I had been playing about with the height and angles, my pole is a 10m fish pole. I settles on 6m high (not taking the higher sections with me) and a 8m radius. At those dimensions 40m just fits (ends about 50cm above the ground)
I havent chosen this time to do 30m and 60m, as my CW is attrocious (but i love it, so really must improve it) and i dont have the 60m NoV as yet.
I might try a bit of CW whilst im in scotland, so if you hear some terrible, erratic, but slow morse, it could be me. Note that i have a tendency to send wayyy faster than i can take it, so expect lots of calls to QRS!
As my CW is also atrocious, terrible, erratic and slow etc we should manage OK.
Don’t be afraid - just doooo it!
I shall be operating as F/M0TUB/P in the next week or two so will look out for you. The is only the one SOTA summit within a couple of hours drive our /P QTH and I am not sure if the Managing Director will grant me a leave pass for the day. Perhaps I will take her shopping and see if I can earn a few ‘Brownie’ points!
It will be sometime in the week starting 27th that im in scotland. It was going to be just me and my eldest lad, but the boss wants to come up the hills too (she loves walking but has no radio interest!), but its an extra person to carry a spare battery
No Balun. I doubt a balun would have any advantage, and is just more weight.
Exactly! I have been using coax-fed HF dipoles for over 50 years, and I have never found a balun makes the slightest difference. As far as I’m concerned, it is quite unnecessary. (It’s a different story on VHF/UHF).
My dimensions for a 20m dipole are 16ft 6 inches per leg, fed with either 50 ohm or 75 ohm coax. The impedance of the coax and the thickness of the wire are NOT critical!
Its based on being a time served communications engineer, public safety and
broadcast.
Yes, there could well be some common-mode current due to the unbalanced feed,
but its effect is likely to be minimal, and other than pattern degradation,
its likely to be of little concern. Im not likely to cause much RFI on a
mountain top!
There speaks the voice of experience … and common sense!
I used soldered radio control bullet connectors in my linked dipole
Thanks for the suggestion Richard. I use 2mm “banana” plugs with the socket mounted on the link plate, but they’re quite expensive for what they are - very easy to use though and no fiddling about when it is sub-zero. I kept the links as small as I could small as they can be a pain when using wire winders… especially when they wind in just as you are about to change direction.
I find the bullet connectors do the job. They are rated to quite a high current, but the size is small so they don’t get in the way on the winder. I don’t have any problem changing the links as they mate quite nicely. My first link dipole used anderson powerpoles, but I had a couple of these break off. These have lasted a lot longer.
I used 14/0.2 wire to keep the weight down, and the 2mm connector is about the same diameter.
I use 4mm banana plugs on my linked dipole. In fact, I still use the original cable tie “insulators” I first fitted when I made the thing. Cheap, light, strong & easily replaced.
A photo of one of my very cheap links is below.
Also, as I tend use the same coax feeder for various bands / antennas, I thought it prudent to fit an appropriate balun to a short length of feeder as close as possible to the antenna feedpoint. On HF this is simply a few turns of coax & I have never had any problems, so in my opinion, they are worth fitting, & certainly for upper HF & VHF use.
Well, just before taking it all down, I was showing my lad what his jobs will be on the hills, and on retesting the 20m section, it was now showing as resonant at 12MHz! So likely yet another damn crimp has failed. Glad ive ordered the 4mm connectors/switches. I’ll rebuild the whole thing when they come.
Incidentally, i use Dacron kite string as my guy line for the antennas, as its so thin and light (yet immensly strong),and as i have a 1km drum of it, I run the guy from the feedpoint insulator, and cable tie the antenna wire to it. No bulky insulators needed at the links, and no risk of the whole lot collapsing should a link come apart.
Slightly concerned that you are having so many failures with crimps. These have been used in vehicles, and in many other applications, for many years and if there was a tendency to break the wire vehicle manufacturers, for one, would have ceased their use (OK - before the pedants get me - they have now ceased their use!).
Two questions to ask - is the crimp connector the correct size for the wire (or vice versa) and second are your crimping pliers the correct size for the crimp?
