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I was all cocked and ready to tell you that you do not have it quite right, until you said check SWR at the antenna. Most of us QRP operators adjust our antenna to be resonant at the frequency we intend to use using an analyzer at the antenna, which also gives the SWR reading. I might add it is also a good idea to check the SWR at the coax before it inters the transceiver because running portable operations the coax is put thru more bends and connected and re connected many times. Good to know if your coax is in good working order.
Thx for the informational video. Interesting statement that "Reflected Power is NOT Lost Power". Seems technically correct, but not practically correct. I presume that reflected power has latency, and would be out of phase, so not useful or problematic. Just thinking out loud. Cheers.
Great explanation debunking the myth. There are antennas that will give you a flat response across the entire HF band without the need to retune. It's called a terminated coaxial cage monopole or TC2M for short. Mine is 0.8 meters in diameter, 44 feet tall (I purposely tuned it long for 6.9MHZ, has six cage wires, ten-wavelengths of wire at 40 meters under it for radials, is terminated in the antenna's characteristic impedance - about 260 ohms, has a broad-banded, bifilar wound 3.5:1 Unun and a 3,000-ohm Common Mode choke at the input. The worst SWR is at 5 MHz (2:1) but I don't care about that band. It requires no tuning from 1.8 to 60 MHz and is 1.2:1 or less. In fact, enabling the internal tuner actually raises the SWR - to the detector anyway. To RF it looks like a big fat pipe with 1-meter long, tapered ends - Look way back in the books and look for a 4 to 6 wire cage dipole. It is a beast. This vertical is half that and is only the weight of the DXE telescoping 46' fiberglass mast. It's guyed at the half-way point. It has very little to no gain, but nothing affects it either (very low "Q"). Neither rain, snow, trees, or me standing beside it making measurements affects it. I use LMR-400 series coax and N or BNC connectors. I'm too old to climb so a vertical is my choice. The CM split ferrite beads placed randomly along the feed line help a lot with QRM. If running under 500 watts, use RG-58 or LMR equivalent cable and wind a 4-turn choke on a 1-inch split bead, and stick it at the input of any antenna to decouple it from the third path (the outside of the coax braid) back to the rig. OK, I'm done. 73's all.
Very nice. I wish I could get my wife to drive the RV while doing this! As someone said the lucky part is you have a supportive wife. (My wife is supportive just not comfortable driving the RV) Nice vid.
why would i listen to this channel....... they over charge for everything they sell... the place is a joke and a rip off. even before c19 hit. they were over priced
Mike can you sell a hardware kit for mounting the AH-PB109 dish to the tripod? And also for mounting dishes that have already been modified for horizontal polarization? De N2YTF
The Icom dish is vertically polarized. However the way I mounted it on my tripod makes it horizontally polarized. I had to modify the mount slightly to hold the dish and the transverter. DXE does not currently sell anything for mounting other than what is supplied with the dish. Thanks!
Use the USB cables with ferrite cores added on to keep noise out of your system. I had to add extra ferrite cores in order to get mine to act correctly
Great video Mike! Glad you were able to get your first and second Q's on 10GHz. Still chasing my first rain scatter contacts but have made other close with other ops who have been extremely helpful.
Hi Mike, Thank you for posting great video. You have already exceeded my best distance on 10G with my 905 and give me some added encouragement. I have worked 477 miles on 2304 with the 905. Gedas and Mike, IUP, and I have tried RS a few times and will continue to. Look forward to working you, too. K4LY EM85 Inman, SC
Hi Mike. Thank you for recording our QSO and sharing it with the entire YT community. You did an absolutely wonderful job setting up your equipment and making the contact. This should help show others just how easy and fun it is to use our 10 GHz band, even with very low power levels. Look forward to many more contacts. 73
Thanks for the video. I’ve a question: why reflected signal from antena, arriving the transmitter, is reflected back if at this point we don’t have impedance mismatch (between transmitter and cable)?
