Posts Tagged ‘dipole’

Just Get On The Air! (A Makeshift Temporary Dipole Shortwave Antenna)

It might not take as much antenna as you may think would be necessary to make two-way contacts on shortwave radio (as an amateur radio operator putting an HF transceiver on the air). However, often, makeshift antennae are effective enough to be viable–just look at all the contacts many amateur radio operators make with their low-power (QRP) rigs (transceivers) using short, helically-wound, mobile antenna sticks. If they can work magic with such inefficient antenna setups, surely your effort at an antenna would pay off to some degree. Right?

Of course, I want to make a proper dipole out of this example antenna. But, while I wait for the rest of the parts I need to complete this antenna project (pulleys and a ladder, and maybe a potato launcher), I’ve put this makeshift antenna on the air, with it just high enough so that I can enjoy some time on the shortwave bands.

With this antenna, I’ve made successful two-way voice and Morse code contacts (QSOs) with stations in Europe and across North America. I am able to tune it on the 60-, 40-, 30-, 20-, 15-, 17-, 12-, and 10-Meter bands. Reverse beacon detection picks up my Morse-code CW signals, especially on 40 meters (the band on which it is tuned physically).

The bottom line: just get something up in the air and start communicating. Improve things over time. You’ll have much fun that way.

73 de NW7US dit dit

10m antennas

As you will have noticed by now, 10m is one of my favourite bands.  Although quiet at many times in the solar cycle it always comes to life with Es from late April until September. Alert 10m operators will sniff out Es at other times too, but there may be long periods of noise, as on 6m. WSPR is an ideal mode when the band may otherwise seem quiet.  It is good for local nattering at any time and F2 N-S DX  is often there even at solar minima.  Antennas for the band are small and easy to make such as the design on my website for a 10m halo. See .

A video of K7AGE making a dipole for 10m is available at YouTube.  See   In this video, Randy is making a dipole for the USA technician’s band, so to cover the main SSB band (28.4 to 28.6MHz) you will need to make the wire slightly shorter.  In my experience if you cut the wires for the centre of the band it will still have a pretty low SWR at the band edges. Even a very simple ATU will bring the SWR down to 1:1, although  unless your rig has a problem with a mismatch of around 1.8:1, I would not bother, as the difference in radiated power is negligible (fraction of an S-point).

Because of the short wavelength, 10m antennas don’t have to be that high to be effective. When the band is in good shape, worldwide DX can be had with simple wire antennas and low power. It is a rewarding band.  What is more, 10m multi-mode transceivers can be bought at low cost.  In summary, 10m is unique: low cost transceivers, simple antennas and good DX potential.

New Antenna in the ATTIC!

66′ Dipole ready for the attic!

Over the 3 day weekend I finally squeezed in some time to get my 66 foot ladder fed dipole up in the attic.  One leg of the antenna is basically straight, but the other leg had to do a bit of zig-zagging through the trusses – it gets a bit crazy up there!

The ladder line drops down into my garage and then down to the basement where my shack is located.

Last night I built the BL2 1:1 or 4:1 balun from Elecraft.  The ladder line terminates at the balun and a 3′ piece of coax goes from the balun to my KX3.

Wrapped this all up last night about midnight – and then started doing some testing.  The internal tuner on the KX3 tunes ALL bands 40-10 meters almost down to 1:1 SWR.  Very nice.

I tuned around 40 meters and only heard a couple stations that time of night.  The noise level last night was between S4 and S5 – not sure if this is the normal noise level or not, but I suspect it is.

I did a bit of testing using the RBN – I called CQ on 40 meters for a few minutes and ended up with spots North, South and East of Kansas – good sign.  Then I switched antennas back to my 9:1 UNUN 30′ wire in the attic and did the same thing – so reports.  So good news is that my performance on 40 meters is GREATLY improved.  The reports on my 66′ Dipole were from 10-18 DB SNR on the RBN – all with 5 watts out of the KX3.

At 1:00 am local time I heard  K0GPA calling CQ – he was 559 here.  So I threw out my call and he came back to me with a 559 as well.  Turns out he was running a KX3 also – he was at 10 watts, and I was at 5 watts.  The QSB got him a bit, but I think he was using some type of loop – just missed what type.  It was a nice QSO with Bob – and it proved I was getting out!

