Login Join Maker Pro

# Antenna for channel 36

P

#### Peabody

Jan 1, 1970
0
I need to bring in a distant TV station, and would like to build an
antenna specifically for that channel. It's physically channel 36,
which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.

I just told you everything I know about antennas, and haven't had
much luck on Google. I need it to be about 3-4 feet long, and it
will be indoors. If anyone knows of a fairly simple design that
might work, I would appreciate a link.

I have a $10 indoor antenna, and it gets all the local channels, but not the distant one. The tuner shows the channel is there, but at low strength, and I'm hoping an antenna with the elements optimized for channel 36 will be enough to bring it in. S #### Sylvia Else Jan 1, 1970 0 I need to bring in a distant TV station, and would like to build an antenna specifically for that channel. It's physically channel 36, which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm. I just told you everything I know about antennas, and haven't had much luck on Google. I need it to be about 3-4 feet long, and it will be indoors. If anyone knows of a fairly simple design that might work, I would appreciate a link. I have a$10 indoor antenna, and it gets all the local channels,
but not the distant one. The tuner shows the channel is there, but
at low strength, and I'm hoping an antenna with the
elements optimized for channel 36 will be enough to bring it in.

The Wikipedia article on Yagi antennas points to this document

http://tf.nist.gov/timefreq/general/pdf/451.pdf

indicating that the design is far from straightforward.

I'd just get a normal rooftop UHF (band IV/V) wideband antenna, and see
how well it works indoors.

Sylvia.

M

#### miso

Jan 1, 1970
0
The Blonder Tongue BTY-10-U is a high gain UHF antenna that spans a few
channels. It is not cut for one channel, but you would get the one that
spans channels 57 through 69. I have my doubt how well this will work
indoors.

Unless your time is 100% free, I'd get an antenna off the shelf. When
you roll your own antennas, it is an exercise in material science. You
can build out of aluminum, but there is always that nasty connection to
copper. If you build out of copper, the thing is heavy. Plus copper
isn't cheap.

P

#### Peabody

Jan 1, 1970
0
Jeff Liebermann says...
If you want to see whether you have a chance, plug your
<http://www.tvfool.com>
and check if you will have enough signal from the
station of interest. All the antenna gain on the planet
will do you no good if there's no signal to receive.

Yes, I've done that, and also confirmed with the station
engineer that under normal conditions people in my area
do get the channel. But in my particular case, I'm on the
backside of a large hill with respect to the station's
antenna, so I may just be blocked no matter what I do.

I'm 35 miles from the antenna, but a friend of mine 10 miles
farther out can get it ok. But he's out on the flat plains,
and has a rooftop antenna.

Remember the analog-to-digital transition? Well I got one
of those voucher-paid converters, just in case, which I
haven't used until now. It's a Zenith DTT901, and it can
display a little signal-strength meter in real time. The
local channels that I get just fine come it at about 70% on
the meter, or close to that. It does detect channel 36, but
at about 35%, and the tuner just can't make sense of it at
that point - it doesn't even display the nominal channel
number.

But that's with a RCA ANT111, with just the basic single
loop for UHF. So I thought with maybe a little better
antenna, I might be able to receive the channel.

