H & X TV aerials.

[FLY2 10,108]

It's never X'd my mind either, or K or H shaped.

However, I've just been outside to investigate, and mine is like two grille shaped bits, with a piece down the middle shaped like the big bit of a cricket bat. Fascinating!

[loppylugs 8,427]

That would be a horizontally polarized uhf aerial, Fly.

[FLY2 10,108]

I hope so LL, it cost enough !

I was horizontally polarised last night after three large Jack Daniels!

[colly0410 1,181]

You don't want to get your dipoles, directors & reflectors mixed up: A dipole is just under 1/2 the wavelegnth of the signal to be received, a reflector is a bit longer & about 1/2 a wavelegth behind & inductively coupled to the dipole, a director is a bit shorter than the dipole & about 1/4 wavelgth in front of the dipole & capacitively coupled to the dipole - they often use many directors. However the addition of reflectors & directors to an aerial lowers the impedance of the dipole which is normally about 75 ohms so they use a folded dipole or use a delta match to bring it up to 75 ohms to match to the 75 ohms cable. Most H aerials were a dipole + reflector behind & most X's were a backwards bent dipole with a forwards bent director, not sure about the K shaped ones. UHF aerials usually have 2 to 4 reflectors, then a folded or delta matched dipole, then up to 18 directors sometimes X shaped. Fascinating stuff init.

[FLY2 10,108]

Yeah! Seriously, there's far more to this than meets the eye. You couldn't elaborate further could you colly?

[colly0410 1,181]

Fly2.

I think your aerial is 2 phase linked dipoles with a large mesh type reflector & no directors, the 2 dipoles will will almost double the amount of signal you receive with only one dipole & give it a wide bandwidth, & the large mesh type reflector will give it a good front to back ratio so cutting down on co-channel interference. They were popular in the USA for UHF reception when I was there. A good choice in a fair signal area..

[FLY2 10,108]

That's reassuring as it cost me £346 several years ago.

[colly0410 1,181]

When ITV started in 1956 it used a much higher frequency than the BBC did, some people got passable reception on their BBC aerial (we did, although a bit of ghosting on ITV) but most had a toast rack shaped aerial. This was usually & folded dipole about a 1/4 the length of the BBC aerial with a reflector at the back & 3 to 5 directors at the front, the 2 aerials were combined into 1 down lead usually using a diplexer but sometime using a combined feed point. When BBC2 started on UHF this complicated things big time, most people didn't bother with UHF till the early 70's...

[FLY2 10,108]

Gotcha ! Thanks.

[NewBasfordlad 3,599]

#54 Absolutely riveting or did they ..........................use another method of joining the bits together...............

[colly0410 1,181]

Think some of them used grub screws & some probably did use rivets. Now there's a whole new subject: are rivets or grub screws or self tappers better for aerials? Fascinating subject..

[denshaw 2,871]

Or spot welded?

[colly0410 1,181]

Spot welding, brazing, soldering, all good, got to have a good connection with the co-ax cable. Bit of a hoo-ha on a TV technical forum on whether baluns are required on TV/FM aerials - some say they are & others say they are not. Do ham radio guys use baluns on balanced aerials like dipoles if using co-ax?

[catfan 14,793]

Some do, some don't !

[colly0410 1,181]

Heard it said that a transformer type balun takes about 2 or 3 Db's off the signal, & not having a balun takes about 1 or 2 Db's of the signal, so I suppose they're a waste of money & effort. Someone said on a TV technical site "loop the co-ax a couple of times as near to the aerial as possible & it'll act as a near lossless balun & stop the co-ax downlead from picking up any signal!" Done that to my FM aerial (a vertical dipole) & not noticed any difference, didn't cost me owt though.. 

[colly0410 1,181]

When I've bee abroad I've never seen an X shaped aerial, it just seemed to be a British thing to have weird shaped TV aerials for some reason. I saw some monster TV aerials when out in the sticks in America, most were combined for bands 1, 3 & UHF (Low band, high band & UHF) they were high up on poles with rotators so could point in any direction. The 10'th floor apt I rented on Miami Beach had a rabbit ears V shaped aerial on top of the TV, it got the main 5 stations (PBS, ABC, NBC, CBS & FOX) OK'ish with just a bit of ghosting, all the dozens of UHF stations were snowy. I expect those in the sticks use satellite or internet TV nowadays, been a few years since I've been to the USA so probably changed a bit since my last visit... 

