I have 2 radios and 2 antennas. One beam and my vertical. Running one radio on 10m and the other on 12m at the same time - takes a print screen from pskreporter. Then swapping the antennas on the 2 radios - and another ft8 run for 10 minutes - and comparing the view on pskreporter. Often I find that one day the vertical is doing better - another day the beam. Or also 1 hour later it can change. Only by using both antennas at the same time - are giving me real data to compare. The conditions are changing so fast and so often that comparing data from different hour or day do not really telling you anything. This I have learned the hard way. But keep up experimenting - that what a hobby like this is ment for 73 - Knut
Chip, I don't know any other way to say this. I want to try and give you a graceful out. Though I am expecting a diatribe about your faux sense of being disrespected, feelings/beliefs, ivory tower science mumbo jumbo, and bizarre pop culture references. Many of us do not fundamentally care how you feel about this video, our versions of radio, or the validity of the use of observations in science (i.e., otherwise considered the foundation of the scientific method). Do not interpret this to be fueled with emotion. Read what I said. I simply do not actually care about your opinions. You have, with these ongoing posts, become someone I do not have faith in when it comes to my particular learning and interest in ham radio. So what? Clearly you have supporters of your philosophies and do not need me on your team so to speak. No need to try so hard to change my mind on this, i.e., let it go. I will borrow the phrase, you do ham your way. Recognize too that I am trying to just speak for myself here, not trying to say I am taking your posts personally. You called us hillbillies. You made fun of our intellect. You picked on our integrity with the amateur radio service. You invalidated our carefully thought out opinions as an emotional response (which I recognize as the "logical" vs. "emotional" argument often used against certain sectors of society to discredit them). You have even gone so far as to try to make the case that we are violating FCC statutes by not listening to you. You now are accusing us of trying to cancel you. If I were in your shoes, I would just step away from the keyboard for a few days. Clearly you are a highly knowledgeable RF professional. I do want to highlight the word professional here. Do yourself a favor and realize that if you actually want to be seen as a guru of amateur radio, you have to earn that. You can't force it on people. You can't stand on a hill top, yelling out that you are the best and brightest and expect people to bow down to it. And honestly, I will add in some "feelings" here now. This thread is actually detracting from my joy of ham radio. Now, I am too old and well-established of ego to let any one person effect my happiness in life. But think of the kids, new hams, and others that you are driving away. And please realize that your posts are driving people away. I feel the need to say that you do not represent those of us in amateur radio, lest others think we are all like this and get turned off to the hobby. As someone espousing the creed to further the radio arts, you are actually doing a very poor job of it. There is a difference between art and science as any medical doctor will tell you. One is practicing with cold, hard facts, the other is doing so with finesse. Perhaps a spit shine on your delivery would earn you a bit more respect amongst your peers? It certainly would be better for the hobby overall. I am a very easy person to get along with and do not typically hold grudges. I suspect many of us are like that. Step away, reflect, and take a new approach, and you may get more positive results. Just my final 2 cents on this topic. Mindy
Unless you thoroughly choke the coax at the feedpoint, the coax is part of your antenna system, for the other bands. This 'radiating coax' is not always a bad thing, as you are attesting. It's not optimal, but it does work. 73 Chip W1YW
I understand your scientific intensions and your sight of view. I cant say that this is false. And your approach is maybe more elegant and unneeded precisely than other solutions. But believe in, that all roads lead to rome. That is what you have to accept. 73, Cornelius DO1FER
Cornelius, Please read my comments with greater care. I already stated that there are other ways of testing for power patterns. The one I presented-- 'A/B' comparisons with an RF attenuator for RSSI-- is the one most relevant to the observation that KM9G was making in the OP. Its not elegant at all. Its just one that removes systemic errors, avoids unscientific use of variables and unknowns, and allows greater precision than an S meter, or an FT8 SINR value, alone. Apparently using this method in ham radio is more common than you think: MFJ sells an attenuator (MFJ-762) that it advertises for just this purpose. So some folks do this method. Just few, if any, on this thread. To wit the MFJ-762: "Plot accurate antenna patterns -- connect it between you receiver and antenna and use your S-meter as a precision calibrated field strength meter" You can get used rotary precision attenuators at ham fleas for a fraction of the price of new. Is this method a 'best practice' for the case being considered? Yes, it is. That is why we don't follow cow paths to Rome, or ancient dead ends, but take major hiways--or hiway in this case. 73 Chip W1YW
