This channel contains videos of presentations made at Denver Radio Club meetings and training sessions. The D.R.C. was formed in 1917 - it is the oldest Amateur Radio club in the Denver metropolitan area (Denver Colorado, U.S.A.). The club meets monthly - on the third Wednesday of each month, at 19:00 local time. The monthly meeting is preceded by an "Elmer" session for new (and all) hams to ask questions, at 18:00 local time. Details on location, directions and upcoming meeting topics can be found on our website at: w0tx.org
Grasias admiro tu trabajo y tus ideas mas tu conocimiento y escuela que brindas por este medio y toda sabiduria que me as brindado ,muchas grasias te deso lo mejor❤❤❤❤
Well that was a REVELATION! My DIY Dual loop of 20mm Dia. Copper tube that hangs on my shack door at top for my SDR RX works so well on 40M compared to my Wires and 300 yard 6 ft high all metal Back Fence UNTUNED! My Kenwood AT180 makes slight improvements in signal but not clarity of Dual Loop. But I obviously have more work to do to build your optimised design to make more comparisons! May have to make a Rectangle to fit on back of door though, as you have indicated shape does not matter. Have downloaded a few of your .pdf's for more reading in this area of antennas. I have plans to actually use the aluminium house guttering all around as an RX SDR Antenna for my inside Kenwood R2000 for 40 M. Thank you for passing on your extensive knowledge! 43AX05 Greg.
A mag loop radiates in the same plane as the loop with nulls 90 degrees to the plane of the loop. Does this still apply to the vertical and how does this apply to NVIS work?
Had a great idea to mount my 40M dual loop horizontally hanging from the roof with cap at easy reach. Usually hangs on the back of the small shack door where it optimally works with door closed and poor with door open?? BUT it was terrible with massive noise when on roof so guess it nulls where it needs to with door closed...
OK but does this not also apply to the linear application as you are suggesting unless you have found foil in sufficient length and width to completely cover the 4 inch plastic pipe without overlap or creases.
This was great! I built two test devices. One, I call a common mode current probe, which is the split toroid with analog meter. Then, I built another with two split toroids to connect to each side of the current choke. They both connect via coax to my meter which has a port A and port B switch. The idea is to set the sensitvity of the meter to full scale while sampling port A, which comes from the antenna. This is becomes a reference point. Then switch over to port B, and monitor the common mode current after it leaves the choke. I will post a video on the consturction and demo soon. Every radio operator should see your video!
At the Hamcation in Orlando today I was told to try a magnetic loop antenna so I asked if my 1969 ARRL handbook would have magnetic loop antennas listed. Heading for my book shelf!
Very inspiring and instructional video, finally some real facts and analysis have been shared around the loop antennas. I was wondering: Is the use of a commom-mode (or balun) necessary at the entry point of the small loop an option, in order to minimise any potential interaction (i.e. loading/detuning/currents on shielding, etc) of the coaxial line to/from the radio with the main loop? tnx, 73!
OK we've completed the 4FT version but we used 2" PVC.. I'm not sure about what the wiring needs between the antenna and my PlaySDR srcdx. What do I use to power the antenna? I can see the capacitor makes some difference but I'm unshure how to tune the bottom clamp.
Mr Fortune, thank you very much for sharing your design with us. When my daughters and I complete our Magnetic loop we will send you photos. You are very kind.
Non of these lectures tell you what kind of ferrite to use for true high power operation. Ask any Winning contest station and they will tell you to get rid of all ferrite material that is used in the transmitting circuit. 99.999% of all ferrite material is used for RF suppression suppression
This video would be a lot more interesting if you showed us how you measured each side, showed how you actually connected the coax, showed how you made the tuning device, etc. Unfortunately we don't know how you measured it. We don't know how you hooked the coax to it. We don't know why you didn't use a small loop inside it. We don't know how high you have it off the ground. In fact you didn't inform us of much of anything at all other than the shape . Very disappointing
Basically, there is no good mag loop antenna in typical sizes. Just different degrees of bad loop antennas. I get it, it’s a compromise, it’s small, “but I live in an apartment or HOA”, ect…. If it’s all you can do, it’s all you can do. No judgement. If you want better efficiency, multiple bands, no tuner needed for applicable bands, cheap, and you can fit in your pocket or at worst a small bag, get an end-fed half wave.
I have used ferrite cores to wind impedance transformers. I learned how to select the type of material from this RU-vid. Always weak in this knowledge but knew the very basics. Keep up the good work! WA0QQX
I constructed a magnetic loop antenna tuned to 144.30 MHz in the 2 metre band. This was made out of copper water pipe of 22 mm diameter. The loop was square with external dimensions 156 mm x 156 mm. The necessary capacitor was formed by using a 22-to-15 mm "reducer" by which a short 15 mm pipe was inserted into the 22 mm pipe. Hardly a "variable" capacitor! The co-axial feeder cable was connected to a wire loop of much smaller size located inside the antenna. I used the antenna mounted horizontally a few feet above the roof of my car. This antenna worked very well (within the limits of the fixed frequency to which was tuned). My impression was that it was at least as good as a half-wave dipole. I had a QSO with a French station from southern England during a "lift". Frankly I wouldn't recommend it. Its function would be severely upset by rain, and the very narrow bandwidth is a great disadvantage. Also I was fearful of damaging the Tx output transistor by transmitting at a non-resonant frequency, hence into a gross mismatch.
