REFLECTOR: Radio weak and scratchy

[Dale Alexander]

Hi all,

SWR stands for Standing Wave Ratio. It is a measurement of the amount of 
reflected output power in an antenna system. The lower the value the better. 
When I installed my Bob Archer VOR and Comm antennas in the wings, I 
measured the values and both were close to 1:1. Anything up to 2:1 is 
acceptable. Over that and you will start damaging the output section of the 
radio with reflected power coming back.

As far as the Comm radio mounting trays, I had a Musketeer that had one 
radio that would show transmission, but nothing would be received outside 
the plane...unless someone pushed on the faceplate and seated the radio in 
the back connectors. It would seem that over time with a little vibration, 
the connectors would loosen up and become intermittant. The solution? It is 
not A&P acceptable, but why not cut out a portion of the back tray and 
install a pigtail for both the antenna and cables? Leave enough slack to 
allow removal of the radio for service. That way the antenna and cables can 
have a positive screwed together connection that is imperious to vibration. 
This might be the source for the "slot one" problem.

Waiting for the slings and arrows from Al G,

Dale Alexander


> ----- Original Message ----
> From: Tom <tomcat05 at comcast.net>
> To: reflector at tvbf.org
> Sent: Thursday, September 3, 2009 7:17:18 PM
> Subject: Re: REFLECTOR: Radio weak and scratchy
>
> I used this for my #2 radio and it outperforms the embedded winglet
> antennas.
>
> http://www.miracleantenna.com/AirWhip.htm
>
>
>
> Dear Radio Wave Gurus,
>
> I have a number one radio that is weak and scratchy per ATC. I have dual
> Garmin 430s with Shaw wings and embedded ant.? I cleaned all my 
> connections
> in the radio stack and the BNC connectors to the wing ant connection.? I
> confirmed continuity of the shielding and central conductor.? I had made 
> no
> changes in over 300 hour of flying without problem.? So I sent it in to
> Garmin who "realigned something" and charged me $1,000.00 through my
> avionics shop.? It is no better.? Can only partially be heard by atc on 
> the
> taxiways.? I suspect and antenna or wiring problem but I am unsure what to
> do next.? I have run a new coax outside of the plane to the wing BNC and 
> no
> difference.? If it is the antennae what can it be and how do I check it?? 
> If
> it is the rack - ideas?? My next thought was to replace the BNC connector 
> on
> the antenna itself but I was reluctant to if I was just missing something.
> I now have upgraded both 430s and can swap them in the rack and it seems 
> to
> be slot one problem.? I don't think it is a Garmin problem.
>
> Any help would be appreciated.? Is there a Radio Shack fix?
> Rene'
>
>


>
> Message: 3
> Date: Fri, 4 Sep 2009 14:12:14 -0500
> From: "Rene Dugas" <dugasd at bellsouth.net>
> Subject: Re: REFLECTOR: Radio weak and scratchy
> To: "'Brett Ferrell'" <reflector at velocityxl.com>, "'Velocity Aircraft
> Owners and Builders list'" <reflector at tvbf.org>
> Message-ID: <006001ca2d93$9cd4e1c0$d67ea540$@net>
> Content-Type: text/plain; charset="us-ascii"
>
> Brett,
> Good idea.  I'll check.
>  I don't know how to use an antennae meter but I'm trainable.  Is there
> some other way to check?  Could I connect my handheld to the wing antennae
> or will it explode(kidding).  Will the hairs on my arm stand up if I stand
> close to the wing while transmitting.  Just probing.  Not my area of
> expertise.  I'm a good crimper though.  What does SWR stand for?
> Rene'
>
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