Classic "cancel-culture". Sorry Mindy. I will continue to enjoy ham radio and my fellow hams, and contribute to the enhanced knowledge base of the service for the forseeable future. Sorry you are having a bad day. Please stay to comments relevant to the topic, and not attacks of an intentionally personal nature. This is not CB. Hams should not act like (the negative aspects of) CB'ers. Just 'chill'... Roger? (BTW, I have a farm in KY and have enjoyed hillbilly swimming pools many,many times. It is a clever solution when bears want to tear up your hot tub. An F-150 is de rigeur.)). Wishing you the best. 73 Chip W1YW
Should I allow myself to say a few more words about this by testing changes on antennas etc, when you only have one to compare with:: I have knocked down 3 x 2 meter long copper tubes as earthing points at the base of my vertical - and initially connected these to the ground plane on the antenna. Thought mostly about any lightning strike or static charge in the antenna. It is 26 meters high. Then read that this might not be the best thing to do. Tried to disconnect - run back to the radio, test - then run back to the antenna and reconnect etc, but it did not make sense. By the time I spent making these changes, conditions had changed - and my relative testing on the S meter did not make sense. Therefore, I connected a larger car-light relay (can handle large power, but not so high voltage) - and pulled a power cable into my shack. Then I could easily connect the earthing in and out while listening to a remote station. Found out then that this grounding was actually a somewhat good thing at higher frequencies, but did not do anything at lower frequencies. It was therefore removed. Same thing, I wanted to insert a 100K resistor as a bleeder for static. Used the relay again and found that connecting it to the screen / ground on the coax did not make much difference, but when I connected it to ground rods, it got much better. ( got rid of close to all on 160m) I could test it all out by using the relay - and connect it on and off in real time. Again - the conditions change so fast (at least at higher frequencies) that one must be able to test either on two comparable systems at the same time - or in my case here - be able to turn on and off in a very short time to be able to compare. NB! This I found in my settings , ground conditions etc etc - and my not be the same at your place and conditions 73 - Knut
Radiating coax can be a good thing for TX but the flip side is that it does very well as a receiving antenna for all the local noise. In the past, local pre noise generators and ferrites, hams used a radiating coax without realizing it. The EFHW alone can also be a very noisy receive antenna even with a ferrite choke(s).
I don't recall making such reference, so I'll assume it was someone else in the thread. On second glance, I suppose you're suggesting that the height of the mast means the oax becomes a better radiator. And I suppose that would be true, if the antenna were not solidly tied to the ground system at the TOP of the pole. Additionally, I'm running chokes on ALL my antennas, including the IMAX. So, I'm unclear how much radiation is actually happening common mode.
You mentioned (post #75) that the antenna works well outside of the band it was made for. In those cases, radiating coax happens, and is the reason why tuning is relatively easy. If you had put a line isolator ( a very good choke system ) at the feed you would not see such out of band performance. 73 Chip W1YW
Yes. That's it. And when the ground system is raised above ground and is not isolated, it can and does radiate (at those other bands). I have always been astounded how coax, for example, wants to radiate Oftentimes a large number of ferrite collars are needed to provide enough reactance to stop the coax from radiating. More than logic might suggest. The easy way to tell if the ground line is radiating (at the out of bands mentioned) is to take a field strength meter near the ground system , above the ground. 73 Chip W1YW
One more thing - I had 4 different antennas for 10 meter up. And used a coax switch to select them. Found that when one was working best one day - it could be the opposite the next day. Vertical vs horizontal etc
While true, have a look at the second para that I added after the fact. The thing is noted in many circles as being a very wide-banded beast. Observe for example.... https://wb3anq.com/the-solarcon-i-max-2000/ So that means that the I-MAX 2000 is a 5/8 wave antenna on 11 meters, (27MHz CB band) as advertised. But on 10 meters, it works out to a sweet .64 wave antenna. This is a very good thing. And it just so happens that the unique length of this antenna turns out to be a virtual nice little 1/2 wave on 15 meters. With 17 meters being close to 15 meters, the I-MAX 2000 will load up nicely there too with an antenna tuner. The antenna is wide banded enough to cover 12 meters very well also. Don't misunderstand, I'm not being critical of your point, here except to say that the design of this imax means that common mode radiation is less a problem than with most out of resonance operations, because it does in fact resonate on bands outside the original design criteria. In this (specific) case that doesn't even come into play for this unit until you get to perhaps 17m and beyond. Even at 6m, you're dealing with about a 2.7/1 match, because I suppose of it actually resonating fairly well on 12m (About 2/1) . That means at 6m you're getting perhaps 11 or 12% of your TPO bounding back down the coax? (HA! OTOH, I have a random wire on a 4/1 that raises serious hell with my shack...... It's coming down today)
Yep. All sounds good. Maybe someone wants to NEC model that antenna to see how it works on the other bands. If you don't measure the SWR predicted (by modeling)at the other bands, that's a pretty good, but not infallible, rule of thumb that the coax or ground line is part of the radiating system (and hence contributing to the different SWR from the model) at those other bands 73 Chip W1YW
