How to make antenna for a Weather Radio

Use RG-6 (TV coax). If you have any left over, you can make a large (12") loop out of it, anywhere along the way, so you might as well get a length already cut with connectors attached. The connectors will be "F" connectors for TV's etc.

Buy an F to RCA adaptor, but I doubt that it's an RCA connector. It's probably a MOTOROLA connector that looks like a long RCA one. A Motorola connector will fit in (and stick out) of an RCA jack, but not vice versa.

My experience with places like radio shack is that you will have to buy an F to UHF adapter and then a UHF to Motorola. Maybe not, ask. Radio Shack has lots of motorola plugs and adaptors, but their web site is not indexed well and I don't feel like paging through them all.

As for the antenna, you can buy one, or make a simple ground plane or dipole antenna. For example, a simple dipole would be two 18 inch aluminum tubes, separated with about an inch of plastic rod. Connect each side of the coax to one rod, and stack them vertically. You can put plastic caps on the ends of them to prevent water getting in, but don't paint them.

You can play around with the location, orientation (horizontal or vertical) and direction of the antenna for best results.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Occam's Razor does not apply to electronics. If something won't turn on, it's 
not likely to be the power switch.

Here is a link to the owner's manual:

It is 50 ohm, not 75.

It is a RCA/Phono connector. I have the same unit. Use the right connector if you want good reception. You can see it in the photo of the rear panel on page 5.

You don't need any adapters.

A VHF ground plane cut for 162.475 MHz will cover the VHF frequencies used by NOAA: 162.40, 162.425, 162.45, 162.475, 162.50, 162.525, 162.55 MHz

There is a sketch on the NOAA website showing the proper dimensions:

The NOAA transmitters use vertical polarization.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
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** Use an indoor TV antenna - the kind with a pair of telescopic rods for VHF reception.

Spread the rods wide apart and set each to about 18 inches long - get an extension antenna lead if you need to and an adaptor for the plug to go to RCA.

Should all be fine if kept out of the rain.

.... Phil

Something very like the latter should work fine, as long as you have one or two ground-plane radials as well.

One example is at

You don't have to use a socket-and-plug arrangement if you don't want to - simply soldering wires to the center and braid of the coax will work. Might not be as rugged, though.

Another thing you could do is use a piece of flat plastic a few inches on a side as a junction point... fasten the vertical element, radials, and coax to it with twists of wire or plastic zip-ties run through holes drilled in the plastic.

Weather radio is around 162.5 MHz - plug that into the formula on the page above to determine the lengths of the elements needed. You can get away with just 2 radials of you wish, and don't need to be excessively accurate in the measurements.

The type of wire you use to the make the antenna itself won't matter much. Any copper wire (e.g. appliance wire from the hardware store) should work fine... odds are you have something in your spares-and-junk collection which will work perfectly well. If you bend a loop at the top of the vertical element you can even hang the antenna from it!

Depends to some extend on the length. If you need a couple of hundred feet of coax, using a lower-loss type such as RG-6 or RG-8 will give you more signal strength. For lengths of 20' or so, ordinary TV-antenna coax should do just fine.

Some coaxes have a 50-ohm characteristic impedance (used for CB and ham and other transceiving applications). TV coax usually has a

75-ohm characteristic impedance. The ground-plane antennas shown above are designed for 50-ohm operation, but (once again) in a non-critical receiving application like this you should be able to use either type and get acceptable results.

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Doesn't matter. RG-6 has taken over the low end coax market, it's well made, cheap, easy to find and can be gotten in regular, direct burial and long distance hanging (with attched steel wire) versions.

For reception, the difference in impedance is meaningless and many hams are using it for transmitting. Most hams use it for transmitters of 100 watts or less, but some have reported using it for 500. (ouch).

That's a lot easier. I have RG-6 compression RCA connectors. Strip the coax with simple tool, trim the center conductor and squeeze. I bought

50 of them off of ebay including the compression tool for $50.

F to RCA adapators are easy to get an cheap.

Ground planes are more difficult to make, he asked for cheap and simple and a dipole will do it. Almost anything from 15 to 20 inches a leg will do. I picked 18 as it's a foot and half and simple to measure and make. Making it out of tubing instead of wire makes broadband enough that it will cover all of his VHF scanning needs.

Two meter ham band antennas, of which I've made many, need to be 19 inches, so 18 is close enough for 162mHz, and is simple. If the person building it buys 3 feet of tubing, and cuts it in half, it will work well.

Good to konw, and it probably will be what he needs, but he may have reflections, hills, buildings, etc in the way so it always is better to try than not.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Occam's Razor does not apply to electronics. If something won't turn on, it's 
not likely to be the power switch.

The steel wire is called a messenger wire. I live in a forest, and such coax is really handy for preventing cable breakage when a big branch fall on the coax.

I agree. 75 ohm coax is cheaper, generally better made, lower loss, and nice and stiff for building a coaxial antenna (by slipping the braid back over the outer jacket). The loss of typical 75 ohm coax is less than the equivalent 50 ohm coax thus compensating nicely for any mismatch losses.

For what it's worth, I have rolls and rolls of 75 ohm coax, that I use for literally everything from HF antennas to WX satellite. The only time I would consider demanding 50 ohms is when the mismatch is guaranteed to cause a problem, such as detuning a repeater cavity duplexer, when I need the absolute lowest loss as in satellite work, or when running high power.

See the max power versus impedance graph:

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# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
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Yes, it's dirt cheap, but I still use the right cable. If you looked at that NOAA sketch you will see that the connector was a SO-238 UHF connector. You can get an adapter for RG-59 for the PL-259 mating connector, but I haven't looked for any for the newer RG-6 Double braid/double shielded coax. Hams around here prefer RG-8X.

Difficult? I've made them in less than 15 minutes with a 1/4 electric drill and hand tools. It would be less than 10 if you have access to a drill press and a drill vise.

How are you going to keep dirt and water out of the top end of the coax with a dipole?

I have always had good results with a ground plane antenna, and poor with anything else. A Yagi could be used, but less than 1% of the US is in an area that needs the gain. Most areas can pick up two or three different transmitters, but you want to use the closest, because of NOAA's S.A.M.E that can tailor the alerts to a single area.

I have used a weather radio or scanner on NOAA for decades.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.