So now I am looking forward to putting it through the paces a bit more and see just how much my reception will improve with more wire in the air!  I hope to at least have time to look at the waterfall tonight on 20 meters PSK31 to see what it looks like compared to my old antenna.

I will keep you posted!

Show Notes #091


  • It’s Second Spring in Texas, and Autumn is beginning in Arkansas, so sit back and enjoy another exciting episode of LHS.


  • Paid subscribers to LHS may have noticed the web site certificate had expired. That problem is fixed.
  • Welcome new subscribers Michael S., Michael C., and Bill A. Thank you!
  • Sign-up for the LHS mailing list.
  • Our LHS Ambassador to Ohio LinuxFest will be Scott, N8VSI. Thanks, Scott, and we look forward to hearing all about it.
  • Please donate to the podcast and click on the affiliate links on the website.


  • HF Antennas, Horizontal vs. Vertical
    • Tonight, our hosts discuss the pros and cons of horizontally and vertically polarized HF antennas.
    • One thought is that once the RF radiation hits the various layers in the ionosphere, the polarization doesn’t really matter much as it gets reflected to and fro.
    • Richard offers the practical reason for preferring horizontal antennas for HF: it’s easier to build and erect the long antennas necessary for these frequencies. However, for chasing DX, those long-distance contacts, many hams prefer vertical antennas as they tend to have lower angles of radiation.
    • Also mentioned: GAP antennas and the G5RV antenna.
    • Wire horizontal dipoles are inexpensive and easy to construct. Verticals are a good choice when space is limited and can have a lower take-off angle, providing a good ground radial system is installed beneath them.
    • Horizontal antennas can be more directional. A dipole wire running north and south will have a better propagation east and west. A vertical is omnidirectional, radiating equally in all directions. To complicate matters, a horizontal antenna lower to the ground will radiate at higher angles than the same antenna that is higher. This can be useful for communicating with stations that are close to you.
  • A new section of the podcast: Russ’ Rant!
    • Russ has a Yaesu FT-7900R, a dual-band UHV/VHF mobile radio. It has a removable front panel, allowing the main part of the radio to be hidden and the display can be easily mounted on the dash. However, the speaker is on the body of the radio, so you can’t hear it if it’s hidden under the seat or in the trunk! Russ thinks the head unit should also contain a speaker, perhaps a very small one like in an mp3 player. Or put the speaker in the microphone.
  • Returning to antennas, Richard recommends that KD8SZG (in the chat room), should try building his own wire antennas for HF. Any of the antenna books written by Doug DeMaw, W1FB, are good resources. His Antenna Notebook is one. (I also like the various ARRL antenna books, like the Simple and Fun Antennas for Hams. -Ed.)

Contact Info:


  • “A Little Time” by Not From Georgia, from their album Love & Umbrella, courtesy of Jamendo.
  • “Metal Heart” by Zamza, from their album Songs for Jukebox, courtesy of Jamendo.

Show Notes #084


  • No music this time; just one hour jam-packed with LHS goodness!


  • Remember to sign up for the following LHS services:
    • The LHS SubReddit
    • The LHS Mailing List
    • The LHS Mobile app. Follow our updates via the mobile applications available for iPod, iPhone, iPad and Android devices.
    • Be an LHS Ambassador! Please join our Ambassador program. The event calendar has expanded quite a bit and we need your help. These events are now world-wide, so we could use some help outside the US as well as all over the country from California to Maine.
  • YFKtest: Yes, there really does seem to be a problem. It’s been confirmed by John, EI7IG, that the program does not log contacts for the ARRL Field Day contest. Other contests work fine. Russ plans on emailing the developer, DJ1YFK, with these observations.
  • From the “Yes, It’s an Antenna” File: Multi-band HF dipole made from horse fencing.
  • Pulling a Lunduke: Holding Source Code Hostage. Our hosts discuss this blog post by Tom Nardi about Bryan Lunduke’s recent move to open source his software. Bryan is one of the hosts of The Linux Action Show.


