Recent posts
#11
HF and Propagation / EFHW?
Last post by DU2XXR - Mar 24, 2024, 06:34 AMby Warren Allgyer WA8TOD
https://www.facebook.com/share/p/ZUzzT4hjWguWQ6vQ
One of the insidious things about the very popular end fed antennas matched by ferrite impedance transformers is the effect of losses in those transformers on the overall performance of the antenna system.
For reasons beyond the scope of this post, losses in the transformer mask the actual SWR of the antenna. In reality the higher the transformer loss, the lower the SWR reading at the transceiver. And the higher the actual SWR at the antenna, the higher the transformer loss.
One very practical issue has prevented a lot of us from understanding this and being able to quantify it. While every ham has an SWR meter almost no one has the ability to measure power at an impedance of other than 50 ohms. So while we wind 9:1 UNUNs for antennas we assume to be in the 400 - 500 ohm range, and 49:1 UNUNs for resonant half waves, we have no way of determining how well they actually work because we do not have the instrumentation to do it.
In the diagram I show a method of adjusting a normal tuner to replicate the impedance of an unknown wire at a particular frequency. Once that is done I feed the test transformer output to the tuner in reverse so the high impedance terminals of each match and the low impedance terminal of the tuner then reflects the power level that has survived the transformer and the tuner together. Since the tuner loss is normally less than 1 dB we can discount it in this test.
One caveat: While the input impedance of the reversed tuner will closely match that of the antenna, its reactance sign will be opposite that of the wire. I don't THINK that adversely affects the accuracy of the loss measurement but I will gladly entertain viewpoints to the contrary.
https://www.facebook.com/share/p/ZUzzT4hjWguWQ6vQ
One of the insidious things about the very popular end fed antennas matched by ferrite impedance transformers is the effect of losses in those transformers on the overall performance of the antenna system.
For reasons beyond the scope of this post, losses in the transformer mask the actual SWR of the antenna. In reality the higher the transformer loss, the lower the SWR reading at the transceiver. And the higher the actual SWR at the antenna, the higher the transformer loss.
One very practical issue has prevented a lot of us from understanding this and being able to quantify it. While every ham has an SWR meter almost no one has the ability to measure power at an impedance of other than 50 ohms. So while we wind 9:1 UNUNs for antennas we assume to be in the 400 - 500 ohm range, and 49:1 UNUNs for resonant half waves, we have no way of determining how well they actually work because we do not have the instrumentation to do it.
In the diagram I show a method of adjusting a normal tuner to replicate the impedance of an unknown wire at a particular frequency. Once that is done I feed the test transformer output to the tuner in reverse so the high impedance terminals of each match and the low impedance terminal of the tuner then reflects the power level that has survived the transformer and the tuner together. Since the tuner loss is normally less than 1 dB we can discount it in this test.
One caveat: While the input impedance of the reversed tuner will closely match that of the antenna, its reactance sign will be opposite that of the wire. I don't THINK that adversely affects the accuracy of the loss measurement but I will gladly entertain viewpoints to the contrary.
#13
General Radio Discussions / Amateur radio - opening opport...
Last post by DU2XXR - Mar 19, 2024, 01:54 PMIn a recent meeting with fellow radio amatuers, one of the things we discussd (as an agenda matter) was how to leverage the numerous youth-oriented activities we have been doing so far. There were the scouting events like JOTI/JOTA, and Infex. There were also membership oriented activities that encouraged the children of current or aspiring club members to be also active in club activities.
One great thing raised was that all of these need not be simply done for the sake of direct involvement in amateur radio itself. Most might not be aware, but there is much much more to encouraging the youth to get active on amateur radio than merely getting them on the air. Amateur radio provides exposure to the world of electronics, communications, engineering, sciences, and other similar fields. It is thus hoped that the younger generations gain an interest in these and also make a positive contribution to these fields and the world in the future.
For example, did you know that the ARRL, for one, has a scholarship program available to both U.S. and non-U.S. hams who are studying in STEM and related fields? These scholarship funds and grants provide thousands of students with support in their college education, in the hopes that their being interested in amateur radio also extends to an active interest and pursuit of STEM fields.
These scholarships are usually supported by trusts or funds provided by S.K. (deceased) hams who want a legacy of supporting the future generations. Some are also fnded/supported by projects that focus on ensuring quality education for young hams. Still other projects and funds provide financial and other support for young radio amateurs and aspiring young hams (such as scouts).
