My friend just passed her Technician exam, and is interested in getting on digital modes. In the US, that means she’s limited to 10m and 6m (and higher, but probably not much dx there). I’m going to help her build an antenna, and I’m thinking a linked EFHW antenna will be a good choice for summits.
Has anyone done tests to determine which toroid mix is the best for the matching unit?
The -43 mix seems to be the choice for antennas in the lower HF bands, but it could be more lossy on 10&6. I haven’t seen any results for the best choice on these bands.
Actually, you don’t have to use ANY toroid, if you don’t want to. M0UKD’s web site suggests that a more than 3:1 frequency range can be covered with a “coil/capacitor” tuned RF transformer, which, I suspect, has less loss, and could be built with a pill bottle or small section of PVC pipe. He does not have a specific design for 10/6, but you could obviously scale his 40/10 jobbie.
73
John, VK4TJ
You could try building a vertical with two wires, one for each band coming off the same unun. To give a bit of separation between them (although I’m not sure how necessary it is) the unun could be on the ground to one side and the wires went to different points on the mast, perhaps with a bit of shock cord for the final foot or so. A counterpoise or two completes it. The mast probably only needs to be 6m to support a halfwave 10m wire. Alternatively, create a fan dipole which for just two high bands would be compact and easy to deploy.
1/4 wave GP. 10m is 4 pieces of wire 2.5m long. Make it up and trim for resonance. The make a new 6m section nominally 1.5m long. Replace 10m radiator and trim to length. Simple, light and no matching unit to make.
The big plus of EFHW antennas is that they are easy to mount. But as @MM0FMF said, 1/4 wave verticals are easy to build and reliable, when nobody trips over a counterpoise. Linked dipoles are also a viable possibility.
But when deciding for an EFHW, instead of using a broadband coupler, there are other matching techniques that may give better results on higher frequencies, but only for a single band, e.g. Zepp, Fuchs or simply using an LC-network.
By coincidence, yesterday towards the end of my activation on HB/BL-014, I experimented with a 12m-band vertical EFHW, by just hanging a wire down my glass fiber mast. This lead to a contact with Belize:
Well, I’d be careful there. It’s possible to make the matching network efficient so the losses in the matching network are the same order as a length of coax. There’s loss in both so careful design and construction is needed to ensure a low loss repeatable design.
However, for people new to the hobby and construction I would always recommend a centre fed dipole as the first antenna to build as it’s the most likely design to just work. Then they can play making it a link dipole or trapped dipole. Then enter the world of end-fed matching units. But certainly they should be building wire antennas.
When you say you want an EFHW, do you mean with a wideband transformer, or with a choke? You can just wrap a few turns of coax round a ferrite and it would still work as an End Fed, although it would technically be a dipole or Windom. They are multiband and very simple to make:
The technique is also used for the Flowerpot antenna:
I haven’t got any data to show, but type 61 is often recommended for higher frequencies. Do you have an antenna analyser? If so, why not get both type 43 and 61 and post the results here. What others have said is true, at higher frequencies you may not need a ferrite at all; an antenna analyser is what you need first and foremost.
4x 1/4wave wires. In mine, the 3 radial wires meet at the earth side of a BNC coax socket and the radiator attaches to the centre of the coax. The 3 radials slope down at 45degs. and trim to 50Ohm. Mine is fed with about 3-4m of RG58 which is low enough loss at 24/28MHz. The radials have a Bulldog paper clip at the ends and they just clip onto the guys for the mast. Takes seconds to erect.
Just a humble suggestion for 6 metres. Build a Extended Double Zepp for 2 metres and fold back both ends about 1.5" should put you resonant for 6 metres as well. 2 bands, 1 antenna.
Most solutions suggested already are definitely good choices for portable operations and easy to erect. However, thinking of gaining experience with self-built antennas, I would not rule out the 50 Ohm Oblongs as described by DK7ZB. DK7ZB Oblongs I built the 10 m version myself and was very pleased with its performance.
Vy 73 de Peter, DO4TE
Hi,
I use RG316 if coax weight is an issue. About 8 m. The loss on 6 m is no more than the ferrite loss on 6 m imo. On 10 m it is probably less.
I have several EFDs and can see no difference in their erection compared to a centre fed dipole if you are using a single mast.
If you are using it as a sloper from a tree then yes it might be better. I find erecting a 7 m pole without guys fast enough and the inverted Vee shape gives some vertical radiation for CF and EF
I have used RG58 on dipoles and by taping it to the mast I avoid additional bending.
Some folk seem wedded to the end fed concept. Fine. Some say it was the end fed antenna that caused the arc that destroyed the Hindenburg. I don’t know but in an airship an end fed is sensible. Just reel it in before landing.
