Is there a simple, DIY, antenna suitable for HF receive only?

Question

So the antenna I'm thinking about doing might be^* way too large for my property.

Is there another simple, cheap, DIY antenna I could try on my receiver? I know I'm going to want to hook it up and have a listen before the last solder joint has cooled. Ideally it would cover 160 m to 10 m reasonably well.

The most complicated antenna I've built was a Gray Hoverman for UHF reception. It would be nice if it weren't much more complex, but if it's inexpensive and good enough I'm willing to do a bit of work for an antenna I'll use a long time.

I'm not interested in aiming right now, so an omnidirectional antenna would be best. I do have a 25' attic I can use if needed.

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Answer 1

Receive antennas are the easiest thing ever. You just need two things:

1. something that conducts electricity
2. another thing that conducts electricity

Attach one to the center contact on a BNC connector. Connect another to the shield. Boom, done. If you can't find two things, then one can be the Earth.

Alternately, you can use two ends of one thing that encircles something that permits magnetic fields (like, air).

Until you are approaching a significant fraction of a wavelength (like, 1/4 wavelength), then making either thing bigger will get you more signal. However, once you have enough signal that you are well above your receiver's noise floor, more signal won't make you receive any better: it will just give you louder noise. I'd say, however much space you have, make it that big.

Don't worry about tuning, or impedance matching. This also will increase the fraction of the energy received by your antenna coupled to the receiver, but again, once you have enough to overcome the receiver's noise, more is of absolutely no help. See What is the relationship between SWR and receive performance?

Don't worry about polarization. At HF most of your signals will arrive via the ionosphere which is constantly swirling and changing the polarization of received signals. Whatever polarization you pick, it will be the wrong one in 30 seconds, so don't worry about it.

If you really must worry about something, worry about getting your antenna away from noise sources. Your house, being full of all varieties of noisy digital electronics, is very noisy. If you can get an antenna away from these things, that's good. You must also take care to avoid making the feedline part of the antenna. See Using a balun with a resonant dipole Although that question asks about resonant dipoles, the answers apply to any type of antenna.

Answer 2

There is nothing simpler than a random length wire. It doesn't have to be strung up or even straight, though, obviously, those would improve it's performance. Of course the ironic thing about a random length wire antenna is that the most effective lengths aren't actually random. They work best when the antenna is at least a quarter wavelength at the lowest operating frequency, 65' for 80m, for instance.

To maximize the effectiveness, and have something useful down the line, you could build a small tuner. An L-network random wire tuner is probably the simplest matching network in existence, designs about on the net. Like this one: How to Build a Cheap Antenna Tuner or this one: SWL Receiving Antenna Experiments.

Answer 3

Not real thrilled about the attic; if you can go outdoors, I'd recommend a random length horizontal loop, as described at http://www.k4qky.com/the-station/the-antenna and http://www.smeter.net/antennas/large-transmitting-loop.php for its design simplicity.

Answer 4

For receiving horizontal antennas pick up a lot less manmade noise than vertical ones. So if I were you I'd try to put up a horizontal one.

Answer 5

I'd say, if you plan on putting it in the attic /loft, then figure out where your wiring is, and in what orientations, and let that dictate the size and orientation of your antenna. Smaller might be better if it means you avoid closer interactions with noisy wiring.

Most of my wiring runs horizontally EW along the loft and vertically down the house, and my lowest noise loft antenna was NS along the inside of the roof (actually at a diagonal) therfore at eight angles to most of the closest wiring.

I put a horizontal wire in the garden and it picks up more local noise, probably due to orientation relative wiring in to the houses around...and the huge number of dishwashers and washing machines generating the noise.

My property is small. All my antennas are tuned or loaded. The best receive I eve had though is on a small tuned loop. You can null out a particular source of noise, and it's pretty narrow bandwidth. You can make one out of cheap stuff if you're not planning to transmit.

Answer 6

The "LoG" or "Loop on Ground" is a simple antenna to get you going. http://www.kk5jy.net/LoG/?fbclid=IwAR0dDk21M6XqZg7IwQ5NE7ggmS5Ux6Ivc_-_gtSZpE9Qbeu4EB9h5T4NGyU

Like you, I have limited space in my yard, so the LoG works out nicely at a perimeter of 60 feet.

You don't have to build the transformer yourself, as Black Cat Systems makes one for receiving already: https://www.blackcatsystems.com/rf-products/cyclops_rf_ham_shortwave_radio_matching_transformer.html. Chris at Black Cat is a Jedi Master of HF receiving antennas and can get you squared away.