I have used crimped bullets for several years on my SOTA antenna and have only once had a failure (because I hadn’t done the job properly!). On the other hand I have had numerous failures of tie wraps, usually the two I use to connect between the pole & dipole centre.
I think I must have got a duff batch Barry. Its always the female side thats failed. I think thats one reason it confounded me for so long, ive never had this sort of problem with them before
All though not an active HF operator for SOTA, I do use a link dipole when at the beach, on holiday or on the HuMPs! My antenna is a 80/60/40m link dipole. I play enough on VHF and UHF so did not want to go into double figuures on the MHz read out for HF, hence the NVIS bands were selected.
After a discussion with Walt (G3NYY) on the air, I started with a 40m dipole. he said cut them to 33’ and you will be somewhere near! I did and then I kept chopping away until it was happy at 7.1 MHz. Walt is a CW man so his has to be longer of course!
In terms of links, I used crimp tags! I stripped plenty of insulation off and then fold the exposed wire back on itself. This means the crimp has plenty of wire to grip! I then crimped and have not had a problem since!
The crimps I use are the Spade shaped ones with the corresponding female version! It works well, however I will definetly consider soldering them at some point.
My insulators are clear perspex rectangles with two holes drilled in them! The strain relief is creaetd by doubling back the wire and cable tieing! Really very basic but effective.
After soldering 350 12 pin Nato plugs, then crimping the other end into a control panel! You soon get the hang of crimp tags!!! However at the same time RSI sets in!!!
Balun or No Balun? I use an 8m length of RG 58 up to a BNC socket mounted on a bit of clear perpex with 3 holes! One for the fishing pole and 2 for the wire!! I have no balun attached and it seems OK, but this is purely guess work! I have no idea if a balun will help for 80/60/40?
The best system I have seen for HF is Paul G4MD! 4 way flat ribbon/headphone/computer cable, use the inner two as strain relief and the outer 2 as open wire feeder to the legs! Then take an ATU with a balanced output and use a doublet. No need to get up and take links out and will work on almost any band. A great compromise antenna. If only people at home would chop the coax off their G5RV and extend the 300 ohm ribbon into an ATU with balanced outputs.
I have a 40m vertical for it, but its used from lower sites where the time needed to lay out the radials is more convenient. I also have a 10m slim jim, again used from lower sites. These are all part of my mobile equipment. Due to the height of these summits ive decided on the dipole for convenience. AT 6m im using only the sturdy sections of the pole (the higher sections have been removed), where the 10m would have more awkward windloading.
At 6m agl, 20m band is over a quarter wavelength high, which is no longer a ‘low’ dipole in wavelength terms.
Just how many radials are you using? Mine have only 3.
The foot print of the vertical is far less than a dipole and I can set mine up quickly and easily anywhere as I don’t have to look for anything extra to support it like a fence. In practical use it often out performs a dipole on a summit.
This time of year when 80m is closed during the day and 60m unreliable it is my antenna of choice.
The thin vertical radiator (9.5m ish) will easily load to give ½ wave at 20m and 5/8 wave at 17m; three bands with one piece of wire!
6m apex angle with a dipole on 20m is still a low antenna! It will still have a radiation pattern that is omni-directional sending the vast majority of the signal vertically upwards, not what you really want.
Carolyn
The criteria for my antennas:
They have to be simple.
They have to provide a good match to 50 ohm with out a tuner over various “ground” conditions (one of my amplifiers will die if it sees any miss-match!).
They have to be easy to erect in the worst of the weather.
Above all they have to be efficient if I’m going to carry them miles to the tops of mountains.
The old adage says “if you cant hear them you can’t work them”
I’m quite tempted to try a vertical Moxon for 20m. The claimed gain of just under 8dB sounds useful. The downside being it’s quite big (approx 3m x 7.7m) suggesting a 9 or 10m pole. Easier if you make one that you set up in a fixed direction say NA or VK etc. The size is easier to manage on 15/10m of course if the ionosphere is prepared to play. That gain sounds handy to make up for the advantage Rober G0PEB has in working S2S with VK. He’s 6degs South of me overlooking a sea path.
My maths says an inverted-V on a 6m pole for 20m with an 8m radius at the base would have the ends of the dipole around 3m AGL.
