Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Antenna length

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

Rob Henderson

Joined: 10 Jun 2011
Posts: 16

Posted: Tue Jun 19, 2012 12:12 pm Post subject: Antenna length

Hi all

I would like to make a couple of antennas for my Glastar.

Does anyone know what the length is for dipole, or any reason not to “role my own”.

 

Transponder:

Comm:

Nav:

Marker:

Glide Slope:

UAT:

 

I will be using Garmin

GTX327

SL30

GMA340

Navworxs ADSB

Thanks in advance for all advice

-Rob Henderson

  [quote][b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

peter(at)sportingaero.com
Guest

Posted: Tue Jun 19, 2012 1:21 pm Post subject: Antenna length

It is straight forward to figure out the length required from the     frequency of the signal,

     

     velocity = frequency x wave length

     

     so wave length = vel/freq

     

     Using SI units (coz its just easier than imperial)

     

     Velocity = 3 x 10^8 m/s

     Freq = 118 to 137 MHz (so centre freq is 126.5 x 10^6 Hz)

     

     So wave length = 3/1.265 m = 2.37m ( about 93 inches)

     

     Most dipoles are half wave, a lot of aircraft antennas are quarter     wave.

     

     Wikipedia (or the Aeroelectric connection) can probably explain     better than me - less change of remembering the basic physics wrong!

     

     Peter

     

     On 19/06/2012 21:11, Rob Henderson       wrote:

     

     [quote]                       <![endif]-->   <![endif]-->                

Hi all         

I would like to make a couple of antennas           for my Glastar.         

Does anyone know what the length is for           dipole, or any reason not to “role my own”.         

          

Transponder:         

Comm:         

Nav:         

Marker:         

Glide Slope:         

UAT:         

          

I will be using Garmin         

GTX327         

SL30         

GMA340         

Navworxs ADSB         

Thanks in advance for all advice         

-Rob Henderson       

        	  Quote: 	
		  

	
     [b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

john.maccallum(at)bigpond
Guest

Posted: Tue Jun 19, 2012 3:55 pm Post subject: Antenna length

A rough rule of thumb for a free space dipole is:-

299.8/126.5=2.3669m                     (speed of light divided by the Frequency)

2.3669 * 0.97=2.2989m                   (Adjusted for the end effect)

2.2989/2=1.1494m                           (divide by 2 to make a half wave dipole)

 

1.1494m /  0.0254                             (because the US still has not converted to  metric)  (Couldn’t resist that one )

 

 

45.25 inches                                       (but make it slightly longer maybe 45.5 inches so you can adjust it by trimming equally on both sides)

 

Cut this in two to make the two halves of the dipole and keep the feed points reasonably close together,

Say around ½ an inch, then check with an SWR meter. (If the lowest SWR is below 126.5 mhz then the antenna is trimmed slightly on both ends by say 1/16” a time)

And the SWR rechecked. 

 

If you want to make a qtr wave antenna like the Comant Antennas you see on a lot of Aircraft then make the Antenna about 22.8 inches long and

Once again trim for desired SWR spread with an SWR meter.

 

Just remember not to try a use a Dipole inside a Carbon fibre structure since the Carbon fibre is conducive. 

 

In the end even though I have made many antennas over the years I decided to buy Comant Antennas for my RV10.

 

Cheers

John MacCallum  VK2 -GCN

Builder #41016

VH-DUU

 

 

 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Peter Pengilly

Sent: Wednesday, 20 June 2012 7:20 AM

To: aeroelectric-list(at)matronics.com

Subject: Re: Antenna length

 

It is straight forward to figure out the length required from the frequency of the signal,



velocity = frequency x wave length



so wave length = vel/freq



Using SI units (coz its just easier than imperial)



Velocity = 3 x 10^8 m/s

Freq = 118 to 137 MHz (so centre freq is 126.5 x 10^6 Hz)



So wave length = 3/1.265 m = 2.37m ( about 93 inches)



Most dipoles are half wave, a lot of aircraft antennas are quarter wave.



Wikipedia (or the Aeroelectric connection) can probably explain better than me - less change of remembering the basic physics wrong!



Peter

On 19/06/2012 21:11, Rob Henderson wrote:

 	  Quote: 	
		  

Hi all

I would like to make a couple of antennas for my Glastar.

Does anyone know what the length is for dipole, or any reason not to “role my own”.