HAH, I have just today measured out how I intend to do similar on the roof of my Jeep! But for 27.385 CB DX. It will be based on my experience and experimentation with Co-Phased DDRRs that have a 12 inch high main conductor that will turn into a flat horizontal rectangle. The capacitance is supplied by the 8 inch or so gap where the end of the radiator comes back around to meet the main upright. Will be supported by plastic tube uprights at each corner with pipe clamps on the Jeep standard roof racks. So will be only 12 inches off roof unlike a similarly performing 9 foot quarter wave stainless whip. that will take out all the lights at a gas station! ;-)
Thanks for the video guys. In the 1950's, W1NJM(?) (no joking matter) Roger Hart ran a system of high speed contests at area ARRL hamfests by sending a reel-to-reel tape to a volunteer for the club sponsor. Competitions were held and awards given out in form of a certificate. Used to win them regularly. The contests fell out of favor, due to lack of ARRL support, as the years progressed. :-) Sad that the ARRL didn't sponsor, at any time, sending a team to EU. I also inquired about it and got the same budget answer. Oh. Roger got support from the Connecticut Wireless Association for expenses. At the time we weren't allowed typewriters, so pen and paper. So it got to be a memory buffer contest at the time. Everybody I knew from the era are silent keys. I am QRT after moving last year and downsizing with no antenna system. Good to see you on video Barry. dit dit Chuck, ex-K7QO P.S. My mentor was W3CVE, Red Barger, who was at the CIA until Dec 1961.
Hi Chuck - good to "hear" from you. I had heard you QRTed, but didn't know why. Now I do. I recall our many conversations, including those related to your book to CW work, and the subsequent WSJ article. 40+ years ago, I got a CP-60 certificate from W1NJM, when he ran his online code practice and qualifying runs from 30-60 WPM. There's still a small group of us that meet on the weekends for QRQ QSOs on 40m (usually 7.017, time dependent on sunset time). 73/Barry W2UP
Trivia question: There were two previous sites for 146.34/.94 repeaters in Denver metro area. Where were they? Also, there was a previous ham repeater at the W0WYX site. What was it and how did it work? Bob had a regular column in the DRC Roundtable where he documented the comings and goings on Squaw, what the camp robbers (the animals, not nefarious humans) were up to and what birds were at the feeder. When the forest service mothballed the lookout, Margaret regularly commuted to Idaho Springs to work at the service's information center on Colo 105 and I 70. Lots of memories of long ago. Great to hear Dave (I remember him more as WB0BAE) and Rita who was the movie critic at 9news when I worked there. 73 de Craig KC0KP (formerly WA0WTG).
First of all thanks for this wonderfull presentation ! But there's one thing i would really wanted to mention. We don't think about it a lot but aluminium oxidises very easy. The minute you stop sandind/filing it it will oxidise. Thats why you cant't solder it in the tradional way. I,m affraid the foil/pvc elbow method will induce al lot of junction-resistance. This wil negatively impact the "Rr". Maybe not measureable with a normal multimeter, but it will be noticeable with a dedicated resistance meter (for low resistances). I dont't want to split hairs here, but low resistance is key for magloops .. Best Regards and 73's
Found this Very interesting, surprised you only have one comment. Knowing about the skin effect, I have been wondering how a full wave loop in the diamond configuration fed at the bottom, with Rg 59 and 1:1 balun. Constructed out of copper tubing or let's say 1/2' EMT rigid steel conduit at 10-12 meters? Perhaps, PVC with your foil tape idea didn't think of that. On a side note; I happen to use an Alpha LM-400 Equivalent that has a Stranded center conductor, they advertise the Skin Effect, as well as its flexibility. 73
Rather than PVC pipe: what about perspex? One (or more) strips of perspex, 4 inches wide, with foil on one side (or maybe both sides). Carefully apply heat to bend the loop into the shape you want.
I have built this antenna with poor results. The use of PVC pipe degrades the antenna Q. The 2:1 SWR bandwidth is about 130KHz at 14, 18 and 25 MHz. This indicates a fixed lose due to the use of PVC. I have since read a number of articles about the poor performance when using PVC for inductors or capacitors.
Hi, I am just now looking into building an antenna for use on a bus I am converting to a mobile home. My armature radio use has been hindered since I got my license years ago due to stringent home owner societies that I did not want to fight in court to defend my rights. But on the motorhome would be my chance to finally use more than 2 meters. <LOL> and mag loop looks like the way to go. I do have 2 questions about mag loops though. 1) because of the radiation patterns of the loops being rather directional <ideal if you are trying to reach someone that you know the exact location of> and a lack of side side to the plain of the loop would it be ideal in keeping a low <close to the roof> profile if laid parallel to the roof and radiating 360 degrees toward the horizon? and 2) How does the tape used in this design stand up to the bakeing of the sun and the corrosive effect of the weather?
