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antenna problems

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jfrjr(at)roadrunner.com
Guest

Posted: Mon May 03, 2010 2:10 pm Post subject: antenna problems

Last week I indicated a problem of not receiving glide slope information on my SL-30 but was getting good localizer data, and the 430 was getting both loc and gs from the other ant.  Both radios get the VOR stuff normally. I have switched the ant. leads and found that now the 430 isn't getting the gs (but still gets the loc) and the SL-30 gets both nicely.  Thus I have an antenna problem but only in the frequency range of the glideslope (I think the gs freq. is much higher than the loc. freq.)  So what gives?  And more importantly what do I do?  The ant. in question is in the port wing tip fastened to the lower aspect of the fiberglass fairing, and grounded to the wing skin (just like the other nicely functioning ant. in the other wing tip).  The marker beacon ant. is also in that wing tip but fastened to the upper aspect of the fairing.  Is there anyway that the mb ant is interfering? Thanks,  Jay Rowe #40301

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jesse(at)saintaviation.co
Guest

Posted: Mon May 03, 2010 4:00 pm Post subject: antenna problems

Do you have any connectors in the wing root?  I would maybe try removing the MB antenna to see if that makes any difference, but my guess would be that either there is a no-so-great connection in one of the cables somewhere or there is a problem with the actual mounting of the antenna, or a problem with the antenna itself.



do not archive



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

Cell: 352-427-0285

Fax: 815-377-3694



On May 3, 2010, at 3:54 PM, <jfrjr(at)roadrunner.com> <jfrjr(at)roadrunner.com> wrote:



 	  Quote: 	
		   

 

 Last week I indicated a problem of not receiving glide slope information on my SL-30 but was getting good localizer data, and the 430 was getting both loc and gs from the other ant.  Both radios get the VOR stuff normally. I have switched the ant. leads and found that now the 430 isn't getting the gs (but still gets the loc) and the SL-30 gets both nicely.  Thus I have an antenna problem but only in the frequency range of the glideslope (I think the gs freq. is much higher than the loc. freq.)  So what gives?  And more importantly what do I do?  The ant. in question is in the port wing tip fastened to the lower aspect of the fiberglass fairing, and grounded to the wing skin (just like the other nicely functioning ant. in the other wing tip).  The marker beacon ant. is also in that wing tip but fastened to the upper aspect of the fairing.  Is there anyway that the mb ant is interfering? Thanks,  Jay Rowe #40301

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Kellym

Joined: 10 Jan 2006
Posts: 1706
Location: Sun Lakes AZ

Posted: Mon May 03, 2010 4:47 pm Post subject: antenna problems

Any chance the MB and VOR antenna cables got mixed up?

I think MB antenna would sorta work for VOR/loc freqs, but not GS.

 	  Quote: 	
		   On May 3, 2010, at 3:54 PM,<jfrjr(at)roadrunner.com>  <jfrjr(at)roadrunner.com>  wrote:



    

> 

>

> Last week I indicated a problem of not receiving glide slope information on my SL-30 but was getting good localizer data, and the 430 was getting both loc and gs from the other ant.  Both radios get the VOR stuff normally. I have switched the ant. leads and found that now the 430 isn't getting the gs (but still gets the loc) and the SL-30 gets both nicely.  Thus I have an antenna problem but only in the frequency range of the glideslope (I think the gs freq. is much higher than the loc. freq.)  So what gives?  And more importantly what do I do?  The ant. in question is in the port wing tip fastened to the lower aspect of the fiberglass fairing, and grounded to the wing skin (just like the other nicely functioning ant. in the other wing tip).  The marker beacon ant. is also in that wing tip but fastened to the upper aspect of the fairing.  Is there anyway that the mb ant is interfering? Thanks,  Jay Rowe #40301

>

>

>

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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

carl.froehlich(at)verizon
Guest

Posted: Mon May 03, 2010 4:52 pm Post subject: antenna problems

Jay,



Interesting problem.  You are correct, Glide Slope is three times higher in

frequency than VOR or LOC transmissions.  Since antenna are resonate at odd

multiples of operation frequencies, VOR/LOC antennas work just fine for

Glide Slope.



