I’ve always used coax to feed my dipoles on activations. I use a length of RG174 that is long enough to run up the pole and extend a metre or two back to the summit “shack”. Sometimes I end up sitting right underneath the antenna and the excess feeder remains loosely coiled on the floor.
So the question is for those who used balanced twin feeder… what do you do with excess feeder? You’re not meant to leave it on the ground or coil it up. Or does practical experience say that leaving the excess flapping about or sat in a heap not have any significant effect on performance?
Personally my open wire line is always the right length. It’s easily achieved by tying a cord to one of the spacers half way along the line. You then simply peg this cord such that the line forms a shape that allows you to sit where you want. That way there is no line on the ground and no need to coil any up.
Coincidentally I have just today been writing a short e-mail newsletter about different feeder types including open wire line. My newsletter subscribers will find it in their in-boxes tomorrow.
In reply to MM0FMF:
HI Andy!
We are using 300 Ohm TV-cable to feed our doublet antenna. http://www.ha5lv.hu/sota/065/065.html#doublet
If there is a rock or a tree, we are lifting up and hanging the cable on it otherwise we leave it on the ground (not coiled up).
We found it non critical.
In reply to MM0FMF:
I use cheap “figure of eight” speaker wire to feed my 30m dipole. For 12m I have a dipole made of twisted pair pulled from a length of CAT5 data cable (the stranded type used for patch leads). No joints, just the top 3 meters split or untwisted and spread out, in both cases.
Both feeders are cut to length on the same basis as yours - long enough, plus a bit.
In practice, I haven’t noticed any ill effect from having either of them lying on the ground, or coiled up.
I’d hazard a guess that the outer of your coax (unless you use a choke balun)is as “live” as my roughly balanced feeders.
Mind you, I am not trying to squeeze maximum performance, just get at least four contacts!
For half of my mountain goat I was using a 2x 6.7m inverted V fed with 8m of CQ553 (either with no balun, 1:1 balun or mostly 4:1 balun).
Along the Sotapole I use velcro (or tape) to fix the feeder otherwise you get in trouble in high wind. For the last meter I position my KX3 the way that the feeder stays in free air. A few examples:
a good one:
a bad one in high wind:
The only time I had my feeder on the ground:
every time I moved the CQ553 a few centimeters I had to retune my ATU.
Now I migrated to an 13.1m Inverted L with 5x 4m radial. It’s much easier to errect and survives the UK storms:
Both antennas (Inv-V and Inv-L) work perfectly on all band between 40 and 10m.
If you use split figure-of-eight wire and tie an underwriter’s knot* at the centre, then both the feeder and the radiating arms of a dipole may be fashioned from a single continuous length. With no joints to break or otherwise fail, this would have positive advantages when used over and over again on multiple windy hill-tops. Could an antenna be any simpler?
If you use the sort of twin feeder used in the G2DYM antenna which is individual sheafs in an outer sheaf, a shortish length can lie on the ground without ill effect. I also found no effect from letting ladder line lie on the ground for a few feet though I suspect it would get lossy if you did it over any distance. FWIW I lie the counterpoise of my W3EDP antenna on the ground too, but intend to experiment and see if there is any practical benefit from elevating it.
In reply to MM0FMF:
I’ve always left it lying on the ground/heather/rocky cairn, there is usually only two or three feet, so long as doesn’t coil back on itself I’ve not had any issues. I’ve only used the thin ribbon 300 Ohm feeder for activations.
I use 300-ohm TV twinlead for my doublet and always take the time to route it around so that it is off the ground, not on live or wet vegetation (or conductors), not crossing or coiled, and with bends and turns as gentle as possible. I also try to route it straight down from the center of the doublet and use a small velcro strap to secure it part way down my mast:
On this activation I used another small velcro strap to attach the twinlead to the end of a dead branch that happened to be hanging down exactly where I needed it to be:
None of this may actually be necessary, but I feel better knowing that I’ve done all I can to keep the feedline balanced, thereby preserving the pattern of my doublet and minimizing feedline loss.
