Antenna Performance Comparison

Selecting an antenna type is always a trade-off between size and performance - quest is finding the best antenna with the smallest footprint, ease of construction and lowest RFI / electrical noise pickup.

What you need to know

1. Half-wave monopole is best (wrap conductor around one end and you're there) with good noise characteristics.
2. Add one (dipole) or two (as radials) elements to braid to  decrease noise floor in a high RFI / electrical noise environment.
3. Materials make no difference, coat hanger wire still reliably receives VHF signals.
You will get similar results on other frequencies between 100 and 1100 MHz, if you know the frequency you want to hear.
Use results here to construct an antenna for your preferences.

Importance of wavelength

A specific frequency has a corresponding radio wavelength. To get the wavelength in metres, divide 300 with the frequency in question. For instance, AIS is 162 MHZ, so the wavelength will be 300 divided by 162 = 1.85 metres. Calculations are the same for other frequencies.
Common marine antennas are 0.9 metres, (half-wave) 1.8 metres (full-wave) or 0.45 metres (1/4th wave). Other variations exist such as huge 5/4th wave antennas measuring 2.4 metres, which are solely the domain of larger vessels such as motor yachts and ships.
Antenna types tested are for VHF and up, from broadcast radio to ADSB signals. Use info here to select an antenna for a quick and easy job, lowest noise (Half-wave with 2 radials) or a compromise for size vs performance (Quarter-wave with 2 radials).
Strong shortwave signals are possible to receive even with a rubber ducky. Weaker signals need larger antennas, but shortwave is an entirely different cup of tea.

Setup

No fancy cables, equipment nor noise reduction measures used to simulate a beginner setup.
Indoor location, antennas taped to floor-to-ceiling windows. If you live in a condo, need a college dorm antenna, or cannot erect an outdoor version, select from the following options. Indoor vs outdoor is a separate question, for reference, comparison at the end of this post.
Nooelec RTL stick, cheapest 20 feet / 6 metres RG-59 coax with no shielding, no noise reduction apart from metal removed from end of USB connector.
SDRSharp 1.0.0.1174 with the excellent Level Meter Plugin, this allows me to measure peak power easily. Same gain, cables and location for all antennas, only variable is antenna to ascertain comparative performance.
Signal: local airport info system, steady signal with the same recorded voice repeated over and over again. Antennas optimised / cut using the above formulas to get full, half and quarter-wave elements.
Distance to signal 2.7 nautical miles / 5 kilometres, no line of sight, signal path over electrically very noisy environment, called "city" in english.
Materials: best available used, 2.5 mm diameter house grounding wire as antenna material just to be on the safe side, not that it really matters: see material comparison below.

Antenna types tested

Monopole: receiving element connected to center conductor. Full, Half, Quarter and 1/8th wave tested.
Dipole: two elements connected, one to braid and one to center conductor. Half and Quarter Wave tested.
Two radials: one element to center conductor, two to braid, forming a Peace-sign / Mercedes symbol. Half and Quarter wave tested.
Rubber Duckies: common on handheld transmitters and scanners, Icom (FA-S280C, around 20 USD), Uniden (stock, around 11 USD) and Baofeng (upgraded stock from UV-5B, around 13 USD). Adaptors required to connect to BNC shown.

Discone: Skyscan V1300 with 12 feet / 4 metres 50 Ohm cable, around 60 GBP / 72 EUR / 95 USD.
Evaluating performance by received audio is subjective, printscreens are not. Received signal is on the left under red vertical line, this should be as high as possible. Yellow speckles and small waves are noise, lower or less visible is better.

The Full Picture

If you use SDRSharp already and understand the following images, please draw your own conclusions.
Antennas organised by peak signal, gives you an idea what to expect noise-wise.

Quater-wave dipole and half-wave monopole same length, dipole needs twice as much (two) electrical connections. The single greatest cause of electrical problems at sea is connectors, hence the monopole recommendation.
Monopole - stock is the supplied telescopic antenna that comes with the RTL stick.
Ducky refers to rubber duckies, separate comparison against a monopole below.
Full-wavelength antennas in any form will be a challenge to mount, as 1.8 metres for marine band (156-162 MHz), and 2.5 metres total length for airband (118-134 MHz).

Adding elements to braid

Adding one or two elements (same length of wire as receiving wire) to braid reduces noise pickup, resulting in better signal-to-noise ratio.

Rubber Duckies

Common on transceivers, noise pickup is significant in an urban environment. Included here for reference, recent testing confirmed previous findings (See Marine AIS antenna post above) that with antenna at 3-4 metres above sea level e.g. cockpit mounting reliably picks up AIS signals out to around 3-4 nm.
Compared to a simple half-wave antenna the performance difference is striking, the lower noise floor is evident side-by-side.

Indoor vs Outdoor

All antennas taped to a window: this 1) simulates  common scenario when you can not erect an antenna outside, and 2) heavy rain and gale force winds outdoors.
Here's a direct comparison with a discone:

1. Outdoor means antenna 1 metres from window. 10 dB increase visible means 100 times more signal received.
2. All antennas, especially discones, should be outdoors. The concept of an indoor discone is a heavy compromise, buying a 100-dollar antenna then placing it in the corner is pointless.
3. If you cannot have an outdoor antenna, add two radials and tape antenna to window. Lower noise floor than a discone, better signal-to-noise ratio.

