How to choose a NAV antenna?

I've decided to install two NAV antennas on my -10, one wingtip archer and one whisker-type on the VS.

While looking at the many options for the whisker-type antennas, I'm a little lost on how to select one - the specs looks nearly identical for most of them (e.g. Comant has the CI-157, CI-158, CI-159, CI-215, CI-259, RAMI has the AV-520, AV-525, etc.). RAMI documents the different drag force for some of its antennas, but Comant doesn't, so I can't even really compare based on that.

I'm wondering what the real difference between the antennas is - can anyone provide some insight on what to look for?

Thanks!

Any pointers, anyone?

Thanks in advance

rdamazio said:

Any pointers, anyone?

Thanks in advance

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No one can figure out why you would want two.

Perhaps you might pose your question to Don Pansier of Delta Pop Aviation.I do not believe he sells any NAV antennas, but he has been very forthcoming with advice for the experimental guys.

Don

Could be not much data here on nav antennas because many vfr guys don't have one.
VOR, what's that?
Of course you need one for ifr, but I have not had a use for one in a long time.
GPS trumps VOR totally for vfr ops.

I would think that having NAV antenna capability, would be a good idea if the OP plans to fly to other countries, no? Two antennas would give stronger reception than one antenna with a splitter, plus it would give each NAV radio it's own antenna, which could prove to be useful if one antenna went INOP while in flight. Isn't ground-based navigation still prevalent in other areas of the world?

Thanks for the responses.

ppilotmike said:

I would think that having NAV antenna capability, would be a good idea if the OP plans to fly to other countries, no? Two antennas would give stronger reception than one antenna with a splitter, plus it would give each NAV radio it's own antenna, which could prove to be useful if one antenna went INOP while in flight. Isn't ground-based navigation still prevalent in other areas of the world?

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Yes, I do plan to fly internationally, especially in South America, but even in the US some of the airports I fly into have much lower minimums for ILS than for GPS/LPV (and LP is not widely available yet - I'll be surprised if it is by the time I complete the plane ).

It may be an incorrect assumption on my part that I'd need two antennas to feed NAV1/NAV2 - should I be looking into a single antenna for both? (other than from a failover/reliability standpoint - I haven't heard of any NAV equipment failures where the cause was the antenna)

cfiidon said:

Perhaps you might pose your question to Don Pansier of Delta Pop Aviation.I do not believe he sells any NAV antennas, but he has been very forthcoming with advice for the experimental guys.

Don

Click to expand...

Thanks for the hint - I'll definitely get in touch with him.

rdamazio said:

Thanks for the responses.



Yes, I do plan to fly internationally, especially in South America, but even in the US some of the airports I fly into have much lower minimums for ILS than for GPS/LPV (and LP is not widely available yet - I'll be surprised if it is by the time I complete the plane ).

It may be an incorrect assumption on my part that I'd need two antennas to feed NAV1/NAV2 - should I be looking into a single antenna for both? (other than from a failover/reliability standpoint - I haven't heard of any NAV equipment failures where the cause was the antenna)

.

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It is very common - I'd say standard - to split a single nav antenna into 2 VOR/Localizer signals plus 1 or 2 Glide slope signals.

You are correct, LP approaches will usually not have lower minimums than LPV s.

Nav antenna comparison

The vee dipole antennas seem the same because they mostly are, except for the ruggedness of the termination between the rod elements and the cable. The simplest ones from the 1940s containing steel rods flattened and bolted to a phenolic insulator are OK. Another variation is that some of them require a balun made of coaxial cable to transform the balanced feed from the antenna to the unbalanced coax to the radio, while others use a ferrite balun transformer. Both work fine, and nothing wrong with one of those antennas. See http://www.aeroelectric.com/articles/BALUN/Balun_Fabrication.html

Wingtip/embedded antennas can be fine too, but nearly every installation I have seen has strayed far from Bob Archer's or Jim Weir's recommendations, which are critical. The antennas get blamed when the real problem is all the other conductive stuff out there in the wingtip that distort their pickup pattern. The nav light wires don't know they they aren't part of the antenna.

When you have your installation done, go fly and check reception at some of the VOR airborne check locations (published in the A/FD) near you. See how far away you can receive a distant VOR, and see whether it's the same in all directions (fly a slow 360 while listening to the ident and watching the needle -- if you get the same signal strength in all directions you did the installation right.)

VOR/LOC reception for actual IFR is very tolerant of poor antenna design -- if it's on the chart as a waypoint you are expected to receive at a certain altitude, FAA has tested it with a big margin for antenna loss, which means you can use a wet noodle for an antenna and it will work okay. But a single vee dipole or a "towel bar" or dual fin antenna will be fine, run through a passive splitter that can feed two NAVs and a GS receiver (it helps that GS is almost exactly 3x the frequency of NAV, allowing a 1/4 wave antenna on one band to be a 3/4 wave antenna on the other.)