[loppylugs 8,427]

Don't see too many standard antennas out here at all in these days.  Mostly a sat dish or folks are on cable.  I bought an antenna a year or two ago and it was more like the old bbc 2 antennas.

[colly0410 1,181]

Only aerials I've got up are 2 UHF TV aerials in the loft, 1 for the lounge TV & t'other for bedroom TV, both pointing at Waltham, got an FM aerial propped up on the front bedroom window sill, keep saying I'll put it in the loft, but I can't be bothered & it works OK so bu**er it, I'm afraid I'm in lazy mode..

[Ayupmeducks 1,730]

Dave, all the old antennas are useless now, since going digital, all the old TV frequencies are empty, they were assigned much higher frequencies and use less bandwidth than the old analogue TV system.

Not tried to receive anything from where I live, I doubt I'd be able to receive anything here, nearest stations are at Springfield and Jonesboro in Arkansas, I think way too far for digital channels.

 

[loppylugs 8,427]

Hooked it up and tried it a year or two ago, John.   Got around fifteen channels out of the Atlanta area.  Mrs L didn't like it because we couldn't get some of her favorite cable channels. H&G etc.. Also no dvr so we stayed with Directv.  I don't care.  I hardly ever watch the drivel anyway. Two hundred channels and nowt to watch.  If I'm ever left on my own the telly will be the first thing to go.

[Jill Sparrow 10,304]

You wouldn't miss it Loppy. I don't! 

[Ayupmeducks 1,730]

You probably was receiving them on the UHF side of the antenna Dave, I forget where the FCC sold them frequencies now, but the broadcasters lost all the VHF frequencies and most of the UHF frequencies.

I have an antenna for the new digital TV channels and the elements are much shorter than my amateur radio 70cm band. (400Mhz), which suggests above 500Mhz.

[loppylugs 8,427]

I probably should qualify that a bit, Jill.  All outside connection would go.  I have always enjoyed home video.  I actually use a video projector for that.  I have a lot of home video of our travels, plus many of my old 8mm movies of right back to the 70s now on DVDs.  So I would keep the projector at least for that.  Lots of decent documentaries and old movies on DVDs too.

 

John.  Not sure what frequencies the stations I could see were on, but it was an antenna advertised for the new digital stations.  All were coming in in HD so I had assumed they were digital.  Seemed even sharper than Directv.  I understand the sat stations compress their signal to get more channels on but that degrades picture quality a bit.

[Ayupmeducks 1,730]

From what I read Dave, even digital terrestrial TV is compressed data, I've never watched digital TV, don't have an antenna in the air, no cable available in the country and no satellite, budget's too tight for that.

I used to pirate  Dishnetwork and the Canadian birds until they changed to Nag3 encryption. They went after the coders big time, sites lawsuits etc. So no hack available for Nag3.

Ironic, as the CEO of Dishnetwork made his money hacking encrypted satellite receivers for a living years back and got busted, fined and served a couple of years behind bars for it. But being on the other end now, he frowns on hacking. It was called "chipping" in his day, where he'd reprogram the EPROM chip, was a big earner in the big dish days of the late 80's early to mid 90's. Mind the only encrypted stuff back then was "feeds" and porn channels, most everything in the big dish days was news, sports and feeds.

 

[colly0410 1,181]

Been reading up & there are a few digital TV transmitters running on VHF in America, some of them on low band, (info from 'No Cable') but most have migrated to UHF. Las Vegas seems to have a lot of VHF stations for some reason, Miami where I mostly was has 2 multiplex's = 7 & 10 on VHF, all the others are now on UHF. Funny thing is WPBT (the Miami PBS station) says it's on channel 2, but is actually transmitted on a multiplex on channel 17 at UHF, channel '2' is a virtual channel. Here BBC1 is on channel 1 on freeview but is actually transmitted on a multiplex on channel 49 along with BBC2, 4, News 24 & other BBC channels if your on Waltham.  All this multiplex & virtual channel numbering can be quite confusing..