Materials

Same lengths, from top to bottom: Commercial telescopic antenna with BNC connector, stock telescopic, antenna from a radio, 2.5 mm diameter solid copper grounding wire, 1 mm multi-stranded copper wire, 220 V power cable.
Click on the image below to check they aren't the same, no difference whatsoever by ear.

Doubtful? Repeated test with quarter wave antennas from: Grounding wire, 220 V power cable, and gym locker hanger, all cut to the same size. Center conductor wrapped around wire, as basic as possible.

Note that signal height is the same in relation to noise floor, same performance on-screen and by ear.

Shootout: Shortwave for 50 dollars

Disclaimer: I purchased all products in this review from my own funds, no manufacturer involved.
Shortwave Listening (SWLing for short) is still a popular pastime: a simple 50 dollar receiver and turning a dial results in a cacophony of foreign broadcasts and exotic tunes.
Using a software defined radio makes finding stations easier, as you actually see the signals.
An RTL-SDR and Upconverter combo is around 50-60 dollars, a mid-range portable, such as the Eton G8 can be also had for around 50-60 dollars.
Apples to oranges? Absolutely. The RTL setup has a steeper learning curve, but rewards with more settings available to fine-tune the signal, the portable requires 3 AA batteries and your finger to find a station.

The real question is: should you get an upconverter or a portable shortwave receiver? How to spend 50 bucks? Usability, portability and personal preferences aside, the bottom line is: listening to shortwave stations. 

In the standalone corner: Eton / Grunding G8 Traveler II Digital

A palm-sized receiver with mostly positive reviews from the ham community, digital frequency readout with 1kHz tuning steps, alarm, more details in the user guide.

In the Software Defined Radio corner: Ham-It-Up Upconverter from Nooelec.

Probably the most widely used upconverter, as alternatives are more expensive. Same cost SDR UP 100 is out of production, and as I had good customer service from the manufacturer, I'd recommend this.

Testing setup

Test is purely about shortwave reception capabilities, so please no comments on either system's perceived advantage over the other; same money on the table after all, the rest is personal bias.

"SDR setup" in this text refers to Nooelec RTL 2832 820T stick + Ham It Up; "G8" refers to the Eton / Grunding G8 Traveler II Digital.

Built-in antennas: for indoor testing, the SDR setup has no antenna so I connected a telescopic antenna via adaptors to the ANT IN of the upconverter.
External antennas: two identical longwires thrown outside, lengths 20 feet / 6 m. Longwire directly connected to antenna input for the SDR setup, and wrapped around the G3's telescopic antenna base. No preamp.
Note on antennas: no-frills setup, no antenna isolators nor electrical noise reduction of any kind.
RFI: Both receivers equal distances from laptop (same electrical noise pickup), in front of a window, wire led outside and swinging 10 feet off the ground.
Power: Ham It Up powered by USB cable from laptop. G3 powered by three non-rechargeable AA batteries.
Audio setup: Laptop's built-in speakers and G3's speakers equal distance from listening position. Identical sound level ensured by tuning to broadcast FM station and measuring sound pressure level at the listening location; two free apps installed on two smartphones and a tablet utilized as I have no SPL microphone, the resulting six different readings gave identical SPL levels, so any difference in audio level or quality is due to the actual receiver system.
Gain: Gain, digital noise reduction and filter bandwidth used in SDRSharp to find best compromise between signal to noise ratio and intelligibility; no gain nor DX / local switch available on the G8.
Timeframe: both setups tested for several days, side-by-side, night and day.
Your operating enviroment will be different from mine; I devoted the largest part of my book to electrical noise reduction, as 1) simplest, 2) cheapest and 3) most effective way of improving reception. No noise reduction used in this test, because using 100+ dollar worth of cables, antenna isolators, stubs, or a better antenna system will yield better results.
The question is: should you get an upconverter or a portable shortwave receiver? How to spend 50 bucks?
This test tries to simulate an average user connecting a longwire to either receiver hoping to listen to a station of his/her choice.

Test Results

Sorry, no video this time, I made one but no audible difference with major stations / strong signals, weak signals are noise interspersed with voice, not video material.
If you can clearly see the signal in SDRSharp the G8 can receive it without any problem.
If you have to strain your eyes or play with contrast - G8 will receive it 1kHz below indicated SDRSharp frequency. Faint, but still audible.
Indoors: same performance. No surprise here, placate wife and neighbors, erect an outside antenna.
20 feet / 6m outdoor antenna: Major broadcasters - government propaganda, religious and foreign  language programming all booming in. No difference between Ham It Up and portable shortwave for enjoyment factor.
20 m (around 14.2) CW and SSB chat caught on Ham It Up, indistinguishable with the G8.
Ham It Up is very slightly better with lots of software tweaking, gain and digital noise reduction is your friend. The difference is there, but really, really small. More often than not, you end up with voice fading in and out.
Weak signals are a hit-and-miss with either setup, at least with the RTL setup, play with contrast,  gain and digital noise reduction and click on the faint waterfall. Many minutes later you might get a voice from the other of the globe. Or not.

Recommendations

1. You will be better off with a portable shortwave receiver. Easier to use. Better to listen to.
2. The Ham It Up needs a preamp. Badly. When I got tired of noise I plugged in the LNA4HF.

The Ham It Up is slightly better in terms of reception capability, added software features make it an enticing proposition. But if you're hunting weak signals (read: love to listen to hissing noise) a proper antenna, noise reduction tricks from the book and a preamp is a must.
The "better to listen to" part is impossible to explain. Live music will be always better than recorded, and to my ears, the portable is better for listening.

For shortwave listening spend your hard-earned money on a portable.

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