How to build a Coaxial Trap. Dipole, Vertical or EFHW Great for the smaller garden
ฝัง
- เผยแพร่เมื่อ 13 ต.ค. 2024
- The Coaxial Trap, great for more than one band on a single antenna. The coax trap will also shorten the length of the wire antenna, making it perfect for the smaller garden.
In this video I show and explain how to build a trap for the 40 metre band this can be used on an antenna for 80 metres giving you both 80 and 40 metre on the same antenna..
Needed for this build:
2 metres of RG58
40 mm former (an old mastic gun tube or waist pipe)
Something to drill a hole the same dia as the coax
wire strippers or knife
soldering iron and solder.
Enjoy
I do hope you enjoy it and subscribe for more..
Many thanks
Mike - M0MSN
To get notified of the next upload Please click that bell.
Mike, you are becoming a very good ELMER for folks everywhere, for the relatively short time in the hobby your DIY experiences are becoming a long list. I watch every video several times finding something new to think about each time. When I get able to do things again, my list of projects will absolutely include many of the things you graciously learned by doing, sharing with all of us while getting there. You certainly are a tribute to the SPIRIT of the hobby and an asset to all that come in contact with you. Thank you for sharing and giving some much to our hobby!!
Very kind words, Thank you AWO. :)
I agree, love this guy!!
Having just had my second upgrade of "Astra Zeneca" and with it being based on a Chimpanzee virus, I’m finding it hard to stop watching any video with bananas in the thumbnail. :-) keep them coming and don't drop the bananas!
Ha ha! love that...
Very helpful and informative regarding the build. But I’m new to all this so stepping back a bit, what is the coil for? What’s its purpose??
Thanks Mike!!!
Very interesting video. Great to see the build done in real time.
Thanks 👍
Mike, you do GREAT WORK!.... I ALWAYS stop by to see what project you are up to next!! LOL! Then, I file them away, until I come to the same point in my own designs, to see a different 'slant' on the same subject!! You always are doing things that are MOST unusual, but I learn from you, each and every time!! THANKS, Mate!..73's, K6PAM
How to build a Coaxial Trap. Dipole, Vertical or EFHW Great for the smaller garden 😀
Channel yang sangat bermanfaat buat saya 🙏🙏✅👍😊❤️
1) So many people overlook a Grid-Dip Meter however it is at their peril. I can't stress enough how useful a GD meter really is. In reality, it's only 10 quid's worth of parts but they're worth their weight in gold - especially if you've left it behind.
2) Mike, what's in the circular shallow red dish on the window sill ? It looks like something from The Colonel.
To point 1, could not agree more. To point 2, used tea bags (my wife uses them for some thing??)
@@mike-M0MSN Did you know that a lot of tea bags are actually thermal plastic ?
Yes, I kid you not. People thrown them in their garden and they break down as micro plastics.
Look into it.
As George Carlin said "The earth plus plastic"
Mike...please give
details on the making
of your DG meter used
on your MFJ analyzer.
Thanks
So.. the dip measurements showed 6,5Mhz... does it mean the coil length ( coax) was a bit too short? 10 rounds would maybe get you even closer to 7Mhz? Just trying to understand how it works.
I like your "zero waste" approach as it comes to the silicon tubes! I've tried the coax traps couple of times wound on the piece of a plumbing pipe and I liked how it worked serving for the W3DZZ and the EFHW ( trap for 10mhz) antennas. What is interesting these traps also act as loading coils, so the wire after the trap comes to be shorter than the regular resonant length. Nice job! 73! Linas LY2H
Cool, thanks
I tried to make an efhw with multiple coax traps, for 10, 12 , 15, 17, 20. No chance to make it working. I suppose the frequencies are too close...
@@eduarddavidescu119 Well, 5 traps in a row might be a bit of too much of a hassle :)... You would probably need to recalculate ( or , actually , empyrically find out) the every segment of the wire in between the traps making adjustments for the shortening effect of each trap-coil ... To add more trouble, so many traps in series might incure substantial losses in the overal antenna system. For these resons, you would hardly find many antenna designs with more than two traps in a row. Or, if you do, the traps would be of a very high quality with carefully selected values of the trap's inductor and capacitor in order to get higher Q ( equal lower losses). And it is not possible to choose the C value in the coax trap... So , in order to have an effective and simple resonant 5 band dipole, I would go for a linked dipole design. Or, in the case of the EFHW, for the classical 49:1 transformer-based with max 1 trap for the 30m band. Good Luck! 73! Linas LY2H
@@Linas_LY2H Thanks for the answer, and congratulations for your channel, I'm a subscribers 😀.
