Pulled the trigger on this on March 26, 2016 from Ham Radio Outlet. I have not been this excited in years!
REFERENCES:
Tuesday, March 29, 2016
My New Toy - ICOM 7300
Pulled the trigger on this on March 26, 2016 from Ham Radio Outlet. I have not been this excited in years!
REFERENCES:
Thursday, March 24, 2016
Antenna Analyzers
This post relates to antenna analyzers useful to amateur radio operators. I will list my experiences with these in this article.
Array Solutions AIM 4170
I don't recall what I paid for my AIM 4170. It is an older version and has been replaced with the AIM 4300 ($519). The AIM 4170 exceeded my expectations. It is well worth the price if you are doing any kind of antenna work or network characterization.
The software runs under Windows 7 and works very well. I have not tried to port it to Ubuntu.
The following plot is from a balun I build back in '07.
This plot is from an antenna feed balun I built. Here is a photo:
Driving a Balanced Antenna with an Unbalanced Coax - Why A Balun Is A Good Idea
In a recent conversation about the need for a balun on a dipole fed with coax, the comment was made that no balun is needed because the dipole radiates in a balanced manner.
Well, maybe...
If a dipole is positioned above uniform ground and there are no trees, hills, fences, buildings, or powerline poles, then the statement above might be.
However, the real world has trees, has hills, fences, wet and uneven ground, and powerline poles. It would be rare to have one side of a dipole driving the same free-space radiation impedance as the other side. If there is an unbalance, then the outer shield of the coax will radiate RF to make up the difference. An easy way to think of it is to imagine that one side of the dipole radiates 10 amps of RF and the other side radiates 9 amps due to the imbalance. The difference of 1 amp has to get made up. It gets radiated from the outside of the shield of the coax. Stated differently, the coax center conductor carries 10 amps. The inner shield carries 9 amps and the outer shield carries 1 amp.
An extreme case of this condition would be the feeding of an off-center fed dipole. Clearly, such a design is very much out of balance. A good example of this antenna as well as the method of feeding it is found at [7]. I have used this type of antenna many times in the field at campgrounds. The advantage is that the "long end" can be shot up over a tall pine tree and the short end tied off near the ground. The feed point is, then, relatively close to the operating position.
RF on the outside of the coax will radiate and may radiate RF inside the shack.
My favored method for driving a dipole is to feed it with coax and have a balun at the antenna feed point.[1][2]
Properly constructed, the balun will force all of the current coming out of the center conductor to equal the current returning on the inside of the shield. Common mode current is reduced to nearly zero.
This post prompts an idea for a project - a longitudinal RF ammeter. Feedline imbalance can be detected by measuring the current in both legs of the feedline. If there is a balance, the currents will be equal. An easier way is to construct an RF ammeter to directly measure the imbalanced current. Such a device is depicted in [7, 8].
REFERENCES:
Well, maybe...
If a dipole is positioned above uniform ground and there are no trees, hills, fences, buildings, or powerline poles, then the statement above might be.
However, the real world has trees, has hills, fences, wet and uneven ground, and powerline poles. It would be rare to have one side of a dipole driving the same free-space radiation impedance as the other side. If there is an unbalance, then the outer shield of the coax will radiate RF to make up the difference. An easy way to think of it is to imagine that one side of the dipole radiates 10 amps of RF and the other side radiates 9 amps due to the imbalance. The difference of 1 amp has to get made up. It gets radiated from the outside of the shield of the coax. Stated differently, the coax center conductor carries 10 amps. The inner shield carries 9 amps and the outer shield carries 1 amp.
An extreme case of this condition would be the feeding of an off-center fed dipole. Clearly, such a design is very much out of balance. A good example of this antenna as well as the method of feeding it is found at [7]. I have used this type of antenna many times in the field at campgrounds. The advantage is that the "long end" can be shot up over a tall pine tree and the short end tied off near the ground. The feed point is, then, relatively close to the operating position.
RF on the outside of the coax will radiate and may radiate RF inside the shack.
My favored method for driving a dipole is to feed it with coax and have a balun at the antenna feed point.[1][2]
Properly constructed, the balun will force all of the current coming out of the center conductor to equal the current returning on the inside of the shield. Common mode current is reduced to nearly zero.
This post prompts an idea for a project - a longitudinal RF ammeter. Feedline imbalance can be detected by measuring the current in both legs of the feedline. If there is a balance, the currents will be equal. An easier way is to construct an RF ammeter to directly measure the imbalanced current. Such a device is depicted in [7, 8].
