EFLW with IC-7300

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K8INA, May 5, 2017.

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  1. K8INA

    K8INA Ham Member QRZ Page

    Has anyone tried or have knowledge of using an endfed longwire with the antenna tuner in the IC-7300? I am wondering how well the tuner will work with either a random wire or endfed antenna. Thanks for the info...

    Jeff K8INA
  2. KD6RF

    KD6RF XML Subscriber QRZ Page

    There are so many different configurations for end-feds, that there really is no one answer. With some of the hodge-podge "designs" found on the web, you may be able to get a "tune", but all one may really be doing is warming up the soil, heating your house wiring, cauterizing your CQ finger, etc. :eek:

    Anyway, the point is that being able to find a match may just be a sign that the antenna system is inefficient - it often says more about the inefficiency of the antenna or coax or cores than anything else, especially when dealing with internet-lore-end-feds.. :rolleyes:
    NH7RO likes this.
  3. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    The tuner in the 7300 might work the trick just fine if you terminate the end fed wire "outside" using a 9:1 or higher ratio Unun (most commercially built end-feds for ham work come with one) and run coax from the rig to that.

    There are several EFHW's on the market that cover several bands using a particular radiator length and a Unun built to work with that length that will yield VSWR on coax <3:1 or so, which the 7300 tuner should handle.

    If you just plug the end of a wire into the 7300, that's unlikely to work well at all.
  4. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    This site has pretty easy to understand instructions on how to build a 9:1 unun that will work okay up to 100 watts:

    KD6RF likes this.
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    But even that is reliant on a specific wire length, not just "any old length" wire.

    With a real half-wavelength wire, the 9:1 may work but a 49:1 or so actually works better, to cover more bands.
    KD6RF and WB5YUZ like this.
  6. KW4TI

    KW4TI Ham Member QRZ Page

    I don't think this will work too well. I have a IC7300 and a 9:1 unun, and I still found you need an external tuner anyways. The internal tuner can only up to 3:1 SWR, but unfortunately most longwires are going to have a widely varying impedance, even with a 9:1 unun. The 9:1 unun reduces the SWR, however, it does not match the long wire sufficiently for the IC7300 tuner to work on all bands. It does get the SWR down to about 5:1 or less for all bands for which the antenna is longer than a quarter wavelength. Most end-fed wires that are not exactly at resonance (either the quarter or half wave resonance) have a large reactance which is difficult to match. I think you are much better off with an external tuner. Best to keep the SWR low for your expensive transceiver, and let the external tuner handle the large variation in loads. I use a MFJ-929 with the IC7300 and it works perfectly, but there are many tuners that probably work just as well, and are compatible with the ICOM interface.

    The earchi 9:1 unun uses a iron powder core which is generally inadequate for transforming the impedance of a high impedance long wire. Use a transformer made with a ferrite such as type 61, or just buy a FT240-61 toroid and wind the unun around that instead, you'll be much better off. Or you could just buy a 9:1 unun which already uses a ferrite core. You will also need a decent grounding system, which means radials mostly likely for your end fed wire to work. If the resistance of the grounding system is too high, the RF power is going to be dissipated in the grounding system or counterpoise, and not in the radiating wire.

    If you use a 49:1 transformer you need a true half-wave wire, and you can get away with a higher resistance grounding system.

    If you are interested, you can read all the information I wrote about putting up a longwire vertical antenna and the calculations and such on my qrz.com, as well as how to build a end-fed half-wave if that's what you want to do. You could also consider an off-center-fed dipole as well if you want a multiband antenna, such as the W8JI version, which I recommend is used with a two core 4:1 Guanella balun.

    KJ4VTH and KD6RF like this.
  7. KD6RF

    KD6RF XML Subscriber QRZ Page

    You gotta love Dan's LobbLollies - I have my 90 ft Inverted-L up in a pair of tall LobbLollies as well :) Dan's article is a good read.

    I would add to Dan's work that it's usually a simple matter to use the 9:1 Unun for the upper bands - but with the addition of a loading coil (instead of the 9:1), you will have picked yourself up one band lower (especially useful where the radiator wire is around 3/8 wavelength on the lowest band)

    In my case, I use a 90 footer up in the trees, with a decent radial system (16 radials + chain link fence) for 160 M through 6 M.

