Jim Heath W6LG discusses Vf or Velocity Factor related to coax cables and antenna wire.
Пікірлер: 63
@tixilx3 жыл бұрын
“Spend time in the company of a wise man son and you will become enriched” ...... Well after spending time with this wise man I certainly leave enriched ... Thank you Sir ☘️
@MrDeeejaaay4 жыл бұрын
Thanks for another excellent video, Jim. Good to talk to you tonight. 73, WA7DJS
@greasydot4 жыл бұрын
Good morning Jim. Nice to see/hear you. Thanks for the info.
@angelhelp68194 жыл бұрын
Hi Jim good morning 🌞 I like that video are you feeling better I'm glad you're talkin any new video very excellent 👌 videos I am glad you're back and making them you're feeling okay just take your time you still making new ones and I'm gladI was thinking of you hope he's feeling keep making them okay I hope your medication side effects with no side effects 😃☘️☀️ good luck ☘️
@batfalcononyoutube4 жыл бұрын
Since you already have a great experience on cable manufacturing, it would be a nice extension to this video a study of how and why they choose each and every dielectric for each cable, therefore what type of cable shall we use / choose for the lower ham radio bands and what for the upper ones. As always, thanks for the knowledge you are spreading. 73 de SV1SLB
@S_m2.004 жыл бұрын
Great video.. Mr Jim
@Brandon_B.4 жыл бұрын
thanks Jim very helpful & informative
@DonDegidio4 жыл бұрын
Hi Jim, Glad to see another video and that you will be producing more. I think generally the solid dielectric coax has .66 and the foamed has .82 VF. Stay safe. 73 WJ6U
@aldimore4 жыл бұрын
I feel smarter! Thanks Jim
@TI2GBB4 жыл бұрын
Happy to see your videos back! Thanks for clarify this important topic for us. 73s From Costa Rica! TI2GBB
@MrRegzxzx4 жыл бұрын
Thank you Jim, always very informative 👍
@virginiabugbee59734 жыл бұрын
Thanks for another interesting and informative video. Just passed my technician exam and wanted to thank you for your good explanations! 73!
@miken6imy4 жыл бұрын
Looking forward to seeing the coax feedline comparison in your next video Jim.
@hornhospital4 жыл бұрын
I finally understand what velocity factor means with regard to coax thanks to your excellent explanation. Thank you.
@DK5ONV3 жыл бұрын
Thx for another great documentary video, Jim. Hope you are save and doing fine. Vy 73's de Günter from germany. By the way, I passed my licence upgrade exams to A-Class last tuesday 3rd of November. And I signed up for a second youtube acount with my new final callsign "DK5ONV" Happy sunday @cross the HAM Nation
@K1QS_Radio4 жыл бұрын
great explanation of coax. Please keep the fundamental explanations coming. I am honored to call you my virtual Elmer... Oh, BTW. can you cover real ladderline? not the windowed plastic stuff, but the 600 ohm ladder line. Losses, care and feeding.. etc? thanks.
@alanjames45264 жыл бұрын
Hi, Jim. Great video and looking forward to the next one comparing coax. 73 Alan KZ6B
@hellominions16044 жыл бұрын
Great content, never understood this till today, thanks very much.
@PF9Z-HamRadioDXStation4 жыл бұрын
i'm sure that i can write a book already with all the nice learned things of ya ;) Keep on Going Jim...73s Sascha PD9Z
@dudeski9344 жыл бұрын
Thanks for the good informative video
@mcnugget914 жыл бұрын
Thanks Jim, I always learn something new from your videos. You are a great Elmer to us all! 73 NF1T
@johnbailey46644 жыл бұрын
Great stuff Jim
@duanecjohnson4 жыл бұрын
Hi Jim; I use 4” open wire 400 ohm balanced line, about 150’. This drives a 250’ center fed Duplex antenna. I like the the open wire line because the velocity factor is about 0.95 and the loss is about 2db/100’. This works very well. Of course this requires a transmatch antenna tunner. Mine is an old Johnson Viking 250W. Will you be discussing open wire line in the future? redrok AD0TJ
@battlestarone4 жыл бұрын
Great vids,,i an sick of arguing with ham about velocity in wires and coax cable and the effect on accurate swr readings in the shack,,to the point i have gave up trying to explain how important it is to take these factors into account when installing an antenna...regards Gm7jds
@margaqrt4 жыл бұрын
The velocity factor is needed when calculating the electrical length of your coax. Some purveyors of amateur radio folklore contend that certain lengths of coax transmission line are to be avoided. I suspect this question is mostly superfluous in amateur antenna applications. When the feed point impedance of the antenna matches the characteristic impedance of the coax, we are concerned only with loss. However, every myth has a grain of truth. Certain lengths of coax are used as matching stubs--they are an impedance transforming device, when we are dealing with a load whose feed point impedance is a mismatch. Suppose you have a half wave dipole for 40 meters and you chose to operate it on 20, the feed point impedance will be through the roof. The impedance is essentially infinite in this scenario and it would be impossible to deliver energy to the antenna. If you had an odd multiple of a quarter wave of 20 meters as the length of your feed line it would invert the high impedance at the feed point to a low impedance in your shack, at the tuner. The operator sees a nice low SWR reading and assumes he is good to go. Perhaps electrical length (as computed via velocity factor x physical length) is an important consideration after all. 73 Jim.
