Thanks again Jim. I have worked 120 countries since last January using 10w and dipoles in my attic. It has mostly been done by making sure I was at the radio during grey line periods. I don't monitor DX cluster or specifically go looking for DXpeditions. My antenna is tuned for 20m,17m and 12m but I get 3:1 vswr on 15m and with a tuner it does work some decent DX. Another thing which can help on SSB if you don't have an optimal station is a properly set up speech processor. I was fortunate to have someone in Germany record my audio and help me work out what the best settings were. It has certainly helped. GM4SVM
You have a great point regarding the SSB signal. I had problem with basy audio being mentioned by all. Finally it improved after changing settings sent to me over QRZ forum by another ham from New York, who was having the same FT-710 as I have. 73 de Jon, VU2JO
Great video Jim. The table helps to clarify things.interesting to see the comparisons. I have been licensed for almost 20 years and have only used dipoles and a 100 watts. A resonant dipole and decent coax can work the world. Thanks for all you have done for ham radio.
Thanks Jim!!! The best explanation and data on this subject. looking, and sounding good!!!!! keep it up, stay strong Jim!!!! We're all hear for ya! 73, N8SOT
Thank you Jim for your excellent advice on all your RUclips videos and I hope you’re able to meet your medical bills. I’m from the UK and I did give a little bit to Callum Russell charity know what it’s like to have long-term illnesses so any little bit I hopeand try keeping your
Good video, Jim! Thanks for mentioning the effect that SWR has on receive. This is what I try to get my fellow hams to consider. Once you can tune the antenna system to hear, it is not so difficult to come up with enough power for them to hear you. We see SWR and think about transmission line loss on transmit, but it means probably even more on receive. All the data you presented is spot on to help evaluate the system. Thanks for the great work!
Jim, perhaps you know about this, I would like to advise you to visit a bathhouse, steam room, or sauna, with an oak broom, and after the steam room you should definitely plunge into a pool with ice water, perhaps this will make your life easier. I'll be glad to hear from you 73 GOOD LUCK!
Thank you for the post, interesting subject. Looking at your table I have a question about the two entries for 100 feet of ladder line at 28.5 MHz. For 3.2:1 SWR the SWR loss is indicated to be zero and the overall loss is 0.5dB while in the 1:1 SWR entry the SWR loss is again zero but the overall loss is now 0.1dB. I would expect that the overall loss would be the same in both entries since the SWR loss was assumed zero in both cases; and the frequency and lengths are also the same.
Am I interpreting this correctly? While set up a local park, 100watts on FT891, horizontal dipole... I should use ladder line for the best ERP? No balun required? Correct? AD3i
You will never achieve a "perfect" match of 1:1. Especially not over the entire band. And certainly not a multiband antenna unless it has separate traps and elements. If you pick the center of the band, it may not favor where you are typically transmitting. Pick the center of where you can legally operate, then tune the antenna there for best match.
One thing I am still in doubt is about the theoretical no loss feedline with multiple back and forth reflections finally sending the power out in full even if VSWR is high. What about the difference in phase of the signal with each reflection and mixing with the signal coming in at that instant from the radio? Will it not produce some distortion? Or do you mean that due to the speed at which radio signal travels, this effect will be minimal? 73 de Jon, VU2JO
So we don't scare away new operators or those thinking of getting their license that they have to spend a lot of money to get into the hobby there are other things to consider. They should know that even with horribly lossy coax and a not so great antenna at a not so great height that has a so-so SWR they will still be able to make contacts. Will they make contact with that rare DXpedition on some remote island in crowded conditions, probably not. However they will be able to make contacts to a lot of operators around the world. I tell new Ham's to just get on air with what you have and enjoy it. Make improvements to your system as you can afford it. I tell them when they start out in the hobby they can take advantage of the other operators great system to help compensate for their poor system. Their horrible system that is 10dB down from a good setup talking to someone who has a fantastic system with 10dB of gain works out to a signal each way with 2 operators with only good systems.
