If you are convinced that jumper length makes a significant difference then you are making coax sellers very happy. And after a couple of the other misconceptions he has, he shouldn't 'poo-poo' those other people who post mistaken ideas.
Great video! Thanks for taking your time to make it! I like to look at it just a bit different, a quarter wave (3 foot jumper) at the rig to the input of the amp sees 180 degrees out (246/27 x .66 VF is a quarter wave). Simply said, if you have low impedance at the rig, then using a quarter wave matching section will see the reverse.. now a Halfwave matching section sees the same at both ends. Using. (246 x 2 / 27 MHz times .66 Velocity factor = 12 feet. This is providing the input of the Amp has a low impedance input. I am an ex Bird Calibration Tech., worked there for 12 years.. use to run into this all the time. 73's. David.
I am wondering here and learning this stuff, am i doing something wrong? i put in 27X.66 and come up with 17, i have tried it with 27.000X .66 and still come up with 17, how would i go about figuring out how long of a run of coax would be needed to run to a antenna? i am lost when it comes to this stuff, i was also wondering if the length of coax to a antenna switch box would matter, is there something i can go by as a basic to always use, i have been into radio for only a few years, i have been told that coax length doesn't even matter, so many different ideas and ways of doing things im lost hahaha i will be getting a antenna analyzer on in a couple of weeks to help me with some of it so hopefully that helps
Velocity Factor is how much the Speed of Light is Slowed Down, to reach the inner of the coax, Different brands and size are all different from RG142, Rg58, RG58x RG213 + Mil Spec, LMR400, Hleiax 450/550/650, so .66VF is not right when RG213 is .86VF
I had trouble with my amp oscillating with a 6 foot jumper, switched to a 4 foot and it fixed the issue. I fixed my reflect issues by making the coax longer after the amp.
I don't get it! This makes no sense. If different lengths of coax are making this much difference you have a problem, I suggest you have r.f. on the outer of your coax which needs sorting out, especially if you have a problem with r.f. jumping and coax crossing and melting I've never had any problem with different lengths of coax or crossing them or coiled up and certainly no melting. How much power are you using? G4GHB
hey bill. im with you. Unless these cber's have alot of COMMON MODE floating on the shields of thier coax i dont get it!! But he says he's using a dummy load so..... Its impossible to really tell what they are using or doing with these videos. Craig call sign KY4PI. Extra Class ham here.
When you put the directional couple at the shack end the reflected power reading is consumed in the coax and inaccurate. When your antennae is 50 ohms and your transmitter is 50 ohms, it doesn’t matter what length the coax is as long as the coax is 50 ohms. When everything is the same impedance you will have maximum power transfer with little standing waves. It is hard to see how your connection are made in the video. A diagram would be helpful. I empathize, a picture is always better ( in my description as well, we use what we have to work with). It appears you have connected your transmitter to your feedline (reference plane), with coax and have a mismatch and are trying to match impedances at that point in your shack. (Stub matching). While a match at this point protects your transmitter) you are doing nothing to match the feedline at the antenna feedpoint. You need to match the feedline at the antenna as well. This can be done with a stub, balan/unun, etc. if your using coax you should put your directional coupler right at the anttena feedpoint up in the air, only then will you get a correct swr reading. When you use a match box, you are matching Z between your transmitter and the matchbox, thru a piece of coax. If the feedline and antenna are both 50 you have a match. This usually is not the case, at which point you need to tune your antenna. The output of your match box in the shack is the reference plane which is matched to the feedpoint of the antenna by adjusting it’s capacitor and inductor. If your antenna is other than 50 ohms then the feedline has to changed to match. If you use ladder line at the output of your match box you are matching it to the antenna, while matching the transmitter to the input of the match box.
Loss for RG8X roughly 2 db per 100 feet at 27.5mhz. Thats .2 db per 10 feet. Now, with 3 foot jumper you had 250mw reflected. Increase that jumper to 12 feet and loss for barrel, with 250mw reflected at the amp, the radio would see 100mw less just because of coax loss. You're not matching anything. You're also cutting your forward power by 100mw too. The goal is to match the radio and amp input impedence. If they're matched, the shorter the jumper the better would still give you 1:1 match. If you want a thumbnail without matching radio to amp's input, look at the output power of amp, then swap input jumpers for highest output.