Excellent, many thanks. Most important take-away: "If the SWR is low over a wide frequency range, something is very wrong." Please ask yourself if your super-wideband DC-to-Daylight shortened and heavily mismatched antenna really works so well or just heats up the atmosphere. 😄
I've been asking similar questions about the guy who sells a 40 / 80 meter antenna in a one-gallon plastic bucket for $450 and says to hang it in a tree. Snake oil magic antennas are generally just that.
You were off to a bad start babbling terrms and values as if their definitions were already understood by your audience. You're just another self appointed YT channel "expert" that can't teach a dog to sit, let alone explain electronics.
Reflected power is not lost power. Take a 50 ohm load ,at the end of a half wl of 500ohm open wire tx line. 10:1 SWR . If the power was lost only 33% of the power would reach the 50 ohm load. How much power do you think reaches the 50 ohm load?
Reflected waves are subject to the same losses as the primary wave, and also travel twice as far along the coax. And because the wave reflected back to the antenna is going to see the same impedance mismatch as the primary, part of it will be reflected back to the source and of course reflected back to the antenna. It is continuous. So not all the reflected power reaches the antenna. On a modulated transmission the modulation on the reflected wave is displaced in time by the time spent traveling back to the antenna after the primary wave has been radiated. In broadcast television this shows up as ghost images. All the power that is traveling to the antenna is measured by the directional watt meter, including reflected waves. Same with the reflected power. The watt meter has no way to differentiate the primary wave from reflected secondary waves.
Resistance can change by frequency. Impedance is resistanc + reactance. A perfectly resonant antenna (at one frequency) exhibits only resistance, i.e. radiatin resistance. The resistance (and reactance) will change when the frequency changes. A dummy load should exhibit only resistance and hopefully not change that resistance over the usable frequency rangs. Antennas, however, do change resistance ad reactance by changinf frequency.
This is a great presentation and illustrates the often overlooked effect that coax has on an antenna system. To paraphrase the editors of the ARRL Antenna Book: a sufficiently long enough piece of RG-8X will present a perfect 1:1 match from any antenna.
To say that the reflected (and re-reflected, and re-reflected and so on) wave does not impose a current and voltage upon the final output stage of the transceiver would be to say the incident wave does not deliver energy to the antenna. The reflected power is lost. And is done so in several parts of the system. Each reflected, and re-reflected wave experiences transmission line loss. Energy is lost as current is imposed in the final transistors opposite to the direction of normal flow (collector->emitter). Not much current flows, but some does, and it does exhibit additional strain on the output stage. The majority of the energy is lost in the reflections. If you wish to refute my position place a wattmeter ammeter at the end of the transmission line and simulate the mismatch conditions cited in your presentation. The reflected power, in an impedance mismatch scenario, is not delivered to the load in any appreciable way. That, my friend, is why we have 'antenna tuners.' Also, odd and even multiple electrical lengths of transmission lines, have impedance transformation characteristics. One very common application is matching stubs.
I was thinking the same thing. I've seen several amplifiers destroyed because of high SWR and they always heat up quickly. Does he really think that power reflected back into the final output device isn't at least partially or mostly dissipated by it??
Without a tuner the power isn't produced to the difference of amount of reflected power ,the reflected wave will reflect back towards antenna at the mismatch radio coax junction, the impedance at this junction is what causes the transmitter to heat up trying to put power into a mismatch, place a tuner at this point the radio produces its maximum power ,the reflected power is in phase with the forward power back to antenna, at hf frequencies with moderate swr and low loss cable loss isn't too much of a worry
On the whole pretty good info ,you could have mentioned that it's the impedance the radio sees that the feedline length and reflected wave have transformed that really kills you radio , for those who thought that it was the reflected power going back into radio
Thank you, this is helpful. If you are receiving only, and not transmitting, is the SWR reading at the feed end a good indication of the antenna’s resonant frequency? I use some SDR dongles for receiving signals from passing weather satellites and have tuned the antennas based on the SWR numbers. Is that a correct method?