1. If you understand the block diagram of a transmitter, there is a voltage source and there is a series resistance. By convention, our series resistance, for analysis purposes is 50 ohms. Also, the resistance of the signal source is, by definition, zero since any impedance to ground inside this RF source is added to other values to create the 50 ohm output impedance. 2. Power does not get reflected. The initials are VSWR, not PSWR. A voltage is reflected and the voltage creates a standing wave. So a voltage is therefore reflected. For practical purposes, we can now think of the reflected power as a forward power heading straight back to your finals. 3. What do we know about an RF voltage heading down a coax towards a 50 ohm dummy load? I believe that we know that the voltage will indeed be dissipating power in that 50 ohms. 4. Since we had a mismatch at the antenna, the impedance of the reflected signal at the transmitter will not be 50 ohms, so a small amount will be reflected back towards the antenna. Very small. Not worth discussing, actually. We must acknowledge this or deny that any power is ever dissipated into a dummy load. 5. Much of the reflected signal will be dissipated in the finals. That's one reason old transmitters had glowing plates. It's why today's transistor units have the transistors blown. 6. If a tuner is used, the tuner at the transmitter will load up the line and the antenna as one big radiating device. No voltage will be reflected to the transmitter. Try this. Take a DC voltage source in a lossless system. Your voltage source is 141.4V. The voltage source has a 50 ohm series resistive impedance. Your load is 50 ohms. It's easy to see your current here is 1.414A. 141.4V / (50 + 50) = 1.414A Then we can see I (1.414) squared R (50 in the load or antenna) is 100 W. 1.414 squared is 2 and 2 times 50 is 100. You are delivering voltage for a 100 W output to the load. Now for a 3:1 VSWR, we see a load is now 150 ohms. 141.4 / (50 + 150) is now 0.707A. Current squared times load is 0.707 squared times 150. We can see that we now have 75 watts. Not close to your 3.2:1 VSWR scenario. And this is at DC without and loss. Without loss, a 3:1 VSWR allows us to transmit 75% of what we would expect. The VSWR losses bring that number down even lower. I have no idea why so many want to disregard real world situations. Losses can be great even with "lossless" transmission lines.
Isn't the reflected voltage reflected back towards antenna at the mismatch at the transmitter same way it does at the antenna therefore no damage to transmitter, Isn't the cause of transmitter damage caused by the transmitter trying to put power into this mismatch?
@@paulm0hpd319the signal reflected back to the transmitter is a signal terminated by a 50 ohm dummy load. Have you worked with circuit analysis with distributed and lumped considerations? It would be easier to understand.
@@BusDriverRFI you also say if a tuner is in line it will load up the antenna and line as on big radiating device, this isn't necessarily true this depends on the antenna balance or if there's an adequate groundplane to prevent common mode current on the braid of the feedline
You explain things better than any RUclips ham. In this hobby, you are The Man.
Great summary Jim, thank you.
The chart and the explanation are more helpful than 100 other youtubers going through this topic in Nth detail!
Thank-you Jim... my first Elmer!
Thanks again Jim. I have worked 120 countries since last January using 10w and dipoles in my attic. It has mostly been done by making sure I was at the radio during grey line periods. I don't monitor DX cluster or specifically go looking for DXpeditions. My antenna is tuned for 20m,17m and 12m but I get 3:1 vswr on 15m and with a tuner it does work some decent DX. Another thing which can help on SSB if you don't have an optimal station is a properly set up speech processor. I was fortunate to have someone in Germany record my audio and help me work out what the best settings were. It has certainly helped. GM4SVM
You have a great point regarding the SSB signal. I had problem with basy audio being mentioned by all. Finally it improved after changing settings sent to me over QRZ forum by another ham from New York, who was having the same FT-710 as I have. 73 de Jon, VU2JO
Clear and accessible explanation, as always. Now, if I can just get that Yagi past the HOA! You're a treat with a treatise, and we all appreciate YOU.
Tell them it's your Christmas tree. You just keep it up and turn it sideways to store it during the year.
This video is one of my favorites regarding SWR! Thanks so much for this excellent content! 73 ~ AC7WH
Great explanation of SWR, loss, types of coax / ladder line and even factor in with gain antenna! 73 sir.
As always, a very clear and pleasant explanation. Very appreciated content and a pleasure to watch your channel. 🌷
Thank You.