@akcma57052 жыл бұрын
great info, thankyou!
@JimN5QL4 жыл бұрын
Great video Jim! I knew about velocity Factor and I knew how to use velocity Factor but I never knew why until now! Thanks for the great video looking forward to your next one.
@sarbog14 жыл бұрын
Thinking about getting my license again.. I was Wa0tiu back in the 1960's so much has changed with ham radio...... love software defined radio.......
@elmoreglidingclub30304 жыл бұрын
Great stuff, Jim. I’m brand new to amateur radio (about to take the Tech exam) and I learn a lot from your videos. This video rekindled something I’ve wondered about: Insulated versus bare wire dipole antennas. Several have told me it makes no difference. But since the obvious use of insulation on wire is to insulate the electrons from the environment it’s hard for me to imagine how the insulation doesn’t, then, affect incoming and relatively weak signals.
@sarbog14 жыл бұрын
Velocity factor is a property of the space that an E&M wave passes through ....... not the the electrons ...... love your videos .........
@sarbog14 жыл бұрын
When light passes through any medium other than free space it slows down.......
@1fanger8884 жыл бұрын
Hey Jim. Good to see ya! Thanks for the teaching. KC3BXZ Joe 73
@TomG2NV4 жыл бұрын
Hi Jim, First class as always! Hope your well and back on the air? 73 from your friend Tom in England G2NV
@JayN4GO4 жыл бұрын
For some reason KZbin isn’t notifying me on your vids Jim. Bell checked , all. 🤷🏼♂️
@af4od024 жыл бұрын
Thanks for the info. Looking forward to the next video. 73
@lwoodt14 жыл бұрын
For many of us, the coax is a very confusing part of our radio system.
@Proc30004 жыл бұрын
Love the videos Jim. Love the explanation of velocity factor. All your videos are easy to understand. I wish I bothered looking at those things when choosing a wire. Im running probably 45-50 ft of LMR 400 ultra Flex though for VHF/UHF so its probably not a big deal. But for the future I know I need to look at other items.
@paulhastings31094 жыл бұрын
Thank you Jim. Trying to duck the Hurricane I hope it keeps going East. Have a good day
@MenAtWorkMedia224 жыл бұрын
You are the man!
@abfig783 жыл бұрын
Love your videos! Can you make one on the mag mount antenna and a bolted on antenna and the difference. Also talk about the ground plan dealing with both.
@ham-radio3 жыл бұрын
Thanks. For what band? Frequency makes a difference. 73, Jim
@abfig783 жыл бұрын
@@ham-radio 2 meter and I play with 11 meter too. I know a lot of hams don't like it, but most of us cut our teeth on the ol CB radio.
@tomw5vlt1194 жыл бұрын
Jim, haven’t worked with velocity factor since the Exam, and frankly forgot. A practical example would add a lot to a video on the subject, including the math that I recall is not difficult. So going from memory, and you started to do an example, it’s “used when” calculating an antenna length, and so if “in application” one wanted to measure a 20m antenna length, you would multiply ... go through the math on a white board please ... to illustrate the example clearly.
