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SL30 Installation help

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John Wighton

Joined: 18 May 2010
Posts: 241

Posted: Fri Jul 30, 2010 10:26 am Post subject: SL30 Installation help

Hello everyone,

I am installing a Garmin SL30 into G-IPOD and wish to know the best place for the NAV antenna.  It's a tri-gear and l have the standard fin mounted COMM antenna.



Many thanks,

John

rlborger(at)mac.com
Guest

Posted: Fri Jul 30, 2010 11:03 am Post subject: SL30 Installation help

John,



I put my Bob Archer Nav antenna against the roof behind the baggage bay.  There are pics on my build site.  I can provide more info after I get home from KOSH if you are interested.



Bob Borger



Sent from my iPhone



On Jul 30, 2010, at 13:26, John Wighton <john(at)wighton.net> wrote:



 	  Quote: 	
		   

 

 Hell everyone,

 I am installing a Garmin SL30 into G-IPOD and wish to know the best place for the NAV antenna.  It's a tri-gear and l have the standard fin mounted COMM antenna.

 

 Many thanks,

 John

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=306833#306833

davidjoyce(at)doctors.org
Guest

Posted: Sat Jul 31, 2010 12:02 am Post subject: SL30 Installation help

John, My antenna is also in the top bit of the fuselage just behind the 

baggage bay, with transponder on floor by the tailplane counterweight tower 

and the com antenna in the tail fin. Works well.

Regards,  David Joyce, G-XSDJ

---

paul.the.aviator(at)gmail
Guest

Posted: Sun Aug 01, 2010 5:58 pm Post subject: SL30 Installation help

John,

  

 I have the same setup up as David and I am using Bob Archer antena's.  I believe that they are "J" dipoles and the set up works well.

  

  

 Paul

 On Sat, Jul 31, 2010 at 3:02 AM, David Joyce <davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk)> wrote:

 [quote]--> Europa-List message posted by: "David Joyce" <davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk)>

 

John, My antenna is also in the top bit of the fuselage just behind the baggage bay, with transponder on floor by the tailplane counterweight tower and the com antenna in the tail fin. Works well.

Regards,  David Joyce, G-XSDJ[b]

frans(at)privatepilots.nl
Guest

Posted: Mon Aug 02, 2010 12:56 am Post subject: SL30 Installation help

On 07/30/2010 08:26 PM, John Wighton wrote:

 	  Quote: 	
		   

 

 Hell everyone, I am installing a Garmin SL30 into G-IPOD and wish to

 know the best place for the NAV antenna.  It's a tri-gear and l have

 the standard fin mounted COMM antenna.


	


I have built the NAV antenna for my Garmin SL30 into the belly of the

airplane. There is a picture of this in my build log

www.privatepilots.nl/europa/building.htm



I decided to mount the antenna on the floor, because I have the strobe

power supply mounted against the roof. This provides better routing of

the cables (I could wire the wing tip strobes and tail strobe

symmetrically so the noise spikes null themselves out) and in case of a

fuel leak the strobe unit doesn't ignite the fuel as easily.

Another reason to mount the antenna on the floor is that there is simply

more space there for an antenna.



The NAV antenna works very well in this position. Sensitivity is

omni-directional, and I have no signs of strobe or other noises leaking

into the NAV system. The anntenna consists of two aluminium tubes in a

V-shape and I tuned them to the proper frequency. The coax is coiled up

close to the antenna to work as a balun.

Don't believe marketing stories, a simple V-shaped dipole is the best

you can get in terms of efficiency and radiation pattern. It is mainly

omni-directional, with a slight favor for the forward position, which is

probably the best for our purposes.



Don't worry about the engine "shadowing out" the antenna, the engine is

smaller than the wavelength and has little influence on the reception of

the signal. Apart from that, I believe that the NAV signals are

transmitted off the ground, so the engine is simply above the "line of

sight" of the antenna. 



Frans

paul.the.aviator(at)gmail
Guest

Posted: Mon Aug 02, 2010 2:32 am Post subject: SL30 Installation help

Hi Frans,



I had my antenna mounted on the floor but I ended up relocating it to the roof.  While I found that the VOR and Localizer worked fine I seemed to have trouble getting the Glideslope to work until I was with in a few NM of the outer marker.  It seems to work better on the roof for me.

 

Paul

  [quote][b]

frans(at)privatepilots.nl
Guest

Posted: Wed Aug 04, 2010 4:12 am Post subject: SL30 Installation help

On 08/02/2010 12:20 PM, Paul McAllister wrote:



 	  Quote: 	
		   I had my antenna mounted on the floor but I ended up relocating it to the

 roof.  While I found that the VOR and Localizer worked fine I seemed to have

 trouble getting the Glideslope to work until I was with in a few NM of the

 outer marker.  It seems to work better on the roof for me.


	


Keep in mind that the glidescope information is transmitted on a

frequency that is very different than the VOR/LOC frequencies. It is

recommended to use a splitter and a separate antenna for reception of

the glidescope info. You might get away with just a VOR/LOC antenna, but

this depends on the properties of the antenna. The antenna is deeply out

of tune on the glidescope frequency, and in general, antenna's that have

been reduced in size, have more problems with this and some are even

effectively shorting out the glidescope frequencies.

