Interesting experiments Jim. We've all heard about losses in coax and how larger diameter coax is better than the small diameter, but actually seeing it is another thing. Keep the informative videos coming Jim. Thanks David M0XQZ
Hi,Thank you for writing. I am sending this same response to many. On Tuesday, November 2nd in the morning at 0300 I was taken by ambulance to the local hospital with severe shortness of breath. I had been having a problem breathing for more than a year. A blood test in the Emergency Room showed my D-Dimer score of 12,281. A D-Dimer of over 500 is considered high. I was told that I set a new record in the ER at 12K. My oxygen level was about 82%. A CT scan showed I had a bilateral pulmonary embolism with almost total blockage. I was close to dying. A powerful blood thinningmedication was injected many times over the next several days. I was in the hospital for 5 days. I was sent home Saturday evening. I was on oxygen full time for a few days and mostly at night. I must use a walker. I can only walk a short distance on a level surface. Treatment for the blood clots is 6 months. It will take that long for some of them to go away. While in the hospital many came by to ask me questions about how I was able to live the last few months. I had been to 3 doctors recently and not correctly diagnosed. The outlook is good. I must follow the doctor's orders carefully. I do not feel strong enough to have vistors and don't want to risk infection at this time. My wife is taking excellent care of me. I will beuploading a video about Pulmonary Embolism soon. All of us who sit for a long time are at risk. Again, thanks for your message. 73, Jim W6LG
You look after yourself !! I've just been warned by my doctor and will be making adjustments to my lifestyle as well. Hope you recover quickly . . . Mike VK3FMPA
Hi Jim, just want to let you know that your videos are really great. Keep 'em coming please. I love ham-radio related, informative videos. Thank you for your hard work and effort. 73 from Germany de DL7XT, Nico
This is why everyone should be running a minimum of 1.875" hardline, not only does line loss reduce power to the antenna, it also reduces signal streanth on receive.
As measured here, a 100' run of RG8X is roughly 15% more lossy than a 100' run of RG213, but it costs (DXE bulk price as of May 24, 2021) less than half as much at $.48/ft vs $1.09/ft. If your runs are short (
I love balanced line ! I love balanced line ! I love balanced line ! I love balanced line ! I love balanced line ! Hope all is good with you and yours !
1.55 dB loss in the RG8X and .87 dB for the RG-213. A 100 watt slug would help with accuracy too. According to this site: kv5r.com/ham-radio/coax-loss-calculator/ The loss in the RG8-X should be 1.65 and 1.105 for the RG-213. So your measurements are better than expected. Good video! Thanks 73 Jim W7RY
Excellent, very relaxed and enjoyable presentation Jim, such a contrast to many on UA-cam, I must admit I rarely use 10M in the last few years and on the lower bands I guess the RG213 and RG8X are just fine for most hams out in the real world, 100W and a wire antenna and not too long a run. Thanks again for a great series of videos learned a lot despite being QRV since 1970 Vy 73 Tony G3ZRJ
FB Jim. I use 8x as short run patch cable where the losses won't amount to much. I do have one 50ft run I use for field work, and now I'll need to check the losses on that.
Hi Jim, I like what you are doing, coax can be used for a lot of things. It can be used for jumpers in the shack, antenna feed line, chokes even a antenna can be made out of it plus a lot of other things. However as you proved it is not the most effecient conductor of RF. I hope you get into open ladder line window line balons etc. I am looking forward to seeing more of good common sence articals you put on the tube. 73 jim kf4gnj
The loss of cable can be calculated of course but this is really a neat 'show tell'. Point is: Coax definitely has loss as length and frequency is increased. Note that Jim has the coax terminated into its characteristic impedance. Otherwise the loss would be greater as we realize reflected power. Indeed the reflected power in part gets sent back up the line and is radiated but the coax does not like standing waves. At the poihts where the incident and reflected voltage peaks (they sum), the coax starts to kinda cook!!!!! Of course that RF power is lost in the form of heat and does not infact get radiated as RF. So...with SWR the loss in the line is even greater. We need to live with coax loss as we increase freq. Also try to terminate the coax into a tuned antenna (that presents 50 ohms). We kinda know this too. Maybe one way to 'get over' loss in coax (even when 1:1) is to consider whether the guy on the receiving end would hear a difference if, for example, the rig pumps up to 120 watts to make up for a 20W loss when the rig is doing just 100W into the coax. You know what? The guy on the receiving end will NOT hear any difference!! HOORAY!!!! So...we try to 'get past' losses don't we : ) !!! BTW: Ladder line is maybe 2% loss even at 10M but better be sure the feedline is balanced. Now that is another story!!!! Unbalanced ladder line radiates (like the antenna) and this can get into appliances, etc. Hm...another bag of worms!!!! Thanks Jim for the video my friend.