I appreciate all the suggestions. I think I have enough
information now to build a yagi. And with the wavelength
being only about 1.6 feet, it shouldn't be that expensive.
I have some twinlead, and a balun, and maybe even some
copper wire that would work. It turns out that there is the
right Blonder Tongue antenna on Ebay for $100 plus shipping, but, you know, I may learn something about antennas doing it myself. The wooden boom and electrical wire prototype will be a quick test to see if the exercise is worthwhile. If you get a good signal, then either clean it up so that it will survive outdoors, or build a real Yagi antenna out of aluminum tubing. Also have a local ham or RF expert put the antenna on an antenna analyzer to check if it's properly cut and tuned. If it doesn't work well, and you can't find any obvious faults in the construction, it's likely that an aluminum tubing version will work no better. That was my thinking. If I build one for cheap, and the signal strengh is only marginally better, then it's unlikely even a good antenna would do the trick. But if I get major improvement, even if not quite good enough, then it may be worthwhile to build, or buy, something better performing. Just to clarify a couple things - it appears that the reflector and the directors are continuous elements - not cut in the middle, whereas the driven element is cut. Is that right? And does it matter where the twinlead is attached to the driven element - does it have to be at the inside ends? Thanks for all the comments and suggestions. A #### amdx Jan 1, 1970 0 HOW distant is the station? That is the most important parameter, and then maybe if there are any big hills between you and them. Many years ago, I built a very simple 3-element Yagi to pick up a distant FM radio station, and it worked surprisingly well. Distance was about 90 miles. Much of the path was over the Chesapeake Bay, which probably helped some. The front 2 elements were just straight coat hanger wire. The back element was a folded dipole, also coat hanger wire, feeding 300 Ohm twinlead. I got the design out of "Reference Data for the Radio Engineer" and scaled appropriately. I hung it from the ceiling, and tilted it up into the sky about 10 degrees. Your frequencies sound suspect, I don't think broadcast TV has a 96 MHz bandwidth. Jon You're right Channel 36 is 602Mhz to 608Mhz. http://www.csgnetwork.com/tvfreqtable.html Mikek M #### Mark Zenier Jan 1, 1970 0 I need to bring in a distant TV station, and would like to build an antenna specifically for that channel. It's physically channel 36, which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm. I just told you everything I know about antennas, and haven't had much luck on Google. I need it to be about 3-4 feet long, and it will be indoors. If anyone knows of a fairly simple design that might work, I would appreciate a link. I have a$10 indoor antenna, and it gets all the local channels,
but not the distant one. The tuner shows the channel is there, but
at low strength, and I'm hoping an antenna with the
elements optimized for channel 36 will be enough to bring it in.

There were plans for an easy to build four bay Hoverman on a website
back a few years ago. This is a broadside array, not a boom antenna.
But it's basically just some sticks, a couple lengths of bent wire,
(and an optional screen if you want it to be unidirectional, instead
of bidirectional). It will probably have as much gain as you can get
with a convenient Yagi. This would be a low effort try just to see
if more antenna will help.

Somebody here in the newsgroup built it, try and see if google groups has
the traffic (with the URL) from around the time of the digital conversion.
Or google for terms like "UHF", "Four Bay", "Hoverman". I vaguely
remember it as being on a Canadian web site.

Mark Zenier [email protected]

J

#### Joerg

Jan 1, 1970
0
Peabody said:
Jeff Liebermann says...

Yes, I've done that, and also confirmed with the station
engineer that under normal conditions people in my area
do get the channel. But in my particular case, I'm on the
backside of a large hill with respect to the station's
antenna, so I may just be blocked no matter what I do.

Once you get a Yagi going try pointing it in the opposite direction if
you can't catch enough signal. May sound weird but sometimes it can pick
up a station via reflection from a gutter or metal roof far away, from a
house that can "see" the station.

I'm 35 miles from the antenna, but a friend of mine 10 miles
farther out can get it ok. But he's out on the flat plains,
and has a rooftop antenna.

Remember the analog-to-digital transition? ...

That <censored> transition was a major loss for us. Many evenings we can
barely receive a single station, on account of multipath reception.

[...]

Just to clarify a couple things - it appears that the
reflector and the directors are continuous elements - not
cut in the middle, whereas the driven element is cut. Is
that right? ...

Correct.

... And does it matter where the twinlead is
attached to the driven element - does it have to be at the
inside ends?

Yes, it has to be connected in the center.

[...]

J

#### Joerg

Jan 1, 1970
0
Jon said:
Oh, forgot to mention, the "beam" of the antenna was a broken-off
broomstick!

