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Antenna Selections

Noah

Noah

Well Known Member
Planning antennae purchases for RV-7A. GNS430W (NAV/COM/GPS), SL-40 (COM), and GTX-327 (txpdr) are planned. Here's what I'm thinking:
1. CI-122 bent whip belly mount for the GNS-430
2. CI-121 top mount com antenna for the SL-40
3. Bob Archer AS-001 wingtip mount VOR antenna
4. CI-101 for the transponder

Questions:
1. Will the Archer wingtip ant work for glideslope or is a separate glideslope antenna required?
2. Is a separate DME antenna required? (Do I even need DME)?
3. Is a marker beacon antenna required? Is this where stripped coax can be used?
4. Any thoughts on the combo antennas which combine XM or GPS with a com function? These seem pretty expensive.
5. Debating a Ryan Howell "rypole" vs. a RAMI AV-14 belly mounted antenna for APRS transmitter (144.39 MHz). Will probably go with the Rypole for drag reasons - anybody using the AV-14?

Don't know much (ok, anything!) about antennas. Any comments appreciated.
 
Based n my recent experience fooling around with antennas....

1. The Archer works for GS and VOR, but as you are feeding it into a 430, which has separate antenna inputs for each, you will need a splitter, which costs significant bucks (compared to, say, a splitter for cable TV) and cuts the signal strength in half. It is really simple to build a GS antenna from a chunk of coax - this is my recent configuration change, and it works really well!

2. You didn't list a DME in your equipment list, so unless you are adding one, the answer is NO. With an IFR GPS, why would you spend the money?

3. No, a Marker beacon is not, according to the latest interpretations of IFR requirements. (That should start a debate, but someone will cite the appropriate Advisory Circular soon enough, and that is enough to convince me). Of course, if your Audio Panel has a beacon installed, then you might as well hook it up.

4. No idea - but you'll need to use a GPS antenna specified by Garmin to make the 430W IFR legal.

5. Sorry - I have no APRS experience!

Paul
 
Thanks for the insights Paul. I will be installing an audio panel with a marker beacon. Does the marker beacon receiver typically reside in the audio panel? Or is this something that a separate nav radio / beacon receiver is required for? Or does the 430W include the marker beacon receiver? What type antenna is required for the marker beacon?

Nobody's used a RAMI AV-14 for their APRS installation??

Thanks again for the help.
 
Noah said:
Thanks for the insights Paul. I will be installing an audio panel with a marker beacon. Does the marker beacon receiver typically reside in the audio panel? Or is this something that a separate nav radio / beacon receiver is required for? Or does the 430W include the marker beacon receiver?
Click to expand...

Many audio panels are available with or without a marker beacon. You used to be able to buy a marker beacon separately - probably still can - but they are easy and cheap to put in an audio panel. The price difference (with/without) is usually a couple hundred bucks.

The 430W doesn't include one (well, I am CERTAIN that the 430 doesn't....)- with the GPS telling you exactly where the Outer Marker is, why woudl it need to?;)

Marker Beacon Antennas ae little "boat" shaped antennas, but I think you can easily make one with stripped Coax.

Paul
 
Marker Beacon Not Required

FAR 91.175(k) references the requirements for an ILS procedure. DME, NDB or VOR fixes published on the IAP can be substituted for an outer marker. GPS (IFR approved) is an allowed substitute for NDB and DME, which by extension allow GPS to be a substitute for an outer marker in those circumstances

91.175 Takeoff and landing under IFR.

(k) ILS components. The basic components of an ILS are the localizer, glide slope, and outer marker, and, when installed for use with Category II or Category III instrument approach procedures, an inner marker. The following means may be used to substitute for the outer marker: Compass locator; precision approach radar (PAR) or airport surveillance radar (ASR); DME, VOR, or nondirectional beacon fixes authorized in the standard instrument approach procedure; or a suitable RNAV system in conjunction with a fix identified in the standard instrument approach procedure. Applicability of, and substitution for, the inner marker for a Category II or III approach is determined by the appropriate 14 CFR part 97 approach procedure, letter of authorization, or operations specifications issued to an operator.

As noted above, the rules are a little different for Cat II and III approaches, as they also require identification of the inner marker.

It should also be noted that FAR 91.205 specifies the equipment requirements for instrument flight rules. As such, it references Appendix A only for Cat II operations, while there is no marker beacon requirement for Cat I operation

Appendix A to Part 91?Category II Operations: Manual, Instruments, Equipment, and Maintenance

2. Required Instruments and Equipment

(3) A marker beacon receiver that provides distinctive aural and visual indications of the outer and the middle markers.

(10) For Category II operations with decision heights below 150 feet either a marker beacon receiver providing aural and visual indications of the inner marker or a radio altimeter.

Hope this helps.

Scott
7A Finishing
 
AHA!

Thank you Scott. So if I read this correctly, for Cat I approaches, a marker beacon receiver is not required if you have a 430W as an IFR approved GPS is a substitute for a marker receiver. Therefore, I can save a few bucks and get an audio panel WITHOUT a marker beacon receiver. Flights to 150' DH would be QUITE unusual for my mission profile.
 
Noah said:
Nobody's used a RAMI AV-14 for their APRS installation??
Click to expand...

I've never seen it used for APRS but it should work fine since it is tuned for the 2 meter band. I would be more inclined to use a conventional com antenna for APRS so it could also be used with a backup com handheld.
 
Ted antenna

Ted Xponder antenna works great on my 9, but they are nickel plated brass, and are brittle and a bit fragile. I snagged mine wiping down the belly last summer and snapped it right off. Replaced it with another ted. Well made little guy, with a good gasket and BNC connector. just be careful cleaning around it.

Regards,
Chris
 
Noah, just strip the coax for the marker antenna

I put 40 inches (I think that is the correct length) in my wingtip. A little fiberglass in a couple of spots to keep it from moving. I placed this in the same wing tip that has my Archer Nav antenna in it. I all work great.

Kent
 
Ironflight question

Ironflight said:
Based n my recent experience fooling around with antennas....

. . .It is really simple to build a GS antenna from a chunk of coax - this is my recent configuration change, and it works really well!. . .
Click to expand...

Paul, can you tell me how you built your own GS ant?
 
Alton

You can probably search on "GS" for the thread, but simply take a chunk of Coax and strip off 16" of outer braid - leave the central conductor and it's insulation. Put a BNC connector on the other end. mount it in your cowl, on your roll bar, down a gear leg fairing....it should work at ILS ranges!

Paul
 
Wow...VAF is so timely. I came to VAF tonight to search for the answer to the MB required or not required question. Following my ritual I hit "New Posts" and sure enough in the first thread was my answer!

You guys are awesome.

Thanks,
JDP
 
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