https://www.marcelpost.com/wiki/index.php?title=Low-cost_antenna_shootout_70cm&feed=atom&action=historyLow-cost antenna shootout 70cm - Revision history2024-03-29T05:52:44ZRevision history for this page on the wikiMediaWiki 1.39.5https://www.marcelpost.com/wiki/index.php?title=Low-cost_antenna_shootout_70cm&diff=2869&oldid=prevAdmin at 22:34, 14 August 20172017-08-14T22:34:15Z<p></p>
<p><b>New page</b></p><div>These days, many low-cost antennas for the 70cm ISM band can be obtained from online sellers though eBay and Amazon. I was curious to see how well they performed in a variety of environments. I was also interested to see how well my own design, the 'Captcha' PCB dipole, would stack up against these commercially available antennas.<br />
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<br />
Here, we put several models to the test.<br />
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The contestants are:<br />
<br />
{| style="background-color:#f9f9f9;" cellpadding="10" cellspacing="0" border="1"<br />
|style="background-color:#f2f2f2;"|<b>Name</b><br />
|style="background-color:#f2f2f2;"|<b>Radiation Pattern</b><br />
|style="background-color:#f2f2f2;"|<b>Gain (specified)</b><br />
|style="background-color:#f2f2f2;"|<b>Price</b><br />
|-<br />
|[[File:433-centre-loaded-quarter-wave-vertical.jpeg|none|thumb|250px|centre-loaded quarter wave vertical]]<br />
|Omnidirectional<br />
|3dBi<br />
|AU$7.67<br />
|-<br />
|[[File:433-j-pole-pcb.jpeg|none|thumb|250px|J-Pole on a PCB]]<br />
|Omnidirectional<br />
|?<br />
|AU$1.52<br />
|-<br />
|[[File:433-short-helical.jpeg|none|thumb|250px|short helical quarter wave]]<br />
|Omnidirectional<br />
|2-3dBi<br />
|AU$1.20<br />
|-<br />
|[[File:433-sleeve-dipole.jpeg|none|thumb|250px|sleeve dipole]]<br />
|Omnidirectional<br />
|6dBi<br />
|AU$3.59<br />
|-<br />
|[[File:433-captcha-dipole.jpg|none|thumb|250px|captcha pcb dipole]]<br />
|Omnidirectional<br />
|?<br />
|US$9.01<br />
|-<br />
|[[File:433-moteino-monopole.jpg|none|thumb|250px|quarter wave vertical 'monopole' 150mm wire antenna]]<br />
|Omnidirectional<br />
|?dBi<br />
|(free)<br />
|-<br />
|[[File:433-PL259-short-helical.jpeg|none|thumb|250px|short helical with PL259 connector]]<br />
|Omnidirectional<br />
|2.5dBi<br />
|AU$14.09<br />
|}<br />
<br />
<br />
How the range was determined<br />
<br />
<br />
I tested these antennas on low power at 2.5uW (-26dBm). For range testing I wrote two sketches; one for a stationary 'base' unit, and one for the mobile unit that I took with me whilst walking away. The mobile unit is equipped with a LED and a piezo buzzer and sends out a packet every 2 seconds. When the base unit receives a packet, it re-sends it at full power (100mW, 20dBm) back to the mobile unit. When the mobile unit receives the re-sent ack packet a short beep is sent to a piezo transducer. That tells me that the base station can still receive the packets. I know that I've reached the range limit when I stop hearing confirmation beeps. For this test I did not rely on GPS as the distances are relatively short and GPS would probably introduce a significant measurement error of several metres. Instead, I just walked it out and counted my steps. This test is all about the relative range between the various antennas, NOT the real range when using radios at maximum power.<br />
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[[File:Range-test-antennas 2017.jpg|none|thumb|250px|The Candidates]]<br />
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Terrain <br />
<br />
[[File:Range-test-base-station 2017.jpg|none|thumb|250px|The Base Station and terrain]]<br />
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I tested in a small park surrounded by trees and residential buildings, a level field, no immediate buildings nearby, dry soil ground.<br />
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The distances shown below were obtained by attenuating the signal down to -26dBm using a 30dB SMA attenuator. This was done purely to limit the range to well within the size of a small park where I did the testing.<br />
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[[File:Range-test-mobile-unit 2017.jpg|none|thumb|250px|The Mobile Unit with a 30dB attenuator]]<br />
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<br />
The results:<br />
<br />
<br />
{| style="background-color:#f9f9f9;" cellpadding="10" cellspacing="0" border="1"<br />
|style="background-color:#f2f2f2;"|<b>Name</b><br />
|style="background-color:#f2f2f2;"|<b>Distance</b><br />
|style="background-color:#f2f2f2;"|<b>Rank</b><br />
|-<br />
|centre-loaded quarter wave vertical<br />
|50m<br />
|4<br />
|-<br />
|J-Pole on a PCB<br />
|21m<br />
|6<br />
|-<br />
|short helical quarter wave<br />
|58m<br />
|2<br />
|-<br />
|sleeve dipole<br />
|55m<br />
|3<br />
|-<br />
|captcha pcb dipole<br />
|75m<br />
|1<br />
|-<br />
|quarter wave vertical 16cm wire antenna<br />
|31m<br />
|5<br />
|-<br />
|short helical with PL259 connector<br />
|N/A<br />
|N/A<br />
|}</div>Admin