@mikebavoso26 Жыл бұрын
Hello Jim, another great video. You mentioned a video about building your own coax connectors. I was unable to find it and wonder if it could post a link to my question. Thank you
@carolmartin70424 жыл бұрын
Thanks. Glen, N0QFT
@kc8njnsunday244 жыл бұрын
Like your content! Unrelated- Are you worried about EMPs, lightening and power surges beyond a normal GFI protection? I’m reading about devices that can protect your whole house.
@2metercrew3894 жыл бұрын
👍👍👍
@leighdexter74934 жыл бұрын
Happy to find your videos. Any tips for someone learning and listening in eastern Nevada county?
@ham-radio3 жыл бұрын
There used to be a very active club up there. I think there were also a couple of contest stations. Maybe you can do a check for callsigns using the zip code. I am sort of finding my way around Placer on line. I am confined to home for the obvious reasons. Listen on HF. Listen on 40 and 20 meters. 73, Jim.
@potshot232 жыл бұрын
Very good info, Jim. one thing I'm not sure about is if you extend the length of the coax, but you use 2 coaxes with different velocity factors, what happens to the velocity factor??
@ham-radio2 жыл бұрын
I asked a very good friend about that exact question. The answer appears to be; just do a weighted average. How that sound to you Steve? 73, Jim
@JSambrook3 жыл бұрын
Is there any difference between electron movement on the inside of the shield vs. the outside of the shield?
@chrismayer77624 жыл бұрын
Great explanation....73 KE0ZSU
@battlestarone4 жыл бұрын
Jim what are your thoughts on Walt Maxwells idea that feedline length and swr have nothing to do with each other,,i work with the odd multibles of a 1/2 minus velocity factor of the cable always and that works for me,,i get the same reading at both ends of the cable,,,but so many disagree..,,regards Brian gm7jds.
@ham-radio4 жыл бұрын
Well, excellent question!!! Maxwell knew more than anyone. Sure the 1/2 wavelength will given good results when analyzing an antenna. I am convinced that it makes not difference. The energy is radiate no matter the length if the antenna and feedline match. That is very important. A 1:1 SWR may or may not be the resonant spot or frequency. The resonant frequency may have an impedance of 30 ohms. Where reactance brings the SWR to 1:1 is not the same place. 73, Jim
@robertramos364 жыл бұрын
good day i was wondering why do hf radios have tuning on them when you need a tuner for antennas never can figure that one out have a great day KF6SIF.
@ham-radio4 жыл бұрын
Jim W6LG 5:59 PM (1 hour ago) to KZbin Hi Robert, I have read your question 3 times and I am not sure I know what you are asking. But, I will give it a try. First, most of us old guys we don't call them radios. They are transceivers. Radios are receivers. You said that "hf radios have tuning on them...." Did you mean that they have so called antenna tuners built-in? If so, not all transceivers have antenna tuners. Some of mine do not. Antenna tuners or transmatches or matching networks are not necessary. Tuners have a small amount of loss. They encourage guys to transmit into antennas that are not way off in frequency. As a result, in some cases, more than half of the signal is lost in the system. tuners can just make it worse. I ran QRO power into my yagi and never used a tuner. Design and build the antenna system so that it works without having to invoke some box to make the transceiver happy. I did work every country in the world over 50 years Tuners should be a very last resort...and not a good one. Did that help or answer your question? 73, Jim W6LG On Fri, Sep 11, 2020 at 5:10 PM KZbin wrote:
@rentacowisgoogle4 жыл бұрын
If I wanted to make a VHF J-Pole to put way up in a tree and connect it to my scanner, could I use any old coax and still get good reception? I've got a bunch of satellite TV coax RG6, but I don't know the velocity factor for the calculator i'm using.
@ham-radio4 жыл бұрын
You can go to a table or list that will show the loss of RG6. In round numbers, you will lose 60% with 100 feet in the coax. 73, Jim
@rentacowisgoogle4 жыл бұрын
@@ham-radio Thanks Jim! I'll try to find some data sheets for the stuff I'm using to find the exact numbers, but ~60% seems like a good place to start. I'll let you know how the reception is! 73
@eekmeout4 жыл бұрын
Do you miss Wolf Mountain?
@ham-radio4 жыл бұрын
I do! I really do. There is a ton of noise here and the ground, topography is relatively flat. But at least I am now on the air; QRV. Thanks! 73, Jim
@bobrunge75944 жыл бұрын
What the heck is KZbin Elmer? I get this on your video titles. Bob Runge W1LSZ