 	  Quote: 	
		  From your note you point out the both VOR antennas are identical and mounted

in similar fashions, one in each wingtip.  As such both antennas must work -
	


unless there is some other problem.  Your note say both work at VOR

frequencies.  I wonder however if both work equally well at VOR frequencies.

My guess is they don't.



I would first look at the most common culprits for such things, the antenna

connections or less frequent a bad run of coax (the coax perhaps damaged on

installation).    The best way to do this is with an antenna analyzer.  Most

amateur radio operators have one.  You might try the local ham radio club.

Someone will jump at the chance to help.  Here is a standard analyzer that

will do anything you need:

http://www.mfjenterprises.com/Product.php?productid=MFJ-249B



My thinking is the problem is not so bad that you do not receive any VOR

signals, but such problems tend to have more of an effect at the higher GS

frequency.  I would not suspect the MB antenna unless it is very close (a

few inches) from the VOR antenna.  Come to think about it, make sure your MB

and VOR antenna leads are not swapped.  A MB antenna will make a poor VOR

antenna, but it will work with strong signals.



Carl Froehlich

RV-10 (systems install)

RV-8A (525 hrs)

--

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Bob Turner

Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA

Posted: Mon May 03, 2010 6:11 pm Post subject: Re: antenna problems

This is a long shot - is it possible the GS is "shadowed" by the fuselage? The GS transmitting antenna is slightly offset from the runway, while the localizer is off the far end. Easy test: while on the ILS, swing the nose around 5 deg or so, to the right (if the problem antenna is on left side), see if that makes any difference.



Otherwise, I'd make sure there are no GS/LOC splitters inadvertently in the line from that antenna.

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_________________
Bob Turner
RV-10 QB

jfrjr(at)roadrunner.com
Guest

Posted: Mon May 03, 2010 6:36 pm Post subject: antenna problems

Thanks for the suggestions. I even talked to bob archer today. The  

problem, he thinks, is an "unhealthy" connection at the ant.  I did  

not discuss  the possibility of switching the mb and nav ants but that  

may be a possibility since the runs are side by each all the way. That  

will be very easy to check out. I'll have more info tomorrow.  Jay



Sent from my iPhone



On May 3, 2010, at 8:40 PM, Kelly McMullen <kellym(at)aviating.com> wrote:



 	  Quote: 	
		   



 Any chance the MB and VOR antenna cables got mixed up?

 I think MB antenna would sorta work for VOR/loc freqs, but not GS.

> On May 3, 2010, at 3:54 PM,<jfrjr(at)roadrunner.com>  <jfrjr(at)roadrunner.com 

> >  wrote:

>> 

>>

>> Last week I indicated a problem of not receiving glide slope  

>> information on my SL-30 but was getting good localizer data, and  

>> the 430 was getting both loc and gs from the other ant.  Both  

>> radios get the VOR stuff normally. I have switched the ant. leads  

>> and found that now the 430 isn't getting the gs (but still gets  

>> the loc) and the SL-30 gets both nicely.  Thus I have an antenna  

>> problem but only in the frequency range of the glideslope (I think  

>> the gs freq. is much higher than the loc. freq.)  So what gives?   

>> And more importantly what do I do?  The ant. in question is in the  

>> port wing tip fastened to the lower aspect of the fiberglass  

>> fairing, and grounded to the wing skin (just like the other nicely  

>> functioning ant. in the other wing tip).  The marker beacon ant.  

>> is also in that wing tip but fastened to the upper aspect of the  

>> fairing.  Is there anyway that the mb ant is interfering? Thanks,   

>> Jay Rowe #40301

>>

>>

>>

>>

>>

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