A problem I'm dealing with raised the same question
Now I got the answer. Thank you, Jim!
Great video Jim. The table helps to clarify things.interesting to see the comparisons. I have been licensed for almost 20 years and have only used dipoles and a 100 watts. A resonant dipole and decent coax can work the world. Thanks for all you have done for ham radio.
Thanks Jim!!! The best explanation and data on this subject. looking, and sounding good!!!!! keep it up, stay strong Jim!!!! We're all hear for ya! 73, N8SOT
I always enjoy your clear-cut explanations Jim, many thanks. 73
Thank you Jim, Excellent advice and super useful information.
All the very best to you Jim. Your RUclips channel brought me back into radio.
Best wishes from Anglesey, North Wales, UK.
73
All comes down to good feedline. Another great example
Thank you Jim for your excellent advice on all your RUclips videos and I hope you’re able to meet your medical bills. I’m from the UK and I did give a little bit to Callum Russell charity know what it’s like to have long-term illnesses so any little bit I hopeand try keeping your
Anther great video that cuts to the chase!! Thanks Jim. Robert K5TPC
Thank you Jim. Like the others mentioned, you are the Best. Appreciate your channel, always. 73 KD4VJP
I DX like that too, going around the
bands and listening. 😊Thanks,
73 de Ray W2CH NH. 😊
Marvelous! Thank you.
Thanks Jim
You and David Castler - Gold.
Thank you Sir for the explanation.
Great explanation! thank you
Nice explanation
Good video, Jim! Thanks for mentioning the effect that SWR has on receive. This is what I try to get my fellow hams to consider. Once you can tune the antenna system to hear, it is not so difficult to come up with enough power for them to hear you. We see SWR and think about transmission line loss on transmit, but it means probably even more on receive. All the data you presented is spot on to help evaluate the system. Thanks for the great work!
Great info, as always. Thanks. NX3H
Jim, perhaps you know about this, I would like to advise you to visit a bathhouse, steam room, or sauna, with an oak broom, and after the steam room you should definitely plunge into a pool with ice water, perhaps this will make your life easier.
I'll be glad to hear from you 73 GOOD LUCK!
This is great info. Thank you Jim!!!
73,KE2CQF
Top Banana!
I keep my SWR down as much as possible, especially when I'm using my Solid State Amplifier which would trip to a fault if it was high.
Thank you for the post, interesting subject. Looking at your table I have a question about the two entries for 100 feet of ladder line at 28.5 MHz. For 3.2:1 SWR the SWR loss is indicated to be zero and the overall loss is 0.5dB while in the 1:1 SWR entry the SWR loss is again zero but the overall loss is now 0.1dB. I would expect that the overall loss would be the same in both entries since the SWR loss was assumed zero in both cases; and the frequency and lengths are also the same.
Always good information. So with 3.2:1 SWR on 100ft, of RG-58 is like having almost a 3db attenuator TX/RX. 73 88 😇
Am I interpreting this correctly? While set up a local park, 100watts on FT891, horizontal dipole... I should use ladder line for the best ERP? No balun required? Correct? AD3i
Jim thank god for your common sense, compared to that other know all on YT. The other tuber is a joker 🃏
Great video Jim!!!!KD2QMJ
I wish we had higher power privileges, only allowed 100watts with standard license. Or 400watts with advanced license in Australia.
👍👍
You will never achieve a "perfect" match of 1:1. Especially not over the entire band. And certainly not a multiband antenna unless it has separate traps and elements. If you pick the center of the band, it may not favor where you are typically transmitting. Pick the center of where you can legally operate, then tune the antenna there for best match.
We all agree that a perfect SWR is elusive. That's not the point of this video at all.
U just made that man sit down. Lol. Love it. You’re correct.
Agreed that other guy is a joke
@@kumasu I know the point of the video. I am reinforcing what Jim is talking about.
One thing I am still in doubt is about the theoretical no loss feedline with multiple back and forth reflections finally sending the power out in full even if VSWR is high. What about the difference in phase of the signal with each reflection and mixing with the signal coming in at that instant from the radio? Will it not produce some distortion? Or do you mean that due to the speed at which radio signal travels, this effect will be minimal? 73 de Jon, VU2JO
Going to be a lot of broken hearts with this one.
