Why So Little Loss? (
Вставка
- Опубліковано 6 жов 2024
- Why is ladder line so much less lossy than equivalent coax? The answer has to do with impedance.
Subscribe: / davecasler . Ask Dave Playlist: goo.gl/inaQeB. Tip Jar: ke0og.net/tip-jar
To learn more about me, visit: www.dcasler.com...
Tip jar (on my website): www.dcasler.com... (provides a method to use your credit card via PayPal, Also describes Patreon)
To pose an Ask Dave question: www.dcasler.com... or www.ke0og.net/a...
To order the most recent and up-to-date Amateur Extra videos on a thumb drive: dcasler.com/aev...
Theme music is "Sour Tennessee Red," by John Deley and the 41 Players, courtesy UA-cam Music Library.
I use drawings from OpenClipArt.org, including the "walking man"
Technician training videos, see www.ke0og.net/t...
General training videos, see www.ke0og.net/g...
Amateur Extra training videos, see www.ke0og.net/e...
List of the Ask Dave videos, see dcasler.com/ask...
Thanks to my sweet wife, Loretta, KBØVWW, for both audio and video assistance! (Her website is www.aldea-art.com.)
My primary website: www.dcasler.com
The ham radio part of my website (direct link): www.ke0og.net
My publishing website: www.mtsneffelsp..., where you can find my fantasy and science fiction books, as well as some local history books I publish for the Ridgway Railroad Museum and the Ouray County Historical Society
My Amazon author page, which lists my print and Kindle books: www.amazon.com/....
I'm often asked what equipment I use to create the videos. The devices include the Panasonic DMC-G7 camera, Panasonic HDC-TM90 video camera, GoPro Hero2 HD camera, Tascam DR-05 audio recorder, Audio-Technica ATR-3350 lapel microphone, Sony Cyber-shot DSC-W560 digital camera, the Kodak Zi-8 video camera, my iPhone 5S. Software used: CyberLink PowerDirector 17 on an HP Gaming Pavilion, also using Smoothdraw 4.0.5.0, FastStone Image Viewer 5.3, FastStone Capture 8.0, Audacity 2.1.1, LibreOffice 5.0.4.2, and Ink2Go 1.7.2. You can see how my studio is set up by viewing • Tips for Making Instru... .
Twitter: @dcasler
Dave this video makes up for the last one your back to being the man. I would like to point out that most manual tuners have a 4 to 1 balun and tuners are designed to handle high impedance very well not so much with low impedance. Don't use a 9 to 1 balun on a multi band antenna because you will have some frequency with very low impedance not good. The tuner would actually be better with a 1 to 1 instead of the 4 to 1 they come with. Now show how much better it is at 3:1 swr then 30:1. Watch all your video's. You teach new hams a lot. Keep up the good work.
Don't forget dielectric losses! Vacuum is best, air is close to a vac. It takes power to align the electrons in plastic insulation especially at RF. That's why LMR-400, Belden 9913 etc have a plastic spiral around the center conductor. It's mostly air. Twin lead is mostly air as well for the same reason. So, at lower impedances copper losses dominate, at higher impedances dielectric losses dominate.
Yes. I think it is misleading to say that only characteristic impedance is responsible for losses.
Great info as always. But it makes me think... why don't we use high impedance coax instead?
Similarly, utility companies feed high-tension, cross-country power distribution wires at very high voltages to avoid the I2R losses.
What coax used today has a small 16 gage wire. That would be RG58! I would not use RG58 for a 100 run! I use RG 8,or RG213 for that long of a run. The 450ohm wire I see listed is 18 gage. The 400 ohm I just got is 16. The G0GSF made his antenna with 400 ohm. Some use 450 because it is more common.
Thank you for another great video. I think this is more complex than adding just 9:1 balun between your Trx and the ladder line. The length of the line matters too, as you will experience both current and voltage nods in the line (depending on frequency). I think anyone who is planning to use balanced line should read any manual for any balanced line tuner. Also, there are antennas like; G5RV and ZS6BKW using balanced line as a match and they do not need 9:1 balun either. Perhaps topics for a third video on balanced line? My 2 cents...
I made an assumption early on that the SWR was 1:1, therefore no standing waves on the line.
@@davecasler Yes, I agree with you. You made this assumption. I wrote this more in the context of the doublet antenna shown in your video and its practicality.
That was good. I will file it under gotta know not good to know.
Thank you.
thank you. thumbs up and added to my favorites. you explained impedances and line loss clearly.
Love the way you teach.
Thank you! 😃
Reading my mind? I was just googling this exact topic for a new wideband antenna SDR feed and 9:1 baluns.. Great timing Dave! 😀
Thank Dave. Very interesting topic.
A very good video, well explained as always, however I take some issue with the usage of a voltage balun to feed the line UNLESS the line is terminated with its characteristic impedance.
In the example for instance of an openwire fed doublet (with a common mode choke/current balun) I believe it is better to present the reactive load direct to the tuner. Most tuners are more efficient at driving high impedance loads than they are at matching low impedances.
Very few hams (if any) match impedance both at the transmitter and at the antenna. I know I sure don't. I made that assumption so I would have no reflected waves on the line.
