digital tv antenna - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th December 2012, 02:47 AM   #1
Hayden is offline Hayden  Australia
diyAudio Member
 
Join Date: Aug 2004
Location: Mackay Australia
Default digital tv antenna

I was told you need a digital antenna to receive digital tv obviously not because I'm picking most channels up with an antenna that's like nearly 40years old.

I'm missing like 2 channels out of the 30 i can receive in the area so am i better to replace my antenna? is there any difference in an analogue to a digital? I can't see much difference anyway just by looking at them.
  Reply With Quote
Old 12th December 2012, 03:21 AM   #2
diyAudio Member
 
Join Date: Jan 2008
Location: Carp
I live out in the country about 30 miles from the local transmitters. I have a box full of old tv amplifiers and I used to have several analogue antennas. I used to enjoy Dx'ing tv stations and I tried just about any antenna/ preamplifier I could get my hands on. Satelite tv stopped all that stuff. Digital tv uses the same frequencies as analogue tv did, therefore the same antennas will work. When switching to digital, many tv stations changed to another frequency but used the same channel number. ie a local channel where I live that used to be on OTA (over the air) 4VHF is on digital 17UHF but it is still called 4.1 Go figure. With analogue it was possible to receive snowy or weak stations or turn the antennas till the picture was as good as possible. With digital, you either get the channel or you don't. There is no in between. It is possible that the station you wish to watch is a bit weaker, or further away or the transmitter is in a different location and you need to turn your antenna a bit and look for the station. You might also need a larger antenna. Find out the frequency of the station you need and where the transmitter is, then you can find the appropiate antenna. It is no good to buy an 8 bay bowtie antenna for UHF frequencies channels 14-65, when you might need one for low vhf channels 2-6. For some reason none of my old analogue tv rf amplifiers ( signal boosters) work well with the digital channels. The digital tuner seems to overload very easily and I get next to nothing. A good friend of mine used to be happy getting 8 snowy analogue channels at his cottage now he gets 0 digital. he is not happy.
  Reply With Quote
Old 12th December 2012, 03:24 AM   #3
poynton is offline poynton  United Kingdom
diyAudio Member
 
poynton's Avatar
 
Join Date: Mar 2005
Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
Believe the Hype !!!!

You NEED a replacement antenna !!

That's if the 2 missing channels are important to you.

_____________________

We had the same story here in the UK.
You must change your antenna to receive a digital signal.
Remember the year2000 clock stories of planes crashing etc?
Or that you needed to change your loudspeakers to cope with 'digital' music from CDs?


Andy
__________________
If it ain't broke, break it !! Then fix it again. It's called DIY !
  Reply With Quote
Old 12th December 2012, 03:32 AM   #4
freax is offline freax  Australia
diyAudio Member
 
freax's Avatar
 
Join Date: Sep 2007
Location: NSW
Quote:
Originally Posted by poynton View Post
Believe the Hype !!!!

You must change your antenna to receive a digital signal.

Andy
Its ok to believe it, there is some truth to it.

There is actually a dead spot in most Yagi UHF antennas that are installed these days which doesn't necesserially cause any issues but will cause this issue as the OP has said, those 2 extra channels are within the dead spot, hence the hooplah around digital antennas which don't have this dead spot.

But its all rubbish that they put on anyway!!

Its also a good idea to give that 15 year old antenna a refresher if you live in an area that gets a lot of salt air or birds, And masthead amplifiers aren't exactly new either.

But if it works then don't fix it!
__________________
"It seems that perfection is reached not when there is nothing left to add, but when there is nothing left to take away" - Antoine de Saint Exupéry

Last edited by freax; 12th December 2012 at 03:40 AM.
  Reply With Quote
Old 12th December 2012, 11:06 AM   #5
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
The quick answer is that there is no such thing as a digital TV antenna.

The slow answer is that TV antennas were often very poor implementations of the brilliant Yagi-Uda design. They had lumpy patterns, lumpy frequency response and in most cases no balun so interference was picked up on the coax cable screen. Fotunately, analogue TV was fairly robust and offered graceful degradation.

Terrestrial digital TV has a more fragile signal and suffers from the digital cliff. It is particularly upset by impulse interference, such as that commonly produced by unsuppressed switches in household appliances. Cheap chinese SMPS can create a general RF mush in any modern house. 'Digital TV' antennas typically have wider bandwidth, smoother patterns and include at least a crude balun. When used with decent coax (which can be hard to find these days) they should give a more reliable TV experience, unless you are fairly near the transmitter when an old 'analogue' antenna will be good enough.

