reason I fitted a new one was because it finally gave up the ghost. Or so i thought. After climbing on the roof and removing it from the chimney I found the coax had severed at the gutter through years of rubbing
I can't wait to put a silver rod and PMR antenna up now. Then key up with a burner when love island is on
Nige, did you keep the old 'H' aerial, if so you could chop it up and build a couple of beams for pmr. Have you considered that bunging loads of power back down the tv coax won't only wipe out Love Island it could also wipe out a few hundred quid for a new TV.
Good luck, Tony
keithgriffin1962 likes this post
Sharpshooter Major contributor
Call Sign : 163-CT-329 Posts : 489 Times Thanked : 13 Join date : 2022-04-05 QTH or Location : Deeside, Flintshire Equipment Used : A growing list
Subject: Re: PMR446 antenna near freeview aerial question Wed Jul 13, 2022 12:43 am
Tonyvic wrote:
Sharpshooter wrote:
I fitted my TV aerial in the loft. The mrs was crying out we needed a digital aerial even though I pointed out we were receiving digital and analogue at the time on the old H aerial
The only reason I fitted a new one was because it finally gave up the ghost. Or so i thought. After climbing on the roof and removing it from the chimney I found the coax had severed at the gutter through years of rubbing
I can't wait to put a silver rod and PMR antenna up now. Then key up with a burner when love island is on
Nige, did you keep the old 'H' aerial, if so you could chop it up and build a couple of beams for pmr. Have you considered that bunging loads of power back down the tv coax won't only wipe out Love Island it could also wipe out a few hundred quid for a new TV.
Good luck, Tony
No it's long gone many years ago Tony. But I do have a TV antenna in the shed I used for caravaning. It was new but took down during the digital con by an unsuspecting poor bugger. So I've thought of converting that.
The TV Aerial I fitted in the loft goes to a powered splitter box and coax to each room in the house. The TV in my caravan was much cheaper.
But hey, I don't watch much TV these days so good riddance
keithgriffin1962 and Tonyvic like this post
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Subject: Re: PMR446 antenna near freeview aerial question