I am proud and happy that such a community of youth-oriented radio amateurs exist, and that i am part of it!
If you are a young licensed radio amateur in college or getting into college soon, or if you have children who are, you might want to look into these opportunities. My club W1PTG and Radioscouting RadioScouting orgnanizations would be happy to share information and guidance.
One great thing raised was that all of these need not be simply done for the sake of direct involvement in amateur radio itself. Most might not be aware, but there is much much more to encouraging the youth to get active on amateur radio than merely getting them on the air. Amateur radio provides exposure to the world of electronics, communications, engineering, sciences, and other similar fields. It is thus hoped that the younger generations gain an interest in these and also make a positive contribution to these fields and the world in the future.
For example, did you know that the ARRL, for one, has a scholarship program available to both U.S. and non-U.S. hams who are studying in STEM and related fields? These scholarship funds and grants provide thousands of students with support in their college education, in the hopes that their being interested in amateur radio also extends to an active interest and pursuit of STEM fields.
These scholarships are usually supported by trusts or funds provided by S.K. (deceased) hams who want a legacy of supporting the future generations. Some are also fnded/supported by projects that focus on ensuring quality education for young hams. Still other projects and funds provide financial and other support for young radio amateurs and aspiring young hams (such as scouts).
I am proud and happy that such a community of youth-oriented radio amateurs exist, and that i am part of it!
If you are a young licensed radio amateur in college or getting into college soon, or if you have children who are, you might want to look into these opportunities. My club W1PTG and Radioscouting RadioScouting orgnanizations would be happy to share information and guidance.
#14
General Radio Discussions / How to deal with gatekeeping?
Last post by DU2XXR - Mar 19, 2024, 01:53 PMI usually keep an open mind when someone critiques or even criticizes the things I do. I don't presume to know it all, but I don't think I stress this enough--I am aware that many follow my websites and feeds for the information or knowledge that I share.
Again, I am merely a learner myself. Whatever I share, I also learn from experimentation and experience. Sometimes I do stupid things so you won't have to. Many times, I doubt myself. And I am aware that amateur radio is a very technical hobby, which requires some knowledge of regulations and electronics, which is for good reason.
However, in the recent days, I encountered what I can only describe as gatekeeping.
I do look up to a lot of fellow radio amateurs in our local community, especially those who have made considerable achievements and sharing of knowledge. Many are helpful, especially to newer hams and newer enthusiasts who are very eager to learn, experiment, and explore.
There are a few exceptions, however. There are people, whom I would describe as very intelligent and knowledgeable, but who seem to take too much pride in their own achievements at the expense of bringing other people down.
For example, some are classist when it comes to regulatory licensing class and who look down upon other hams with different license classes. Some would not even bother to talk to you if you don't have an advanced electronics or engineering degree and would talk negatively about you personally or condescendingly pick on details where you were wrong.
I am sharing this, even though I know that things will never change with some people. For some, that is just how they are, and it will be pointless for me to hope for change.
What I am writing here is probably just a reminder to myself, because I tend to be too naive and over-eager. I get ahead of myself in excitedly sharing my discoveries. But I also have insecurities because of my own limitations in skill, credentials, and resources.
I am also not completely innocent myself, too. Please excuse me if there were times you sought insights but I was unable to help (I only have limited time and energy, after all).
My message for those eager to learn and discover is this. If you have ever felt alienated in this radio hobby of ours, or if you have encountered gatekeepers who consider only their own interests to be important (be it mode of operation, license class, knowledge of certain matters. etc)--you are not alone. I know it can be discouraging. But focus on the things you can achieve, and work on things you are interested in. And be mindful and selective of the people you trust and deal with. The internet and social media, after all, only work to amplify both the best and the worst in human nature.
Again, I am merely a learner myself. Whatever I share, I also learn from experimentation and experience. Sometimes I do stupid things so you won't have to. Many times, I doubt myself. And I am aware that amateur radio is a very technical hobby, which requires some knowledge of regulations and electronics, which is for good reason.
However, in the recent days, I encountered what I can only describe as gatekeeping.
I do look up to a lot of fellow radio amateurs in our local community, especially those who have made considerable achievements and sharing of knowledge. Many are helpful, especially to newer hams and newer enthusiasts who are very eager to learn, experiment, and explore.
There are a few exceptions, however. There are people, whom I would describe as very intelligent and knowledgeable, but who seem to take too much pride in their own achievements at the expense of bringing other people down.
