A Better Off-Centre Fed Dipole - Part 2
Vložit
- čas přidán 28. 06. 2024
- This second video in the series shows the build, tuning and testing of my 40m multi-band off-centre fed dipole using the 4:1 transformer and 1:1 choke/balun that I built in the first video • A Better Off-Centre Fe...
For the design of the transformer and balun used in this antenna, my thanks go to Peter aka TRX Lab on CZcams. His comprehensive explanation of the build and testing of both the transformer and balun in a professional lab can be found in part 3 of an excellent series of videos - Part 3: • #105 Balun PART 3: How... (I recommend you watch all three parts!). Peter's tests also show typically greater than -30dB rejection of common mode currents across the HF bands.
Part 1 of this series can be seen at: • A Better Off-Centre Fe...
This is one of many amateur/ham radio related videos on my channel. Please feel free to browse 👀, like 👍🏻 and subscribe 🔔, remembering to hit the bell so you’re notified of new videos as soon as they're published and you don't miss out.
0:00 Introduction
1:22 Antenna Build
3:36 Antenna Testing & Tuning
10:46 SWR Comparisons
12:39 On-Air Contacts
Thanks.
Ian. - Věda a technologie
Great Job Ian, nice first test contact on 20m. Looks like a quality install. I definitely liked it. Enjoy buddy.
Yes, works a treat Brian! Just need some more air-time to stretch its legs 😀
Thanks for part 2 Ian, performing well. I have an FT1000MP Mark V, also 200W, I need to get one of these build
Thanks Adam! Yes, a keeper 👍🏻
Hi Ian,
Thanks for demonstrating the new antenna. As they say the proof is in the pudding. Stay safe. 73 WJ3U
Thanks Don. Really happy with the early results 😀
Great video again Ian. That FTDX 5000 looks a nice radio. A real looker.
Ha ha yes Tim, unlike it’s Dad! 😁
Good result Ian.👍🇬🇧
Thanks!
Another interesting antenna video. That FT-5000 really is a nice piece of kit. Hope all is well Ian and all the best. 73 Chris M0RSF
Thanks and yes, all good this end Chris. Might catch you on 70 and/or 6 this week? 👍🏻
Hi there, good stuff , I built this a few years ago , from the TRW channel , works very well. I made a 3D printed case for mine . Still in use . I’ll look at building this open version , looks an interesting way of building one .
The 1:1 Balun ( for common mode ) and followed by the 4:1 . I even got an VNA and tested it , super results.
I have fitted a solar system for off grid , getting a lot of QRM, probably off the inverters, so looking at curing this noise on HF.
That sounds great! Good luck with the noise 👍🏻
I just built these baluns for a W3EDP junior. When I have the space though I'm not going to use a windom I'll make a doublet and use either the 4:1 or peters 9:1 design with a 1:1 cmc. So the ladder line will drop down to the balun/impedance match then there will be the 1:1 cmc with either M&P hyperflex 13 or LMR600 or 1/2" Heliax either of the three going to the shack with another 1:1 cmc before the tuner.
So if I'm getting 1000ohm at the feed point the 4:1 would drop it to 250ohm or the 9:1 will be around 100ohm. These impedances on big thick coax are manageable with say a 30m run.
The benefit to this setup is as long as you're at 5/8th wave of the biggest wavelength you want to use you'll get that and every other band.
Sounds like you’ve got a well thought out plan Shane 👍🏻
Nice video - I am wondering if you tried to compare your setup by using a more modern Transceiver to see if the audio quality is improved - it would be interesting to see if the new technology improved audio signal at the end compared to FT-5000
Hi Edin, no just the 5K to play with this end. Thanks.
19.5 / 80.5% split will give the WARC bands and 15M, see DJ0IPs analysis, very thourogh..
Thanks for the info.
Thanks for the video, Ian. Do you think the common mode currents are tamer than the previous version?
Thanks and yes. The SWR readings are what I would expect from the antenna without the extra choke, so as though it’s not there. The original antenna changed once I put the extra choke in-line, which to me only went to show that the coax was radiating too and the choke stopped it, hence the different SWR readings. If I can summon up the will, at some point I’ll take that choke out of line to prove the point 👍🏻
I hope you get to see this question. I would like to know at the very top of your 4:1 the two wires that will attach to the each leg of the dipole, does it make any difference if the red or black wire goes to the short side or long side? thank you.
