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Loft/Attic antenna ideas?

Hi. I have recently moved into a new house and I’m looking at putting an antenna up in the loft/attic. It is around 6metres wide (East/West) and 7metres(North South). The ridge of the roof runs East/West. The loft is large enough to stand up in the middle.

I’m thinking a simple dipole to start but possibly could fit a wire beam in there, I know it wouldn’t rotate. I prefer to use 40m,20m and occasionally other bands, 17m,15m,10m, 6m rarely but nice to have

any past knowledge of this? tips? tricks? warnings?

Thanks
Anthony
M0VED

Hi,
a good tip voor you:
get the book Stealth antennas (RSGB) written by Steve Nichols G0KYA starting at page 29: Using your roof space.
Starting page 37:stealth antennas for the loft.
Hope this helps you.

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Hi Anthony,
A magnetic loop antenna would fit your requirements, but (presuming you built it yourself) you would need to work out how to tune and rotate it remotely (there are commercial models that do all that, but in my opinion, they are too expensive).

You could install a full wavelength horizontal loop for 20m, that with an ATU could be made to work on 15 & 10m (no balun, just a Q-section in the feed). Then if you break the connector at the shack and just use the centre conductor of the wire you have a random length wire, that with an ATU (with Hi-impedance input, e.g. MFJ-993B) you could tune against a ground stake and probably use it on 40m.

Alternatively rather than breaking the coax braid out, if you connect it and the centre core together, and tune agaist that ground stake again, you have capacity hat loaded vertical that again with luck should work on 40m.

The problem you can have with löoft antennas is the closeness to all of your electrical equipment which could generate RFI, that an external antenna might not pick up so strong or even at all.

Hence if you can manage to get a wire outside to work as an antenna it will be better than a loft mounted one.

Are the gutters on your house metal or plastic? If metal, they have been known to work well as a transmitting antenna but be carefull that they are not close enough for someone to touch while you are transmitting, especially if you are in a shared building.

73 Ed.

PS: Just a thought - watch out for metal backed insulation bats - if they are up there in the loft (as they often are these days) they will detune whatever antenna you put up there!

Hi Anthony,
I once had a Lattin multiband antenna in a roof space. The problem was all the TV antennas were up there too.

I suggest you make up an off centre fed dipole. Feed it with 75 ohm low loss tv coax.

Leave both ends about 2 ft long on the short end and 4 ft long on the long end. Run the dipole diagonally across the slope of the root from one corner to the opposite one. This will accommodate about 30 ft of wire. The physical centre of the wire shold be at the ridge. Bend the ends to run parallel with the 20 ft widths. Keep the wires about 4 inches clear of the roof and
4 inches away from the building. This will help with minimising detuning in wet weather.
Run the last bits of wire back along the longer sides. Keep 4 inches clear of the building.
Run the coax at right angles to the main part of the antenna as much as you can on its way to the shack.

Check for resonance in 40 and 20 m. If you are lucky the SWR will be less than 3:1. No problem if it isn’t. So long as the minimum is somewhere near the frequency on 40 m you want to use you will be able to use an ATU to make the rig happy. For 20 m the ATU should match up OK too.
If the 40 m and 20 m resonances are too low reduce the radiator length. If too high, add wire. Adjusting 40 m towards the lower end of the band will put the 20 m resonances near the top end.

I would concentrate on getting 40 m right and accept whatever you get on 20 m.

I would not expect much on other bands. This is an attic antenna not a multi band Yagi at 100 ft.

If you want the maximum number of bands then cut the dipole for 6 MHz and connect the centre to a 4:1 balun and install as before. Connect the bslun to a remote tuner with a short length of coax. Feed the tuner with 50 ohm coax. You should be able to get a match on most bands from 5 to 50 MHz

73
Ron
VK3AFW

Hi Anthony, we moved to the South Coast in late 2012, the rear garden is only 30ft x 20ft, I installed an OCFD from M0VCO not long after that it is 66ft long, the balun is fixed to an upright beam, just above the hatch, the short leg goes left, then runs the length of the attic, the long leg to the right, at floor level, then back towards the balun at head height, I use it every day on Data modes (FT8) and have worked all over the World, a few years ago I worked in to the USA on 10m using 5w SSB. Good luck with your experiments.