My dipole setup probably works better for this than any commercially

available antenna.



Frans

mikenjulie.parkin(at)btin
Guest

Posted: Wed Aug 04, 2010 10:04 am Post subject: SL30 Installation help

Frans,



 	  Quote: 	
		  >It is recommended to use a splitter and a separate antenna for reception

of
	


 	  Quote: 	
		  >the glidescope info. 


	


This statement is incorrect!!!  The installation instructions for the SL30

recommends a single antenna installation.  See SL30 Installation manual Page

16.



I have dipole antenna mounted in the right wing...  the ILS works fine.



Regards,



Mike

Do not archive.



Checked by AVG - www.avg.com 

15:22:00

John Wighton

Joined: 18 May 2010
Posts: 241

Posted: Wed Aug 04, 2010 11:20 am Post subject: Re: SL30 Installation help

Thanks chaps, Garmin make a big thing about the advanced design of the SL30.  Hopefully that is one of the reasons why most users seem to be able to use a single antenna.  Some circles think that a splitter corrupts the signal - but that is conjecture!



I have ordered the Bob Archer antenna and plane to fit it on the fuse floor.  



I dont currently have room for a CDI/HSI although the Dynon D10a can be configured to work in this way l think.  Phase 2 of my avionics upgrade may include a separate CDI (this will involve removing the DI).  This should then give PFD function for D10a and the Garmin can talk to the CDI directly.  Otherwise l need a Dynon HS34 (but there is no space for it).



I guess one only gets all the toys in the right places if you start with a clean sheet (panel) and then add Â£Â£.



Thanks for all your help on this one.

frans(at)privatepilots.nl
Guest

Posted: Wed Aug 04, 2010 11:54 am Post subject: SL30 Installation help

On 08/04/2010 07:01 PM, Mike Parkin wrote:

 	  Quote: 	

 <mikenjulie.parkin(at)btinternet.com>

 Frans,

>> It is recommended to use a splitter and a separate antenna for

>> reception

 of

>> the glidescope info.

 This statement is incorrect!!!  The installation instructions for the

 SL30 recommends a single antenna installation.

I was not parotting a product manual, but explaining simple physics. The

glidescope signal is transmitted somewhere around 330 MHz, while VOR/LOC

is transmitted around 110 MHz. A quarter wavelength antenna for 110 MHz

is simply far too long for 330 MHz, it is then acting as a 3/4 wave

antenna, which has no impedance of 50 ohms, the impedance the coax cable

is designed for. Losses are huge if you try to implement it this way,

and no product manual can change this simple fact of physics. IF you go

this route, a lot depends on the actual antenna configuration and lentgh

of the cable, cable routing, and so forth. (With a 50 ohms impedance the

length and routing of the cable doesn't matter, but with a huge mismatch

cutting a centimeter of a cable can make a significant difference) For

the average homebuilder without measuring equipment it is a matter of

simple luck and trial and error... or one can go the safe route and

install a splitter and an antenna which is optimized for 330 MHz and

outputs a nice 50 ohms impedance at this frequency. Pick your choice.

Complaints about the SL-30 manual should be directed to Garmin, not to

me. 

Said this, I revert to my original statement that a simple dipole most

likely offers more signal at this mismatched 330 MHz frequency than some

fancy commercial antenna specifically built for 110 MHz.

In my setup this works well, but again, it IS a mismatch and the result

is probably hard do duplicate because it is dependant on cable length

and other hard to determine properties. Relocating the antenna can make

a difference, if not just only for a different cable routing and length.

If I had to fly IFR and my life would be depending on proper signal

reception, I would for sure use a dedicated 330 MHz antenna and a splitter.

Frans

frans(at)privatepilots.nl
Guest

Posted: Wed Aug 04, 2010 12:01 pm Post subject: SL30 Installation help

On 08/04/2010 09:20 PM, John Wighton wrote:



 	  Quote: 	
		   Thanks chaps, Garmin make a big thing about the advanced design of

 the SL30.  Hopefully that is one of the reasons why most users seem

 to be able to use a single antenna.


	


No, it is not. The receiver has nothing to do with it. If you want to

receive two frequencies spaced that far apart, you need two antenna's,

or suffer huge losses due to cable mismatches.



 	  Quote: 	
		   I have ordered the Bob Archer antenna and plane to fit it on the fuse

 floor.


	


I suspect that the Bob Archer antenna is specifically designed for

reception of VHF signals (VOR & LOC), and performs poor (if at all)

around 330 MHz (The frequency of the glide scope) It may well simply act

as a short cut for these frequencies.

If you want to go this route, ask the manufacturer how the antenna

performs for 330 MHz signals. It might well be that he objects about

using the antenna for this purpose.



Good luck and let us know how it works out.



Frans

mikenjulie.parkin(at)btin
Guest

Posted: Wed Aug 04, 2010 12:38 pm Post subject: SL30 Installation help

Frans,



I would be the last to argue the technicalities of antenna losses with you.

However, what I do recognise is a useable ILS Glideslope when I see one.  My

antenna is the standard copper tape type fitted under the fibre glass skin,

I have tried the ILS system on quite a few occasions now and it works fine.

It is true that the system is probably not up to certification standards,

but I consider it a possible life saver.



Regards,



Mike



Do not archive

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