Radio Geniuses... a question

dmccormack

dmccormack

Touchdown! Greaser!
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May 11, 2007
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Lancaster County, Pennsylvania
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Dan Mc
I have a non-electric Aeronca Chief and have been flying out of a Class D field (only hangar available).

My handheld works ok as long as I am facing the tower and am within 3 miles. So whenever I leave I give them and ETA and I circle over the lake until they see me and then clear me to land. Not good.

I'd like to mount an external antenna, using the aluminum wing fairing as a ground plane with a doubler underneath for rigidity (the fairing is rather thin).

My questions are: What type antenna should I use (and what model and source)? Does this installation require a field approval? How do I connect the Sporty's SP-200 to the external antenna? Is there a way to place the antenna inside the empty fuselage area behind the seat?
 
Look in to one of these.

http://www.aircraftspruce.com/catalog/avpages/antennasystems.php

If you have all wood wings, as in wood ribs as opposed to aluminum, I would think you would have better results mounting the antenna in the wing. Otherwise, I think it can be mounted in the fuselage somewhere.

As far as connecting it to your radio, If I am not mistaken, the whip antenna on it will detach and it is a standard BNC (???) connector. No big deal.

As to the rest of your questions, I will have to defer to those who are more knowledgeable.
 
Greg Bockelman said:
Look in to one of these.

http://www.aircraftspruce.com/catalog/avpages/antennasystems.php

If you have all wood wings, as in wood ribs as opposed to aluminum, I would think you would have better results mounting the antenna in the wing. Otherwise, I think it can be mounted in the fuselage somewhere.

As far as connecting it to your radio, If I am not mistaken, the whip antenna on it will detach and it is a standard BNC (???) connector. No big deal.

As to the rest of your questions, I will have to defer to those who are more knowledgeable.
Click to expand...

I think you're right -- the Sporty's connector is BNC.

I'll take a look -- thanks!
 
those dipole antennas are probably pretty good, if you've got the room for them. I think that comm antennas are supposed to be oriented vertically though, not sure how putting one of those in a wing would work. although you might be able to lay one of them up on the inside of the fuselage, behind your baggage area. in the glider, i made a ground plan out of a ~1.5 ft square piece of aluminum and then bought an antenna kit from wingsandwheels.com. Ended up just using a piece of welding wire for the antenna, trimmed it to length using one of those tuner dealios that makes sure you arent reflecting much energy back into the radio. I oriented it so the antenna was pointing DOWN since i usually want to talk to people under me. I just stuck it in the back of the glider, I had a place to mount the flat ground plane. Works great so far.
 
dmccormack said:
Is there a way to place the antenna inside the empty fuselage area behind the seat?
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The Champ has a steel-tube fuselage. Putting the antenna inside that cage will reduce signal strength a whole bunch. It belongs on top. You already have range problems toward the rear with your handheld because of the steel structure back there.

Dan
 
Dan Thomas said:
The Champ has a steel-tube fuselage. Putting the antenna inside that cage will reduce signal strength a whole bunch. It belongs on top. You already have range problems toward the rear with your handheld because of the steel structure back there.

Dan
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This is a Chief, but I assume it has the same issue.
 
Dan Thomas said:
The Champ has a steel-tube fuselage. Putting the antenna inside that cage will reduce signal strength a whole bunch. It belongs on top. You already have range problems toward the rear with your handheld because of the steel structure back there.

Dan
Click to expand...

In my Porterfield (which has a steel tube fuselage and wooden wings) I have a standard "bent whip" comm antenna mounted on a flat aluminum plate inside the fuselage behind the rear seat and it works pretty well. I'm sure the range would be improved by mounting it on top of the wing (with a suitable ground plane) but as it is I can hear the tower from 30+ nm and they can hear me reliably from 10-15 nm out. At my speed that's plenty far enough.
 
And on the Stinson L-5 having that same whip antenna mounted on the belly 'tween the gear was a problem. We could hear at least 60 nm distant in all quadrants but depending on bearing, they could/could not hear us even at distances of one mile.

Moving that antenna to behind the rear seat improved some of the problems and created others.

Moving that antenna to the top of the turtle deck behind the green house glass was not a good solution.

The best solution was moving it aft on the belly. But too far aft created those original problems plus interfered with landing in grass, etc.

I suspect each plane will present it's own picadillos.

EDIT: IIRC, our ground plane had to be at least 18" sq to work correctly.
 
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dmccormack said:
I assume a ground plane cannot be too big?
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I'll leave that to the radiomen. But I know it can be too small. Now before you go thinking, Well, that's obvious...consider that 15" sq was too small. Not much difference, you'd think.
 
Richard said:
I'll leave that to the radiomen. But I know it can be too small. Now before you go thinking, Well, that's obvious...consider that 15" sq was too small. Not much difference, you'd think.
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I just ordered a 2'x2' 6061T6 .025 sheet from Aircraft Spruce (along with whip antenna and cable).

On the Aeronca boards the advice is divided between top of the wing using the wing root fairing (thin aluminum strip) and inside the rear fuselage.