Probably could have glued it but told your wife it's beyond repair
because you had already mentally repurposed the broomstick piece

W

#### whit3rd

Jan 1, 1970
0
I need to bring in a distant TV station, and would like to build an
antenna specifically for that channel. It's physically channel 36,
which is [602 - 608 MHz}
... designs for a bunch of ham-radio frequencies...
If you take one of the 421 MHz designs (the longer ones have more
elements and more gain), and scale all of the dimensions down in size
by the ratio of (421/603), and wire it up, it should work quite
decently.

I did this very thing a few decades ago, and would offer three more bits
of info.

First, the yagi design is very directional; find the correct bearing to your
transmitter with (for instance) info from antennaweb.org.

Second, long range transmission is limited by line-of-sight, and the curvature of the
earth. Higher antennae see farther. If you can't get your antenna high, look for
high items that act as reflectors (my best reception was with the antenna
aimed at a nearby ham operator's high antenna mast).

Third, lots of folk will suggest amplifiers; they do NOT GENERALLY HELP
because your signal-strength limit is on signal/noise ratio, which is
not improved by any addon amplifiers. Amplifiers amplify noise just like
they amplify signal.

T

#### tm

Jan 1, 1970
0
whit3rd said:
I need to bring in a distant TV station, and would like to build an
antenna specifically for that channel. It's physically channel 36,
which is [602 - 608 MHz}

Third, lots of folk will suggest amplifiers; they do NOT GENERALLY HELP
because your signal-strength limit is on signal/noise ratio, which is
not improved by any addon amplifiers. Amplifiers amplify noise just like
they amplify signal.

This is certainly not correct. The loss in the feed line adds directly to
the noise figure. Put a LNA right at the antenna and you establish the
system NF to that of the LNA.

U

#### [email protected]

Jan 1, 1970
0
I need to bring in a distant TV station, and would like to build an
antenna specifically for that channel. It's physically channel 36,
which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.

Where are you living ? In Americas or the rest of the world ?

Channel 36 with 602-608 MHz might suggest this is about America.
I just told you everything I know about antennas, and haven't had
much luck on Google. I need it to be about 3-4 feet long, and it
will be indoors.

In order to have any advantage of a "high gain" (=directional)
antenna, you _must_ be able to use an outdoor antenna !!
If anyone knows of a fairly simple design that
might work, I would appreciate a link.

If you are limited to indoor antennas, there is no point in using long
(directional) yagis, _unless_ you have a direct view from your window
towards the transmission station.

U

#### [email protected]

Jan 1, 1970
0
whit3rd said:
I need to bring in a distant TV station, and would like to build an
antenna specifically for that channel. It's physically channel 36,
which is [602 - 608 MHz}

Third, lots of folk will suggest amplifiers; they do NOT GENERALLY HELP
because your signal-strength limit is on signal/noise ratio, which is
not improved by any addon amplifiers. Amplifiers amplify noise just like
they amplify signal.

This is certainly not correct. The loss in the feed line adds directly to
the noise figure. Put a LNA right at the antenna and you establish the
system NF to that of the LNA.

Since the OP was not able to use an outdoor antenna, the issue of
antenna amplifier gain or feeder losses are quite irrelevant.

J

#### Joerg

Jan 1, 1970
0
Jon said:
Ahhhh, this was LOOONG before I got married! Now, with kids, a broom
handle lasts about 2 weeks around here, the threaded end gets broken off.
Of course, most of that crap is now tinfoil rolled into a tube with a
plastic threaded piece crimped to the end. You can crumple the
handle just by rough handling. Sometimes you still see a wood handle,
though.

Tell your boys that this is _not_ a baseball bat and also not for
playing hockey

K

#### [email protected]

Jan 1, 1970
0
Once you get a Yagi going try pointing it in the opposite direction if
you can't catch enough signal. May sound weird but sometimes it can pick
up a station via reflection from a gutter or metal roof far away, from a
house that can "see" the station.