REFERENCES:
- "Baluns: What They Do and How They Do It,", Roy W Lewallen, W7EL, http://www.eznec.com/Amateur/Articles/Baluns.pdf
- "Feeding a dipole using a balun", https://en.wikipedia.org/wiki/Dipole_antenna#Feeding_a_dipole_using_a_balun
- "A Cost Effective Current-mode 1:1 Balun", http://www.arising.com.au/people/Holland/Ralph/CMBalun.htm
- RF Current Meter http://vk6ysf.com/RF_Current_Meter.htm
- "A Transmission Line Balance Test Meter, "Lloyd Butler VK5BR", http://users.tpg.com.au/users/ldbutler/Line_Bal_Test_Meter.htm
- "Measurement of relativity between the Longitudinal and the Differential currents in the Transmission Line", Lloyd Butler VK5BR, http://users.tpg.com.au/users/ldbutler/Line_Diff_Long_Meter.htm
- "Array Solutions OCF Dipoles", "", https://www.arraysolutions.com/Products/ocf_dipole.htm
- "Study of the Off Centre Fed Dipole Antenna", "G8ODE", https://rsars.files.wordpress.com/2013/01/study-of-the-ocf-dipole-antenna-g8ode-iss-1-31.pdf
Tuesday, March 22, 2016
SDRPlay Radio Installation Notes
Overview
These notes pertain to the installation and implementation of an SDR (Software-Defined Radio) on Linux and Windows-based machines.
I was able to get the SDRPlay device installed for Windows and for Linux.
Windows Installation
Early on, my attempts to install SDR software on a Linux Ubuntu 14.04 machine failed due to, apparently, missing modules on the workstation.So, I decided that, if I could get it to run under Windows, it would prove that the device worked and would give me confidence that it could be installed under Linux.
The Windows 7 Pro installation went well and I was able to get an SDR running in that OS.
Linux Ubuntu 14.04 Installation
Linux was tricky.
The following links were useful to get this running:
- http://cubicsdr.com/
- http://sdrplay.com/linux.html
- https://github.com/cjcliffe/CubicSDR/wiki/Build-Linux
- http://www.sdrplay.com/linux.html
The order of the steps was not correct in the Build-Linux document. In short, the support modules, listed at the end of the document, must be compiled first before the other items. This is not, for a new user, an obvious requirement.
GNURadio Installation
These notes pertain to installing the GNURadio software.In short, I have no clue as to how this GNU Radio is useful. Today...
More later...
REFERENCES:
Wednesday, March 16, 2016
Friday, March 4, 2016
Operating Remote Receiver and Local Transmitter with Digital Modes
Over the past few years, many SDR receivers have been put online and can be accessed over the Internet. This allows one to monitor the bands from receive locations far from the operator's local area. This is very useful to determine if your signal is getting into an area. I have used it to monitor the Wyoming Cowboy Net from an SDR receiver in Sedona, AZ (http://w7rna.dyndns-remote.com:18901/).
It occurred to me that one could use a remote SDR receiver to counter problems with local noise. In order to test this concept, I've installed two programs on my Ubuntu 14.04 Linux box, as follows:
FLDIGI(1) - a powerful digital mode encoder/decoder program
PULSE AUDIO VOLUME CONTROL(2) - a software package that allows one to direct audio from various sources to various outputs.
Once these are installed, the web-based SDR receiver can be chosen from the site: websdr.org
The audio produced by the web page is routed, using the Pulse Audio application, to the FLDIGI software.
For my experiment, I connected to http://radman.no-ip.ca:8903/ (New Brunswick, Canada) and set the receive frequency to 14.070 MHz. There were many signals on the band and I was able to decode many, including SP6QKS (Poland), OK2MI (Czech Republic), F5POJ (France), and IU8ALH (Italy).
While I have a West Mountain Radio Rig Blaster Pro, I do not have it interfaced to my rig and have no plans to do so.
One other aspect of this method is the question of authenticity. When one operates an SDR receiver located in a remote area but transmits from a local area, does that bring into question the validity of the QSO? That is a question for another article.
REFERENCES:
ADDENDUM
- Working "split remote" will not work in contesting due to the delay. Much like Echolink in that sense. If you hear a station issue QRZ, your response will be too late.
- As is often the case, messing with sound cards with multiple inputs and outputs, it is easy to mess things up. In my case, on Ubuntu 14.04, the sound system selected "Dummy Output" for an output. Thus, no audio from the speakers. Google to the rescue, offering this sequence of commands that fixed it:
pulseaudio --kill
sudo alsa force-reload
pulseaudio --start
Subscribe to:
Posts (Atom)