DAVID.
G0FVH.

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i actually have a 34ft commercial windom antenna i used to have at the old house until the weather brought it down. I think I’ll just try and string that up for now. see how it goes. It doesn’t tune on 40 though i dont think.

Hi Anthony @M0VED
I don’t remember where I copy this but try an similar design if you can !
Nearly yours dimensions :wink:

73 Éric

Magnetic loop is your antenna, if you can DIY go and have a look. will not talk about building one because there are plenty instructions online.
I’ve made one myself and h’ve used on SOTA also. Great performance. Can do all band’s and don’t need that many space.

see this site: http://home.alphalink.com.au/~parkerp/projects/projmag.htm
or this: https://www.youtube.com/watch?v=J2QBQ45C0b0

73’s
Mata
CS7AFM

If new is actually new, then at least you shouldn’t have a cold water storage tank up there! Having said that, my 2m and 70cm verticals and my two 6m antennas (delta loop NNE/SSW and Moxon WNW) are in the loft and they seem to cope with it okay.

Presumably your house has a restrictive covenant if it is a new build. The same applies here, but as the houses were built in 1987 no-one gives a fig any more.

It was build around 1996, there is no water tank in the attic however it has been removed by previous owners. I do have a garden with a eucalyptus tree in it. I might just use portable antennas in the garden for the time being. Getting the neighbors and XYL used to antennas in the new house/garden slowly :smiley:
I also might get round to finishing building the resonant endfed with 1:64 transformer like on PD7MAA site. the 40,20,10 version is only around 11.5m long(<40ft) that would fit on my 10m fishing pole as a sloper. The fishing pole and installation would only take minutes.

I think there is in effect a 20 year time limit on restrictive covenants - but you may need to be able to prove it has been broken for 20 years. We have a sun room which breaks a covenent - and no-one gives a fig, but after 20 years it is now unenforceable. Now if only I could get away with a sixty foot mast the same way… :slight_smile:

Oh and a combination of DX Wire Ultralight and clear perspex insulators can hide an antenna quite well, I struggle to see the 160m doublet in the wood - and that is when I know what I am looking for.

Do the classic “screw-with-mind” trick. This was told to me by an old guy (now SK) from my old club who moved into a McCarthy & Stone retirement apartment. There was no specific antenna limit but he knew human psychology very well. He got some 3mm black nylon cord and made sure he was seen running it from a 1st floor (2nd floor in US) bedroom to a tree in the gardens. He left in place and left all his HF gear boxed in a different room and waited. He didn’t have to wait long till the knocks on the door started about him creating interference. A few days later the site warden came around and started laying down the law about legal proceedings if he didn’t remove the antenna as it was causing everyone in the complex interference problems. Once the warden had done his spiel the ham said he had no idea what the guy was on about and invited him in to show him the aerial. His description of the warden’s face when he saw the antenna was nylon string and the rest of the spool was sat on the windowsill was wondrous. “I’ve put that up to support bird feeders near the windows so I can watch them easier. Now if other residents are complaining about interference then it can’t be anything to do with me. I don’t want a written apology from you this time but if there is any more slanderous gossip I’ll seek legal advice.” The warden skulked away. A few weeks later he swapped the nylon string for a black wire and used it as a long wire with the central heating pipes for earth. He never had any complaints.

So set up the fake black string first to draw out neighbours etc. so you can sow the seeds of doubt in their minds before you do anything. XYL can get used to what will be dangling in the garden.

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A while back (at my previous QTH) I guyed a vertical (about 25 feet tall IIRC) using some thin black guy rope I had at the time. They were hard enough to see that the pigeons would fly into them from time to time…

At that previous QTH it was all of a day or three between my putting up my first outdoor HF antenna and getting my first complaint about mobile phone interference.

The HF antenna I tried in the large loft there never worked that well.

It’s been nearly 4 months now since my upgraded aerials went up. A couple of friendly enquiries, but no complaints (where’s the fingers crossed emoticon?)

Back to the op - plus one for the stealth antenna book. I went for the OCF dipole in the end; going to trees at either end of the garden. It is quite unobtrusive. The mast and VHF vertical are the main visible elements.

:crossed_fingers:

None of my neighbours have complained about RFI - but they are all socially dstanced by at least 2m, vertically :rofl:

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