Post by thread:[OT] Connecting a TV aerial

I need to put up another aerial. The one in these pictures http://home.clear.net.nz/pages/joecolquitt/aerial1.jpg http://home.clear.net.nz/pages/joecolquitt/aerial2.jpg I brought it from a previous house, and it's been stored under this one unused for a while. I've forgotten how it was connected. Can't see anywhere obvious that the cable connected to before The elements marked with a red circle are insulated from the central beam. Opposite elements of that group are connected by the criss- crossing strips. All other elements are screwed to the centre beam Do I assume correctly that co-ax shield would go to one criss-cross and signal to the other ? Or shield to centre beam and signal to one criss-cross ? Looked around the web but wiring is all about the TV end TIA

The antenna is designed to be fed with 300 ohm twin lead to the cris cross, not coax. You should put one of the 300 ohm to 75 ohm transformers to the cris cross and then use co-ax. I would assume that there were 2 wing nuts somewhere that would make connections easy. bill Jinx wrote: > Do I assume correctly that co-ax shield would go to one criss-cross > and signal to the other ? Or shield to centre beam and signal to one > criss-cross ? > >

Bill, > The antenna is designed to be fed with 300 ohm twin lead to the cris > cross, not coax 300 ohm ? Oh. Didn't expect that > You should put one of the 300 ohm to 75 ohm transformers to the > criss-cross and then use co-ax Okey-doke. Now, could I take a 300-75 balun that you'd find on rabbit ears and turn it around ? eg http://www.dse.co.nz L4456 (indoor type, socket + spades) or http://www.dse.co.nz L4465 "TV Balun Indoor/Outdoor- For matching 75 Ohm coaxial cable to 300 ohm ribbon terminals on your TV tuner or antenna. It's weather- resistant so can be used indoors or out" I have an exterior VHF/UHF mixer too. Would that help ? > I would assume that there were 2 wing nuts somewhere that would > make connections easy Wing nuts all over the place

2008/7/17 Jinx <spam_OUTjoecolquittTakeThisOuTclear.net.nz>: > Bill, > >> The antenna is designed to be fed with 300 ohm twin lead to the cris >> cross, not coax > > 300 ohm ? Oh. Didn't expect that > >> You should put one of the 300 ohm to 75 ohm transformers to the >> criss-cross and then use co-ax > > Okey-doke. Now, could I take a 300-75 balun that you'd find on > rabbit ears and turn it around ? Should be OK until the water gets in. If it's weather resistant or properly sealed, it should be electrically OK. Depending on what sort of signal strength you get or need you'd probably get away with connecting a coax directly to the aerial as - is. It will be a bit more susceptable to interference however. RP {Quote hidden}> eg http://www.dse.co.nz L4456 (indoor type, socket + spades) > > or http://www.dse.co.nz L4465 > > "TV Balun Indoor/Outdoor- For matching 75 Ohm coaxial cable to > 300 ohm ribbon terminals on your TV tuner or antenna. It's weather- > resistant so can be used indoors or out" > > I have an exterior VHF/UHF mixer too. Would that help ? > >> I would assume that there were 2 wing nuts somewhere that would >> make connections easy > > Wing nuts all over the place > > -

> 300-75 balun that you'd find on rabbit ears and turn it around ? > > Should be OK until the water gets in. If it's weather resistant or > properly sealed, it should be electrically OK. So would a short length of 300 ohm ribbon be OK ? Say 2m from the aerial to under the eave, then a transformer and then the co-ax run to inside the house