You completely go by the fact that with an SWR of 3.2 there is a reflected power of 27%! That's a very bad omission.
So we don't scare away new operators or those thinking of getting their license that they have to spend a lot of money to get into the hobby there are other things to consider. They should know that even with horribly lossy coax and a not so great antenna at a not so great height that has a so-so SWR they will still be able to make contacts. Will they make contact with that rare DXpedition on some remote island in crowded conditions, probably not. However they will be able to make contacts to a lot of operators around the world. I tell new Ham's to just get on air with what you have and enjoy it. Make improvements to your system as you can afford it. I tell them when they start out in the hobby they can take advantage of the other operators great system to help compensate for their poor system. Their horrible system that is 10dB down from a good setup talking to someone who has a fantastic system with 10dB of gain works out to a signal each way with 2 operators with only good systems.
BOB BECK JIM.... KG5TEL..................
Why do amatuers post their name and address on the internet?
1. If you understand the block diagram of a transmitter, there is a voltage source and there is a series resistance. By convention, our series resistance, for analysis purposes is 50 ohms. Also, the resistance of the signal source is, by definition, zero since any impedance to ground inside this RF source is added to other values to create the 50 ohm output impedance.
2. Power does not get reflected. The initials are VSWR, not PSWR. A voltage is reflected and the voltage creates a standing wave. So a voltage is therefore reflected. For practical purposes, we can now think of the reflected power as a forward power heading straight back to your finals.
3. What do we know about an RF voltage heading down a coax towards a 50 ohm dummy load? I believe that we know that the voltage will indeed be dissipating power in that 50 ohms.
4. Since we had a mismatch at the antenna, the impedance of the reflected signal at the transmitter will not be 50 ohms, so a small amount will be reflected back towards the antenna. Very small. Not worth discussing, actually. We must acknowledge this or deny that any power is ever dissipated into a dummy load.
5. Much of the reflected signal will be dissipated in the finals. That's one reason old transmitters had glowing plates. It's why today's transistor units have the transistors blown.
6. If a tuner is used, the tuner at the transmitter will load up the line and the antenna as one big radiating device. No voltage will be reflected to the transmitter.
Try this. Take a DC voltage source in a lossless system. Your voltage source is 141.4V. The voltage source has a 50 ohm series resistive impedance. Your load is 50 ohms. It's easy to see your current here is 1.414A. 141.4V / (50 + 50) = 1.414A Then we can see I (1.414) squared R (50 in the load or antenna) is 100 W. 1.414 squared is 2 and 2 times 50 is 100. You are delivering voltage for a 100 W output to the load. Now for a 3:1 VSWR, we see a load is now 150 ohms. 141.4 / (50 + 150) is now 0.707A. Current squared times load is 0.707 squared times 150. We can see that we now have 75 watts. Not close to your 3.2:1 VSWR scenario. And this is at DC without and loss. Without loss, a 3:1 VSWR allows us to transmit 75% of what we would expect. The VSWR losses bring that number down even lower.
I have no idea why so many want to disregard real world situations. Losses can be great even with "lossless" transmission lines.
Isn't the reflected voltage reflected back towards antenna at the mismatch at the transmitter same way it does at the antenna therefore no damage to transmitter, Isn't the cause of transmitter damage caused by the transmitter trying to put power into this mismatch?
@@paulm0hpd319the signal reflected back to the transmitter is a signal terminated by a 50 ohm dummy load. Have you worked with circuit analysis with distributed and lumped considerations? It would be easier to understand.
@@BusDriverRFI your saying much of the reflected signal is disapated in the finals, how so if there's a mismatch at the transmitter
@@BusDriverRFI you also say if a tuner is in line it will load up the antenna and line as on big radiating device, this isn't necessarily true this depends on the antenna balance or if there's an adequate groundplane to prevent common mode current on the braid of the feedline
@@paulm0hpd319 no. I don't agree with you.
Thanks Jim another awesome video thank you N7ZXG
Always a wealth of knowledge thank you sir! KQ4OHB