  • Software Defined Radio (SDR)
    • A common topic Russ encountered at Dayton was about the available Linux options for software defined radios.
    • GNU Radio Project
      • Version 3.6.0 released in early May, 2012.
      • Version 3.2.2 is in the Debian Sid repository.
      • The latest version can be retrieved with git. (Install git with the command “apt-get install git”.) To download the software, issue the command “git clone git://”.
      • Build instructions are available for most of the major Linux distributions.
    • SDR Hardware
      • Ettus USRP series works with the GNU Radio Project software. There are various models ranging in price from $700 to $2000, depending on the frequency range and options. Various modules allow receive and/or transmit on bands from 30kHz to 5.9GHz. Unfortunately, power output appears to be just 50-200mW, depending on the bands provided by the transmitter daughter board chosen.
      • Funcube Dongle costs £128 (~$200) and is a receiver only. The Funcube Dongle is a “radio receiver designed to allow anyone to try their hand at reception of satellites like FUNcube”. It covers 51.5MHz – 1.7GHz, less the region from 1.1GHz to 1.2GHz.
      • Perseus SDR costs $1000 and is also receive-only. It receives 10kHz to 40MHz.
      • SoftRock SDR is a kit available in various models from $20 to $90. Most are receive-only, but the Ensemble is a 1W HF transceiver. Some models are unavailable at the moment. The SoftRock RXTX Ensemble Transceiver Kit will allow you to build a 1W transceiver for one of the following bands or band groups: 160m, 80m/40m, 30m/20m/17m, or 15m/12m/10m.
      • RTL-SDR Devices range in price from $20 to $200 and are receive-only. More on the RTL-SDR project in an upcoming episode.


  • Stewart, VA3PID, wrote to say that Russ was the first person, possibly ever, to correctly place his Scottish accent at Hamvention. He also remarked (in reference to a discussion in episode 71) that Chirp has come a long way; it can now program his Yaesu FT-857D!
  • Jonas recently re-discovered LHS and expressed his appreciation for the show. Thanks, Jonas!
  • Stefano, IZ3NVR/KD2BGM, asks for more help getting so2sdr built on his Linux machine. Russ suggests installing the compiler with “apt-get install g++ build-essential”, installing Qt and several other packages as described in Episode 83, then try building the so2sdr program again.
  • Lastly, David Dominicki left a mostly unintelligible comment in response to Episode 78. Um, thanks… we think.

Contact Info:


  • None.

LHS Show Notes #057




  • Richard and Russ talk about the origins of the LHS podcast name. See Linux on the Desktop podcast.
  • Richard talks about how to build a Delta loop antenna, and using a piece of 75 ohm coax to act as a matching transformer between the antenna and the 50 ohm feed line. He also describes velocity factor for coaxial cable. Here’s an illustration of a 20m Delta loop similar to what Richard describes.
  • Just for fun: Fab’s Crap Alert
  • linSmith, in the Debian repositories, is a program for plotting Smith Charts, and more.
  • Richard then talks about Henry Allen W5TYD, formerly K5BUG, of Texas BugCatcher antenna fame, and the inductors he wound around Plexiglas forms. (Henry ceased production of his antennas in 2009 and has retired. -Ed.)
  • Russ uses an Alpha Delta DX-CC multiband dipole, in preference to a G5RV dipole.
  • Other antennas mentioned:
  • Impedance of transmission lines: 50 ohms for communications coaxial cable, 75 ohms for cable TV coaxial cable, 300 ohms for the old TV twinlead, 450 ohms for window line, and typically 600 ohms for ladder line.
  • Richard explains Standing Wave Ratio (SWR).
  • Richard relates an Field Day story from several years ago… Commodore-64 running packet radio on the tailgate of a truck in 100-degree heat, and burning up the C-64.


  • Audio feedback from Frasier K. thanking our hosts for the podcast. He’s currently studying for his ham license via HamTestOnline, and learned about Linux from the podcast. He’s now running Ubuntu 10.10 on his laptop and rockbox on his iPod. He’d like some sort of automatic calendar reminder service to alert him when a new episode will be recorded. Thanks, Frasier, and we’ll look into that.
  • Mitch, KC2MBN, says that he enjoys the podcast. He’s now an Extra class licensee, but is new to Linux. He recently tried dual-booting Windows 7 with Pinguy OS and reports some troubles, and asks for some recommendations for a distro. Thanks, Mitch. If you have a spare machine, it would be better to run Linux on that rather than going to the trouble and risk of dual-booting. You might try actual Ubuntu, Debian or Linux Mint. Crunchbang Linux is also easy to install, as is PCLinuxOS.

Contact Info:


  • “Bad Boy (For You)” by Rebolt from the album “Made in Spite EP” courtesy of Jamendo.
  • “Daylight” by Singleton from the album “The High Seas” courtesy of Jamendo.

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