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Acft Spruce Com antenna for experimentals install

Dgamble

Well Known Member
I bought a Yaesu handheld to supplement the single comm radio in my RV12 in case of failure and I would like to install a separate antenna for it. Aircraft Spruce has a $45 antenna that I think will be good enough for occasional use. The installation instructions are somewhat sparse, as can be seen in the (hopefully) attached image.

I have a couple of questions. I am assuming that the physical installation will require a backing plate as the skin of a 12 is very thin. I’m also thinking that I will need a mounting hole matching the diameter of the area of the Delrin nut with the #2 arrow pointing at it, and the steel nut threaded onto the end of the antenna will be tightened and secured to hold the antenna in place.

With regards to wiring, I think the copper wire referenced in the installation instructions is the center wire of the coax cable, and it will be twisted around the threaded portion of the antenna indicated by the #1 arrow and it will be captured as the Delrin nuts are forced together. If that is the case, does anything need to be done with the braided shield wire of the coax cable? If that is not the case, how should it be done?

The other end of the coax already has a BNC connector on it, so that part seems to be ready to go.
 

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This looks just like the RAMI AV-534 antenna they sell at Aircraft Spruce. Yes you should use a doubler. The center conductor of the coax gets attached to the tip of the antenna (threaded) with a rig terminal. The coax braid gets attached to the ground plane via the solder lug ring terminal and lock washer, shielded from the antenna core by those delrin bushings. The instructions below show the antenna mounted on the top of the aircraft skin, so if you mount it on the belly, just turn the drawing around.


https://www.aircraftspruce.com/catalog/pdf/av534install.pdf
 
Those old style non shielded antennas can create RF problems, IMO you'd be much better off installing a 'modern' com antenna.
 
I have one of these that I never installed (the Rami branded version). Will make you a great deal if you go that way. I wouldn't recommend it for most installations, but will be quite adequate for emergency handheld use.

Larry
 
I have one of these antennas. Mounted on top of my hangar, it works great for my "shop" radio.
 
I used one of those old-school antennas on my RV-6 for several years but always had some issues with RFI getting back into the engine monitor. I replaced it with a Delta Pop antenna which works better.

http://www.deltapopaviation.com/VHF_Com_Antennas.html

However, I presently use the simple antenna on the belly of my biplane with a handheld radio and it is a huge improvement over the rubber duckie. If you just want an external antenna for the handheld it may be suitable for your application.
 
Great info, thanks!

Yes, it’s intended only for handheld use if/when my single comm radio quits. The antenna that came with the handheld is marginal - I’m just trying for a decent backup. My primary radio is a Garmin-badged Apollo SL40 and I periodically have issues with it. Removing it from the tray and reinstalling it clears it up, but I don’t want to count on that always working. It seems prudent to have a backup.
 
Dave,
I also have one of these RAMI antennas that I can sell you. I have the instructions for installation....... and I can bring it to you (Bolton Field). You might want to consider the inside the wingtip Archer antennas also. On my RV4 this antenna had some RFI that was affecting some of my GRT engine indications, probably similar to Sam’s experience.
 
Those old style non shielded antennas can create RF problems, IMO you'd be much better off installing a 'modern' com antenna.

Perhaps a bit of an explanation is in order.

In a metal skin airplane you want the coax cable shield going all the way to the skin. None of the center lead in the coax cable must be unshielded inside the skin. From the photo it looks like part of the antenna sticks inside the skin. That means part of the antenna radiates inside the airplane. Intercom and other electronics inside the airplane may find that objectionable.

The "modern" antennas have a BNC connector sticking inside the skin. That's fine because the center conductor is shielded (and grounded) all the way to the skin by the BNC connector and only becomes unshielded outside the skin.

In a glass or tube and fabric airplane that's not so important -- you don't have a metal "box" where the radio signal can bounce around in.

Finn
 
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