    If interested in this multi-band scheme, here's some info re
    Why we use a Base Matching Unit (BMU) with End/Base-Fed Verticals and Inverted-Ls" ===> http://vtenn.com/Blog/?p=1158

    Last edited: May 6, 2017
  8. KB4QAA

    KB4QAA XML Subscriber QRZ Page

  9. W6OGC

    W6OGC Ham Member QRZ Page

    The ideal way is to get and use an Icom AH-4 remote tuner. I've had one for ~10 years, very satisfactory. With a 7300 and most other Icom transceivers, it's one touch tune, 160-6m. Just be careful to avoid wire lengths that are 1/2 wl on any band. There is an Excel spreadsheet on the yahoo groups site to handle that.
  10. KJ4ADN

    KJ4ADN Ham Member QRZ Page

    YES - I actually did. Built an end fed, fan dipole, not a "random wire" length, but 1/2wl at 40-20-15, was able to tune it with the IC-7300 and it actually performed fine on the air. I'll probably never do that again, though - I hung the feed point at the porch, and ran the fan elements out to a tree... it wasn't straight out (90 degrees) from the house, but about 60 degrees... ouch!

    After turning on and off the stereo, and everything with an electronic control - I remembered, the radiation pattern is like an "X" not like a figure-8 of a dipole - and I was right in one of the lobes... I kinda liked the antenna, but that awful pattern - gave it away at a HAMfest to a guy who thought EFLW was the greatest thing ever, and didn't want to screw around with matching and odd lengths - this one had resonate points on 3 bands and matched at 1.6:1 or better at resonate points... the auto-tuner on the IC-7300 handled it easily across all 3 bands - without a 9:1 balun.

    I did add a 16' wire to the coax shield (just let it hang from the feed point), to improve the match, so you could say it was almost an inverted "L" - the AIMUHF analyzer also confirmed it was better than just (3) 1/2wl parallel wires. I should add, the antenna was directly over 35' of aluminum pipe (and OMTA I was working on... there's your ground reflector). From Virginia, I worked several stations west of me, including Wyoming - a friend was helping with testing on 20 & 40m. From the angle of the antenna, NNW, I'd say he was probably close to the opposite lobe that was pounding the house's electronics. I did put a +KW through it ... which lit up the house (not the IC-7300)...

    My goal of the afternoon project, a 3 band, resonate fan long-wire - or variation for fast deployment, an alternative to a portable vertical - my conclusion, MEH! Think about the radiation pattern and what are your really trying to do, where do you want to communicate, and what is interference you don't want to hear?

    I've been screwing around with fan dipoles for years... just put up a 160-60-80m fan dipole (parallel elements, 1.75" apart), it was a one-cut-to-tune. Resonance came in at 1.910MHz 1.15:1SWR, 3.830MHz 1.14:1SWR, and 5.380MHz 1.3:1SWR. (just a tad high, or short on 60 meters) Worked out so well, I'm making a second one to put up at 90 degrees. The NULLs off the ends are definitely there, in some conversations, I literally cannot hear a 3rd party, or they're so weak the K3 doesn't register them over the noise. Those in the pattern, say barefoot is strong, and 800-900 watts is +60 on 80m & 160m.

    If you build a EF antenna, try hanging a 1/4wl wire at the feel point from the coax... and while your at it, CHOKE the feedline for any stray common-mode (might become a problem with coupling). This one worked well with 75ohm coax... bandwidth "OK", but sharp & return loss at resonance was -35db or better (I like that). I don't like that goofy "X" pattern & 4 constantly changing NULLs with frequency changes... and don't forget to bring a ground reflector.... but for the SOTA guys, who don't care about not hearing what you wished you had, after climbing all morning - a vertical is quite reliable & trustworthy... IMO... and you don't need trees, sling-shots & rope (which pisses off NPS and Rangers). I've never killed a 60' tree with paracord - but try explaining that to a Ranger on the Blue Ridge Parkway.

    KJ4ADN - Bill

    Experiment & find out for yourself, it's what makes the hobby interesting, what works at my QTH will not necessarily work at your QTH - regardless of modeling & RF engineers convincing arguments.

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