Quadrifilar Helix - Revision history

WikiSysop at 05:18, 11 August 2022

2022-08-11T05:18:00Z

← Older revision		Revision as of 05:18, 11 August 2022
Line 91:		Line 91:
	==Results==		==Results==
	[[File:Z.png\|thumb\|400px\|left\|Impedance of the QFH over the frequency range of 410MHz-460MHz.]]		[[File:Z.png\|thumb\|400px\|left\|Impedance of the QFH over the frequency range of 410MHz-460MHz.]]
	[[File:~~SWR~~.png\|thumb\|400px\|right\|SWR of the QFH over the frequency range of 410MHz-460MHz.]]		[[File:Swr.png\|thumb\|400px\|right\|SWR of the QFH over the frequency range of 410MHz-460MHz.]]

	The antenna is fairly well matched, with an impedance of 55.3 + j18.4 ohms at the design frequency of 445.925MHz. The SWR is 1.43 at the design frequency and stays below 2.0 for the 430MHz-450MHz US Amateur band, corresponding with an effective radiated power of 96.9% at the design frequency, and 88.9% over the Amateur band (calculated by the formula Power % = 100 * (1 - ((SWR-1)/(SWR+1))<sup>2</sup>) ).		The antenna is fairly well matched, with an impedance of 55.3 + j18.4 ohms at the design frequency of 445.925MHz. The SWR is 1.43 at the design frequency and stays below 2.0 for the 430MHz-450MHz US Amateur band, corresponding with an effective radiated power of 96.9% at the design frequency, and 88.9% over the Amateur band (calculated by the formula Power % = 100 * (1 - ((SWR-1)/(SWR+1))<sup>2</sup>) ).

WikiSysop: /* Results */

2016-01-08T23:02:51Z

Results

← Older revision		Revision as of 23:02, 8 January 2016
Line 90:		Line 90:

	==Results==		==Results==
	[[File:~~QFH_Z_Plot~~.png\|thumb\|400px\|left\|Impedance of the QFH over the frequency range of 410MHz-460MHz.]]		[[File:Z.png\|thumb\|400px\|left\|Impedance of the QFH over the frequency range of 410MHz-460MHz.]]
	[[File:~~QFH_SWR_Plot~~.png\|thumb\|400px\|right\|SWR of the QFH over the frequency range of 410MHz-460MHz.]]		[[File:SWR.png\|thumb\|400px\|right\|SWR of the QFH over the frequency range of 410MHz-460MHz.]]

	The antenna is fairly well matched, with an impedance of 55.3 + j18.4 ohms at the design frequency of 445.925MHz. The SWR is 1.43 at the design frequency and stays below 2.0 for the 430MHz-450MHz US Amateur band, corresponding with an effective radiated power of 96.9% at the design frequency, and 88.9% over the Amateur band (calculated by the formula Power % = 100 * (1 - ((SWR-1)/(SWR+1))<sup>2</sup>) ).		The antenna is fairly well matched, with an impedance of 55.3 + j18.4 ohms at the design frequency of 445.925MHz. The SWR is 1.43 at the design frequency and stays below 2.0 for the 430MHz-450MHz US Amateur band, corresponding with an effective radiated power of 96.9% at the design frequency, and 88.9% over the Amateur band (calculated by the formula Power % = 100 * (1 - ((SWR-1)/(SWR+1))<sup>2</sup>) ).

WikiSysop: Created page with "This is a project to create a UHF quadrifilar helicoidal antenna for use with a ham radio to transmit APRS data from the high altitude balloon payload. File:QFH-5.jpg|thumb..."

2015-08-06T22:24:29Z

Created page with "This is a project to create a UHF quadrifilar helicoidal antenna for use with a ham radio to transmit APRS data from the high altitude balloon payload. File:QFH-5.jpg|thumb..."

New page

This is a project to create a UHF quadrifilar helicoidal antenna for use with a ham radio to transmit APRS data from the high altitude balloon payload.

