Copyright © 1999-2011 by Harold Melton KV5R. All Rights Reserved.
Understanding Shortwave Antennas: Page 4
The shortwave spectrum is divided into bands. You need a basic familiarity with this to use a shortwave radio effectively. The shortwave spectrum is about 25 times larger than the AM broadcast band (.55 - 1.7), so you need to know what is where, and when.
The bands are called “Meter” bands and are identified by their approximate wavelength in meters.
- M = Meter
- Ham = Amateur
- BC = Broadcast
- P = Popular, somewhat congested band with many stations
|1.8-2.0||160 M Ham||Late Night|
|2.3-2.4||120 M Bc||Late Night|
|3.2-3.4||90 M Bc||All Night|
|3.5-4.0||80/75 M Ham||All night|
|4.75-5.07||60 M Bc||All Night|
|5.9-6.2||49 M Bc, P||All Night|
|7.0-7.3||40 M Ham||Eve, Night, Morn|
|7.1-7.4||41 M Bc (foreign)||Eve, Night, Morn|
|9.4-9.9||31 M Bc, P||Morn, Day Eve|
|10.1-10.15||30 M Ham||Morn, Day, Eve|
|11.65-12.05||25 M Bc, P||All day|
|13.6-13.8||21 M Bc, P||All day|
|14.0-14.35||20 M Ham||All day|
|15.1-15.6||19 M Bc, P||All day|
|17.55-17.9||16 M Bc, P||All day|
|21.0-21.45||15 M Ham||All day|
|21.45-21.85||13 M Bc||Not used much|
|25.67-26.1||11 M Bc||Not used much|
|26.965-27.405||11 M CB||Lots of noise|
|28.0-29.7||10 M Ham||All day, sometimes|
Notice that 40 meter ham and 41 meter broadcast overlap. This is a big problem we are working to fix in the next international radio conference.
As you can see, the broadcast bands starting at 5.9, 7.1, 9.4, 11.65, 13.6, 15.1, 17.55 are the main place where most all your shortwave broadcast listening will be concentrated. Note, however, that some stations fall slightly outside of these ranges, so make sure to tune above and below them. Also, band edges, and broadcasters’ frequencies, change from time to time. So, it pays to keep fresh frequency schedules. Search the internet for “shortwave shedule” and you’ll find plenty. Locate one that you like, and that has fresh data. Shortwave listening magazines, and their web sites, are also good sources.
Most Amateur communications uses single-sideband. You need an SSB-equipped radio, or one with a “BFO” control, to receive them.
I have about 65′ of Flex Wire and a center fed Budwig connector, there are no available trees. My coax to the receiver is via an attic vent located at the top of roof gable. I am located in West Tenn. I do not live in a restricted subdivision.
I want to listen to amateur ham radio on 40,20 and 10 meter bands. Additionally I like to listen to some foreign broadcasts ( Voice of Vietnam, Radio Romania, etc.).
What is the best way to string out my long wire? I was thinking of running an inverted “V” using the sides of the roof up to the peak of gable where the attic vent is. ( approx. 17′ on each leg = 34-35′ total).
Would just one single 65′ long wire away from the house be better than the inverted “V”?
Can I use just one end/side of the Budwig connector and make it an end fed connector?
Which direction should the long wire be strung out N to S or E to W?
Which direction would give me the best coverage for U.S.A. amateur ham bands?
Thanks for your time!
A dipole is always better than an end-fed, particularly when feeding it with coax. Use your entire 65 feet of wire (to listen down to 40 meters), inverted-v on the gable, then bending the ends around the corners of the eaves. Staple it to the backside of the fascia boards — virtually invisible.
As for getting foreign SW broadcasts, low horizontal antennas get the most signal at high angles, like 45-90 degrees (good for a few hundred miles). For DX, you need low angle, like 10-20 degrees, and for that you need a vertical — telescopic aluminum, or a flagpole, or (cheapest) a couple sections of 1-3/8″ chain-link fence top-rail. 34 feet high will get you down to the 40 meter band and a decent angle for DX. But for a vertical monopole you need a tremendous ground system or it’ll perform very poorly.
I sometimes hear Asian BC on my 20 meter vertical dipole, but it sounds horrible, lots of fade and multipath distortion; better off to just find those guys on the internet or FTA satellite receiver.
As for wire direction, it won’t matter much at all. For Asian DX E-W might be a little better, since dipoles receive off the sides and Asia is more-less North of USA (great circle route). But remember that many modern SW BC stations use satellites and to feed SW transmitters located nowhere near the country of origin, so it’s hard to tell where a signal is really coming from.
Could you explain briefly why for a vertical long wire you’d need “a tremendous ground system or it’ll perform very poorly”? Isn’t the only purpose of grounding the one of letting high voltages charges discharge in a safe way?
I said “vertical monopole” not longwire. Vertical monopole (aka “ground plane”) antennas mounted at ground level need like 60 buried radials to create the inverse image plane. Note that RF grounds are not the same thing as DC, static, or lightening grounds.
In the context of the previous reply, the OP was looking for a low-angle antenna to best receive DX stations, and I replied that would be a vertical monopole with its necessary RF ground radial system — however, in practical terms, a horizontal dipole, mounted at least 1/2-wave high, is a lot easier to deploy.