> home.clear.net.nz/pages/joecolquitt/aerial1.jpg > > home.clear.net.nz/pages/joecolquitt/aerial2.jpg > > I brought it from a previous house, and it's been stored under this > one unused for a while. I've forgotten how it was connected. Can't > see anywhere obvious that the cable connected to before As previously mentioned on PIC list, 300 ohm twinlead should go to one pair of wing nuts. Ahhh, but which pair... Are you willing to try hooking the 300 ohm (either twinlead or balon) to various wingnut pairs and see what effect it has on performance? > The elements marked with a red circle are insulated from the central > beam. Opposite elements of that group are connected by the criss- > crossing strips. All other elements are screwed to the centre beam Insulated are the driven elements; non-insulated are directors. Wow, I've never seen an antenna with this many criss-cross pairs and this many attachment points (i.e. wingnuts). Higher resolution photo would be really nice (I'd like to inspect center section in more detail). It almost appears that you can use the wingnuts to remove some of the criss-cross pairs and thus adjust the antenna. Is it possible that the antenna has a manufacturer & model number on it? That might allow a datasheet to be found. How interesting. Lee Jones

2008/7/17 Jinx <.....joecolquittKILLspam@spam@clear.net.nz>: >> 300-75 balun that you'd find on rabbit ears and turn it around ? >> >> Should be OK until the water gets in. If it's weather resistant or >> properly sealed, it should be electrically OK. > > So would a short length of 300 ohm ribbon be OK ? Say 2m from > the aerial to under the eave, then a transformer and then the co-ax > run to inside the house > > -- That would work fine. You could run the 300ohm ribbon right to the TV if required. >From memory, the balun is connected to the second longest pair of insulated dipoles in the array. But I may be wrong. If you get stuck, let me know & I'll climb into my roofspace & photgraph my antennae which is similar. The problem I have is that the signal strength is too much & overloads the sky decoder vhf/uhf input so I have had to add an attenuator. RP

>>> 300-75 balun that you'd find on rabbit ears and turn it around ? Yes. If rated for outdoor use, it may last an acceptably long period of time. If rated for indoor use, it still may last a longish period of time -- but less likely. >> Should be OK until the water gets in. If it's weather resistant >> or properly sealed, it should be electrically OK. > So would a short length of 300 ohm ribbon be OK ? Say 2m from > the aerial to under the eave, then a transformer and then the > co-ax run to inside the house I'd put the balun right up at the antenna. Cheap twinlead does not last well in direct sunlight; you need the better grade. In the US, good grade outdoor twinlead is no longer common. Also, twinlead has no shield, so signal field extends outside the insulation (coax sheild contains signal within the cable). If you tiewrap or electrical tape twinlead to the metal pole which is supporting the antenna, it will effect the signal. You need to buy standoffs that strap to the pole and hold the twinlead ~6" (150mm) away. Such standoffs were common -- 30+ years ago. They're probably still available but I haven't seen them in a long while. Downlead is now almost always coax. I'd either get a 300 ohm to 75 ohm balun that is weatherproof or use an inexpensive balun plus some weatherproofing (either designed for the purposse sealing tape _or_ judicious use of silicone seal plus electrical tape plus tiewraps [it doesn't have to be pretty, it just has to keep water out]). I seal both ends of the balun -- where the twinlead comes out and over the entire F connector (from balun body over connector to coax insulation). Lee Jones

> Are you willing to try hooking the 300 ohm (either twinlead or > balon) to various wingnut pairs and see what effect it has on > performance ? I guess, but I don't fancy running up and down a ladder all day like a flipping budgie ;-) In a pretty strong signal area so might not have too many problems > Wow, I've never seen an antenna with this many criss-cross pairs > and this many attachment points (i.e. wingnuts). Higher resolution > photo would be really nice (I'd like to inspect center section in > more detail). As happens on a regular basis, at this time of night, in these here parts, it's very dark outside. I'll sort that out for you in the morning Thanks for the insights

:: but I don't fancy running up and down a ladder all day :: like a flipping budgie ;-) Hmm wouldn't that be more like a Galaah or one of those windscreen wiper destructive birds that NZ has. Perhaps you could train them to fly the cable up to the aerial. Colin -- cdb, colinKILLspambtech-online.co.uk on 17/07/2008 Web presence: http://www.btech-online.co.uk Hosted by: http://www.1and1.co.uk/?k_id=7988359 Friendship multiplies the good of life and divides the evil. Baltasar Gracian