Oooh right,cool...had some problems with impedance and got it to an 1.5 swr on the radio,but i run out of cable...strange thing is that i have impedance problems on one mobile amp and not on the base amp(both kind of similar,the b501 zetagi and the klv 550) Cool video!!!!
It seems you are trying to match impedances by using jumper lengths and'sizes'. That tells me that the devices you are connecting do -not- have the same impedances because they are not constructed well or close to well. From the devices shown, that's not hard to believe at all. Why not just do it right to start with? Of course that requires you to know what 'right' is to start with (you may know but your explanation doesn't explain it).
You do know an SWR meter is not an isolator? You think one side is separate from the other? Coax on one side has no effect on the other side? The SWR meter is a fancy connector with a meter just like any coax coupler! It makes no difference cutting cable to specific lengths because they join together inside the meter making one cable. G4GHB.
Different coax behave differently? It appeared you used different types as jumpers. Joined different types together... You have seen crossed coax allow RF to jump from one to the other melting down coax? Really? Color me skeptical.
LOL is that a little model of E.T. sitting up there by the meters LOL I used love watching it when i was a kid.I just noticed it when i was watching this vid second time around.LOL
+Kealoha Martin Yes it is, I've had it for years. I think it was something someone gave me a long time ago, I also have other nicknacs up there from other people around the country.
Hello guys, what about matching for a multiband amplifier? how i should calculate the length??? i'm using a RF240UF cable .80 factor of velocity. Thanks
Thanks stickman great info as always.Got a quick question what to do with the 12 feet of coax from the radio out any ideas my amp is gonna be upfront where the radio is i know we cant coil it up if I'm not mistaken.Just some ideas on where i could put all the extra coax thanks again.
+Kealoha Martin I hope it helps, that's why I like putting these vids up for you guys. Not everyone knows how things work or what they should do, or how it's done. Some think they do, but most of the time it's hear say lol
+Dropmaul99 I know i tried my best to gather whatever i could of the internet and youtube to get a good idea and i still managed to muff it up.The c.b. radio is one catagory where they dont show to much of whats up do's and donts etc.I know I mentioned already But most good c.b. techs tend to hide in the dark.I have only a couple people trying to help me and make sure im doing it right.Stickman you stand out from the rest man your not afraid to get on here and how a rookie like me whats up.Not afraid to tell me whats worthless and what i should be looking at.Not a problem to stay an hour on the phone with me filling me in diagnosing possible problems not looking to b.s. me to sell me more stuff and make more money of me etc etc.You are honest never tried to scam me and man i thank you for dealing with a green bean like me man.Thanks stickman i promise i will get it together hopefully sooner than later.Alohas from da islands
I found a seller on eBay that sells different lengths of different types of coax and specifically for Cb 11 meter he sells 1/2 wave lengths. So the length of the 1/2 wave will depend on the coax velocity factor. Some are 12.5 feet and some are 14.5 feet. I use 1/2 wave lengths between each. Between radio and amp, amp to meter and meter to antenna in my mobile. A lot of people don’t know about velocity factor.
So a 3ft jumper is okay for using a swr meter? I just setup my first cb in my car with a 3ft firestik and a kl503 and on my meter which shows swr and wattage I’m seeing more carrier on the higher channels so I don’t know which to believe is this due to reflect?
if i send u a pic of my galaxy innards can u tell me what has been done? it has so much jumped, and the texas star i dont think its needed, but my antenna is just a k40 if you are near id about send whole setup to u , but ive had 3 ft jumper ,i went stick external speaker and noticed the hole was blocked so i swapped p.a input over to ext speaker port, i ended up with the setup working for a buddy and he paid me cb setup, which everyone needs old school way reach out, just watched some your vids, and seems you know alot more than anyone i know around here, the main guy i know id take it to him, but he sold me the 3 ft jumper, at rebuilding fried stuff hes awesome but, 3ft call me paraniod but maybe set up lol
SNAKE OIL!! Read about jumper lengths from AARL online articles (real Elmers.) Jumpers will only affect your SWR if the jumper in question is detective. PERIOD!! If your amplifier keeps blowing up when you're using a three foot jumper you might want to stop using that particular jumper. It's sad to see all this false information being spread. Especially when it comes to newbies who don't know any better. One needs to go directly to the source of the correct information, and as I mentioned above ARRL online articles, about anything hobbyist Communications related, are the gold standard in which to gain proper Communications knowledge.
It is nonsense as both coax cables are joined together in the SWR meter so cutting one to length makes no difference as it's all one cable anyway. For 49 years I've cut no coax to specific lengths except for phasing lines. G4GHB.
Thanks Stickman for a really informative video, this helped me so much in terms of SWR & power. Hey I have a Galaxy 939 that I want you to do your thing on.
+Gary P Thats the tricky 1, I play with the caps on the amp to make it think it has good reflect. I've seen a few come in that have had an issue with those radio amps. Best thing to do is not waste money on them as a stand alone amp will always make more watts and is the better value.
hey have been trying different jumper have 1ft up to 12ft but the thing in my car I have a galaxy 979 into 2x8 ds amp with a stryker a10 mag antenna with mini8 20ft cut about 8mm off antenna from the top 1.1 1.3 across 40 11meter but with amp on swr goes 1.5 - 2 what do think about 30ft from antenna or what ???thanks great vid...Floyd the barber
it also a good idea to use or multiples of 12ft to the antenn for 11mtrs cb,,ie 12ft 36ft and so on,,,also mobile most mag mounts come with 9ft of coax,,,change this out t 12ft...always use odd multiples or a half wave with velocity factor calculation for the freq you are working on,,,details on the web,,,this gets over looked even by hams but is so important for a efficient system
If you do not have a perfect ground, that is everything, Radio, Amp, Meter, PSU, Antenna, anything that has DC power running through it, you are behind the 8 ball playing catch-up with coax length's trying to match 50ohm's and fake a ground, Only in a Car we should have that problem. I see nothing grounded in your video, so you are relying on the ground of the coax and there's the problem
Put a 50 footer between Radio and a.m. then you’ll have no reflect. It’s called Line loss. If the box is tuned properly it’ll work with a 3 foot jumper. Don’t believe me go check out Mr. BBI
Coax manufactures go through a lot of engineering to remove length from the equation in antenna tuning. The impedance is constant regardless of length. What you have actually proven is that the input impedance of that amp does not match the impedance of the system. What you are doing is using the coax as part of the tuning circuit to match the radio to the amp which it never was designed to do. A much better approach is to have properly tuned amp inputs that match the impedance of the coax.
@@douglaswhart impedance only remains constant with a purely resistive 50 ohm load. How many folks can replicate those conditions with a mobile antenna?
I don't know how you made this video with a straight face. LMAO! You need to talk to some hams about this. They will set you straight.
If you are convinced that jumper length makes a significant difference then you are making coax sellers very happy. And after a couple of the other misconceptions he has, he shouldn't 'poo-poo' those other people who post mistaken ideas.
Tried all this & none of it works! 12 ft jumper makes no difference then 3ft I use 3 & 6ft jumpers on everything with RG213 coax have for 30+ years!
Great video! Thanks for taking your time to make it! I like to look at it just a bit different, a quarter wave (3 foot jumper) at the rig to the input of the amp sees 180 degrees out (246/27 x .66 VF is a quarter wave). Simply said, if you have low impedance at the rig, then using a quarter wave matching section will see the reverse.. now a Halfwave matching section sees the same at both ends. Using. (246 x 2 /
27 MHz times .66 Velocity factor = 12 feet. This is providing the input of the Amp has a low impedance input. I am an ex Bird Calibration Tech., worked there for 12 years.. use to run into this all the time. 73's. David.
Correction: the 3' quarter wave sees 90 degrees, the 12' sees 180 degrees. Slip of the finger!
I am wondering here and learning this stuff, am i doing something wrong? i put in 27X.66 and come up with 17, i have tried it with 27.000X .66 and still come up with 17, how would i go about figuring out how long of a run of coax would be needed to run to a antenna? i am lost when it comes to this stuff, i was also wondering if the length of coax to a antenna switch box would matter, is there something i can go by as a basic to always use, i have been into radio for only a few years, i have been told that coax length doesn't even matter, so many different ideas and ways of doing things im lost hahaha i will be getting a antenna analyzer on in a couple of weeks to help me with some of it so hopefully that helps
@@mikehannahs 983.6 / 27.205 x velociy x .5 to get half wave.
Thanks I appreciate it 😎😎😎😎😎
Velocity Factor is how much the Speed of Light is Slowed Down, to reach the inner of the coax, Different brands and size are all different from RG142, Rg58, RG58x RG213 + Mil Spec, LMR400, Hleiax 450/550/650, so .66VF is not right when RG213 is .86VF
I use to think I was into CB, but now I know I'm not enough into it to worry about 18 milliwatts being reflected back.
🤣🤣,, you win 🏆
Thanks Chris...Glad you got my amp working. No more 3 footers except to the meter
+C Felipe They do make a difference
I had trouble with my amp oscillating with a 6 foot jumper, switched to a 4 foot and it fixed the issue. I fixed my reflect issues by making the coax longer after the amp.
Great Video ! Thank you for the refresher course my friend
man now you have me doing the coax Shuffle lol thanks for the info time to make more jumpers.
Thanks for sharing very helpful stuff!!!⚡️
Very well explained, thanks!
I cant believe the entire video is misinformation, very impressive!
I don't get it! This makes no sense. If different lengths of coax are making this much difference you have a problem, I suggest you have r.f. on the outer of your coax which needs sorting out, especially if you have a problem with r.f. jumping and coax crossing and melting I've never had any problem with different lengths of coax or crossing them or coiled up and certainly no melting. How much power are you using?
G4GHB
hey bill. im with you. Unless these cber's have alot of COMMON MODE floating on the shields of thier coax i dont get it!! But he says he's using a dummy load so..... Its impossible to really tell what they are using or doing with these videos. Craig call sign KY4PI. Extra Class ham here.
@@cathyrowling111 Hi Craig, yes, I didn't get what he must be doing if he's using a dummy load.
73, Bill, G4GHB.
When you put the directional couple at the shack end the reflected power reading is consumed in the coax and inaccurate.
When your antennae is 50 ohms and your transmitter is 50 ohms, it doesn’t matter what length the coax is as long as the coax is 50 ohms. When everything is the same impedance you will have maximum power transfer with little standing waves.
It is hard to see how your connection are made in the video. A diagram would be helpful. I empathize, a picture is always better ( in my description as well, we use what we have to work with).
It appears you have connected your transmitter to your feedline (reference plane), with coax and have a mismatch and are trying to match impedances at that point in your shack. (Stub matching). While a match at this point protects your transmitter) you are doing nothing to match the feedline at the antenna feedpoint.
You need to match the feedline at the antenna as well.
This can be done with a stub, balan/unun, etc. if your using coax you should put your directional coupler right at the anttena feedpoint up in the air, only then will you get a correct swr reading.
When you use a match box, you are matching Z between your transmitter and the matchbox, thru a piece of coax.
If the feedline and antenna are both 50 you have a match. This usually is not the case, at which point you need to tune your antenna.
The output of your match box in the shack is the reference plane which is matched to the feedpoint of the antenna by adjusting it’s capacitor and inductor.
If your antenna is other than 50 ohms then the feedline has to changed to match.
If you use ladder line at the output of your match box you are matching it to the antenna, while matching the transmitter to the input of the match box.
Coax? I'm still using string! i have the best 2 tin cans you ever heard though...
Loss for RG8X roughly 2 db per 100 feet at 27.5mhz. Thats .2 db per 10 feet.
Now, with 3 foot jumper you had 250mw reflected. Increase that jumper to 12 feet and loss for barrel, with 250mw reflected at the amp, the radio would see 100mw less just because of coax loss. You're not matching anything. You're also cutting your forward power by 100mw too. The goal is to match the radio and amp input impedence. If they're matched, the shorter the jumper the better would still give you 1:1 match. If you want a thumbnail without matching radio to amp's input, look at the output power of amp, then swap input jumpers for highest output.
Loss and swr are different things. Lol ur simple.
Thank you for ur video. What about a tuned circuit on the input of the amp?
Good video I'm in the process of setting up a mobile with a 1x4 box and am currently researching coax and antenna options.
Oooh right,cool...had some problems with impedance and got it to an 1.5 swr on the radio,but i run out of cable...strange thing is that i have impedance problems on one mobile amp and not on the base amp(both kind of similar,the b501 zetagi and the klv 550)
Cool video!!!!
