HAM RADIO: Easy SlimJim / J-Pole Dual band Antenna Build for 2m/70cm .
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- Опубликовано: 2 окт 2024
- HAM RADIO: Easy SlimJim / J-Pole Dual band Antenna Build for 2m/70cm, Thanks to a book I purchased many moons ago, I have found the perfect way to pass a rainy day. make a 2M / 70cm Slim Jim or J-Pole. Not just the standard J-Pole but one that uses a decoupling stub so that you get the maximum power on both bands..........
You need:
1.5M of 300 Ohm ladder line
15cm /6 inches of RG176 or RG316 coax
and that's it, Bobs your uncle.
Many thanks
Mike - M0MSN
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Made this about three years ago as a "Stealth" aerial for a cheap 10W rig in my workshop (I have a neighbour who makes a fuss about "new" aerials going up). Encased it in a plastic tube, sprayed it in camouflage colours and hung it in a tree about 15 ft above the ground. He's never noticed and it gives me infallible access to eight repeaters up to 50 miles away, as well as local QSOs.
I would do the same with the camo paint, unless I had a neighbor that complained then they would get painted bright orange or hot pink or hi vis green, or a myriad of any distracting color.
Thank you for the inspiring instruction - got me making again after a 35 year break from the hobby. My creation tunes at 141Mhz although I followed your measurements obsessively closely - the only difference was the use of RG58 for the trap. Moving the feed point seems to be the only option and I'm guessing to move it up and shorten it is the way to go. What do you think?
Juicy solderwork!
😂
I need one for my realistic scanner and when I get an mature licence 2metres and 70cm
😊😊😊😊😊
I've had one for many years and it's one of the versatile V/UHF antennas that can be rolled up and tossed into a rucksack used for hiking, emcomm or at home. Great video!
Thank you. :)
Great video Mike. I have built a couple of these now and if there is one tip to pass on it is cut your 7mm gap in the middle of the solid section first then measure back down to the bottom. You will have a more robust antenna that can be folded, or wound up, without getting twisted. 73.
Great tip.👍👍
Great video Mike as always. Not sure why but not yet got the bug for VHF or UHF having stuck with HF since getting first licence. No idea why, other than I like the whole idea of propagation further afield. Or, it might be repeaters that still make me scratch my head ..... Will have to try sometime!
nice video. where did/does the braid part of the 316 cable go, that part was skipped over?
braid goes opposite the Centre at the bottom of the SlimJim/Jpole
very nice mike going to make one in the morning if the ladder line arrives lol
thanks again
allan
G6TMO
Thanks for that Mike l will build one this week and let you know how l get on, all the best Allan G6TMO
I think I’ll make one of those for the bottom of the garden and then the handi can be used when sat down that end 🍷 🍗👍🏻
Nice one Mike. This will make a nice addition to my POTA kit
Supertramp!
Dont forget that the US 70cms band is 440 to 450MHz thats why you get a good vswr higher up the band eg 438 repeater input.
However, if you place your antenna into some PVC pipe it will actually lower the resonant frequency, which may help you on uk 70cms. 👍
6:20: These look like fast and efficient insulation strippers. What make are they? Looked for them at Home Depot today and saw nothing like them. Thanks!
73,
John - KK7JBZ
Relative to the two conductors of the ladder line, is the antenna at all directional? I have a repeater target some 4-6 km away and want to turn the antenna however it will best reach the repeater target effectively. 73 Tom KC3QAC
can i replace the 300 ohm ladder cable with the 450 ohm ladder cable?
yep
Hi Mike. Thanks for this video. The problem I have is lack of funds. I build and make as much as I can from bits laying about my garage or peoples skips. They don't seem to sell 300ohm ladder line by the meter and I don't want 10metres. So wondering if I could make ladder line from copper tape with plastic straps. So now looking for dimensions of ladder line spacing. Not found it as yet. Cheers from old George 😢
just use wire and spacers......
I did it in reverse. Made the coffee, then watched the video.😀 nice easy build.👍
Nice.
There's something mysterious here , I am not talking about Coax Trap because it abvious in length and Velocity Factor ,,, But my Question is about the two Cuts in the other side of Antenna ... Perhaps the 1st lower cut belong to isolate 1/4 wave bottom matching part , But what about the Upper Left Cut ??? May someone tell me
I believe they are parasitic elements for 70cm band
Great Vid!… Dr Edison Fong’s improved J-Poles are extraordinary good… but dang it, I had to make myself a coffee… 😂
Hi Mike another great video.
I built one from the ladder line also and it is known as a "slim Jim" just a piece of laddeline and it works amazing on 2/70 even though it leans toward PMR frequencies. Pinned it to the rafters and soldered the RG213 straight to the element before heat shrinking.
What is the bunch of bananas appearing on your videos 😂 you and callum upto your antics again?
Take care Mike hope you're well.
Rab de MM7BVP
What book is that?
Successful Wire Antennas by Ian Poole
Mike or anyone else please, why is RG316 / RG174 used as the matching stub instead of RG58? Is it just down to the diameter of the cable? Could RG58 be used instead? Thanks
Yes and yes
Where can I get the antenna book used in the video?
RSGB book shop
Mike thanke you for"yours" cm . Because sometimes i'm confuse abaute inches. Thanks👍
"It's Raining Again".........Isn't it always? I bought that book about 5 years ago too
Point taken about the teflon insulation, I've just made a Youloop for the sdr and fell foul of the insulation in rg174 giving me melting issues! Nice project, I'll be building one of those in the future. 73 de Mark
Excellent! Thanks for posting.
My pleasure!
I made one today, but mine does not resonate as well as yours.
If longer than 5' of RG-174 coax to the transmitter is used will it affect the SWR? Can it be RG-58?
build and find what works best for you.
I'm liking this antenni it's very stealth & the birds & the bee's won't sit on it .! 👍🏾
Excuse me sir ! Where can I purchase this holy book of antenna 's I have most of the equipment ..
I'll just go by your's 👍🏾
That is nice do think the Coffee will be a cold when it get deliverd in New Zealand
Nice work Mike. I give it 5 Bananas !
Deal!
Nice video Mike, great to finish off with a guineas in a mug too.... 🍺😁
Tried again and it will not resonate at all Lol
Sorry another question. How would this antenna perform against a T2LT based version of the antenna with a mutually coupled wire spaced away from the 2m element giving 70cm coverage. I have a 10m fibreglass telescopic pole and am looking to attach a 2m / 70cm wire antenna to it using tape / tiewraps. Thanks
Don’t really know, why not build both and let me know.
Excuse me. maybe you already wrote it and I haven't read it. What is the function of the two 1/4 cuts on the left side?
I’m not 100% sure ? I will read more into this.
Good stuff here. Thanks.
my fav bit of the video... 2 wooden spoons. This is why your car does not work. You need 2 wooden spoons on the roof for the magic fairies
lol
Does anyone know how it compares to a regular Slim Jim antenna out of 450ohm ladder line with only 1 cut out?
Why not make both and let us know.
Do it sir in mobile base radio
Hi Mike,
I have made one of these exactly as yours using the correct coax for the stub. Only difference I have fed it with some 50 ohm RG 58. I am unable to get a SWR of less than 2.8to 1 which is at the 144mhz end rising to over 3.3 to 1 at top end 146 MHz. Have trimmed about 3 cms off the overall length very Little difference. Also tried the feed point distance. Any help would be appreciated.
the length of the antenna is not going to make that much difference, you need to move the connecting point to mach the the impedance point.
@@mike-M0MSN Thanks Mike will have a check.
Great video thanks for making and posting 👍
Hey Mike I have the plans for the N9TAX Slim Jim Dual Band 2m/70cm Antenna of which there are no build videos of it on YT (or anywhere) only impressive reviews. Whilst this antenna is reasonably priced and available in the states postage to the UK is $60. Did you want me to email it to you?
yes please. use QRZ
I'm going to make one! Thank you for the video!
Where is the best place to order ladder line?
eBay?
@@mike-M0MSN okay thank you!
Hi Mike. You initially cut it a bit longer. Did you have to trim it down to get the SWR right?
Yes Stephen by about 1 cm.
@@mike-M0MSN from the top?
Can you tell us an antenna that it compares to for a performance reference ? Thanks great video
A piece of wet string
Thanks! I just happen to have some of this ladder line laying around.
Glad I could help!
Hi can I use this antenna without a SWR meter?
You can use any antenna without an SWR meter ... as long as you don't mind RFI in the shack and/or cooked output transistors.
How do you keep your ladder line flat?
Heat gun.
Hello Mike, Thank you for the detailed video
Are the measurements for 450ohm ladder line the same as with the 300ohm I was under the impression due to velocity differences they would be different? I've 450ohm laying around I'd like to use. Would appreciate any input please
Yep, should be the same, give it a go and let me know please.
@@mike-M0MSN I certainly will just waiting on some RG174 for the trap. Many thanks
@@Superfandangoo And...how did it go?
@@johnbauman4005 Yes it went well thank you, I made another two as friends asked.
Can you use the thin 300ohm twin lead also?
yep
Just know that 300 Ohm twin lead and 450 Ohm ladder line have different velocity rates, so the dimensions may be slightly off.
You deserved that coffee 😁👍👍
😁
It's an ed fong design
yes it is.
Nice simple build, ladder line is nice stuff to measure and cut I always think for antenna projects 👍👏👏