Hey Dave! Our house is in escrow. We have started to look in Rocklin. I see more doctors tomorrow about a potential surgery; removal of parathyroid glands. Those things are causing severe osteoporosis and kidney stones (man that hurts). I am curious about the ladder line radiating. I had thought that it would not because it is balanced. This is all a very interesting and tricky subject. There is much confusion and it is not easy to explain; as you know. Back to the ladder line, it is almost loss less but the radiating part I have not seen. Let me know your thoughts Dave. Thanks, Jim on Wolf.
I think I had the best success with a 3 way incandescent and I shorted the two filaments. It was just that simple. If you have some bulbs around the house, try them with low power. You can use the built in antenna tuner if there is one in your transceiver. Did you have more questions about that dummy? 73, Jim
You are right! I need to do that. I wonder how far I can be heard on the light bulb? I will do something in the next 2 weeks. Thanks Wayne! 73, Jim W6LG www.hamcq.com
Had one myself. That's how you peaked a tube transmitter back in the day. And yes, you could end up working stations on it. Especially if you had friends nearby.
back in the 70's we used RG-8U but searching online for cable today, RG-8U is quite expensive! in your video RG8X and RG213 are being discussed. has RG8U been replaced by these newer versions or are these newer versions just more reasonably priced?
I think my original reply to did not get posted. Yes, RG8 is hard to find and expensive. RG213 is what most guys use. I don't recommend RG8x except for jumpers. There is no good specification for RG8X. There is also LMR-400 and some copies of that coax. LMR400 tends to be excellent if you buy from a known, good reputation manufacturer. Keep in mind that LMR400 takes a special connector. Always buy good coax from a company that you can trust. No name coax is trouble. No matter what brand, the coax is likely made overseas. 73, Jim
Nice show, and I also am somewhat surprised. The snow at the end inspires a question: One of many reasons we use coax is that it "doesn't care" what is next to it. We can lay it along a metal eaves trough, for example. But is that completely true? If we had some coax lying along the ground and it got covered with a somewhat-conductor, e.g. snow, would that change the losses? And for that matter would it change the effective impedance? Or if we bury the coax? If the shield, braid or braid plus foil or whatever, were perfect then there should not be a change. But in the real world it won't be perfect. Keep up the great shows! 73, WA9D
Hi Jim glad to meet you. I'm new to Ham and just getting my shack set up. I have a run of 50 foot RG213 and need to cut it and place a PL259 and go to the arrestor at about 30 feet, then out of the arrestor through the wall to the transmitter. will this be a good idea or is it something I shouldn't do. Over all the coax from antenna to transmitter will be a total of 50 feet. Do I need to get more coax or will this work?
@@ham-radio You miss understood sir, my question to you was not about the arrestor but about the RG-213. I using a polyphaser arrestor, but I am concerned about having to cut the 50 foot RG-213 coax. Will this make a difference in the coax ability to be a transmission line? or will it change anything in regards to the 50 ohm status or the coax ability to tune the antenna properly?
@@kenthompson143 No. Go ahead and cut the coax to install good quality coax connectors. I use as much as possible silver plated with Teflon insulator connectors. 73, Jim W6LG
@Andrew Lawlor Hi Andrew. Nope. You wouldn’t notice any difference, especially on HF, and probably not on the higher frequencies also. Any real downside is leakage of water into any connectors along the way, if used in an exposed environment. Suffice to say, a single run of coax is the best option in any scenario. I know we all strive for the best signals and lowest losses, but when you get right down low into 20, 40, 80 Metre (meter) bands (and lower), losses become pretty insignificant, allowing even the crappiest coax cable to be used!