Had a great idea to mount my 40M dual loop horizontally hanging from the roof with cap at easy reach. Usually hangs on the back of the small shack door where it optimally works with door closed and poor with door open?? BUT it was terrible with massive noise when on roof so guess it nulls where it needs to with door closed...
This went well until he got to the 49:1 "balun" part where everything fell apart. 1. A 1:1 balun was explained. There was no 4 or 9 to one described. Nothing! 2. The 49:1 is not even a balun, rather it's a transformer with a single ended output sometimes called an unun. 3. Choking is not something a 49:1 unun does. It is an impedance transformer. 4. The 200 ohm impedance number is far too low for decent choking action. 5. He uses 50 ohms in his calculations but you have no idea what the impedance of the common mode circuit being chokes is. This would depend upon the length of the coax and it could be in the thousands of ohms. The choke should have at least 1000 ohms impedance or more. Again...this is not a 50 ohm network. 6. Zip or lamp cord would have a much higher Z than 50 ohms. probably over 100 ohms therefore it would upset the impedance match in a 50 ohm system. It is better to use small, ptfe coax to maintain the correct impedance. So this video has a lot of wrong information in it. I'm not sure why. He repeated how "simple" this is a hundred times but in the end it's just confusion. The only part that is correct would be the 3rd wire of the coax part and even that was vague. Sorry to be so negative but you must be careful who you follow on these topics.
Thank you at least I'm not the only one who thought that and also I didn't like the assumption that "most hams" don't know what a balun is I find that not giving people the credit I certainly find most deserve most people are not stupid accusing them all of not knowing anything seems unfair at best and down right nasty at worst
Hi, I have just finished building a magnetic loop antenna a week ago. I worked on this project for more than one year now. It is now completely installed on the roof of the house with remote control for the (30 to 250pF vacuum) tuning capacitor and hermetic enclosure for the snowy winter. The real McCoy antenna... There is just one problem, it does not work! It has a low gain, both in receive and transmit modes. I am writing this memo in order to get some advise. Please do not hesitate to comment on any incoherent aspect of my design. I am seeking help: The loop is made of one long 30 ft (10m) section of 3/4 in (2 cm) copper pipe coiled with no joint. The antenna diameter is 4 to 5 foot diameter therefore there are TWO turns spaced by about 6 inches (14 cm). The loop is connected to a vacuum capacitor and it tunes very well over the whole 80 meter band. At 3.8 MHz for example, the capacitance is around 120 pF. I don't think there is anything wrong with the resonance itself. But wait, the juicy stuff is at the end. The coupling loop is a simple wire about 20 inch (50 cm) diameter positioned in the same plane as the antenna, the usual way. I will not mention the Q factor nor SWR because I did not precisely measure it in a precise meaner, but I believe this is all normal: when I tune to a station, I can easily go left and right of the station and the SWR goes down to almost perfect 1:1 match. I repositioned the loop placement and saw no change. So, again I do not think there is a problem with the coupling or matching. My antenna has two differences with the most common antennas: i) it has two turns; that means that the radiation pattern is a pure magnetic mode. No interaction that looks like a folded dipole. The radiation pattern has the shape of a perfect symmetrical doughnut. (usual one turn antennas have a slightly directional "cardioid" shape. This can not be the case here because of the symmetric coil having TWO turns). ii) In order to avoid having to use a ROTATOR, I put the antenna IN THE HORIZONTAL PLANE. This way the radiation pattern is truly circular: no need to rotate the antenna... There are two problems with that, and here is the rationale behind that choice: 1 - The maximum transmission angle is horizontal, but the beam width would cover the necessary 15 to 20 degrees necessary. The antenna is mounted on a wooden cage about 20 feet (15m) above the ground. I believed I would get a nice over-the-horizon angle, good for DX. 2 - This is the part that I may have overlooked. The polarization of ground wave is VERTICAL, while our antenna has HORIZONTAL polarization. I am located in a semi urban environment with buildings, trees, electricity lines and hills all around my QTH. At the time I simply assumed that the polarization would quickly rotate to vertical. I drive this antenna with 100 W signal. I can barely go 300 Km BOTH in reception and transmission. From the same location, using a simple wire antenna and the same rig, on 40 meter band, everyday, I do QSOs all over across North America. In spite with the fact that I am a newbie, I never had a 80 meter antenna I really believe that antenna in not usable as it is.. Why? Thank you.
Had a great idea to mount my 40M dual loop horizontally hanging from the false roof with cap at easy reach. Usually hangs on the back of the small shack door where it optimally works with door closed and poor with door open?? BUT it was terrible with massive noise when on roof so guess it nulls where it needs to with door closed...
