Today's Message Index:
----------------------
1. 03:20 AM - GNS 430W Antenna Requirements ()
2. 06:39 AM - Re: GNS 430W Antenna Requirements (Wayne Sweet)
3. 04:23 PM - Re: GNS 430W Antenna Requirements (Noel Loveys)
4. 10:56 PM - Re: GNS 430W Antenna Requirements (John Rippengal)
Message 1
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| Subject: | GNS 430W Antenna Requirements |
4/24/2007
Hello Wayne, Thanks for your input. One more question if I may.
I have read that the connector on the end of the coax cable that connects to
the antenna must be a male TNC connector. Can you please confirm that?
Also I'd appreciate it if you can shed any light on what additional
equipment, antenna, black box, or...........? would be needed if one wanted
to have XM weather appear on their GNS 430W.
Thanks.
OC -- The best investment we can make is the effort to gather and understand
knowledge.
Time: 08:59:22 PM PST US
From: "Wayne Sweet" <w_sweet@comcast.net>
Subject: Re: Avionics-List: GNS 430W Antenna Requirements
I have my GNS430W installed with the antenna mounted on the aft of the
canopy (BUSHBY MustangII); the RG400 coax is about 8 feet in length. No
noticeable difference from the same location prior to the WAAS update.
BTW, I'm having a ball flying GPS approached with ILS like display. In fact
the needles are much calmer than on a ILS approach, and no worry about false
lobes. :-))) Only problem (small), from the approach plate can't tell if
there will be an active GS till I get on the approach and get the LNAV+V
indication. The GS comes active on the waypoint just outside the FAF.
Wayne
Message 2
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| Subject: | Re: GNS 430W Antenna Requirements |
Yes, it does need a TNC connector at the antenna; the dealer that sent mine
in to Garmin for the WAAS upgrade made a pigtail TNC to BNC for me ( $10.00
:-))) ) . Don't know about what additional boxes needed for XM.
Wayne
----- Original Message -----
From: <bakerocb@cox.net>
Cc: <aeroelectric-list@matronics.com>
Sent: Tuesday, April 24, 2007 3:19 AM
Subject: GNS 430W Antenna Requirements
> 4/24/2007
>
> Hello Wayne, Thanks for your input. One more question if I may.
>
> I have read that the connector on the end of the coax cable that connects
> to the antenna must be a male TNC connector. Can you please confirm that?
>
> Also I'd appreciate it if you can shed any light on what additional
> equipment, antenna, black box, or...........? would be needed if one
> wanted to have XM weather appear on their GNS 430W.
>
> Thanks.
>
> OC -- The best investment we can make is the effort to gather and
> understand knowledge.
>
> Time: 08:59:22 PM PST US
> From: "Wayne Sweet" <w_sweet@comcast.net>
> Subject: Re: Avionics-List: GNS 430W Antenna Requirements
>
>
> I have my GNS430W installed with the antenna mounted on the aft of the
> canopy (BUSHBY MustangII); the RG400 coax is about 8 feet in length. No
> noticeable difference from the same location prior to the WAAS update.
> BTW, I'm having a ball flying GPS approached with ILS like display. In
> fact
> the needles are much calmer than on a ILS approach, and no worry about
> false
> lobes. :-))) Only problem (small), from the approach plate can't tell
> if
> there will be an active GS till I get on the approach and get the LNAV+V
> indication. The GS comes active on the waypoint just outside the FAF.
> Wayne
>
Message 3
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| Subject: | GNS 430W Antenna Requirements |
The impedance the receiver wants to have is achieved with the stated cable
at the stated lengths. Too short or too long and the sensitivity of the
receiver will suffer.
Noel
> -----Original Message-----
> From: owner-avionics-list-server@matronics.com
> [mailto:owner-avionics-list-server@matronics.com] On Behalf Of Bob C.
> Sent: Tuesday, April 24, 2007 12:22 AM
> To: avionics-list@matronics.com
> Subject: Re: Avionics-List: GNS 430W Antenna Requirements
>
>
>
> I doubt that it's to attenuate the signal as suggested? More like
> it's to avoid having the feedline (coax) be susceptible to picking
> interference (acting like an antenna) at certain frequencies? I
> wouldn't worry so much why but I'd follow there suggestions.
>
> Regards,
> Bob in SE Iowa
> RV-8 Finishing - Slowly
>
> On 3/9/07, bakerocb@cox.net <bakerocb@cox.net> wrote:
> >
> > 3/9/2007
> >
> > Hello List Experts, It is fairly well documented that
> Garmin wants high
> > quality antenna cable (RGU 142 or 400) to be used for the
> GNS 430W and it
> > must be between 13 and 35 feet long.
> >
> > I can understand a maximum limit. I cannot understand the physics or
> > electronic principles behind the minimum length requirement.
> >
> > Can someone please educate me? Thanks.
> >
> > OC -- The best investment we can make is the effort to
> gather and understand
> > knowledge.
> >
> >
> >
> >
> >
> >
>
>
>
>
>
Message 4
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| Subject: | Re: GNS 430W Antenna Requirements |
The wavelength of the GPS signal is around 8 inches so the advice from
Garmin to use coax feeder of anywhere between 13ft and 35 ft length can have
nothing whatsoever to do with the impedance seen by the receiver. The 35ft
is almost certainly the maximum to use without attenuating the signal too
much. I don't understand the 8ft minimum like 'bakerocb' but it may possibly
be to avoid overloading with too high a signal as he suggests but anyway
it's surprising.
Also the minimum length secures the maximum freedom from pickup.
Those suggesting specific lengths aid impedance matching or minimising
pickup are thinking in terms of HF radio techniques where it is not
uncommon, at least in HAM circles to use coax feeder with large standing
waves on them (high VSWR). It involves cutting the feeder to a fraction of a
quarter wavelength. (in this case within - say a quarter of and inch). You
wouldn't do that at 1500Mhz.
As has already been advised - if Garmin says so, just do it.
John Rippengal
From: "Noel Loveys" <noelloveys@yahoo.ca>
>
> The impedance the receiver wants to have is achieved with the stated cable
> at the stated lengths. Too short or too long and the sensitivity of the
> receiver will suffer.
>
> Noel
>
>> From: owner-avionics-list-server@matronics.com
>>
>>
>> I doubt that it's to attenuate the signal as suggested? More like
>> it's to avoid having the feedline (coax) be susceptible to picking
>> interference (acting like an antenna) at certain frequencies? I
>> wouldn't worry so much why but I'd follow there suggestions.
>>
>> Regards,
>> Bob in SE Iowa
>> RV-8 Finishing - Slowly
>>
>> On 3/9/07, bakerocb@cox.net <bakerocb@cox.net> wrote:
>> >
>> > 3/9/2007
>> >
>> > Hello List Experts, It is fairly well documented that
>> Garmin wants high
>> > quality antenna cable (RGU 142 or 400) to be used for the
>> GNS 430W and it
>> > must be between 13 and 35 feet long.
>> >
>> > I can understand a maximum limit. I cannot understand the physics or
>> > electronic principles behind the minimum length requirement.
>> >
>> > Can someone please educate me? Thanks.
>> >
>> > OC -- The best investment we can make is the effort to
>> gather and understand
>> > knowledge.
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