> :: but I don't fancy running up and down a ladder all day > :: like a flipping budgie ;-) > > :: Hmm wouldn't that be more like a Galaah A galah is a cockatoo from Australia > :: or one of those windscreen wiper destructive birds that NZ has. > :: Perhaps you could train them to fly the cable up to the aerial Keas. Yes, smuggling protected birds from 1000 miles away and training them to wire up what they don't chew to bits certainly sounds like a quicker way to do it ;-) We have lorikeets around here but I haven't seen one yet with a toolbelt on. But maybe I just don't look hard enough

:: A galah is a cockatoo from Australia Indeed, along with Lorikeets, Rosellas and Kookaburras they annoy me with their shreaking in my trees and perching on my washing line. Now where is my slingshot? As for Keas, couldn't you pop down to that nice Swedish furniture store and pick them up there? Alternatively, why not just wire it up and bung it on top of a hedge or car, see if it works and then bung it up on the roof? Colin -- cdb, .....colinKILLspam.....btech-online.co.uk on 17/07/2008 Web presence: http://www.btech-online.co.uk Hosted by: http://www.1and1.co.uk/?k_id=7988359

> As for Keas, couldn't you pop down to that nice Swedish furniture > store and pick them up there? Or get an Apple brand one. An iKea > Alternatively, why not just wire it up and bung it on top of a hedge > or car, see if it works and then bung it up on the roof ? Yeah, probably do something like that first instead of messing about on high

> -----Original Message----- > From: EraseMEpiclist-bouncesspam_OUTTakeThisOuTmit.edu [piclist-bouncesspam_OUTmit.edu] On Behalf {Quote hidden}> Of Jinx > Sent: 17 July 2008 13:55 > To: Microcontroller discussion list - Public. > Subject: Re: [OT] Connecting a TV aerial > > > :: but I don't fancy running up and down a ladder all day > > :: like a flipping budgie ;-) > > > > :: Hmm wouldn't that be more like a Galaah > > A galah is a cockatoo from Australia Is it not also an Oz insult? Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. =======================================================================

Jinx The balum for outdoor use would be the one to use. Connect it to the cris-cross wires somewhere near the mast just so it is easy to fasten the wire so it will not flop around in the wind. I do not think the mixer will do a lot of good. (personal opinion) The antenna should be good to about 100 -125 miles bill Jinx wrote: {Quote hidden}> Bill, > > or http://www.dse.co.nz L4465 > > "TV Balun Indoor/Outdoor- For matching 75 Ohm coaxial cable to > 300 ohm ribbon terminals on your TV tuner or antenna. It's weather- > resistant so can be used indoors or out" > > I have an exterior VHF/UHF mixer too. Would that help ? > > >

Bill, Trivial correction here. The correct term is "BALUN" not "BALUM" It is a contraction for the words "BALanced-UNbalanced. It transforms a transmission line from (or to) one of where one terminal Is referenced to ground or unbalanced like Coax) to (or from) one where the terminals are symetrical and not referenced to ground or balanced like twin lead . Just an FYI. Regards, Jim {Original Message removed}

I have just looked up my copy of 'secrets of RF design' by Joseph J Carr, on page 274, he has a Balun made from shorted co-ax cable, so if you've some co-ax lying around assuming a 4:1 impedance transfer the length of the U shaped co-ax is Length = 492 x V / F where, L is in feet V velocity factor of the co-ax cable F the frequency It then goes on for umpteen pages on transmission line matching tangents and such like. Colin -- cdb, @spam@colinKILLspambtech-online.co.uk on 18/07/2008 Web presence: http://www.btech-online.co.uk Hosted by: http://www.1and1.co.uk/?k_id=7988359

>I have just looked up my copy of 'secrets of RF design' by Joseph J >Carr, on page 274, he has a Balun made from shorted co-ax cable, However while these are fine for narrow band use, like a Ham band, they are next to useless for a wideband TV aerial, unless receiving only one channel. Even then there may be problems like smearing or loss of colour due to the narrow band nature of a coax balun. I would expect a balun out of a rabbits ear aerial to be suitable, after all, before the days of coax connectors on the back of the TV set, such aerials were always connected with 300 ohm ribbon. Many still use ribbon (I believe it is cheaper than coax) down to the plug, which has the balun in it to convert to the unbalanced connector. Just a case of encapsulating the balun in some waterproof coating at the top of the aerial, I would be tempted to use a great glop of contact cement or something similar. Should last a winter at least.