Yes, too much coils and very close to each other. I started with te 10m, put the coil and trim the wire. Then ,a piece of wire and the 12m trap, trim it and so again. The needed wire between the traps is very short and putting more traps destabilise whole antenna.
I will keep trying 😄
73's
Mike was the probe for the mfj home made
I was curious myself as I’m also heading down the trapped dipole route. Thanks for the video.
Yes the probe is home made, simple 20 turn coil on the coax...
Hi Mike,
Enjoy watching your build videos. Do you have a video explaining the coil for the MFJ anaylzer to measure a coils resonance? You and the family stay safe. 73 WJ3U
hi Don, I don't, but I will make a sort video a bit later on this.
Always fascinating videos Mike.
Thanks Nick
Muito boa antenas amigo obrigado 73
Obrigado 73
Mike Do you have a video showing how you made your probe for your antenna analyzer TKS
yes I think so.. you will need to search my videos
Hi do you have a link where you found the trap calculator
Hi sir, can you give the design of that short rg8 attached to mfj. Thank you for sharing.
Great video, but what is the probe made up of? cheers
how about a trap within one band…ie tuned long for say 3650 and then a trap in at the 3850 portion so no tuner needed…will it work
How did you make the probe for the Antenna Analyzer ?
I will make a video on that soon
@@mike-M0MSN good one Mike was about to ask the same thing. Thinking of making a scanner antenna too? :-)
Hello Mike I found yesterday on your channel how to make a coil for use with an antenna analyzer to make it into a dip oscillator, using coax but I cannot find it today . I want to check my resonance of my delta loop on 7MHZ
th-cam.com/video/FkJ1dVDkdyI/w-d-xo.html
@@mike-M0MSN Thank you Mike G4 LMZ
Mike, just so that you know, ( maybe someone else can check as well ) when you were showing the coax calculator screen as an overlay prior to 3 mins in, it was causing quite a lot of pops and crackles on the vid. Once switched off all was fine again.
Andy
I heard that. I think it was delivered done, looks like a vintage video filter was used
Yes it was deliberate like a 1940's insert.....
Hi Mike. I was just wondering why the the trap doesn't have to be resonate in the middle of the the 40M band, at say 7.1 MHz, so as to isolate the extra wire for 80m when tuning the Tx to 40M? Love your videos, I am always amazed at the quality of your builds.
Good question! and I'm not sure of the answer (maybe someone will come to my rescue here) I believe the trap needs to be just below the traping frequency as the impedance is at its highest at the coil resident point. so as you get closer to the trap frequency so the impedance raises, if the trap frequency was lets say 7.1MHz you will never get a low SWR on 40M as the impedance would be to high.
@@mike-M0MSN Yes, I think you are perfectly right here. One rule of thumb is to resonate the trap 1% to 5% below the band edge frequency. Because the trap is a parallel tuned circuit, it will have a very high voltage across it at resonance. So, if you operate it just above resonance it reduces the voltage significantlty and reduces the risk of breakdown. However, you don't want to go lower than 5% or the trap will start to act like a loading coil instead of a trap.
@@Steve-GM0HUU Thank you Steve perfectly explained.
Mike what is the cable stripper you use ? Works amazing on coax
They are from RS...
Hi Mike. I’m sure you are done with video. But incase you are still responding. I have that other analyzer you have in the video can it be used for this? Also what is the name of its battery connector?
Mike d you know if the trap will work high power of 1500 watts? you made it look so simple thanks
I would not like to say, I think not, may be 300Watts
Another great video. Have you yet drilled the kitchen top? Only a matter of time Sir!
Eventually...
@@mike-M0MSN better checkout the price of wooden tops nowadays, that will probably hold you back from drilling it :D
hello, how did you build the reel test? thanks, you are great I always follow you.
I will make a video on that soon
thank you for sharing new ideas new friend too waiting host in our house too tnx in advance
I thought traps are designed to resonate in the middle of the band - why then do your coils resonate at 6.555 MHz for a 40m trap? Even your frequency in the calculator was set to 7.1MHz?
Well, great question. The calculator is only a best guess o meter, due to the coax used, and test show that the trap only needs to be close to the target frequency.
where did you find what the capacitance value to put in?
www.qsl.net/ve6yp/coaxtrap.zip
Nice video. Have you tried similar traps for Endfed antennas?