 

Transponder:

Comm:

Nav:

Marker:

Glide Slope:

UAT:

 

I will be using Garmin

GTX327

SL30

GMA340

Navworxs ADSB

Thanks in advance for all advice

-Rob Henderson 	  Quote: 	
		     	
	


  	  Quote: 	
		   Use the Matronics List Features Navigator to & Download, 7-Day Browse, Chat,    --> http://www.matronics.com/Navigator?AeroElectric-List[/b]     - List Contribution Web Site                    -Matt Dralle, href="http://www.matronics.com/contribution">http://www.matronics.com/c=[/b] 	


  [quote][b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

JOHN TIPTON

Joined: 17 Sep 2006
Posts: 239
Location: Torquay - England

Posted: Tue Jun 19, 2012 11:03 pm Post subject: Antenna length

or any reason not to “role my own"

  

 1)    Time spent could be better  utilized

 2)    Professional manufactured work  out of the box

 3)    Will the 'role my own' product  be readily reproducible in case of damage to the original

  

 John

 [quote]   ---

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

tim2542(at)sbcglobal.net
Guest

Posted: Wed Jun 20, 2012 6:24 am Post subject: Antenna length

Hi John

Not to be argumentative, but IMO foil dipoles are very easy to make, take perhaps 30 minutes to assemble 

and work quite well. Best of all they don't add drag!

The foil and ferrite beads are readily available from ACS, and the leg lengths can be determined easily.

For the gps you probably should use a manufactured product as most of these are powered and amplified

devices. For a glass plane and antennas for VHF, I don't think there is a better option.

RST sells a kit, but I keep hearing reports on an other list of the kits shipping months after the order.

Tim





Sent from my iPad



On Jun 20, 2012, at 12:02 AM, "JOHN TIPTON" <jmtipton(at)btopenworld.com (jmtipton(at)btopenworld.com)> wrote:



[quote]    (at)font-face { 	font-family: Calibri; } (at)page WordSection1 {size: 8.5in 11.0in; margin: 1.0in 1.0in 1.0in 1.0in; } P.MsoNormal { 	MARGIN: 0in 0in 0pt; FONT-FAMILY: "Calibri","sans-serif"; FONT-SIZE: 11pt } LI.MsoNormal { 	MARGIN: 0in 0in 0pt; FONT-FAMILY: "Calibri","sans-serif"; FONT-SIZE: 11pt } DIV.MsoNormal { 	MARGIN: 0in 0in 0pt; FONT-FAMILY: "Calibri","sans-serif"; FONT-SIZE: 11pt } A:link { 	COLOR: blue; TEXT-DECORATION: underline; mso-style-priority: 99 } SPAN.MsoHyperlink { 	COLOR: blue; TEXT-DECORATION: underline; mso-style-priority: 99 } A:visited { 	COLOR: purple; TEXT-DECORATION: underline; mso-style-priority: 99 } SPAN.MsoHyperlinkFollowed { 	COLOR: purple; TEXT-DECORATION: underline; mso-style-priority: 99 } SPAN.EmailStyle17 { 	FONT-FAMILY: "Calibri","sans-serif"; COLOR: windowtext; mso-style-type: personal-compose } .MsoChpDefault { 	FONT-FAMILY: "Calibri","sans-serif"; mso-style-type: export-only } DIV.WordSection1 { 	page: WordSection1 }    <![endif]-->   <![endif]-->  or any reason not to â€œrole my own"

  

 1)    Time spent could be better  utilized

 2)    Professional manufactured work  out of the box

 3)    Will the 'role my own' product  be readily reproducible in case of damage to the original

  

 John

 [quote]   ---

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Rob Henderson

Joined: 10 Jun 2011
Posts: 16

Posted: Wed Jun 20, 2012 6:48 am Post subject: Antenna length

Do not order from RST

I have been waiting for a kit since January it is now almost July.

They took my money though.

They do not answer email and the phone number just rings.

-Rob

 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Tim Andres

Sent: Wednesday, June 20, 2012 7:23 AM

To: aeroelectric-list(at)matronics.com

Subject: Re: Antenna length

 

Hi John



Not to be argumentative, but IMO foil dipoles are very easy to make, take perhaps 30 minutes to assemble 



and work quite well. Best of all they don't add drag!



The foil and ferrite beads are readily available from ACS, and the leg lengths can be determined easily.



