Some of my earlier videos had a poor mic, Today I use an Electro-voice RE 320 and Scarlett 2i2 USB interface. Sorry about the earlier videos, I feel the information is still valuable and decided to leave it up.
You must reconcile with many of your explanations because they are not correct. Especially what you said about current flowing on the outside of the outer shield whenever a current flows on the centre conductor is absolutely wrong. Infact current flows on the inner surface of the shield. CMC (common mode current) tends to flow on the outside of the outer shield only when the coaxial cable from the feed point is not brought vertically downwards but at an angle so that it lies parallel to one of the arms of the dipole. Please read well and do videos. Wish you good luck. De VU2RZA
Current or signal flows on the center conductor, I was talking about common mode current that flows on the ground which is considered the outside of the coax. I will check the video again.
@HamShackReviews thanks for the prompt reply 👍 Yes, I will appreciate if you can go through the video again, titled "how coax works" A coaxial cable, in effect, has 3 conductors. 1. Outer surface of the inner conductor. 2. Inner surface of the outer conductor. 3. Outer surface of the outer conductor. When you connect one end of the coaxial cable to a voltage (power) source (transmitter) and a load (antenna) to the other end, current flows on the outer surface of the inner conductor towards the load and the return current flows on the inner surface of the outer conductor towards the source; this is called the differential mode current. This current is, at any given instant and any given point along the cable is of equal magnitude but of opposite polarity. None of the current flows on the outer surface of the outer conductor. What we want is only the differential mode current and no CMC, vertical current, longitudinal current, or simply antenna current. (Yes, the CMC has these many titles!) If a dipole (a flat top or inverted V dipole) is installed in free space (meaning no nearby objects and the feed point is at least half lambda high above the ground) and the coaxial cable is brought vertically down at least quarter lambda long before you may want to deviate the course to be taken to the shack, there is no need for a CMC choke. But then, a CMC choke, one at the feed point to the dipole, and another at the point of the cable entering the shack is preferred. This arrangement will take care of any RF trash, (EMI) radiated from a nearby strong source (like a BC radio station or one of your own another antenna) OK, let me stop here. De VU2RZA
Best description I've seen yet. Thanks!
👍👍👍👍👍👍👍 No one has explained common mode like this. This is the missing link for many of us. You should absolutely write a book for study.
Agreed on the BAL issue. It does more good to have one in the signal path than the small amount of power lost. Good explanation and diagram.
Good info as always, thanks Vince
Thanks Ron,
cool channel... keep it up
pls invest in a better MIC
ac0v 73
Some of my earlier videos had a poor mic, Today I use an Electro-voice RE 320 and Scarlett 2i2 USB interface. Sorry about the earlier videos, I feel the information is still valuable and decided to leave it up.
You must reconcile with many of your explanations because they are not correct. Especially what you said about current flowing on the outside of the outer shield whenever a current flows on the centre conductor is absolutely wrong. Infact current flows on the inner surface of the shield.
CMC (common mode current) tends to flow on the outside of the outer shield only when the coaxial cable from the feed point is not brought vertically downwards but at an angle so that it lies parallel to one of the arms of the dipole.
Please read well and do videos.
Wish you good luck.
De VU2RZA
Current or signal flows on the center conductor, I was talking about common mode current that flows on the ground which is considered the outside of the coax. I will check the video again.
@HamShackReviews thanks for the prompt reply 👍
Yes, I will appreciate if you can go through the video again, titled "how coax works"
A coaxial cable, in effect, has 3 conductors.
1. Outer surface of the inner conductor.
2. Inner surface of the outer conductor.
3. Outer surface of the outer conductor.
When you connect one end of the coaxial cable to a voltage (power) source (transmitter) and a load (antenna) to the other end, current flows on the outer surface of the inner conductor towards the load and the return current flows on the inner surface of the outer conductor towards the source; this is called the differential mode current.
This current is, at any given instant and any given point along the cable is of equal magnitude but of opposite polarity.
None of the current flows on the outer surface of the outer conductor.
What we want is only the differential mode current and no CMC, vertical current, longitudinal current, or simply antenna current. (Yes, the CMC has these many titles!)
If a dipole (a flat top or inverted V dipole) is installed in free space (meaning no nearby objects and the feed point is at least half lambda high above the ground) and the coaxial cable is brought vertically down at least quarter lambda long before you may want to deviate the course to be taken to the shack, there is no need for a CMC choke.
But then, a CMC choke, one at the feed point to the dipole, and another at the point of the cable entering the shack is preferred. This arrangement will take care of any RF trash, (EMI) radiated from a nearby strong source (like a BC radio station or one of your own another antenna)
OK, let me stop here.
De VU2RZA