Dropit late reply, but it depends heavily on how long the cable needs to be, and what frequency you run. I am in NL, so the cables I can get and so on aren't the same as you have most likely but proper suppliers will have a table where they show cable type on one axis, and frequency on the other axis, this means you can estimate what your loss will be for the frequency you use for different types of cables. The prices of cables typically are close enough that you really want to pick the right one as they can be really really lossy, over 3db easily if you are doing more than a couple of yards. If you are doing a few ft it really doesn't matter as much. 73's
@Dropit Hi Dropit. What length of coax run do you anticipate between your 5W handheld and the antenna? For the purposes of this post, I’ll assume you might be transmitting to an outside antenna, using frequencies around 145MHz and 435MHz. I’ll also give you figures for loss of wattage per 10 feet of coax. Using good quality RG58, loss will be 0.47dB, resulting in 0.5Watts loss of wattage delivered to the antenna for each 10 feet of coax. Using thicker RG213 will approximately halve the loss to 0.26dB, resulting in 0.3Watts loss of wattage delivered to the antenna. At 435MHz, losses are approximately doubled. In a nutshell: 5 Watts / 145MHz 10ft of RG58 = 4.5Watts at antenna 10ft of RG213 = 4.7Watts at antenna 30ft of RG58 = 3.5Watts at antenna 30ft of RG213 = 4.0Watts at antenna 5 Watts / 435MHz 10ft of RG58 = 4.0Watts at antenna 10ft of RG213 = 4.5Watts at antenna 30ft of RG58 = 2.7Watts at antenna 30ft of RG213 = 3.6Watts at antenna It is acceptable (if necessary) to mix different types of coax (of course sticking to 50 Ohms) - all you need do is calculate the losses per each length of coax used and add the losses together. I hope this information is helpful to you. Here is a typical coax loss calculator: www.qsl.net/co8tw/Coax_Calculator.htm
I think it was KV5R. He, if I am not mistaken, has a great deal of information along with the calculators. If that is wrong, let me and I will do some research. 73, Jim
Not on the signal which is being sent up via the central core which is protected from the shielding by the dialectic. But coiling the coax will impede any RF that gets picked up & travels down the shielding (which is why we add coils). What we are measuring here is how much of our signal (which is sent from the transmitter at 100 watts) actually makes it through the full length of our coax (whether you coil it or not) up to the antenna at the other end so we can determine the coax loss. Note Jim coiled his 10m cable to measure his wattage output even though it will be uncoiled when connected it makes no difference to how many watts will be lost in the coax. It is the length of the coax that is critical here. The longer your coax the more of your output power gets lost in the coax and therefore does not reach the aerial. The whole point of this exercise was to measure the coax loss and confirm that it was indeed within tolerance or close to the manufacturers stated figure. You will recall that the impedance of the coax cable presented to the transmitter is 50 Ohms which is what it will be expecting.
Yes. From what I know, it is linear type of thing. The big problem, as I see it, with RG8X is the quality of some cables is really poor. So, go to a brand name or supplier who does not sell that gray RG8X from China that is rebranded. 73, Jim W6LG...thanks for asking a very good question.
Hi I would like to know how you made that light dummy load, it seems like it would be easy but would like to know anyhow, could you do a short video on that please, by the way just found your videos John KF7OMB
For most of us, that is the best choice. I have used it many times. I just tried the 400 coax from DXengineering and it was very good. I highly recommend buying that coax with connectors installed. 73, Jim
richard vaughn ..the work I perform I use both for different applications. If you look at the loss chart for lmr240 it works best in applications under 100feet and under 512MHz. UHF could prove slightly more loss. Above 512MHz and over 100feet definetly 400. But 240 is excellent for most applications. A quick comparison for 240 and 213, 240 seems to be superior for both through power and loss.