Or point the null to eliminate one source of multi-path.
That <censored> transition was a major loss for us. Many evenings we can
barely receive a single station, on account of multipath reception.
I probably should try OTA where I am now but there was no hope where I
was before.

Yes, the driven element of a yagi is a dipole.
Yes, it has to be connected in the center.

It is a dipole. ;-)

J

#### Joerg

Jan 1, 1970
0
Or point the null to eliminate one source of multi-path.

In our case there are many stations such as Fox-40 where there is no
null. You always have tons of signal but sometimes the TV can't decipher
any of it, other times it sorta works. 80-90% of the time, at the most.
That was our "digital dividend" :-(

DTV, what a joke. I think it means "disrupted television" or something.

I probably should try OTA where I am now but there was no hope where I
was before.

Other than evening news (which you can get on the web), some old movies
(if you are lucky and the signal path holds for 2h) and Dancing with the
Stars it's hardly worth it. In contrast to the election our favorite
candidate won yesterday on Dancing with the Stars.

Yes, the driven element of a yagi is a dipole.

It is a dipole. ;-)

Sometimes they are fed a bit off center to find a match compromise. My
portable EMC antenna is like that.

M

Jan 1, 1970
0
If you found the BTY-10-U cut for your channel for 100, I'd get it. Worse comes to worse, you put it back on ebay. That price is about half of what Solid Signal charges. I only build antennas for what I can't buy. It is way more work than you think. If you don't want to buy the BT antenna, I would suggest building a biquad. They don't take long to build. You would probably have to scale a biquad designed for wifi. Your reflector would be Al screen rather than PCB at these dimensions. The thing with yagis or log periodics is that you need to align a lot of things for the magic to happen. The biquad doesn't have many critical dimensions. J #### Joerg Jan 1, 1970 0 Jim said: [snip] In our case there are many stations such as Fox-40 where there is no null. You always have tons of signal but sometimes the TV can't decipher any of it, other times it sorta works. 80-90% of the time, at the most. That was our "digital dividend" :-( DTV, what a joke. I think it means "disrupted television" or something. Well! It _is_ successful. It's breaking you of relying on OTA TV, is it not ?>:-} Yup. But it backfired on the stations. This is a fairly affluent middle-class neighborhood and many people can't see much OTA TV anymore. Got miffed, pulled the plug. Now they get the news via Internet and the movies via Netflix. Guess what that does to the ad revenue of the stations. You mean you're still watching "Dancing with the Has-been Stars ? Until yesterday, that was the grand finale. My wife and I did a lot of ballroom dancing so we always thoroughly enjoy that. And ok, the hi-res is nice for such events. If the signal holds, that is. [snip] I get 1000's of Channels with beautiful picture quality and useless content :-( Now you know why we have neither cable nor satellite TV. P #### Peabody Jan 1, 1970 0 [email protected] says... Yes, the driven element of a yagi is a dipole. It is a dipole. ;-) Well, that brings up the issue of what kind of dipole. From what I've read, using a folded dipole as the driven element has two advantages - it provides a broader bandwidth (which isn't really important in my case because I only need one channel), and it provides a better match to a standard 300/75 balun. Apparently a simple dipole presents matching problems, although to tell you the truth I don't understand why. I found a video on Youtube which looks like a good example for me to duplicate - adjusted a bit for the difference in frequency. It's a 6-element Yagi which uses a folded dipole: Of course this is an Aussie design, so I'll probably have to turn it upside down. A #### amdx Jan 1, 1970 0 In our case there are many stations such as Fox-40 where there is no null. You always have tons of signal but sometimes the TV can't decipher any of it, other times it sorta works. 80-90% of the time, at the most. That was our "digital dividend" :-( Would it be possible to connect two antennas 180* out of phase then find a couple of happy directions to cancel a portion of multi-path of the Fox-40 signal. Just a thought. Mikek T #### tm Jan 1, 1970 0 Jeff Liebermann said: Line of sight is very important. If the hill is big enough, it can completely block the signal. As I mentioned, a big high gain antenna does nothing if there's no signal to receive. I can run the numbers for you if you send me the station call sign, your EXACT lat-long, and the proposed height above the ground. Something like this: <http://802.11junk.com/jeffl/coverage/RST/> The catch is that I'm rather busy during the holiday madness month and may not have much time to do it right. If you want to try it yourself, you can do a fair job with Google Earth. Reading between the lines, are you proposing to build an indoor TV antenna? If so, that will limit the size of the antenna boom. It would still be worthwhile, but not as much as simply putting the antenna on the roof. Think of devious ways you can install a rooftop antenna. I recently built a yagi out of sheet mylar and aluminum duct tape. It worked. Also, if you do it indoors, you will not have much feed line. The purpose of the antenna mounted amplifier is mostly to compensate for the losses of the coax cable between the antenna and receiver. However, if the coax cable is short (less than 10m) don't bother with the amplifier. Indoor antennas through glass has another problem. The IR reflective coating found on all new construction windows is quite effective at blocking RF signals. That's another reason for a roof mounted antenna. I'm trying to forget. There was more garbage sold as converters than I ever saw in my worst nightmare. Fortunately, most of those were either trashed, recycled, or sold on eBay. The channel number has been virtualized allegedly in order to prevent user confusion. Of course, it did quite the opposite. At this time, the channel number has NOTHING to do with the actual transmit frequency. Various frequency lists will have both the indicated channel and the real transmit channel. The Zenith DTT901 is actually one of the better converters. The limiting factor on almost all of them is receive sensitivity but the Zenith box was better than most. Any proper antenna is better than rabbit ears and a loop. That's why I suggested building a crude wooden prototype before diving into a proper constructed version. If the rabbit ears are as bad as I suspect, anything will gain will make a substantial improvement. However, there's nothing sacred about building a yagi. It just happens to be fairly easy to build and delivers lots of gain. There are plenty of other designs that work. Try a Gray Hoverman antenna: <https://www.google.com/search?q=gray+hoverman+antenna&tbm=isch>100 without any mounting hardware or coax. Add a few dollars for
those. I just was forced to buy a 10ft 1.25" mast at Radio Shock. \$32
each. OUCH!
Oh swell. The price went up for Christmas.