Hi, either side is ok. Good luck 👍🏻
@@ianxfs Thank you for replying so quickly! I will wind both 1:1 and 4:1 tomorrow as I received proper wire today. I ran a quick test last evening with light gauge wire for a 1:1 and followed your test method. I found it actually looked pretty good on SWR. I plan to use the OFC I'm making for Field Day in June. Ian thanks much for making your video, very helpful. 73
@@N1SEP- you might have to have a few tries as it stretches the wire insulation and eventually beds in 💪🏻
@@ianxfs You made a nice mount with the transformer over the choke. I have a plastic box, its not long enough to have two in line, so I wondered if it would work with the transformer (4:1) on top of the 1:1 or would that cause an issue in your opinion? if not, do you think some kind of material between the two would be needed?
I could always try, but i would dislike burning these up on my first build :)
@@N1SEP- I think you’re ok with a stack as some commercial ones come like that. They won’t touch due to the windings, so should be ok. I went for the open T-piece as it’s less heaving (antenna sag) and there’s no issue of moisture that you get with a box. You need an air vent hole to allow it to breath, otherwise the air trapped inside condenses with heating/cooling. Worth trying the T-piece method if you can and then avoid the stack and less sag? Anyway, should be ok 👍🏻
Hi again Ian. The plot that you show for the SWR, is that a function of your radio or a separate program or item you use?
Hi Chris. It’s a new shack addition. A DMU-2000 Data Management Unit that connects to the 5000. Bit retro (originally for the FT-2000), but some useful bits too. One is the SWR plot & graph function 😀
@@ianxfs Interesting, just looked up some info and videos about it. Looks a bit of a lump :-) Seems like Radioworld might have One, not cheap though but puts a nice plot out. I am pondering over upgrading my rig, they have a Kenwood 990S £4k ouch which might be a contender, a couple of 5000MP's 2.5k not too bad. IC7610 2.4k and of course considering FTDX101D or MP :-) or D my needs are multi antenna, rx only facility (I know I can use a spare antenna port if I wish) was sort of thinking 240v supply and of course NEED visual output of band. I know your 5000MP ticks all those boxes with the little box thing on the top but also NEED on board Sound card, which I don't think it has. Of course all this stuff might not be in stock. Decisions, decisions :-)
@@chrisbartlett6022 Ah right Chris. Yes factor in an RSP1A and extra monitor into your calcs for the 5000 (= good waterfall) plus an SCU-17 for digital stuff. You can do without the DMU-2000, but mine was a good offer and I fancied a look. Good luck with your coin toss 👍🏻
@@ianxfs Was starting to factor the 5000 out as it looked like it needed "add on's" to make it do what I wanted, looks like a lot of rig for the second hand price though. Starting to lean towards One of the new Yaesu 101's but of course I could buy a Motorbike instead :-) LOVE your connect the Balun and Choke together idea BTW. My Windom seems to still work well, getting 2 to 1 or below on 80, 40, 20, 17, 12 and 10. Over 3 to 1 on 30 and around 3 on 15.
@@chrisbartlett6022 Good luck with what you go with Chris 👍🏻
I also posted this on part 1 of this series.
Do you have good instructions on a web page, not just the video? I'd like to print them off for reference when i build mine.
No sorry, just the video.
Are you actatually operating with an SWR of 3.0??
Of the 200w, how much is really reflected, compared to your total max power out?
I'm not a fan of tuners, in fact i don't use them, nor do i own one..
3:1 SWR loses 25% of the power out in this case 150W going into the coax. That would be hardly noticeable compared to 200 watts on the receive end, way less than 1 S-point difference.
3:1 SWR is an 0.5 reflection coefficient, but the actual *loss* depends on the feedline and the matching network. 3:1 is pretty tame, >90% efficiency isn't hard to get.
Hi Robbie. Yes, on the bands where the resonance is out of band. The rig tuner keeps the rig happy.
Brother--- grab 316
Stainless steel hardware ✔️✅✅
Thanks.