Great videos Jim. Although the audio is a little low on this one. Had to crank the volume all the way up. I'm curious how much loss there is in 100' of RG8? 73, Gary W6FH
Interesting experiments Jim. We've all heard about losses in coax and how larger diameter coax is better than the small diameter, but actually seeing it is another thing. Keep the informative videos coming Jim. Thanks David M0XQZ
Thanks David. 73, Jim
Hi,Thank you for writing. I am sending this same response to many. On Tuesday, November 2nd in the morning at 0300 I was taken by ambulance to the local hospital with severe shortness of breath. I had been having a problem breathing for more than a year. A blood test in the Emergency Room showed my D-Dimer score of 12,281. A D-Dimer of over 500 is considered high. I was told that I set a new record in the ER at 12K. My oxygen level was about 82%. A CT scan showed I had a bilateral pulmonary embolism with almost total blockage. I was close to dying. A powerful blood thinningmedication was injected many times over the next several days. I was in the hospital for 5 days. I was sent home Saturday evening. I was on oxygen full time for a few days and mostly at night. I must use a walker. I can only walk a short distance on a level surface. Treatment for the blood clots is 6 months. It will take that long for some of them to go away. While in the hospital many came by to ask me questions about how I was able to live the last few months. I had been to 3 doctors recently and not correctly diagnosed. The outlook is good. I must follow the doctor's orders carefully. I do not feel strong enough to have vistors and don't want to risk infection at this time. My wife is taking excellent care of me. I will beuploading a video about Pulmonary Embolism soon. All of us who sit for a long time are at risk. Again, thanks for your message. 73, Jim W6LG
You look after yourself !! I've just been warned by my doctor and will be making adjustments to my lifestyle as well. Hope you recover quickly . . . Mike VK3FMPA
I'm running between 1~5 watts. Seriously thinking about putting the PA at the antenna feed point.
Your video's are very interesting and informative.
73's Alan in the UK
I wish I had found/watched this yesterday. I’ve just ordered some rg-8x. Silly me.
Hi Jim, just want to let you know that your videos are really great. Keep 'em coming please. I love ham-radio related, informative videos. Thank you for your hard work and effort. 73 from Germany de DL7XT, Nico
Very nice video Jim profishon work
we thank you for the informition which is very helpful for all hams
This is why everyone should be running a minimum of 1.875" hardline, not only does line loss reduce power to the antenna, it also reduces signal streanth on receive.
Jim,
Nice video series. I enjoy your tess and love your casual, easy-going style. Thanks much for taking the time to make these videos.
George
K2WO
As measured here, a 100' run of RG8X is roughly 15% more lossy than a 100' run of RG213, but it costs (DXE bulk price as of May 24, 2021) less than half as much at $.48/ft vs $1.09/ft. If your runs are short (
I love balanced line ! I love balanced line ! I love balanced line ! I love balanced line ! I love balanced line ! Hope all is good with you and yours !
YES!!! Balanced is better. Thanks Frank. 73, Jim
Thanks for this information as I am putting up a hex beam and want to get everything possible from the antenna.
1.55 dB loss in the RG8X and .87 dB for the RG-213.
A 100 watt slug would help with accuracy too. According to this site: kv5r.com/ham-radio/coax-loss-calculator/
The loss in the RG8-X should be 1.65 and
1.105 for the RG-213. So your measurements are better than expected.
Good video!
Thanks
73 Jim W7RY
Excellent, very relaxed and enjoyable presentation Jim, such a contrast to many on UA-cam, I must admit I rarely use 10M in the last few years and on the lower bands I guess the RG213 and RG8X are just fine for most hams out in the real world, 100W and a wire antenna and not too long a run. Thanks again for a great series of videos learned a lot despite being QRV since 1970 Vy 73 Tony G3ZRJ
True. I don't run RG8X to antennas if at all possible. In any case, get on the air and work some DX. 73, Jim W6LG
FB Jim. I use 8x as short run patch cable where the losses won't amount to much. I do have one 50ft run I use for field work, and now I'll need to check the losses on that.
