[Logo] Anarduino and HopeRF Community Forum
  [Search] Search   [Recent Topics] Recent Topics   [Hottest Topics] Hottest Topics     [Groups] Back to home page 
[Register] Register / 
[Login] Login 
Antenna??  XML
Forum Index » Anarduino
Author Message
edringel



Joined: 15/08/2014 20:30:14
Messages: 1
Offline

Hi,
New to this product, would appreciate any advice or direction about an antenna for the 400 MHz series radios. Looks like a piece of wire would do, but if anyone has specific suggestions about length and/or geometry I would appreciate it. Thanks in advance.

Cheers.

Ed
Rick



Joined: 30/05/2014 22:08:56
Messages: 93
Offline

edringel wrote:Hi,
New to this product, would appreciate any advice or direction about an antenna for the 400 MHz series radios. Looks like a piece of wire would do, but if anyone has specific suggestions about length and/or geometry I would appreciate it. Thanks in advance.

Cheers.

Ed


A simple monopole antenna should work fine.
Many suggest for 433Mhz, you can use #20 guage wire of length 17.3cm (6.81 in).

Did an internet search just now, and found on jeelabs forum, a list of calculated values--which look reasonable:
433 1/4 wave = 164.7mm
433 1/2 wave = 329.4mm
433 full wave = 692.7mm

868 1/4 wave = 82.2mm
868 1/2 wave = 164.3mm
868 full wave = 345.5mm

915 1/4 wave = 77.9mm
915 1/2 wave = 155.9mm
915 full wave = 327.8mm

Anyone else who would like to digress and add to this, you're more than welcome.
There's certainly a plethora of info out there...

This message was edited 1 time. Last update was at 21/08/2014 01:35:38

d00m



Joined: 19/10/2015 17:21:10
Messages: 32
Offline

Online calculator

http://www.onlineconversion.com/frequency_wavelength.htm
jeremyvnc



Joined: 02/11/2015 10:40:42
Messages: 8
Offline

Thanks for the link to the calculator. In my testing with the RFM69HCW modules, I didn't see a difference between the 1/4, 1/2, and full wave antenna lengths. They all seemed to drop off at the same distance and it didn't really hurt or change the close range reliability. I do know that without any antenna, the range is severely limited and easily blocked by a person standing in the LOS.
stevech



Joined: 07/07/2014 18:07:27
Messages: 91
Offline

jeremyvnc wrote:Thanks for the link to the calculator. In my testing with the RFM69HCW modules, I didn't see a difference between the 1/4, 1/2, and full wave antenna lengths. They all seemed to drop off at the same distance and it didn't really hurt or change the close range reliability. I do know that without any antenna, the range is severely limited and easily blocked by a person standing in the LOS.
Differences among those antennas is just 2-6dB or so. Each will differ in impedance matching (VSWR). Best to use 1/4 wave.

Range is more affected by choice of channel width and bit rate than by a few dB of antenna differences. And of course, line of sight-ness.
kjmclark



Joined: 26/02/2016 15:40:00
Messages: 1
Location: Ann Arbor, MI
Offline

Two related questions. (Never sure if the local etiquette is to always start a new thread or find the closest existing one!)

1) OK, but how do you actually attach an antenna? I have some SMA female solder-on connectors I could attach (like these: http://www.ebay.com/itm/1-x-New-SMA-Female-PCB-Edge-Mount-RF-Jack-Solder-Connectors-US-stock-FPV-Antenna-/151662456292?hash=item234fc96de4:g:KWAAAOSwEeFVSAAM), but how would I attach those? Is there some recommended antenna attachment?

2) I have two different antennas I want to attach. I have Yagi antennas tuned for ~900MHz (my anarduinos are all 915MHz) that have a female N-type attachment. I have some male SMA to male N-type cables I was planning to use. I also have some short whip antennas (SMA) that didn't work for what I had intended, but they'll be be really short for 915MHz. They're only a little over an inch. OK for testing maybe. Should I stick with SMA for everything?

My project involves two locations that are only about 100ft apart, and a third that's about 500 ft south of the more southern of the first two. They're all pretty much in a line (with clear line-of-sight). I was planning to use the yagis for the distant ones, with just a whip for the third.

Thanks!
stevech



Joined: 07/07/2014 18:07:27
Messages: 91
Offline

Yagi - needs to connect to a radio board that has SMA or U.FL. If neither, you can wire an SMA to the board using 1 inch or so or less of wire for the center conductor, and for ground, take the braid from coax cable and a hot soldering iron and make a fat ground connection between the ground plane near the antenna connector.

Yagi at 900MHz band would need lots of elements to get enough gain to matter. Like 4 ft. or more long.
Mount radio in weatherproof box on mast with antenna to keep coax from antenna to radio very short.

Choose narrowest possible channel width and data rate - these affect range a great deal.
 
Forum Index » Anarduino
Go to:   
Powered by JForum 2.1.9 © JForum Team