The top-of-the-wing guys all claim at least 10 mile transmit. I'm not quite as concerned about appearance yet, so I'll mount the whip on top of the wing for now.

:dunno:
 
Richard said:
I'll leave that to the radiomen. But I know it can be too small. Now before you go thinking, Well, that's obvious...consider that 15" sq was too small. Not much difference, you'd think.
Click to expand...

Ideally a ground plane should be at least 1/2 wavelength in diameter which would be about 4.5 feet at 108 MHz IIRC. Fortunately, smaller ground planes work reasonably well. And a ground plane need not be a solid plane, as long as the spacing between elements is less than a 1/4 wave an array of connected conductors will be just as effective if the diameter of the array is sufficient. However I think that when you have a smaller than ideal diameter, a full sheet works better because it has more capacitance to the "ether".
 
dmccormack said:
I'm not quite as concerned about appearance yet, so I'll mount the whip on top of the wing for now.

:dunno:
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Well, maybe not for appearance but I think you want to figure it all out before you go fishing wires and punching holes in the fabric.

I for one would love to see work-in-progress pics as you do this. Or, at least an "after" picture with text.
 
gismo said:
Ideally a ground plane should be at least 1/2 wavelength in diameter which would be about 4.5 feet at 108 MHz IIRC. Fortunately, smaller ground planes work reasonably well. And a ground plane need not be a solid plane, as long as the spacing between elements is less than a 1/4 wave an array of connected conductors will be just as effective if the diameter of the array is sufficient. However I think that when you have a smaller than ideal diameter, a full sheet works better because it has more capacitance to the "ether".
Click to expand...
He should be able to get away with a smaller ground plane plate if he also couples it to the aluminum frame.
 
Richard said:
Well, maybe not for appearance but I think you want to figure it all out before you go fishing wires and punching holes in the fabric.

I for one would love to see work-in-progress pics as you do this. Or, at least an "after" picture with text.
Click to expand...

I'll do my best!

:yesnod:
 
smigaldi said:
He should be able to get away with a smaller ground plane plate if he also couples it to the aluminum frame.
Click to expand...

The aluminum wing root fairing is about 4 feet long and 10" wide. I will double that for rigidity of installation with aluminum plate. So there should be a significant ground, n'est pas?
 
dmccormack said:
The aluminum wing root fairing is about 4 feet long and 10" wide. I will double that for rigidity of installation with aluminum plate. So there should be a significant ground, n'est pas?
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N'est. YOu will get good reception and transmission fore and aft with significantly poorer performance side to side. Just before you start punching holes hither and yon, tell me ... because it has been so long since I've worked on a Chief ... the fuselage is welded steel tube, is it not? And the wings are wooden spar with aluminum ribs, yes? No?

Tell me a lot about the structure and we may be able to do something rather trickery. Or point me to a website with a bare naked Chief so I can look at the innards.

Jim
 
weirdjim said:
N'est. YOu will get good reception and transmission fore and aft with significantly poorer performance side to side. Just before you start punching holes hither and yon, tell me ... because it has been so long since I've worked on a Chief ... the fuselage is welded steel tube, is it not? And the wings are wooden spar with aluminum ribs, yes? No?

Tell me a lot about the structure and we may be able to do something rather trickery. Or point me to a website with a bare naked Chief so I can look at the innards.

Jim
Click to expand...

I'll be happy with 7-10 miles in any direction (don't need more than the ability to talk to Class D tower).

AFAIK the Chief is built as you describe. I don't plan on drilling any holes except perhaps one hole through the wing root fairing for the antenna to mount. Of course I'll be working with an IA who has admited he doesn't know much about Aeroncas.
 
dmccormack said:
I'll be happy with 7-10 miles in any direction (don't need more than the ability to talk to Class D tower).

AFAIK the Chief is built as you describe. I don't plan on drilling any holes except perhaps one hole through the wing root fairing for the antenna to mount. Of course I'll be working with an IA who has admited he doesn't know much about Aeroncas.
Click to expand...


That steel tube fuselage makes for one hell of a good ground plane if you can find something electrically attached to it that is big enough to drill through to mount the antenna to.

Jim
 
Update:

I moved the whip antenna to the top of the wing root fairing, reduced the length of the RG-58 Coax from 6' to 3', tested and re-tested continuity, and tightened everything up and sealed it with RTV.

I tested in flight yesterday -- I could hear AWOS clearly 25 miles out, and communicated with MGW (Class D) Tower 15 miles out with no problems.

I was using a Sporty's SP-200 handheld with standard Rayovac AA batteries.

I made at least 10 transmissions total, including a request for the fuel truck when rolling back to the hangar. Direction did not affect reception or transmission.

Thanks for all the advice here -- the Aeronca guys have requested I write up an article with pics for the next type club newsletter. I'll take some pics Monday and post them here as well.

Next project: a gel cell battery to drive the handheld. :D

Then replace the windscreen.

Then replace the floorboards.

(All under the watchful eye of my friendly, local IA, of course!)
 
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