Hi Jim, I like what you are doing, coax can be used for a lot of things. It can be used for jumpers in the shack, antenna feed line, chokes even a antenna can be made out of it plus a lot of other things. However as you proved it is not the most effecient conductor of RF. I hope you get into open ladder line window line balons etc. I am looking forward to seeing more of good common sence articals you put on the tube. 73 jim kf4gnj
Hi Jim! I'm a new subscriber, your channel looks fun, and educational! Looking forward to future videos Sir. = )
nice to see a real world test demonstrating cable loss.. thanks
Thanks Jim
Thanks and 73, Jim back from surgery.
Did YAESU replace the 857 with a similar, but improved model?
Just bought 50 foot PL-213. Hope at this length my loss is substantially less. Running 350 watt on 11 meter with 5/8 at 45 feet.
The loss of cable can be calculated of course but this is really a neat 'show tell'. Point is: Coax definitely has loss as length and frequency is increased. Note that Jim has the coax terminated into its characteristic impedance. Otherwise the loss would be greater as we realize reflected power. Indeed the reflected power in part gets sent back up the line and is radiated but the coax does not like standing waves. At the poihts where the incident and reflected voltage peaks (they sum), the coax starts to kinda cook!!!!! Of course that RF power is lost in the form of heat and does not infact get radiated as RF. So...with SWR the loss in the line is even greater. We need to live with coax loss as we increase freq. Also try to terminate the coax into a tuned antenna (that presents 50 ohms). We kinda know this too. Maybe one way to 'get over' loss in coax (even when 1:1) is to consider whether the guy on the receiving end would hear a difference if, for example, the rig pumps up to 120 watts to make up for a 20W loss when the rig is doing just 100W into the coax. You know what? The guy on the receiving end will NOT hear any difference!! HOORAY!!!! So...we try to 'get past' losses don't we : ) !!! BTW: Ladder line is maybe 2% loss even at 10M but better be sure the feedline is balanced. Now that is another story!!!! Unbalanced ladder line radiates (like the antenna) and this can get into appliances, etc. Hm...another bag of worms!!!! Thanks Jim for the video my friend.
Hey Dave! Our house is in escrow. We have started to look in Rocklin. I see more doctors tomorrow about a potential surgery; removal of parathyroid glands. Those things are causing severe osteoporosis and kidney stones (man that hurts). I am curious about the ladder line radiating. I had thought that it would not because it is balanced. This is all a very interesting and tricky subject. There is much confusion and it is not easy to explain; as you know. Back to the ladder line, it is almost loss less but the radiating part I have not seen. Let me know your thoughts Dave. Thanks, Jim on Wolf.
Hi Jim, do you have a video or resource on how to build that lightbulb dummy load? 73 de K6TJO
I think I had the best success with a 3 way incandescent and I shorted the two filaments. It was just that simple. If you have some bulbs around the house, try them with low power. You can use the built in antenna tuner if there is one in your transceiver. Did you have more questions about that dummy? 73, Jim
back in the old days as well as today I use a G194 side marker light bulb for a dummy load bulb on the cb radio. John KF7OMB
I know nothing about CB. There are probably many bulbs that will work as a dummy load. 73, Jim
Would love to see how you made/make your light-bulb dummy load... did I miss a video someplace? ;)
You are right! I need to do that. I wonder how far I can be heard on the light bulb? I will do something in the next 2 weeks. Thanks Wayne! 73, Jim W6LG www.hamcq.com
Had one myself. That's how you peaked a tube transmitter back in the day. And yes, you could end up working stations on it. Especially if you had friends nearby.
The loss is based on a number of factors, one being frequency, and another is how many connections are on each cable. each adds more loss,
At HF, connectors add no measurable loss. Thanks Joe. 73, Jim
back in the 70's we used RG-8U but searching online for cable today, RG-8U is quite expensive! in your video RG8X and RG213 are being discussed. has RG8U been replaced by these newer versions or are these newer versions just more reasonably priced?
