What is a Coax Phasing Line?
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- Опубліковано 14 жов 2023
- In the main, we use phase lines to split power to more than one antenna. By selecting the right lengths of delay / phase lines, we can skew our energy towards our target. Let me explain.
And here's the calculator link: www.va7st.ca/christman.htm
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I wish I had found your channel when I was studying for my Licenses. I could never rap my head around velocity factors or phasing harnesses until I watched your videos. Thanks.
Happy to help!
Thanks Cal ! You are the professor we all need.
I appreciate that!
Brilliant stuff Callum, you made it very simple to understand. With the Chisrtman method, as with the triangle array, the only way to make sure you get proper current dividing between the elements (without the use of a specialty current divider circuit) is to ensure your elements have the same impedance or as close as you can get it. I will also send you the calculator I use when building the phasing cables. It helps find the proper check frequency to tune them as you cut them. Again Mate... Just Brilliant.
Fab John! Thanks.
This is very interesting stuff. The commercial AM radio stations here in America use this a lot to "steer" their radiation pattern because at night, many AM stations sharing the same frequencies would interfere with each other, so the FCC has them use multi vertical arrays with special phasing boxes and phasing lines to "steer" the pattern in the desired direction. Some hams here in the states lucky enough to have lots of land build what they call "four square" arrays that accomplish this the same way the commercial stations do.
Oh yes!
I actually first heard of this from a video about a set of antennas in the UK. There are four antennas in a line but one of them is offset to the side a bit. They went on to explain how they are able to get directionality out this arrangement and why they needed it. Cool stuff.
This is fascinating, you can do steerable verticals with this, I've learnt! Good to see the return of your prerecorded videos, I often can't make the live ones. 👍
More to come!
Excellent video, again!
Taking the old wives tales out of ham radio may be the most important factor in our growth, 73!
Yes indeed!
Hello Callum: Thank you for this video on coax phasing line. I really enjoy your videos not only from an entertainment experience but you are bringing back such memories & I really enjoy being re-educated. I really haven't done any of this since the 70's & early 80's. Thank you for your knowledgeable attention to detail, 73's , TMP, Unit 22 from N.J.
Many thanks!
Its so strange to me how I struggled so hard with math classes in high school and college (to the point I nearly failed any Algebra classes that I had to take), but watching something like this makes perfect sense to me.
Yes.. I think it's a real-world problem because I was same at school!
I have built a pair of verticals for 80m using the VA7ST guide. Cutting the cable as per the website is easy enough, but having taken so much care over that, I then added connectors, relays and associated (RF) wiring. This changed the phase angle of course, so I ended up re-measuring from the input of the switching box and adjusting the coax length. I also found that the antennas had to be identical to get best F:B - i.e. on the same freq, not just the same length of wire on the same poles. I also found that I had to tune one antenna with the other one folded over on the ground as the passive element altered the resonant point of the antenna under test. This was really worth the effort though - go for it!
Yes, drop the other one to the ground and get them both cock-on.. Like it.
An old school way to get the velocity factor of a hunk of coax involved a "grid dip oscillator", which most modern hams have never seen. Fortunately, you can also use a nano VNA. (A variable frequency oscillator and a scope also work.) You short one end of the coax and measure at the other (open circuit also works. This "coax stub" is resonant on frequencies for which its "electrical length" is an integer multiple of 1/4 wave (90 degrees) long. The LOWEST of these resonances is where it is 1/4 wave long. Divide the coax length by the free space length of 1/4 wave at that frequency to get velocity factor. (A quarter wave, so use 300/4 = 75, so: VF = (length * frequency)/75, where length is in meters and frequency is in MHz.) [Some VNAs may have a TDR (time domain reflectometer) feature that could simplify measuring electrical length, but an sweep showing reactance works fine, since reactance passes through zero at the resonances.]
Good answer!
There was a Maplin grid dip thingie for sale on ebay recently. Might still be there.
@@paulsengupta971 That could be fun if you want to explore old school, but a nano VNA is cheap, easier to use for this, and also solves a lot of different problems as well. If you have a Rig Stick or a Comet or even the MFJ 2XX devices you can probably do it with them as well. I've got an old Heath Kit dip meter (it's young enough to have a FET instead of a grid), but it doesn't get used, and is just a collector's item, like my M-104 microphone, Knight T60 transmitter, etc.).
This is brilliant and lots of clarity,Thanks N9DNB
Easiest video to follow. I hate when people make an hour video talking about this and leaving people more confused than when they started. 😂 I’ve heard 2 verticals phased on a chain link fence worked amazing. Elevated radials. Definitely something I’d like to try.
Hmmm. You got me thinking!
Awfully early on a Sunday morning for a working man even for a video post
Recorded last Wednesday :)
Brilliant mini-series.👍
Tnx!
Awesome!
My current interests are in tuning stubs & matching elements.
I can't thank you enough for getting me interested in MMANA.
Cheers M8
Fabulous!
Lord Callum 😂 I love that ! Best wishes from the Geordie WiFi Mafia 😉
Haha! Darlington here I come..!
Nice explanation!!
Thanks! 😃
Thanks Cal for doing this! I just hope I can find the information when I wont to try it, LOL 👍and find the time to do everything in Radio I wont to try. Thanks Again !!
You can do it!
Well done, mate.
Ah Tnx!
Well done Sir Callum.
Tnx!
Your Math teacher would be very proud of you. 🙂
That's over my head .. Callum
Fascinating and enjoyable ! Mark, 2E0MSR.
Many thanks!
As an unpaid volunteer proof reader I can conform this as correct. I have not built any phasing harnesses for HF but a lot for VHF/UHF. It is remarkably easy to check cable velocity factor but probably beyond the scope of this comment section.
Thanks David!
