Antennas

[spitzy]

Anyone have any good or bad experience with copper foil antennas suggested in the plans for COM or NAV?

 

I've purchased Bob Archer's antennas which are supposed to be much better. I thought spending and additional $300 might make a cheap radio perform better than an expensive one with crappy antennas?

[Marc Zeitlin]

Anyone have any good or bad experience with copper foil antennas suggested in the plans for COM or NAV?

 

I've purchased Bob Archer's antennas which are supposed to be much better. I thought spending and additional $300 might make a cheap radio perform better than an expensive one with crappy antennas?

You probably should have asked the question before spending the $300.

 

While archer's antennae certainly work, they don't work any better than the $5 antennae, designed by Jim Weir at RST, do. The only problem with the copper foil antennae occur when installed incorrectly or on extremely flexible airframe parts. When installed correctly, they work great.

 

Not to mention that these antennae have been discussed to death in the COZY mailing list archives over the years.......

[rviglierchio]

Marc,

On that "other" forum a fellow has not been able to get in touch with RST. He gets an old recording from last summer. Are they still in business? I have a product of theirs I need to talk to them about too.

Dave

[Marc Zeitlin]

Marc,

On that "other" forum a fellow has not been able to get in touch with RST. He gets an old recording from last summer. Are they still in business? I have a product of theirs I need to talk to them about too.

Dave

AFAIK, Jim's still in business, but he can certainly be difficult to get in touch with. WRT antennae, there's nothing that's specific to RST - you can buy all the parts from other sources.

[Remi Khu]

A quick Google search on "copper foil tape" and "ferrite toroids" will provide a list of suppliers for the RST kit components sans Antenna Reference Text.

 

Examples:

Copper foil tape: http://www.stampington.com/html/foil_tapes.html

Ferrite toroids: http://www.surplussales.com/FerToro/FerToro-1.html

[spitzy]

According to Bob, torroids weaken signals meant to reach your radio radio. I've used torroids to dampen noisy signals at work and I immagine there would be some energy loss...

 

I've spoken to a couple electrical engineers and they tell me the length and geometry of an antenna makes a huge difference. Although huge can mean different things depending on the application.

 

I'll seach some of the archives and see what has been addressed in the past.

 

At the very least, Bob was nice on the phone, responsive, and willing to answer any of my questions. He also has some pretty interesting papers on the installation of antennas in composite aircraft.

[dpaton]

The toroids are a TUNING element. They are lossy on purpose, as they help to get the antenna resonant around the frequencies of interest, and not at the ones of disinterest. If you have a perfectly cut antenna, you don't need the toroids, I agree.

 

The odds of that happening in a canard are about a zillion to one. The density, construction, and chemistry of the substrate (glass/foam/etc) has a lot to do with the RF behavior of the antenna. The coax feeding the antenna has a lot to do with it. The humidity even has a measurable effect.

 

The toroids that Jim puts in the RST kit give some cushion to the design, making it more friendly to the radio and generally more reliable from an installation standpoint. I haven't tested them back to back, but I'd bet that Jim's kit is a little more friendly from an RF perspective too. It might not be the bleeding edge of performance, but as a builder and an EE, I'll take the small compromise of the toroids in favor of the increased chance of reliability (RF-system-wise).

[spitzy]

Out of curiosity, I plan to install one of each kind...

 

The plans show the COM wiring going through the hole in the foam core. I believe lights go through the same hole. Seems like the coax cable for the antenna would pick up noise from the lights... Anyone have problems running lights and COM wiring in the same hole? I'm thinking about running my coax through a channel similar to the installation of the rudder cable.

[PH-CAQ]

Anyone have any good or bad experience with copper foil antennas suggested in the plans for COM or NAV?

 

I've purchased Bob Archer's antennas which are supposed to be much better. I thought spending and additional $300 might make a cheap radio perform better than an expensive one with crappy antennas?

I have glued the transponder and the radio antennas in the fuselage. Works very well.

 

Ton

[longez360]

Bill Butter's antennas through spruce work REALLY well, including the all-internal XPDR antenna. No need to ground plane (like an ADF or LORAN), and no need to dangle it out in the breeze. There is no dielectric effect.

[EracerFL]

I was concerned with the copper foil breaking. I made my antenna's using the RST kit and dimensions. http://www.rst-engr.com

 

I substituted copper braid of the same width for the foil. In two composite homebuilts this has worked fine for me with no problems.

[dpaton]

Bill Butter's antennas through spruce work REALLY well, including the all-internal XPDR antenna. No need to ground plane (like an ADF or LORAN), and no need to dangle it out in the breeze. There is no dielectric effect.

I hate to nit pick, but there's always a dielectric effect, even with air. Properly installed, Bill's antennas should work like a dream. They're just designed with a little less tolerance for slop than the RST system. To each their own.

[Nathan Gifford]

...COM wiring going through the hole in the foam core...lights go through the same hole. Seems like the coax cable for the antenna would pick up noise from the lights...

There are plenty of radio noise sources in the aircraft. Using quality coax, taking the time to get the splices correct, and using low noise lights will have a bigger impact. Most nav lights are just a light bulb hung on the end of a wire. As long as it has good connections it should not make much noise.

 

Strobes are a different animal. A good strobe, installed properly, should not generate much noise either.