Yes I have, they work quite well.
@@mike-M0MSN can u share some details of coaxial traps used for 80M EFHD antennas
Hi Mike. Did you use Copper Coaxial Screened cable or was your Coax copper coated steel wire. Could you test with a magnet and drop me a reply. My latest video is worth watching as I am having cable problems. Cheers from old George
Hi George, It's all copper no ali or steel :)
@@mike-M0MSN Many thanks for your reply. Cheers from old George
What do use as a probe?
Home made Coax coil
Hi Mike
Was contemplating crossed dipoles. Thinking half wave elements feed in the center at 60’ up with open spaced wire. How do you think it will compare to my sagging hw dipole (east/west atm) feed point is same 60’ high. Will I notice a gain toward the north south ?? Thank you
You never know give it a go!
Would you solder the braid to the center conductor in all applications? Verticals, dipoles, EFHW ?
Yes John, the coax forms both the capacitor and coil.
Would two be added to a 20m dipole to make 40m? Does it require any wire on the end? Thanks I’m advance Mike.
You need a 80M dipole you add the 40M traps in the centre of each leg and you get a 40/80M dipole
@@mike-M0MSN Thanks for the reply Mike, much appreciated.
where can I can that coax trap program calculator
Google it
Nice demo. And the mfj stub antenna you built. Was that just a short coil built from a piece of coax also? Thanks Vic KE8JWE
Yes and yes, many thanks
I’m hoping to create a 2 m Multi element vertical dipole To use as a base station antenna at home
I would like for all of the elements to be in phase so that they all radiate at the same time
I just don’t know how to create the wiring harness to attach it all to get it to work correctly
Any recommendations or advice would be greatly appreciated
Wow now that's a project, I will have to give that some consideration. :)
Repeaters often use this type set up so I’m told, where there are 4 separate vertically stacked dipoles all supported on the same support pole - and they are wired in phase so that the gain increases to approx 6 dB or 4 times greater
@@PatAutrey Yes if you stack 4 x folded dipoles ( a folded dipole has a impedance of around 200 ohms) in parallel each with the same lengths of coax in to a junction box you should get 50 ohms out....
I have no clue how that would be wired up I found a commercial version of something that I’m thinking about so this is what I’m hoping to build. www.solidsignal.com/commscope-138-150-mhz-6-9db-exposed-dipole-omni-antenna-db224-e?DB224-E&gclid=Cj0KCQjw16KFBhCgARIsALB0g8Jmu9qH66ae-spj9YJccLsmVOtNVC_3Itwub1lJ3OkERQKKpQXwxM8aAojGEALw_wcB
are you able to explain how this would be wired up and how the connections would be made
73.51pour les bande 45m
80m 73.51
73s from PD0ROH
Hi I'm last warrior in my call sign gave me measurment
I'm very confused. I'm getting conflicting results from videos.
These resonate below 7 MHz yet others taken from the ARRL book resonates them at 7.15 MHz.
One video I watched said it's important to not resonate them in the band but just below or just above.
It looks like I'll need to experiment, I want my 60m inverted vee to work also on 40m, maybe put variable capacitors in.
G4GHB
Yes I, like you, did not know which way to go on this so I did the trap and set it at a frequency just below the target frequency and found to worked I then made another at the target frequency and that worked too, finally I made another just above the target and guess what, that worked too the only difference is the bandwidth and tipping point. Which is best for me just below the target frequency…. Hope this helps
@@mike-M0MSN Yes, thanks. It does seem that a frequency just below seems favoured.
G4GHB.
And no holes in the bench. BZ!
Yet!
Привет 👋. Причём тут бананы!?
Привет. Это шутка между DXCommander и мной, он заменил DBi на бананы.
@@mike-M0MSN ну понял. 🤝 Слежу за вашим творчеством.73!
Good video showing how to, excellent for the beginner to help them learn through practice
Wonder if you have tried winding traps with copper enamelled wire and using a capacitor inside pipe to complete the tuned circuit. Vy73 de John G4YDM
Not yet!
@@mike-M0MSN haha Cheers have fun, JOHN G4YDM
do you have a link to that calculator please
www.qsl.net/ve6yp/winpsk.zip
@@mike-M0MSN thankyou Sir.i have made one of your 1/2 wave coax antennas and its going very well. the 5/8 looks a little more challenging. might put the 1/2 wave inside some pvc tube
@@mike-M0MSN i grabbed the coaxtrap software but cant seem to run it on windows 10