@@davecasler, thank you for the reply, I meant that the use of impedance transforming baluns in the shack between the tuner and the feeder..
By your info the 600ohm ladder line is only 1db better than the 450 ohm. I have all the parts to build a field day QRP
antenna using 600 ohm. What balun you use, I read it does not matter. I plan to go within 10 ft of the station and
use a balun and coax to the FT-817.
I so listen to Dave. it is just I don't have anyone around here that I can ask sill questions.
Thanks Dave. Great job.
Awesome video, Dave! I wanted to know, and now I do. Thanks!
SHAME on people that do not listen to this great advice!
While RG8X is not bad there's also a lot better out there that isn't all that expensive. If you study a doublet being non resonant it quickly highlights the benefit of ladder vs say a resonant loop with high grade coax with no balun.
Would love to hear about elevated folded counter poise. Do they replace need for ground radial system and Inverted L fed at top with open feed ? K2AV has a web page but I’m no good with modeling. Also love to hear about base loaded coils to make a 5/8 wave 80m vertical element work on 160. I’m a low band guy trying to do a vertical 😉thanks Dave KC3ONO
I'm trying to keep my thoughts on what you are trying to get across one time or another I have mentioned my lighting strack the lighting hit the ladder line. it came to the ground now the end of the ladder line was unhooked due to a fued with the neighbor Well what I'm looking out can I reuse the ladder line. I'm sure it will need a new Balum
So if a guy was making a large doublet, say 80 or 160 meter, custom ladder spacers, increasing impedance to say, 1000 ohms or greater, with a proper balun, wouldn't be a bad idea for maximum efficiency? Especially for long runs over 100 feet?
What exactly happens when a ladder-line gets too close to a metal thing, such as a rain-gutter? Does the loss get much worse, because a bunch of current spreads out into the gutter, instead of out to the antenna? Or is it more a matter of protecting my house from RF interference?
As long as it's for a very short distance it won't make a noticeable difference. You only have to stay away as far as the balanced line is wide. If your using 450 ohm ladder line that's about one and a half inches.
You're on the right tracks. If the ladder line is very close to a conductive object, the electromagnetic field created by the line's conductors will induce current in the object (gutter). Current flow means energy is dissipated in the gutter. It is lost and not transferred to the antenna.
Yea open wire is the best I use it to my delta loop with 80 meter 600 ohm ladder line to the shack , one question remains , why is it so hard to find baluns for 1:12 so we can connect the ladder to our 50 ohm tx/rx
There isn't any demand for them. You might be able to have one made or make one yourself.
Does not work so well when wet. Even in the early 60's it was more common on VHF-UHF. Many of the popular beams and colinears had balanced inputs and matching networks with adjustable 1/4 sections.
Dave, don't you think the LL section before the balun might pick up more noise?
Thank You
Isn't the MFJ 974HB antenna tuner optimized for windowline use? An experienced ham friend swears by this set up with dipoles.
Yes, the MFJ974HB is an excellent tuner for balanced line fed antennas. That is what I use for my 90' attic doublet. My balanced line is the center conductors of two parallel 75 ohm coax cables (exact same length). The shields of the coax lines are connected together and grounded. This gives me a 150 ohm shielded balanced feedline. I can tune below 1:1.3 SWR from 80-6m. The antenna is too short for 160m. I can work most of the world on FT8 with this setup.
Dave, How much loss will you have in the required balun's or transformers ?
How to get ladder line from the transmitter out the window to the outside?
I've just closed the window on it, but that's not the best way to do it for sure. Take a look at MFJ-4602, which offers a balanced line feedthrough.
@@davecasler I also feed it through the window and close it Dave! ( "Window line through the window"! Seems so appropriate somehow.) it's been working just fine like that for almost two years! lol! 73 Tom.
I read what you said on the thirteen ,8 votes, I have a computer run radio. 7300 like you have . I''m afraid to run it on volt power supply i went with a bigger 45 amp marine supply because I was afraid to put that twenty amp on it . was it the right thing to do?
That simplifies the issue. Thank you. N0QFT
What do the "windows" do and why does my wire skip every third window? Are the windows skipped to adjust the impedance to 450? Thanks for the valuable videos.
A little late but " The advantage of the "windows" is that they lighten the line, and also reduce the amount of surface on which dirt and moisture can accumulate, making ladder line less vulnerable to weather-induced changes in characteristic impedance" twin-lead wikipedia
Trouble is when it rains!!
I think that's where home constructed line would be better with more air between the spacers.
G4GHB
Now, do this again but throw in skin effect. Ohmic losses are significantly higher. (At 30mhz, 20 TIMES higher than d.c. resistance.’
What line spacing distance is ok for 14 gauge homemade ladder line that is feeding a 520 foot loop 150 feet away?
Is there a feed line calculator online?
You can look at Chapter 23 of the ARRL Antenna Book--it has the calculations and some handy graphs.
I've got a problem with something similar. Is there a way to contact you by email? To describe the problem and include illustrations won't work well in the comments here.
Hi de AG7MW
Is it just me or is twin lead really over looked alot