I think my original reply to did not get posted. Yes, RG8 is hard to find and expensive. RG213 is what most guys use. I don't recommend RG8x except for jumpers. There is no good specification for RG8X. There is also LMR-400 and some copies of that coax. LMR400 tends to be excellent if you buy from a known, good reputation manufacturer. Keep in mind that LMR400 takes a special connector. Always buy good coax from a company that you can trust. No name coax is trouble. No matter what brand, the coax is likely made overseas. 73, Jim
Nice show, and I also am somewhat surprised. The snow at the end inspires a question: One of many reasons we use coax is that it "doesn't care" what is next to it. We can lay it along a metal eaves trough, for example. But is that completely true? If we had some coax lying along the ground and it got covered with a somewhat-conductor, e.g. snow, would that change the losses? And for that matter would it change the effective impedance? Or if we bury the coax?
If the shield, braid or braid plus foil or whatever, were perfect then there should not be a change. But in the real world it won't be perfect.
Keep up the great shows!
73, WA9D
Hi Jim glad to meet you. I'm new to Ham and just getting my shack set up. I have a run of 50 foot RG213 and need to cut it and place a PL259 and go to the arrestor at about 30 feet, then out of the arrestor through the wall to the transmitter. will this be a good idea or is it something I shouldn't do. Over all the coax from antenna to transmitter will be a total of 50 feet. Do I need to get more coax or will this work?
Hi Ken,
Most lightning arrestors do very little. Which brand, model do you have? 73, Jim W6LG
@@ham-radio You miss understood sir, my question to you was not about the arrestor but about the RG-213. I using a polyphaser arrestor, but I am concerned about having to cut the 50 foot RG-213 coax. Will this make a difference in the coax ability to be a transmission line? or will it change anything in regards to the 50 ohm status or the coax ability to tune the antenna properly?
@@kenthompson143 No. Go ahead and cut the coax to install good quality coax connectors. I use as much as possible silver plated with Teflon insulator connectors. 73, Jim W6LG
@@ham-radio Ok Thanks and 73 to you
Hi Jim, another good video. Hope to talk the you on the air. 73 Phil
is the coax not acting like a inductor being coiled up ??? i wonder what it would be layed st8 out.
what if you had a 50' section ? I have a 25' of RG8X going into my doublet
Would it make a huge difference if it was a single piece of coax rather than multiple pieces joined together?
I don't think it would. That is a good question. I will look into that when I get time. Thanks, Jim
@Andrew Lawlor Hi Andrew. Nope. You wouldn’t notice any difference, especially on HF, and probably not on the higher frequencies also. Any real downside is leakage of water into any connectors along the way, if used in an exposed environment. Suffice to say, a single run of coax is the best option in any scenario. I know we all strive for the best signals and lowest losses, but when you get right down low into 20, 40, 80 Metre (meter) bands (and lower), losses become pretty insignificant, allowing even the crappiest coax cable to be used!
Great video, thanks for sharing.
nice video.....thanks Jim de NC3U/Sal
What cable should I use as a feed line to the antenna for a 5 w handheld radio ?
Dropit late reply, but it depends heavily on how long the cable needs to be, and what frequency you run. I am in NL, so the cables I can get and so on aren't the same as you have most likely but proper suppliers will have a table where they show cable type on one axis, and frequency on the other axis, this means you can estimate what your loss will be for the frequency you use for different types of cables. The prices of cables typically are close enough that you really want to pick the right one as they can be really really lossy, over 3db easily if you are doing more than a couple of yards. If you are doing a few ft it really doesn't matter as much. 73's
@Dropit Hi Dropit. What length of coax run do you anticipate between your 5W handheld and the antenna? For the purposes of this post, I’ll assume you might be transmitting to an outside antenna, using frequencies around 145MHz and 435MHz. I’ll also give you figures for loss of wattage per 10 feet of coax.
