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Mild Panic Setting in on Antennas

mfleming

Well Known Member
Patron
So first off, I have searched about this topic but have come up dry.

When do I have to make decisions on when and where to install antennas?

I'm building a -7 and only a couple months in on working on a QB fuselage.

Looking around the forum I see QB's that are not much further along than mine with all manner of brackets and holes for electronics and antennas.

The mantra I keep hearing is wait to the last possible moment to buy avionics due to the increasing capability and decreasing cost.

So I guess the other big question is when is the last moment??

I've been hedging my bets on going Garmin or Dynon... and if I can swing it going at least basic IFR.
 
Don't forget to take a look at Advanced Flight Systems (which is part of Dynon). They're in Oregon like us. :)

Antennas are mostly the same from one system to the next (accept possibly GPS antennas, depending on what you're doing - but you generally buy those with the avionics).

Comm/Nav/etc antenna placement is done firstly to ensure a good clean antenna ground plane. Also with consideration for places where you won't knock or rub them off, I suppose. And of course places where they are not an eyesore or introduce unacceptable drag. I wouldn't worry much about antennas until you're quite a bit further along. When it's time to run wires is when this becomes more of a factor, but that's later in the project.

I went with AFS, and am still working on mine. I've had the opportunity to work on installations for a variety of systems on various levels. The AFS/Dynon "Advanced Control Module" (ACM) that comes with their Quick Panel setups is pretty darned nice and allows a level of modularity in decision making and simplification of wiring the first time around as well as when you decide to make changes, which can't really be matched. And their new ACM version with electronic circuit breakers and on-screen alerts/controls rather than fuses just makes it all that much more appealing to a lot of people. You can get the ACM with Advanced or Dynon EFIS screens. Cool stuff.

It will likely take you longer to get to the point where you need the avionics. That's one big reason waiting until you actually need them is recommended. We all plan to need them in 6 months, and then three or four years later find ourselves starting the avionics wiring. That's a lot of how things can get outdated before they fly.
 
Avionics

I'm building an RV-12 right now so I have little choice (Dynon or Garmin) and no choice on where the antennas go. So, it's easy for me. I'm already planning my next build. I'm going with Dynon in the 12 and my next build (RV-9 or 14) as my choice for a number of reasons. That airplane will be IFR capable using avionics as listed by the above poster.

As for waiting until the last moment, do as you choose but, for example, my Dynon system set up is amazing. My Dynon equipment was bought last August or September. It includes everything but the kitchen sink and can do a great job of VFR and in a pinch, it will allow me to land safely using the synthetic vision feature if I am unfortunate enough to need that capability - although, not legal if the RV-12 and I am not IFR certified.

I recommend that if you are considering Dynon and/or Garmin, that you call each manufacturer and ask their technical people where to place the antennas. Likely, they can advise you on that and you could install them or at least plan for the wiring to the antennae locations. Always leave these wires a little longer on both ends than you need - you can cut off excess when you install the antennas.

Also, there are probably many builders at your local airport who could help. And, google 'Electric Bob' (I hope that is his handle) - he has a series of books that will help you. Best to you.
 
im Waiting till I get closer to the end of my build to install antennas or doublers for them. Just not 100% sure what I want for avionics /etc. may make life a little more difficult for me, but since it?s my first build I just don?t know what I don?t know.
 
Fear not Michael. I completely forgot my antenna doublers until after I had painted and bolted the wings on. I managed to make things work, but it sure would have been easier to add them during the build. As everyone will tell you, put the avionics purchases as long as possible, however you can purchase the antennas early, as this technology doesn't change. If you don't want to go this far, you can just get the bolt template, and the radio's can take antennas from pretty much any manufacturer. The transponder doesn't take much of a doubler, however some of the belly VHF antennas are pretty long and require a more burly doubler. I only installed one VHF antenna, under the pilot's seat, however if I had done it during the build I would have installed a spare doubler under the copilot seat also incase I want to go to dual coms in the future.
Tom
RV-7
 
The mantra I keep hearing is wait to the last possible moment to buy avionics due to the increasing capability and decreasing cost.