73,
Eric KU6J
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Free SOTA Spot Monitor Software + RBNGate FAQ: http://www.ku6j.com
I use a “Norcal Doublet” type antenna made out of computer ribbon cable. It’s amazing stuff - incredibly tough for it’s size/weight and the antenna being fashioned out of one continuous length doesn’t have joints to fail. The stuff I use seems to have insulation formed of two layers - a clear very strong one on the outside, and a coloured core within. When you can see the clear insulation at the “feedpoint” bends has failed, it’s time to replace the antenna because a break is nigh…
To return to your subject, I’ve found the disposition of excess feeder (not that there’s a lot, I use 8.5m of feeder with a 7m pole) to be virtually irrelevant to performance.
I’ve the same thing, but with super-cheapo ™ ribbon cable (the ‘normal’ grey sort)
It could do with a good old untangle though as the ‘downlead’ seems to have become rather twisted.
It normally ends up with a mess on the ground of the bottom couple of meters of ‘downlead’ before getting into the tuner.
Got me across to NC with 2.5W SSB earlier in the year, and to vk5 land earlier on this month (although with 50-60W ssb)
I do it much like Eric, KU6J, but I use ladderline - a little bigger and heavier, but it’s what I had available since I use the same stuff to feed my dipole at the home station. I have a fixed length that will come down the mast (also afixed by Velcro straps) and allow me to set up about 6-10 feet away from the mast if necessary. If the situation requires me to have the rig right at the base of the mast, I just tie the excess ladderline to something to keep it out of the way and so it doesn’t coil and isn’t laying on the ground. And I do try to make sure the ladderline isn’t swinging around - again Velcro to the rescue, as Eric shows in his photos.
I do carry an additional section of ladderline that I can use as a spliced in section (with some spade connectors for a quick splice) if I need to set up farther away from the mast, but haven’t had to do so. I use a small MFJ tuner with a self-contained 4:1 balun.
For decades I’ve used only tuned feeders for multi-band wire dipoles, both at home and operating portable, because I just think it is much more efficient and effective than coax. Changing bands is quick and easy, and I’m not losing precious power as I would with coax. YMMV.
In reply to MM0FMF
Hello everyone I just finished a dipole ysterday 22 foot per side and 8m of MFJ-18T050 300 ohm tv twin lead. I used that lenght of ribon as its all i have. I ended up using a ldg 1t1 balun with best results on the end with a short run of coax to my KX3. I did test a 4t1 ldg balun but the rig did not like tuning on 24 mhz but it was better behaved on all bands using the 1t1. It was a very sharp tune on 40m and a few kc qsy would result in a retune.
So now my next experiment today is make it into a 88 foot link dipole to see those results it will tune better on 40m for sure and lower possibly. I have read a lot about the Norcal or 88/44 foot antenna, something else to add to my next session of antenna madness.
73 de Ian vk5cz …
i allways take two short pieces of different lenghts of ladder line with me. at example one lenght of 1,5mtrs and one of 3mtrs…so if its not possible to tune the antenna on a band i add another short piece of ladder line to the given feeding line with small connectors. in most cases i can tune all bands without problems. so everytime i take two short pieces of different lenghts of ladder line with me as a add on to the antenna system if needed !
In reply to G8ADD:
Interesting data, thanks Brian. Very topical for me, as my home station “lighting flex” twin feeder snapped in high winds a couple of days ago, and a new year calls for a new antenna configuration!
In the context of a summit activation, I would still not worry about a meter or two of twin feeder lying on the ground, based on the losses measured by G3TXQ through a 60 foot length.
Keeping the whole length of the feeder clean would perhaps be the more important consideration…
Indeed, Adrian, the performance of my home doublet seems poorer than it used to be, I suspect that a wipe over of the feeder with a dilute surfactant might be beneficial!
Indeed, Adrian, the performance of my home doublet seems poorer than
it used to be, I suspect that a wipe over of the feeder with a dilute
surfactant might be beneficial!
HNY
Brian G8ADD
Does that mean something like Rain-X, the car windscreen water-shedder? Just wondering about getting my spray out of the garage for some home-aerial maintenance…
Les