Using good quality RG58, loss will be 0.47dB, resulting in 0.5Watts loss of wattage delivered to the antenna for each 10 feet of coax. Using thicker RG213 will approximately halve the loss to 0.26dB, resulting in 0.3Watts loss of wattage delivered to the antenna. At 435MHz, losses are approximately doubled. In a nutshell:
5 Watts / 145MHz
10ft of RG58 = 4.5Watts at antenna 10ft of RG213 = 4.7Watts at antenna
30ft of RG58 = 3.5Watts at antenna 30ft of RG213 = 4.0Watts at antenna
5 Watts / 435MHz
10ft of RG58 = 4.0Watts at antenna 10ft of RG213 = 4.5Watts at antenna
30ft of RG58 = 2.7Watts at antenna 30ft of RG213 = 3.6Watts at antenna
It is acceptable (if necessary) to mix different types of coax (of course sticking to 50 Ohms) - all you need do is calculate the losses per each length of coax used and add the losses together.
I hope this information is helpful to you.
Here is a typical coax loss calculator: www.qsl.net/co8tw/Coax_Calculator.htm
Hello, a super informative video! Can you please post a link for the calculator you used?
Thank you.
I think it was KV5R. He, if I am not mistaken, has a great deal of information along with the calculators. If that is wrong, let me and I will do some research. 73, Jim
doesnt the coiling of the coax have influence to?
I was thinking exactly the same thing. There has to be some impedance, especially considering how many loops there were.
its a giant hf choke..
That's what my uncle W0LOY told me years ago, that coiling measures different at different frequencies than straightened cable.
Not on the signal which is being sent up via the central core which is protected from the shielding by the dialectic. But coiling the coax will impede any RF that gets picked up & travels down the shielding (which is why we add coils). What we are measuring here is how much of our signal (which is sent from the transmitter at 100 watts) actually makes it through the full length of our coax (whether you coil it or not) up to the antenna at the other end so we can determine the coax loss. Note Jim coiled his 10m cable to measure his wattage output even though it will be uncoiled when connected it makes no difference to how many watts will be lost in the coax. It is the length of the coax that is critical here. The longer your coax the more of your output power gets lost in the coax and therefore does not reach the aerial. The whole point of this exercise was to measure the coax loss and confirm that it was indeed within tolerance or close to the manufacturers stated figure. You will recall that the impedance of the coax cable presented to the transmitter is 50 Ohms which is what it will be expecting.
Good video Jim.Could you tell us the name of the manufacturer of the cable you talked about.
thanks Jim, is it safe to say 50 feet would be half that on rg8x?
Yes. From what I know, it is linear type of thing. The big problem, as I see it, with RG8X is the quality of some cables is really poor. So, go to a brand name or supplier who does not sell that gray RG8X from China that is rebranded. 73, Jim W6LG...thanks for asking a very good question.
Hi I would like to know how you made that light dummy load, it seems like it would be easy but would like to know anyhow, could you do a short video on that please, by the way just found your videos John KF7OMB
I have done a couple of videos on that. 73, Jim
How about LMR-400?
For most of us, that is the best choice. I have used it many times. I just tried the 400 coax from DXengineering and it was very good. I highly recommend buying that coax with connectors installed. 73, Jim
What would it be like at 3M (10ft) long?
yes, Thanks, Jim
gift of gab
anyone use lmr400
or lmr240?
richard vaughn ..the work I perform I use both for different applications. If you look at the loss chart for lmr240 it works best in applications under 100feet and under 512MHz. UHF could prove slightly more loss. Above 512MHz and over 100feet definetly 400. But 240 is excellent for most applications. A quick comparison for 240 and 213, 240 seems to be superior for both through power and loss.
Great videos Jim. Although the audio is a little low on this one. Had to crank the volume all the way up. I'm curious how much loss there is in 100' of RG8?
73,
Gary W6FH
+Gary Sumner (Grandhamster) Thanks Gary. That depends on the frequency. And, do you mean RG8 or RG213?
+Gary Sumner (Grandhamster) I didn't know any difference, and do broadcast audio mixing for a living! :-) (Warriors and Giants) Your mileage may vary.
+Jim W6LG great answer
+Jim W6LG I mean RG8.
+Geronemo Bauer Thanks Geronemo!
Gary W6FH
People spend all kinds of money on rigs and antennas and then they will turn around and get cheapest china made cable they can find. SMH.
Just use old TV coax. It's usually free.
Great video, great experiment, thanks for sharing!!!