Don't listen to the mantra. Do whats right for you. I purchased and installed the avionics at the end of fuselage construction prior to engine install. Firewall work was MUCH easier and engine install was no more difficult than an engine swap because all the engine connections were ready to go. All of the avionics install was done with the fuselage upside down. Very easy access for wiring. This minimised idle storage time for the engine. Don't underestimate the work required to wire avionics and 12v systems into the craft. Its tedious and time consuming. I know of one builder that has stalled for 6 years at this stage. How do you think his firebreathing custom engine is handling that for the last 8 years? In addition, avionics first may allow a smoother financial path depending on situation and choices.
 
If you haven't already, look on Stein's site. He has a diagram of potential/ common antenna locations.
 
Don't listen to the mantra. Do whats right for you. I purchased and installed the avionics at the end of fuselage construction prior to engine install. Firewall work was MUCH easier and engine install was no more difficult than an engine swap because all the engine connections were ready to go. All of the avionics install was done with the fuselage upside down. Very easy access for wiring. This minimised idle storage time for the engine. Don't underestimate the work required to wire avionics and 12v systems into the craft. Its tedious and time consuming. I know of one builder that has stalled for 6 years at this stage. How do you think his firebreathing custom engine is handling that for the last 8 years? In addition, avionics first may allow a smoother financial path depending on situation and choices.

That's an idea I can get my head around.
I'm not a fan of an expensive engine sitting unused for more than a year. Aero Sport recommended I purchase the engine as close to being finished as was practical.

As far as the mantra of wait for to the last possible moment for avionics is concerned, the current suit of systems seem pretty mature compared to even 5 years ago and I haven't seen any price drops. As matter of fact, things seem primed to get more expensive sooner rather than later. I'm sure there will be advances but really...How much capability do I need. My airline pilot friends say the current offering make their panels look old.
I think I would be happy with a current Garmin/Dynon/Advanced/etc. for many years to come.

I think I'll visit Stein's, get a suggestion on antenna needs and locations and start building doublers :D
 
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.................Also, there are probably many builders at your local airport who could help. And, google 'Electric Bob' (I hope that is his handle) - he has a series of books that will help you. Best to you.

Thanks for the advice on wiring :)

I wish there were some RV builders near me :(
I'm living in rural eastern Oregon. I'm lucky to have someone who built a -9A a few years ago to mentor me but he's almost 2 hours away. That's probably why I ask so many questions on VAF...

Hats off to all those who built RVs (or any homebuilt) before the internet.
 
Don't forget to take a look at Advanced Flight Systems (which is part of Dynon). They're in Oregon like us. :)..............

Right On. I guess when I think Dynon, I'm thinking Advanced also.

And that new Advance digital breaker box that is competing with the VP-X looks pretty cool :D
 
Belly antennas are pretty simple to do after the airframe is done.

Now, if you want a cat whisker on top of the fin------now would be a good time to do that. At least run the conduit for the coax, and make up a mount pad. Perhaps attach the fin fiberglass cap with nutplates......
 