I doubt its an impedace problem. if using 50 ohm coax its 50 ohms lol. put an antenna analyser or nano vna inline and find the problem Craig.ky4pi
@@cathyrowling111 on the dummy i have the same issues...
@@MrRichard57000 try a different jumper to the dummy.
very cool that's why you're slammed with business. always going that extra step.
+Wmc III Enjoy bro.
It seems you are trying to match impedances by using jumper lengths and'sizes'. That tells me that the devices you are connecting do -not- have the same impedances because they are not constructed well or close to well. From the devices shown, that's not hard to believe at all. Why not just do it right to start with? Of course that requires you to know what 'right' is to start with (you may know but your explanation doesn't explain it).
You do know an SWR meter is not an isolator? You think one side is separate from the other? Coax on one side has no effect on the other side?
The SWR meter is a fancy connector with a meter just like any coax coupler! It makes no difference cutting cable to specific lengths because they join together inside the meter making one cable.
G4GHB.
Different coax behave differently? It appeared you used different types as jumpers. Joined different types together... You have seen crossed coax allow RF to jump from one to the other melting down coax? Really? Color me skeptical.
I was always told to have a total of 18’ of coax on the mobile. But I have 100’ on the base so should I just run 12’ on everything?
LOL is that a little model of E.T. sitting up there by the meters LOL I used love watching it when i was a kid.I just noticed it when i was watching this vid second time around.LOL
+Kealoha Martin Yes it is, I've had it for years. I think it was something someone gave me a long time ago, I also have other nicknacs up there from other people around the country.
Thank you very much.Well done and appreciated 541Tx
Hello guys, what about matching for a multiband amplifier? how i should calculate the length??? i'm using a RF240UF cable .80 factor of velocity. Thanks
Thanks stickman great info as always.Got a quick question what to do with the 12 feet of coax from the radio out any ideas my amp is gonna be upfront where the radio is i know we cant coil it up if I'm not mistaken.Just some ideas on where i could put all the extra coax thanks again.
+Kealoha Martin I hope it helps, that's why I like putting these vids up for you guys. Not everyone knows how things work or what they should do, or how it's done. Some think they do, but most of the time it's hear say lol
+Dropmaul99 I know i tried my best to gather whatever i could of the internet and youtube to get a good idea and i still managed to muff it up.The c.b. radio is one catagory where they dont show to much of whats up do's and donts etc.I know I mentioned already But most good c.b. techs tend to hide in the dark.I have only a couple people trying to help me and make sure im doing it right.Stickman you stand out from the rest man your not afraid to get on here and how a rookie like me whats up.Not afraid to tell me whats worthless and what i should be looking at.Not a problem to stay an hour on the phone with me filling me in diagnosing possible problems not looking to b.s. me to sell me more stuff and make more money of me etc etc.You are honest never tried to scam me and man i thank you for dealing with a green bean like me man.Thanks stickman i promise i will get it together hopefully sooner than later.Alohas from da islands
+Kealoha Martin What do you end up doing with the extra coax route it around the cab?
+Jules2950 No prob thanks jules
I think that's what I'm going to do somehow make it look good hide it suspend the cab
Wow! There really is something to coax lengths.
Have you read - My Feedline Tunes my Antenna?
If you're using an end fed half wave antenna yes. That uses a transformer at the feed point. KY4PI
thank you, very informative video. have a question, what length from radio to antenna and box to antenna? thank you
I found a seller on eBay that sells different lengths of different types of coax and specifically for Cb 11 meter he sells 1/2 wave lengths. So the length of the 1/2 wave will depend on the coax velocity factor. Some are 12.5 feet and some are 14.5 feet. I use 1/2 wave lengths between each. Between radio and amp, amp to meter and meter to antenna in my mobile. A lot of people don’t know about velocity factor.
So a 3ft jumper is okay for using a swr meter? I just setup my first cb in my car with a 3ft firestik and a kl503 and on my meter which shows swr and wattage I’m seeing more carrier on the higher channels so I don’t know which to believe is this due to reflect?
So longer is better right?? Does it matter if the jumper is different to the coax to the antenna?