> I would expect a balun out of a rabbits ear aerial to be suitable I picked up an external 300-75 balun and will try it out tomorrow. Pretty much same price as an internal. Difference not worth getting messed up with silicone for Dennis Crawley sent me this picture http://home.clear.net.nz/pages/joecolquitt/pict0777.gif Thanks again Dennis Lee, couldn't really get a better picture of the criss-crosses. The aerial is made by The Multichannel Antenna Co Ltd. I remember asking for a good aerial when it was installed, as the house was in a valley and reception of most channels was very poor. Even with that aerial only one channel was really any good. TV2. And I don't watch TV2. The suburb, Remuera, where all the hoity- toities live (lived) now has much better reception via a repeater In the summertime of the mid-80s it was not unusual to pick up Australian channels as ghosts

> I picked up an external 300-75 balun and will try it out tomorrow. > Pretty much same price as an internal. Difference not worth getting > messed up with silicone for Still watch for possible water intrusion where the F connector screws onto the end of balun. You want to seal it so water is kept out of the balun and the coax cable. Receiving isn't a big deal; low power levels, so nothing gets hurt (except picture quality) if connection corrodes. It's another story if you were using it with a transmitter. > Dennis Crawley sent me this picture > > http://home.clear.net.nz/pages/joecolquitt/pict0777.gif That figure looks like the picture you posted, so hooking the balun up as shown seems quite reasonable ... and "feels" right. :-) > Lee, couldn't really get a better picture of the criss-crosses. Thanks. Just curious why they used all the wingnuts. Normally, I have only seen 1 pair of wingnuts -- point where the twinlead is expected to be connected. If the mechanical construction demands it, there are usually regular hex nuts at other points. But the vast majority of attachments seem to be made with rivits (cheaper to produce). Lee

Lee Jones wrote: > Thanks. Just curious why they used all the wingnuts. Normally, > I have only seen 1 pair of wingnuts -- point where the twinlead is > expected to be connected. If the mechanical construction demands > it, there are usually regular hex nuts at other points. But the > vast majority of attachments seem to be made with rivits (cheaper > to produce). Perhaps so it can be readily folded up for shipping? R

> > Thanks. Just curious why they used all the wingnuts > Perhaps so it can be readily folded up for shipping? It does collapse quite easily and has been stored in a tube. Rivets would not have been a good choice for this design because the cross members have plates with slight indentations that align them to the square-profile centre beam. From memory this particular one was at the upper end of the price range (because of reception difficulties) and therefore I probably paid for the convenience of wing nuts rather than hex nuts

:: In the summertime of the mid-80s it was not unusual to pick up :: Australian channels as ghosts Thats just plain spooky. When I lived in Ipswich (Queensland) during winter, the commercial stations could be picked up from Victoria (3 hours flight away) - not well, but it was annoying looking at two stations showing two different programs superimposed upon each other. Colin -- cdb, KILLspamcolinKILLspambtech-online.co.uk on 20/07/2008 Web presence: http://www.btech-online.co.uk Hosted by: http://www.1and1.co.uk/?k_id=7988359

> I'd like to see a photograph from the side. > There is a model of logaritmic antenna which can be "feeded" by > 50-75Ohm coax line directly With connection points so far apart (100mm), and the exterior balun having 300 ohm spades that can be spread to a Y to get to those points, would you not expect this aerial to be 300 ohms ? Anyway, it is working well with a balun