Basically a 'digital' antenna is just what any good TV antenna should always have been, but often wasn't.
  Reply With Quote
Old 12th December 2012, 11:25 AM   #6
diyAudio Member
 
sofaspud's Avatar
 
Join Date: Nov 2005
Location: San Antonio
Yagis are directional so you might try turning yours to see if reception of the 2 channels improves. If it's possible to raise the antenna height that will improve things too. YMMV but my old Tru-Spec TA12 amplifier works as well as it did with NTSC.
__________________
It is error only, and not truth, that shrinks from enquiry. - Thomas Paine
  Reply With Quote
Old 12th December 2012, 01:37 PM   #7
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
How old is your co-ax cable (or is it twin-lead)? The Sun & the weather are hard on cables.
__________________
Kevin
  Reply With Quote
Old 12th December 2012, 02:02 PM   #8
Account disabled at member's request
 
Join Date: May 2006
Quote:
Originally Posted by freax View Post
Its ok to believe it, there is some truth to it.

There is actually a dead spot in most Yagi UHF antennas that are installed these days which doesn't necesserially cause any issues but will cause this issue as the OP has said, those 2 extra channels are within the dead spot, hence the hooplah around digital antennas which don't have this dead spot.
Whats that ????
What nonsense, next theyll be trying to make the public believe in pigs that fly and whose meat therefore tastes better. All-out for a buck.

I saw the same situation in my country when we last year changed to digital TV.
The announcement was no tv without new antenna, I saw people running about paying upto 400 euros to get new antennas which were unnecesary in 99 % of the cases. The only ones that had to was a result of the closure of some repeater stations and needed more powerful antennas as the next station available was at further distances.
  Reply With Quote
Old 12th December 2012, 02:37 PM   #9
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Digital TV often (at least in the UK) has channels spread over a wider frequency range than the careful planning which went into analogue. Analogue was planned on the basis of providing four high quality signals to almost all the population. Digital seems to be planned on the basis of getting as many channels as reasonably possible with vaguely acceptable quality to most people. Therefore it is more likely that digital will need a wider bandwidth antenna. In some cases this means a log-periodic rather than a Yagi. These are naturally wideband but have less gain so best for strong signal areas.
  Reply With Quote
Old 12th December 2012, 03:20 PM   #10
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Double or triple length rabbit ears, standard balun, and an amp immediately after.
Make last foot or so (open ends away from balun) of lossy iron wire. And do not
use wire covered with insulation (close coupled dielectric will change the velocity).
I tie wrap mine to bamboo (A frame) every foot, so dielectric is mostly not touching.

So anyways, you want to lay this thing flat in your attic with no competing horizontal
wires, ducts or foil nearby, nor in the line of sight signal path. Vertical metal things OK.
The open (lossy) end you point at the stations with 30 to 45 degree spread, no wider.
The balun and amp face away from the stations.

This is a non-resonant UHF V antenna that picks up the entire band and all stations.
But the impedance is all over, even with balun it doesn't match 75 for all channels.
Thats why you need that amp close to the balun, to finish the impedance match.
So your cable doesn't favor stations with strong standing waves and omit others.
The amp must be close, so standing waves can't form.

It is directional toward the open end of the V. If you omit the lossy ends it will
pick up off the back too, but becomes a resonant dipole with standing waves.
The lossy open ends on the long rabbit ears are critical to picking up all stations.

The last foot of mine (#10 ground wire, not grounded obviously) is insulated.
Yeah I know I said don't do that, but its only the lossy last foot. And wrapped
a spiral of iron bailing wire such that it does not touch itself or the antenna.
Its important the spiral wrap not touch itself and make a toroid. That would
cut the antenna short, hard, and probably resonant off the reflection...

Anyways again: This works cause the speed of radio in air is slightly different
than speed of radio in the bare wire (insulated wire speed difference is too great).
Not because anything needs tuned to resonance. Resonance is not your friend.
Look you up Beverage, Longwire, V, and Rhombic for more theory...

Use a low noise RF amp for your antenna. Look for +10dB gain or less.
If it doesn't say, then assume it ain't low noise. Cable TV amps are too noisy.
You want a distribution amp AFTER your low noise amp, might be OK.
But I see too much noisy gain causing problems more often than too little.

Expect +12db directional gain from the antenna itself. KD5ZXG

Last edited by kenpeter; 12th December 2012 at 03:35 PM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Optical Digital out on tv bonsai171 Digital Source 2 12th December 2012 05:55 AM
Digital TV lassipr Everything Else 5 21st April 2012 11:45 AM
DIY TV Antenna 2.0 tubelab.com Everything Else 50 29th April 2011 10:20 PM
amplified tv antenna karma Everything Else 2 23rd July 2004 01:48 AM


New To Site? Need Help?

All times are GMT. The time now is 10:55 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2