Is it ok to use Belden RG-58U? That's because that is all I have.
if i send u a pic of my galaxy innards can u tell me what has been done? it has so much jumped, and the texas star i dont think its needed, but my antenna is just a k40 if you are near id about send whole setup to u , but ive had 3 ft jumper ,i went stick external speaker and noticed the hole was blocked so i swapped p.a input over to ext speaker port, i ended up with the setup working for a buddy and he paid me cb setup, which everyone needs old school way reach out, just watched some your vids, and seems you know alot more than anyone i know around here, the main guy i know id take it to him, but he sold me the 3 ft jumper, at rebuilding fried stuff hes awesome but, 3ft call me paraniod but maybe set up lol
SNAKE OIL!! Read about jumper lengths from AARL online articles (real Elmers.) Jumpers will only affect your SWR if the jumper in question is detective. PERIOD!! If your amplifier keeps blowing up when you're using a three foot jumper you might want to stop using that particular jumper. It's sad to see all this false information being spread. Especially when it comes to newbies who don't know any better. One needs to go directly to the source of the correct information, and as I mentioned above ARRL online articles, about anything hobbyist Communications related, are the gold standard in which to gain proper Communications knowledge.
Amen.
NAILED IT !!!
Stop with all that logic
It is nonsense as both coax cables are joined together in the SWR meter so cutting one to length makes no difference as it's all one cable anyway.
For 49 years I've cut no coax to specific lengths except for phasing lines.
G4GHB.
Thanks Stickman for a really informative video, this helped me so much in terms of SWR & power. Hey I have a Galaxy 939 that I want you to do your thing on.
hat do you do if the amp is built in the radio? That is where it gets complicated for me.
+Gary P Thats the tricky 1, I play with the caps on the amp to make it think it has good reflect. I've seen a few come in that have had an issue with those radio amps. Best thing to do is not waste money on them as a stand alone amp will always make more watts and is the better value.
+Dropmaul99 Thank you sir. I love your videos and admire your work.
+Gary P Thankyou I like to help people and this is 1 of the ways to do that. Instead of misleading people with some of the BS that goes on out there.
hey have been trying different jumper have 1ft up to 12ft but the thing in my car I have a galaxy 979 into 2x8 ds amp with a stryker a10 mag antenna with mini8 20ft cut about 8mm off antenna from the top 1.1 1.3 across 40 11meter but with amp on swr goes 1.5 - 2 what do think about 30ft from antenna or what ???thanks great vid...Floyd the barber
Having the same issue with my 4 pill im getting 1.0 with amp off and 1.5 with amp on like to get it down to 1.3
Diud you know if using coax as the antenna like a bazooka you can adjust the swr by folding the ends? Craig KY4PI
BS
it also a good idea to use or multiples of 12ft to the antenn for 11mtrs cb,,ie 12ft 36ft and so on,,,also mobile most mag mounts come with 9ft of coax,,,change this out t 12ft...always use odd multiples or a half wave with velocity factor calculation for the freq you are working on,,,details on the web,,,this gets over looked even by hams but is so important for a efficient system
Spend more time matching the antenna and maximising its groundplane, length of feedline would make no difference other than the loss in the feedline
If you do not have a perfect ground, that is everything, Radio, Amp, Meter, PSU, Antenna, anything that has DC power running through it, you are behind the 8 ball playing catch-up with coax length's trying to match 50ohm's and fake a ground, Only in a Car we should have that problem. I see nothing grounded in your video, so you are relying on the ground of the coax and there's the problem
Does jumper length matter when jumpin to a SWR meter?
Mr. Kentucky Like you said in the video of the 3 foot jumpers were fine for meters. That includes your SWR meter. Hope that helps.
Where can I get a reflect meter?
Flatbed Trucker any cross needle SWR meter will give you reflect watts. MFJ makes one.
Put a 50 footer between Radio and a.m. then you’ll have no reflect. It’s called Line loss. If the box is tuned properly it’ll work with a 3 foot jumper. Don’t believe me go check out Mr. BBI
Coax manufactures go through a lot of engineering to remove length from the equation in antenna tuning. The impedance is constant regardless of length. What you have actually proven is that the input impedance of that amp does not match the impedance of the system. What you are doing is using the coax as part of the tuning circuit to match the radio to the amp which it never was designed to do. A much better approach is to have properly tuned amp inputs that match the impedance of the coax.
@@douglaswhart impedance only remains constant with a purely resistive 50 ohm load.
How many folks can replicate those conditions with a mobile antenna?
@@douglaswhart all the trick is on the tuning of the amps.
roflmao