For the gps you probably should use a manufactured product as most of these are powered and amplified



devices. For a glass plane and antennas for VHF, I don't think there is a better option.



RST sells a kit, but I keep hearing reports on an other list of the kits shipping months after the order.



Tim



 



 



 



 



Sent from my iPad

On Jun 20, 2012, at 12:02 AM, "JOHN TIPTON" <jmtipton(at)btopenworld.com (jmtipton(at)btopenworld.com)> wrote:

[quote]

or any reason not to â€œrole my own"



 



1)    Time spent could be better utilized



2)    Professional manufactured work out of the box



3)    Will the 'role my own' product be readily reproducible in case of damage to the original



 



John

[quote]

---

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

dlj04(at)josephson.com
Guest

Posted: Wed Jun 20, 2012 1:08 pm Post subject: Antenna length

Rob Henderson wrote:

 	  Quote: 	
		  > Hi all

>

> I would like to make a couple of antennas for my Glastar.

>

> Does anyone know what the length is for dipole, or any reason not to

> "role my own".

>

> Transponder:

>

> Comm:

>

> Nav:

>

> Marker:

>

> Glide Slope:

>

> UAT:

You've seen in other replies the lengths you should plan for, and length 

is of course important. Other parameters are at least as important, 

though. Everything metal in your airplane (including the cable that 

leads to your dipole) is a part of your antenna, and will influence its 

frequency range and directivity, whether you want it to be or not. The 

resin you use in your composite structure can also influence the 

electrical length of your antenna elements.

The only reason not to roll your own is that it takes a while to learn 

what you need, build and test your results. Using wide (1" for VHF, 1/2" 

for txp/DME/UAT) foil tape, genuine current mil spec or land mobile 

grade coaxial cable and connectors, and the factory-specified crimp tool 

for the connectors will make it much easier and more reliable. Surplus 

lengths of mil spec or LMR foam coax cable with the connectors already 

installed with proper factory gear may be your best bet (but avoid 

adapters and splices!) You can lay out your antennas on a thin piece of 

glass cloth, tape it in place on your airplane for ground tests, and 

then bond it in place later.

Transponder is particularly tricky because of the frequency and power 

level, although not so bad with your Garmin GTX-327 as with older types 

that have a cavity tube (which can be detuned by off-frequency 

antennas). You probably don't have a way to check SWR at transponder 

frequencies. Besides reduction in range, high SWR could damage the 

output of the transponder. I would hope but don't know that the Garmin 

is protected against that. You should confirm that it can operate into a 

high SWR load without damage (it should shut down rather than smoking 

the final power amp stage.)

Comm is probably the most critical, particularly now that you need to 

cover the whole 118-137 MHz band. You can use distant ATIS/AWOS stations 

as test signal sources, and compare where you can receive given stations 

with results from a known good installation. A vertical or sloping 

dipole is good if you have the space (about 47") but you may find that a 

quarter-wave monopole and counterpoise ("ground plane") might be easier 

to do and easier to match. Folding dipoles and monopoles is also 

possible but requires a lot of extra analysis and test. Fortunately, 

preserving true vertical polarization isn't that important.

A wing-mounted vee dipole is good (assuming it's far enough away from 

other conductors) but many of the designs I've seen are nearly straight 

-- which means poor reception off the ends. An asymmetrical 

installation, like one of the shunt-fed wingtip antennas, might be fine 

for VOR but can give different results if you intercept a localizer from 

the left or from the right. GS and marker are much less critical.

A wideband transponder/DME antenna will work fine for UAT which is in 

the DME band at 978 MHz. You could put it at the tip of the tail for 

good coverage on the ground, for instance, but this means a lot of loss 

in the cable (unless you put the UAT in the tailcone). Likewise the 

transponder antenna is best placed on the belly, but you need to think 

about reflections from the gear legs. This is one area where you might 

choose a factory type - the "all metal" NI-50 antennas are particularly 

good, rugged, low drag and often found on auction sites (they may have 

an uncommon "C" connector if they come from airline surplus, but these 

are available and very low loss.)

There are lots of military designs that can teach a lot about antennas. 

Sometimes you see slow airplanes and helicopters that look like a 

combination of a porcupine and a circus act, but others have everything 

embedded using patch, slot and notch topologies. I've been a little 

surprised that no one has really embraced some of these designs for 

homebuilts, although they have been used in some airliners over the years.

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum