15 Metres Simple DX Antenna
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- Опубліковано 25 бер 2021
- A simple to make vertical antenna for 15 metres with low angle radiation and NO RADIALS REQUIRED! Ideal for portable or small garden/yard use.
Connect with my channel by subscribing and commenting. 73 - Наука та технологія
Just made one within an hour cut for 15 metres, and it out does my windom proudly. The choke is only about 3 feet off the ground, but listening to some of them low angle stations brilliantly. 5-7 S points difference to my windom on DX. In fact, I can now hear them. Thanks Tim, Alex M0UTA 🙂
Fabulous stuff Alex, enjoy!
Hi Tim. Finally tested your version of this antenna and last Saturday morning 5x7 into Barcelona. The VSWR was 1:2 -1 right across the band. Great antenna build so I recommend it to anyone wishing to get on the air.
Great stuff!
THANKS Tim
went down to local hardware got PVC pipe
had the coax laying around for years not being used
thanks for the educational tutorial
i haven't tested yet but will do in the near future
cheers Greg VK2GMC
👌
I hope you enjoy the antenna Greg!
Keeping the RG58 factories of the world ticking over nicely Tim 😉
Good stuff 👍👏👏
Thanks mark
Well doneTim, you have made it so easy to understand
Thanks! 73
Thanks Tim! Another easy build 👍🏻
Thanks Ian
Another good one. 15m one on my favorite bands. I'm sure it will come alive for the contest.
Fingers crossed
Made one and wow it works well was on 15m today testing it swr was ok but might trim it thanks for the vid brilliant keep up the good work
Glad it works Jon 👍👍
Thanks for this excellent and succinct tutorial Tim. Followed these steps tonight and works superbly. First homebrew antenna I have attempted and very pleased with results. Btw didn't have a 110mm pipe but rolled up some lawn edging I found lying around and tied together at ~110mm diameter and that worked fine. 73 de 2I0WLZ
Brilliant Andrew - glad it worked well!
Hi Tim, thanks for the video clip. Made one over 2 days, SWR 1:3 to 1 on 21.074mhz. I did make it cheaper by using 13amp wite for the top, so saving 3m 39cms of coax. Yes received some DX this morning and was heard in Africa, but qso's just local Europe. Great antenna, easy to put up and down within 5 mins or so. Cheers Tim 73's Andy M6APJ.
Glad it works Andy I wish you well with it
Hi Tim, thanks for your video. I've been looking for a dedicated 15m antenna. I don't have a great deal of space and no space for radials. I made this antenna to your spec, tested it and found it to be much better than all of my other antennas. It's mounted about 3m above ground on a 10m fibreglass pole. Thank you & 73 de VK3DGO
Fabulous Mark, really glad it worked for you
I use one of these for 2m SOTA activation. Absolutely smashing performance.
Me too - can’t fault them
Thanks Tim i will have go making one for 4 meters and 6 meters bands.
Nice one!
Hope you have a good supply of coax, that’s quite a bit of wire. Thanks for educating us on making these antennas. Really appreciate these videos. 73 de N1YLO
Thanks Andrew. Guess what? I’ve literally just run out lol
A useful series of antennas to have to hand.
Thanks 👍
Nice one Tim. I'm sure you will get some decent contacts. Keep us updated.
Thanks Colin hopefully this weekend 73
@@timg5tm941 I won't make it on but hopefully work 2 evening of the CW leg.
Thanks Tim
Well Done Tim
Thanks Michael!
Thanks for this video Tim. What did you think of its performance at your QTH?
Also, have you tried it out portable yet?
It did pretty well Adrian. Haven't been out /p yet but it will live in the boot of the car ready to be used. 73
Hi Tim, interesting antenna that I would like to try also. Thanks for making these videos. Do you think that some light weight rg-316 would also work for this antenna?
Any 50 ohm coax would be fine. 75 ohm might present an ok match
Hi Tim, just wondering, the choke you say is 110mm. Drain pipe is 100mm, will it make much difference as a former?
Keep up the great work, might catch you when I come down to the south coast in may on holiday, fingers crossed.
Try it Steve my guess is maybe one more turn to compensate?
Sounds like this could be made into a nice 6m aerial.
Definitely
Was wondering about the number of turns in the choke. Does the inductance of the coil and distributed capacitance between the turns form a 15 meter parallel resonant trap? This design fits my desire to remain as stealthy as I can even though I have no restrictions against antennas in my neighborhood.
Excellent construction details.
That would be ideal for maximum impedance of the trap, BUT without measurement WHO knows? Also seems like a waste of coax to strip off the jacket and shield for the upper half when could just solder a length of insulated single conductor to the lower center conductor.
Hi John - the choke is based on the work of the late G3TXQ. Search for his choke chart - here he gives information relating to air coils such as these, as well as those using ferrites for different bands. 73
@@timg5tm941 Thanks Tim
Hi Tim, did you measure the attenuation/dip of the 7 turn coax choke? According to my experiences air chokes (technically being an L/C parallel choke) are very narrow banded and can easily be influenced by their sourroundings (changing the C part). I always wondered if it might be a better idea to use a ferrit core broadband choke instead (or even on top?). Just to make sure and save some coax. Talking about saving Coax: does it make any difference if one just solder simple wire to the center of the coax for the upper part of the antenna?
Great points - trying out ferrite chokes with this antenna is on my to-do list for the spring/summer.
@@timg5tm941 Great! I am looking forward to see your results. That far i did not manage to measure coax air chokes properly and reproduceable. There is just to much influences from the sourroundings. You can not just wind them up, lay them on the table and read S21. Even free hanging from the ceiling you won't get reproduceable readings because air moisture etc is changing. Great idea in theory because of the super high notch depth but in my opinion super unpredictable - but maybe i a missing something :)
Nice ! A couple of questions if its ok.
- how many watts can you put thru it
- Could you make a video of the complete construction stripping the coax, forming the choke and mounting which will help us newbies to get started with this type of antenna :)
Thanks again ! 73's
Alan / 2E0FWE
All noted 👍
I run 400 watts through mine. I've got versions for 20, 15 and 10m. The choke and the lower coax section do get noticeably warm to the touch after a period of operating so there's definitely loss there. I'm tempted to remake mine using RG-213 cable but that would add significantly to the weight and the fibreglass pole would struggle. BTW you don't need to use coax for the whole antenna. The top section can just be 1mm wire soldered to the coax inner so no major coax stripping needed
Hi Tim, I have made the 20m, 15m and 10m Flowerpot antennas after watching your videos. They all work extremely well. Are you using a formula for your calculated lengths. The reason I ask is I want to make a 30m version. THANKS. Daryl de VK3AWA
Hi Daryl 468/centre frequency.. you’ll need to do a choke for that frequency .. see the G3TXQ choke chart for air chokes
@@timg5tm941 THANKS Tim.
Thank you for your answer I have already done the antenna but the swr is 1.2. If I use Satec RF5 cable and 70mm tube, how many coils should a choke baloon have? Thank you
I’m not sure of that .. it’s narrower I believe than my choke so a few more turns might be needed
How is the impedance ?
Just a week ago I made a similar antenna: 2 x 3,37 m of RG58, then a choke 240-43 core with 4 windings clockwise and 4 counterclockwise, then 2,34 m of 75 ohm coax then RG 213 to the shack. My impedance is spot on 50,3 ohm and the swr is 1.0 at the bottom to 1.1 at the top.
I use a 9m pole and I am blown away of it’s performance.
Thanks Tim 73 HB3XBL
They work really well! 73
Hey... I just made this antenna yesterday and found out that it was resonating at 7 MHz.... Wonder why... Then I counted the rounds of coax on choke and they were 10... Instead of 7 .... But will that shift the frequency so much?? The length is exactly 3.39 meter each as you have shown.
What could be missing??
Yes you will need to reduce the turns to 7
If I used a Sky Hook, would that be strong enough to hold it up? :-P Nice one as always Tim.
Worth a go!
Hi Tim, made two of these now, and I believe I've followed the dimensions, but it seems the best match is ~22mhz (according to the RigExpert) and I would like it resonant on the CW portion of 15m. Where have I gone wrong please?
Hmmm.. either the choke isn't right or add a few cm to the top portion to lengthen it. What is your SWR around 21.300?
@@timg5tm941 Hello Tim, I've fed a bit more coax thru the choke to length the bottom portion and got it down to 1:1.5 @ 21.1 and I reckon that'll will do for now. Will give it a proper test next week. Cheers for the reply 73's
@@miketaylor253 good job!
how many turns would you put on a coax choke for 17m? Al ve3gam
Hi Al look at the G3TXQ choke chart online. I think it’s 10 turns around a 110mm former.
Can you please make one for the 18mhz band please.
Your wish is my command!
Hi Tim. I’m confused. Shouldn’t the wire lengths each be a quarter of the wavelength? 15/4 = 3.75 not 3.39. Am I missing something?
Unfortunately it isn't always that simple. I used the formula 71/21.000 (latter number being the frequency. 71 stays constant whatever the frequency) this gives the length for each half of the antenna. 73
@@timg5tm941 thanks. I’ve been looking on how to calculate that without luck. Is it best to choose a frequency somewhere in the middle of the band?
@@ianafloat9250 yes for ssb I would. If you are into ft8 or cw then look towards the bottom
@@timg5tm941 thanks. 😎
Have u tried these efhw as a sloper or horizontal antenna?
I haven’t but it’ll work
Hi Tim If I used 90mm pipe how many turns would I need.
For the choke?
@@timg5tm941 Yes
Hi this is 1/4 or 1/2 lambda antena ?
Half wave
Can this antenna be made with RG-6?
Yes it’s possible
just use a 49:1 unun and a half wave of wire
Many designs tend to be quite lossy especially on 10m