For example, some are classist when it comes to regulatory licensing class and who look down upon other hams with different license classes. Some would not even bother to talk to you if you don't have an advanced electronics or engineering degree and would talk negatively about you personally or condescendingly pick on details where you were wrong.
I am sharing this, even though I know that things will never change with some people. For some, that is just how they are, and it will be pointless for me to hope for change.
What I am writing here is probably just a reminder to myself, because I tend to be too naive and over-eager. I get ahead of myself in excitedly sharing my discoveries. But I also have insecurities because of my own limitations in skill, credentials, and resources.
I am also not completely innocent myself, too. Please excuse me if there were times you sought insights but I was unable to help (I only have limited time and energy, after all).
My message for those eager to learn and discover is this. If you have ever felt alienated in this radio hobby of ours, or if you have encountered gatekeepers who consider only their own interests to be important (be it mode of operation, license class, knowledge of certain matters. etc)--you are not alone. I know it can be discouraging. But focus on the things you can achieve, and work on things you are interested in. And be mindful and selective of the people you trust and deal with. The internet and social media, after all, only work to amplify both the best and the worst in human nature.
#15
HF and Propagation / Mobile QRP with the USDR+ and ...
Last post by DU2XXR - Feb 21, 2024, 02:57 PM #16
HF and Propagation / Setting up my battery-powered ...
Last post by DU2XXR - Feb 12, 2024, 11:03 PMAlmost every afternoon, I deploy my portable HF go kit, try to make contacts, and check into the nets. This kit consists of a 10-watt battery-powered SDR. I string up a QRP EFHW across several trees for operating on the 40-meter band.
For the most part, I have been successful at making contacts from Antipolo to Nueva Vizcaya, Baguio toward the north (around 300 Km), and Cebu, Mandaue, Iligan City, Cagayan de Oro toward the south (around 800+ Km).
The east is often my blind spot. This evening, 2024-04-12, I was not able to get heard by the net controller of the evening DU Net, who was in the Bicol region.
This is why we test. This is why we try to improve and improvise. We want to know our gear and our capabilities, and hopefully improve on them. In my case, QRP can only go so far. But I know it works in at least most scenarios except for super noisy environments.
One thing I realize, net members don't usually relay weak stations, which makes the net a little less effective than it probably intends to be, in terms of being a means of grid down communications. Sometimes, we have relays from strong stations or nearby stations.
I am happy to have had Romy DU1SMQ relay my call this evening. Romy is the NTS chairman, and I've always wanted to discuss my suggestions to improving the NTS. He has consistently relayed stations that the net controller has been having difficulty hearing.
This is also one reason one of my club's nets is evolving into a traffic net. We want to contribute toward a better traffic system. Hopefully, we can go to the next phase soon (radiograms, relays to other club Nets, etc.).
For the most part, I have been successful at making contacts from Antipolo to Nueva Vizcaya, Baguio toward the north (around 300 Km), and Cebu, Mandaue, Iligan City, Cagayan de Oro toward the south (around 800+ Km).
The east is often my blind spot. This evening, 2024-04-12, I was not able to get heard by the net controller of the evening DU Net, who was in the Bicol region.
This is why we test. This is why we try to improve and improvise. We want to know our gear and our capabilities, and hopefully improve on them. In my case, QRP can only go so far. But I know it works in at least most scenarios except for super noisy environments.
One thing I realize, net members don't usually relay weak stations, which makes the net a little less effective than it probably intends to be, in terms of being a means of grid down communications. Sometimes, we have relays from strong stations or nearby stations.
I am happy to have had Romy DU1SMQ relay my call this evening. Romy is the NTS chairman, and I've always wanted to discuss my suggestions to improving the NTS. He has consistently relayed stations that the net controller has been having difficulty hearing.
This is also one reason one of my club's nets is evolving into a traffic net. We want to contribute toward a better traffic system. Hopefully, we can go to the next phase soon (radiograms, relays to other club Nets, etc.).
#17
HF and Propagation / FX-4CR radio
Last post by DU2XXR - Feb 10, 2024, 03:26 AMQuoteIn this video we take a look at the FX-4CR HF Transceiver from BG2FX. We cover features, functions, test radio reception and even make a QSO.
Please note that at the start of the video I say that the radio covers from 160m to 6m, but 160m is not supported. The range is from 80m upto 6m (3.5MHz upto 51MHz).
#19