Awesome Cal, now can I have the plain English version?🤯👍😆
Working on it! Might take me a while!
Thanks mate, no worries, I'm not in a hurry. Appreciate all your video's.👍
Awesome vid. Callum, is there a calculation or at least an understanding of just how much energy we can direct?
Yes.. Well, sort of.. I am about to record two videos: parasitic verticals and phased verticals which will start to focus your mind.
@@DXCommanderHQ Excellent. Will be anxiously waiting.
Hey Callum. Can you please give me some ideas on a stealth HF antenna? I live in a rented top flat, of an old house. Antenna that won't catch the eye. I have a couple of Yagi's near, ideally a similar look or inconspicuous. Loft is also available 1.6m high and 10.5m long loft pointy shape.
10.5m long.. You can fit a 20m dipole in there!
I run phased verts on 40 using the Christman design they work but you have to pay attention to the details I spent 42 years designing Radar transmitters and microwave tube pulse modulators and think in time not degrees ie time delays and convert everything to nano seconds much easier to visualize ie so many nanoseconds per cycle and cable having so many nanoseconds delay per foot which the manufacturer list plus you can test with a scope and pulse generator time being the inverse of frequency
What a fantastic way of thinking about that!
Time is much easier to visualize and the velocity factor may seem like mumbojumbo to some it makes sense that signals would propagate slower thru cable than free space and agn the delay is listed on the data sheets. My phased verts utilize your four wavelengths of radials under each one as 1/8 wave wires they work and can be heard around 7.150 most evenings cheers Mike K1FNX near Boston@@DXCommanderHQ
LETS DO SOMETHING OFF THE WALL ONE MORNING LETS PLAY THE DRUMS
Live!
@@DXCommanderHQ yea live that a liven the place up a bit .. all work an no play know what I mean bub🎃
Fascinating stuff! But now it begs the question of how long the original coax should be. Should it be in multiples of 1/4 or 1/2 wavelengths to begin with, or does it not matter since you would probably use a tuner anyway?
In the main, coax length should ONLY be used to work out what your loss is because if the antenna is 50 ohms, the coax is 50 ohms AND the radio is expecting 50 ohms, you have a matched system.. Now, if you have come across from CB, there's a TON of myths about very specific lengths. Please ignore all that.
@@DXCommanderHQ Thank you :)
THE NEXT GENERATION HAM RADIO OPERATORS IS VERY INTERESTED IN GETTING AN UP TO DATE TOUR OF YOUR MANUFACTURING FACILITIES, my son is doing a science project and picked radio communication for his topic he’s looking for antenna construction video
Soon.. I have that ion the list!
@@DXCommanderHQ Thanks
Thinking if phasing DX Commander classic and a stand along 1/4 wave 80m vertical ?
DO it :)
Hey Callum you tease us with the drums and guitars in the room. How about a demo….are you a drummer or a guitarist or both ?
I'm the drummer!
CAL CUP OF TEA NO SUGAR
Does Faraday fabric word as good as ground wires for ground
I saw someone make a video about this recently but never watched it.. Frankly for the price of a bit of scrap ethernet cable, you are wasting your time. And you need to properly connect it from YOUR ground to the fabric (that lasts over ther time period). And if it's not copper or aluminium - and it corrodes at all, you'll hear the electrons going "pop" every few seconds as it oxidises. Does it work? Well, I have more than 40 feet x 40 feet of radials in my field.. No idea how much it would cost to cover that in fabric! (and you only need a concentration of wire in the near-field - not all the way out to 40 feet).
Hi Calum, how can I adapt the Minkowski Loop antenna to 13,56 MHz?
Find one with dimensions listed - then expand it out to chosen frequency - BUT because you will be less than half a wavelength above the ground (I guess), it'll just be a cloud warmer anyway.
@@DXCommanderHQ i was thinking about 200x180 mm PCB . Is there a program that can do that ?
Why would you want to delay the transmission on the second antenna?
Next video.. About 5 days time.. :) I am preparing the way for it..!
👏🏻👏🏻👏🏻👍🏻👍🏻👍🏻 well presented Cal. Thanks.
Long ago on my early ham radio days I had to calculate the length of RG11 to use with 50 ohm RG8 for a Cubical Quad. Three bands, 3 separate coax feeds and 3 different lengths of RG11 and it matched the quad elements perfectly and I did it with pen and paper and no calculator and no Antenna Analyzer then. It worked just great. de KZ5Y dah di dah
Boom! Yes, quads like that.. I think it's a 75 ohm matching section. Perfect.
Without the 75 ohm matching section the SWR would be much higher. Of course back then I was running a TS-520S with tube finals and those rigs were a bit more tolerant of slightly elevated SWR conditions but the RG11 worked great.
Does somebody know where the 71° come from ? The distance between the 2 verticals is 1/4 of a wavelength; I would understand if the phasing line would be 90°.
OK, I have recently found out.. If you add 71 and 84, you end up with a perfect (matching) voltage to the other one.. There's a video coming out about this.. Hang on.
@@DXCommanderHQ From my understanding 84° is for the matching, and 71° is for the delay, if the distance between the verticals is 1/4 wavelength.
It also would be interesting to know which degrees have to be used, if the distance is not 1/4 wavelength, but for example 1/8 wavelength, if there is not enough space.
Metric system makes the most cents. However, 'Murica!
Set Phasers to stun.
😮your hair!!
Yep. It keeps growing.
You need a small light mounted beneath the microphone, shadow problem solved 😁
More "stuff" LOL! :)
71 DEGREES Callum, not percent (%)! (Just to avoid confusion.)
Ah.. Did I not put an overlay? I spotted that in the edit and forgot maybe to put a correction title in..
RG58 🤣🤣🤣🤣🤣🤣