[[File:QFH-5.jpg|thumb|right|Final result of the QFH build.]]

==Summary==
A quadrifilar helix, or QFH for short, is a near-omnidirectional antenna comprised of two square loops usually 1 wavelength long each, twisted a half turn and offset 90 degrees from each other. It is a balanced antenna, so it requires a balun when fed by an unbalanced input (such as coax). In this build, I used a current balun, made of 7 turns of coax around the 0.5" plastic tube. The sizes for the antenna were found using the online calculator at http://www.jcoppens.com/ant/qfh/calc.en.php

The design parameters were as follows:

* '''Design frequency:''' 445.925MHz
* '''Number of turns:''' 0.5
* '''Length of one turn:''' 1 wavelength
* '''Bending radius:''' 1.75mm
* '''Conductor diameter:''' 1mm
* '''Width/height ratio:''' 0.44

The feed point is configured as is shown in [http://w6nbc.com/articles/QST1009QFH.pdf W6NBC's article].

[[File:QFH Feedpoint.png|thumb|right|250px|QFH feed point configuration.]]

The total build time for this antenna was approximately 4.5 hours.

===Bill of Materials===
{| border="1"
|style="text-align:center;" |'''Part'''
|style="text-align:center;" |'''Quantity'''
|style="text-align:center;" |'''Unit Cost'''
|style="text-align:center;" |'''Total Cost'''
|style="text-align:center;" |'''Source'''
|-

|SMA Male Connector
|1/5
|style="text-align:right;" |$2.51
|style="text-align:right;" |$0.50
|[http://www.dealextreme.com/p/sma-1-5-diy-connector-plug-5-pack-5132 Dealextreme]
|-

|RG-174 Cable
|1.5m/3m
|style="text-align:right;" |$1.59
|style="text-align:right;" |$0.80
|[http://www.ebay.com/sch/i.html?_nkw=3M+RP-SMA+Cable eBay]
|-

|8" Bamboo Skewers
|2/100
|style="text-align:right;" |~$4
|style="text-align:right;" |$0.08
|Grocery Store
|-

|1'x0.5" Plastic Tube
|1
|style="text-align:right;" |~$1
|style="text-align:right;" |~$1.00
|Craft Store
|-

|18ga. Solid Core Wire
|4.66'/100'
|style="text-align:right;" |$6.89
|style="text-align:right;" |$0.32
|[http://www.radioshack.com/product/index.jsp?productId=2036274 Radio Shack]
|-

|PCB
|0.25in2/54in2
|style="text-align:right;" |$8.69
|style="text-align:right;" |$0.04
|[http://marvac.com/detail.aspx?ID=22112 Mar Vac]
|-

|'''Total Price'''
|
|
|style="text-align:right;" |'''~$2.74'''
|
|-
|}

===Construction Photos===
<gallery widths=150px heights=100px perrow=5>
File:QFH-1.jpg|Materials for the QFH collected, SMA connector put on coax.
File:QFH-2.jpg|Feedpoint PCB soldered and balun created.
File:QFH-3.jpg|QFH with top horizontal portions soldered to feedpoint.
File:QFH-4.jpg|The larger loop of the QFH complete.
File:QFH-5.jpg|Complete antenna.
</gallery>

==Results==
[[File:QFH_Z_Plot.png|thumb|400px|left|Impedance of the QFH over the frequency range of 410MHz-460MHz.]]
[[File:QFH_SWR_Plot.png|thumb|400px|right|SWR of the QFH over the frequency range of 410MHz-460MHz.]]

The antenna is fairly well matched, with an impedance of 55.3 + j18.4 ohms at the design frequency of 445.925MHz. The SWR is 1.43 at the design frequency and stays below 2.0 for the 430MHz-450MHz US Amateur band, corresponding with an effective radiated power of 96.9% at the design frequency, and 88.9% over the Amateur band (calculated by the formula Power % = 100 * (1 - ((SWR-1)/(SWR+1))<sup>2</sup>) ).