Here's a link to the now famous coat hanger antenna.
There are a couple variations of this but this is the basic idea. It's
mostly a UHF antenna but some guys get upper VHF channels especially
with an added reflector. That version builds the bowties on one edge
of a 2x4 with a piece of plywood (or cardboard) covered with foil
attached to the other edge. You can also combine 2 for more gain and
some guys are mounting them on a rotor.
I built one and set it the back yard and it worked just fine. I used
pieces of romex I found laying around the jobsite for the bowties. I
haven't fished a wire from the basement to the attic yet so now it's
hanging in the floor truss space for emergencies. Basically that's at
ground level and it even works there.
You can buy practically the same antenna for not a whole lot of money
but where's the fun in that?
I'll probably build a seven-element quad much like the 2m (146 MHz)
antenna that let me check into a Rhode Island FM repeater net from my
Minnesota home using a 14W transceiver.
Swingman helped me draw the hubs with SU a while back. :-)
Good electronics, good antennas (IIRC they had a Phelps-Dodge omni at
60'), and a 1200 mile "wormhole" is the only explanation I can offer.
There was considerable surprise at both ends - that's a /long/ way for a
low-power VHF signal to travel.
SU did well until I tried to add a threaded hole for a setscrew. :-(
Me too! I learned a trick or two about 10d nails from that. At this rate,
I'll be ready to test again, oh say, 2012 when the auroras descend again to
the plains states. Wondering if Skynet and Nostradamus will cooperate. (I
worked Moscow on 3 watts in 2000 on an attic wire. That was special enough
Signal propagation is a wonderful thing.
I remembrer one night I was watching something on Channel 4 in Jacksonville,
Florida, and the picture faded out and came back with a different show from
the one I had been watching. Then there was a station break and I found
that I was now watching the Channel 4 that was in some place more than a
thousand miles away (I forget where--that was at least 40 years ago).
On Tue, 21 Apr 2009 22:16:45 -0500, Morris Dovey wrote:
Tropo duct, no doubt.
I think the bandwidth of that quad is going to be a bit narrow for even
one digital channel, let alone a whole range of channels. You ought to
be able to put together a simple log-periodic yagi that would likely do
Hmmm... what would a log-period quad look like?
An interesting question. Configured for the highest gain I've managed to
achieve, the element lengths made a geometric progression, and the
element spacings an arithmetic progression.
Way back I built one for a friend who lived in Philly so he could watch
a NYC sports channel (Channel 9?) and it worked well sitting on a pair
of sawhorses in his garage. He was a /very/ happy camper. :)
On Wed, 22 Apr 2009 09:57:37 -0500, Morris Dovey wrote:
Antenna theory is definitely not one of my arrows, and I've never really
learned/understood the things that go into computing proper (or optimal)
element length and spacing for a yagi or LPY. What you describe sounds
vaguely familiar. I assume your multi-element quads use a single driven
element. But a log-periodic antenna uses multiple driven elements of
varying length, and this is what gives it wider bandwidth. I don't see
why that couldn't be done using quad elements rather than dipole
elements. But as I said, I just don't know.
When I lived in and around Philly, getting most of the NYC channels was
pretty easy with even the simplest roof-top antenna.
I still have no clue what his problem might have been (I was living in
NJ and wasn't much of a TV watcher). He complained one day at work and I
took the antenna to his place the following Saturday morning, we did a
quick test in his garage, and I headed home.
Because with digital TV you need more signal to get any picture at all
compared to analog. If the signal is just below the threshold, you get
a totally useless picture or no picture at all. With analog, the same
picture would just have a bit of snow.
Having said that, the "new better digital" antennas are not different
than antennas before digital. You just *may* need one with more gain
to get a picture.
Shoot. I live so far out in the burbs that a folded dipole gets only a few
FM radio stations. Rabbit ears get only WGN (the station, of course, and
also white gaussian noise elsewise). There's a 20 year old, normal, ordinary
log periodic TV antenna lying in the attic, that hasn't been used in 19.9
years. It would probably work well enough if I mounted it outside where it
belongs, but it serves a useful purpose right now broadbanding the half wave
20m dipole, also inside, so it tunes enough to transmit on 40m and 15m.
We've been on cable and dish since long ago, all digital for at least half
that. Not everyone lives close to the city center.
On Tue, 21 Apr 2009 18:47:59 +0100, J. Clarke wrote
Ahhh.. that's the digital difference, it's very much an "it is or it isn't"
situation from the signal stream right down to end user satisfaction.
Some sort of fractal logic at work here, perchance, the microcosm implicit in
the macrocosm - the opposite of ironic?
In Britain it's become some sort of elitist game. I know plenty of people
with NO worthwhile terrestrial signal unless they hang on to their five
channels of analogue reception while others have a gerzillion channels of
sparkling, crystal-clear worthless junk. It's going to be quite bloody when
the all-noing government pulls the plug on all analogue broadcasts. Some
rural areas are either going to have to go satellite or run 60-foot poles up
on top of their picturesque cottages. My mother-in-law lives maybe 10 miles
from a transmitter but is in a reception shadow (hilly terrain.) Like
everyone else in her area, she has the digital box and an expensive new
antenna rig but still watches analogue because the reception is great,
channel switching is instantaneous and she is comfortable with her
traditional stations and has no desire for forty channels of manga. I had a
play with her set and it takes maybe 20 seconds to change from one channel to
another to find out that it's something you don't want to watch.. Channel
surfing is effectively impossible, and the "guide" takes just as long to
scroll through.. each line takes about 20 seconds to refresh.
Everyone in the village is in a similar situation, so it's not just the
senile old bat going luddite with the technik.
There are 10 types of people in the world: Those who understand bananary and
those who prefer a straight answer.....
I was wondering how they get those subchannels.
I live about 50 miles from the transmitter tower. The analog TVs were never
able to get consistent signals from the UHF stations. Now, however, these
stations come in quite well.
But, since nothing is broken here, there is nothing to fix (yet).
Subchannels are on the same carrier - IOW the same frequency - as the
main channel. The various data streams for all of the channels, both
video and audio, are divided into fixed-length sections called packets.
Each packet includes a few bits that say which stream the data in it
belongs to. Then the packets from the various streams are mixed together
("multiplexed") to create the transmitted data stream.
When you switch among subchannels for a particular main channel, all you
are doing is telling the receiver to pick the packets that belong to the
The frequencies will change due to the need to simultaneously transmit
the digital and analog versions of the channels for some period of time,
and then reclaim some of frequencies from the low VHF and high UHF
channels for other uses once the analog signals are turned off.
Depending upon where you are, you may still need a combination high
VHF/low UHF antenna to receive all of the digital stations in your area.
I know this is true in Philadelphia PA, for example, where WPVI and WHYY
will relocate their digital transmissions to the high VHF band on June
If you ever need a antenna with a bit more capability,
google "HDTV coat hanger antenna". You will likely be able
to receive stations you didn't know were even there. The
added plus is that it is also very economical to make.
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