Antenna for channel 36

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.

Reply to
Peabody
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You want a Yagi antenna. Commercial antennas like you described run about $200, wholesale.

Reply to
Michael A. Terrell

The Wikipedia article on Yagi antennas points to this document

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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.

Reply to
Sylvia Else

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.

Reply to
miso

There are plenty of stand alone and online yagi antenna designers. Google for "yagi designer" and "yagi calculator". If you want it online, add the word "online". The calculator will give you the basic dimensions, the gain, bandwidth, and VSWR. Use the longest boom you consider practical. Bigger is better.

If you want to see whether you have a chance, plug your address into: 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.

For a starter, build the antenna out of #12 copper electrical wire, or thicker aluminum rod. Use a length of kiln dried wood for the boom (green wood doesn't work well). Attach with U shaped staples.

The key part is the driven element. Design for a 300 ohm, folded dipole, driven element and use a commonly available 300-75 ohm transformer balun. That will eliminate any complicated matching networks.

The lengths closest to the driven element are critical. The one's further away are somewhat less important. Element spacing is not hugely critical. Since you probably don't have any test equipment, do your best to cut the lengths accurately.

For an antenna amplifier, just go to Radio Shack and buy something that installs at the antenna, but it's it's power through the coax cable. Use common RG-6/u coax, not twinlead.

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.

--
Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

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

Reply to
Jon Elson

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.

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.

Reply to
Peabody

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 snipped-for-privacy@eskimo.com Googleproofaddress(account:mzenier provider:eskimo domain:com)

Reply to
Mark Zenier

If you want the ultimate gain (or front/back ratio) for a given boom length for a given frequency... yes, the design can be pretty involved. There are software packages which will generate a good Yagi for you, though, based on certain reference designs.

However, you don't need to push for the ultimate. Good enough, will probably be good enough.

One approach you might look into is the "cheap Yagi" design, by Kent Britain. Kent came up with this design in an effort in support of a fellow amateur-radio operator who resides in a relatively impoverished country, where both money and supplies are scarce... it's intended to be something that you can throw together easily, out of commonly available materials.

It's not the ultimate Yagi design, by any means, but it works very well. The basic supplies: something to use as a boom (wood, or white PVC plumbing pipe) and stiff wire (14-gauge copper wire stripped out of ordinary Romex cable works fine; solid aluminum "grounding" wire works equally well for all of the elements other than the one to which you solder the connecting coax) and coaxial able.

Kent has a design document at

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This document shows designs for a bunch of ham-radio frequencies, and there is a set on page 5, for 421 MHz, that are designed for a 75-ohm coax feed such as you would use with a television (it's designed for amateur-radio TV).

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. Even if it doesn't have as much gain as an "ultimate" Yagi, you probably won't notice the difference.

The biggest factor in whether it's successful or not, is probably where you mount it. Higher is better. Up on the roof, on a mast at least a few feet above the roof (with proper static and lightning protection) is best. Hanging it indoors in an attic will probably work unless your roof and walls are too full of metal. Hanging it under your viewing-room ceiling... ditto but moreso.

The longest 421 MHz version is under 5 feet long... scale it down for

603 MHz and it'll be right around a yard long.

Or, take a look at

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and you'll see a more broadly-tuned Yagi which is designed to give compromise gain across a wide span of the television band.

I made one of Kent's designs a few years ago, tuned for around 445 MHz (the middle of the amateur-radio UHF repeater sub-band) out of PVC pipe and scrap wire. Works like a charm, and I think my total expenses were under $10 (even including a 6' PVC mast).

I made a slightly different homebrew Yagi about 15 years ago, tuned for TV channel 11 (VHF high band)... wood, and copper-plated steel welding-rod elements. Worked very nicely indeed.

--
Dave Platt                                    AE6EO 
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Reply to
Dave Platt

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.

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

[...]

Correct.

Yes, it has to be connected in the center.

[...]
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Regards, Joerg 

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Reply to
Joerg

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

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

Oh, forgot to mention, the "beam" of the antenna was a broken-off broomstick!

Jon

Reply to
Jon Elson

But in my particular case, I'm on the

OK, there are a couple ways to deal with this. If there is a big building that is in direct line of sight to the transmitter, you may be able to receive the signal bouncing off that building, or water tower, or whatever. One trick that has been used is a pair of back-to-back antennas at the top of the hill or other good location, to retransmit the signal in your direction.

35 miles should not be a big problem at all, so you just need a way to get around that hill.

Jon

Reply to
Jon Elson

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.

Reply to
whit3rd

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.

Reply to
tm

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

Channel 36 with 602-608 MHz might suggest this is about America.

In order to have any advantage of a "high gain" (=directional) antenna, you _must_ be able to use an outdoor antenna !!

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.

Reply to
upsidedown

Preferrably with an extra 3 to 4 dB gain to allow it to be split for a second set.

Reply to
Michael A. Terrell

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

Reply to
upsidedown

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

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

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.

Jon

Reply to
Jon Elson

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