Incidentally, you can compare many commercial antennas at:

Yep. That's the suggested plan.

All elements are one piece except the driven element. However, you're
not going to be building it like the typical yagi calculator shows.
It's not going to be a simple dipole. Build a folded dipole instead.
The feed point will (hopefully) be about 300 ohms. At the feed point
attach a 300 ohm to 75 ohm balun, and then the coax cable to the TV.
One of these things:

Yes it matters and no it's not a simple 1/2 wave dipole. With a
folded dipole, the 300 ohm feed point is at the wire ends.

A few more details... I suggested building a single channel yagi
instead of a broadband antenna because it's easier and because it
delivers more gain. If you build the yagi from any of the online
calculators, you'll end up with a fairly narrow band antenna. The
more elements, the narrower the bandwidth. When the bandwidth starts
to approach that of the TV channel (6MHZ) you're going to run into
critical design parameters and cut dimensions that can't be worked out
by trial and error. So, don't make it with too many elements and you
should be ok. Otherwise, borrow an antenna analyzer that covers the
frequency range, a reflection coefficient bridge with sweep generator,
a network analyzer, or some manner of RF test equipment that can
determine if you've hit the correct tuning frequency.

A rough guess as to bandwidth for the single channel yagi would be
about 15% or about 90MHz (see bottom graph) so you should be ok.
<http://www.supernec.com/yagi.htm>

Here's an antenna a friend built:
<http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
It should work, but doesn't. Note the creative use of hardware store
materials.

--

I think the connections between the top and bottom dipoles need to cross
over.

Replies
7
Views
976
Replies
11
Views
1K
Replies
0
Views
522
Replies
5
Views
866
Replies
10
Views
859