I typically don?t like to do any wiring until after the interior is painted since I don?t want to paint wires, connectors, grommets, etc.
it is good to try to plan ahead though since you know you will be running wires through the center section and other places where you can put either holes or conduits or both for future use.
Before you put a single wire in make sure you create wiring plans/schematics for all systems to represent how you install them in the plane!!! Also, update them as you go with any changes you make. This will make installation and later trouble shooting much easier.
Even though you may not know which brands you will be using, you should know basically what all you need. (Lights, trim, flaps, mic/phones, etc.) This will give you a good start.
I like to just draw a basic plane outline and start drawing all these things on it and the wires that go to them. That can help give you an idea of the number of wires and where to run them.
I do like to install the wire runs that go to the empennage as soon as I can while it is easier without the top skin, since it is usually just lights and trim. If you plan to put a magnetometer back there you can run those wires too. I roll up the extra and tuck it behind the baggage bulkhead until ready to run to the cockpit.
Antenna mounts can be put in early too since regardless of which avionics you use the antennas will go in the same place. It?s good to check out antenna requirements though since there are different spacing requirements for different ads-b units.
Antenna stiffeners are no big deal after the fact since most basically act like big washers and can just bolt to the fuselage/skin using the antenna mounting screws
Planning firewall penetrations can also be problematic. I like to make penetrations for the EGT/CHT and other sensors close to the motor mount bolts so I can easily attach them to the motor mount tubing in the engine compartment
Wiring an airplane is a big deal and no simple task. It will take a lot of time to get it done correctly and to look nice, but it will be worth it in the end.
Good luck
 
I typically don?t like to do any wiring until after the interior is painted since I don?t want to paint wires, connectors, grommets, etc.
it is good to try to plan ahead though since you know you will be running wires through the center section and other places where you can put either holes or conduits or both for future use.
Before you put a single wire in make sure you create wiring plans/schematics for all systems to represent how you install them in the plane!!! Also, update them as you go with any changes you make. This will make installation and later trouble shooting much easier.
Even though you may not know which brands you will be using, you should know basically what all you need. (Lights, trim, flaps, mic/phones, etc.) This will give you a good start.
I like to just draw a basic plane outline and start drawing all these things on it and the wires that go to them. That can help give you an idea of the number of wires and where to run them.
I do like to install the wire runs that go to the empennage as soon as I can while it is easier without the top skin, since it is usually just lights and trim. If you plan to put a magnetometer back there you can run those wires too. I roll up the extra and tuck it behind the baggage bulkhead until ready to run to the cockpit.
Antenna mounts can be put in early too since regardless of which avionics you use the antennas will go in the same place. It?s good to check out antenna requirements though since there are different spacing requirements for different ads-b units.
Antenna stiffeners are no big deal after the fact since most basically act like big washers and can just bolt to the fuselage/skin using the antenna mounting screws
Planning firewall penetrations can also be problematic. I like to make penetrations for the EGT/CHT and other sensors close to the motor mount bolts so I can easily attach them to the motor mount tubing in the engine compartment
Wiring an airplane is a big deal and no simple task. It will take a lot of time to get it done correctly and to look nice, but it will be worth it in the end.
Good luck

The wiring has been weighing on me lately. It DOES seem like a big job. and it needs to be right. Just this morning I printed out outlines of the -7 and will start marking the wiring runs like you mentioned.

I seem crazy to have to reinvent the wheel for the basic wiring layout but I haven't found a schematic that I'm sure is the right one yet :(

I'm thinking of having Advanced or Stein's help me with the avionics wiring...it looks like a fellow could fry some pretty expensive gear if wired wrong.

Speaking of painting the interior...When do I do that :eek:

It's looking obvious that I need a plan (besides the manual) to move forward efficiently .
 
When I was at your position I had my Fuselage on a Rotisserie and used post-it`s to set up possible antenna positions. As I build a 8 I can only put antennas on the lower side of the fuselage due to the sliding canopy (except the GPS antenna. I then checked carefully the minimum distances from each antenna to the next and placed the post-it`s to meet all criteria. For example the GARMIN XPDR antenna needs a minimum distance to other antennas but additionally it needs at least 3 ft of coax between the device and the antenna.. As I wanted to separate the power wires (lights, trim, flaps etc) from the coax I had to place the post-it`s several times and check again for all requirements....

You don`t have to buy the avionics now as you find most Manuals online (for the mounting requirements).
 
Also consider building and installing brackets for magnetometers, elt, etc. As well as all the antennae. It's also much easier to do a nice job now.
Jack
 
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