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gpugh
10-31-2011, 09:52 PM
Hey everybody
I'm building a Hatz biplane and am wondering about the radio. Got any suggestions to someone with no clue as to what would be the best way to go? Need to keep the radio as small as possible and need to know what/how to install an antenna to do the job before covering the fuselage. Thanks for thinking about it.

rwanttaja
11-01-2011, 01:09 AM
http://www.bowersflybaby.com/tech/velcro.html

http://www.bowersflybaby.com/stories/antenna.htm

...but with your steel tube fuselage, you'll want an external antenna.

Ron Wanttaja

DanChief
11-01-2011, 05:27 AM
I installed a whip antenna in my Chief. Works great with an old Sporty's SP-200 handheld radio!

http://flightmusings.blogspot.com/2011/11/handheld-radio-antenna-mount.html

Bill Greenwood
11-01-2011, 09:42 AM
Dan is right, a handheld works fine, I use a Terra, a little bulky but stronger output than Sporty's.
The vital part is a simple external antenna, for the radio to plug into, otherwise it will not transmit with any real strenght.

gpugh
11-01-2011, 04:20 PM
Thanks guys
I have a Sportys handheld but hadn't considered mounting it. I will now. The external antenna installation looks simple enough. The articles were great. Food for thought...thanks again.
gpugh

DanChief
11-01-2011, 06:55 PM
My "mount" for the SP-200 consists of Velcro on the back and on the panel, with Zip Ties helping to keep it in place.

Frank Giger
11-01-2011, 11:08 PM
Now that we've answered his question....

I'm going to put a handheld radio in my open cockpit plane that is aluminum tube and gusset. Do I need to plan on an extended antenna?

DanChief
11-02-2011, 07:34 PM
My Chief isn't open cockpit, but is aluminum tube and polyfiber. I mounted the whip antenna to the wing root fairing (aluminum strip) and it works great!

Neil
11-02-2011, 08:22 PM
It is surprising how well a cheap radio will work if it is connected to a good antenna that is properly installed. The simple rod type whip antennas will work as good as any for about the first 100 channels, then it starts loosing ground. That's why they are under 20 bucks. For a belly mount the AV-17 from R. A. Miller and the Comant Ci 122 work pretty good for the money. These antennas are wound which I'm told broadens the channel range significantly. The antenna must be mounted to a satisfactory ground plain. Most Biplanes have a large enough alluminum belly panel to create a good ground plain. A minimum ground plain would be about 18" in diameter. Try to keep the antenna far enough back so it isn't blanked out by the landing gear. Don't scrip on the antenna coax. The RG-58U has been used for years and works pretty good but the RG-400U is the new kid on the block and is a better cable, particularly for transponders. Have someone that has the proper tools make up the coax. Many transmit/receive problems come from improper connections.

I have a King KY 97A connected to the AV-17 on the bottom of my Acro Sport and it works well. Even sitting inside a metal hangar with the door down I can talk and receive with airplanes flying overhead

Eric Page
11-04-2011, 08:23 PM
Do I need to plan on an extended antenna?

Short answer is definitely yes. The "rubber duckie" antennas that come with handhelds are a substantial compromise. They give up a lot in performance to obtain small size and flexibility. Pretty much any decent external antenna, properly mounted, will perform a lot better.

wynkoop
11-29-2011, 08:01 PM
It is surprising how well a cheap radio will work if it is connected to a good antenna that is properly installed. The simple rod type whip antennas will work as good as any for about the first 100 channels, then it starts loosing ground. That's why they are under 20 bucks. For a belly mount the AV-17 from R. A. Miller and the Comant Ci 122 work pretty good for the money. These antennas are wound which I'm told broadens the channel range significantly. The antenna must be mounted to a satisfactory ground plain. Most Biplanes have a large enough alluminum belly panel to create a good ground plain. A minimum ground plain would be about 18" in diameter. Try to keep the antenna far enough back so it isn't blanked out by the landing gear. Don't scrip on the antenna coax. The RG-58U has been used for years and works pretty good but the RG-400U is the new kid on the block and is a better cable, particularly for transponders. Have someone that has the proper tools make up the coax. Many transmit/receive problems come from improper connections.

I have a King KY 97A connected to the AV-17 on the bottom of my Acro Sport and it works well. Even sitting inside a metal hangar with the door down I can talk and receive with airplanes flying overhead

Your off just a bit in your idea of a good ground plane.

First let's find the middle of the com band.

137 - 118 = 19 The comm band is 19 Mhz wide

So the middle of the comm band is 118 + 9.5 = 127.5 Mhz

The formula for a quater wave is 234 / Frequency-in-Mhz, so we have 1.8352941 Feet or 22.0235 inches.
In radio a ground plane is normally 5% larger than a quarter wave, so that means 1.1 inch more for a RADIAL length of 23.1235 inches.

Now since that is the size of one radial it means that a good ground plane would be about 46 inches across. A typical 1/4 wave antenna for
VHF has 4 radials of 1/4 wave+5% arranged at 90degree intervals.

In practice if you have a metal ship, or a metal frame, any piece of metal bigger than 46 inches with the antenna at the center of it will yeild good results. If you have a glass or wooden ship you should consider either a dipole antenna or install 4 23 inch radials.


On the cable front LMR-240 is lower loss than the suggested rg-400u, and will give better results.

I hope someone finds this useful.

-Brett

Neil
12-01-2011, 10:19 PM
Just said it was a good ground plain, not optimum. A lot of the tube and fabric airplanes sometimes force you to take what you can get.

flyrgreen
12-13-2011, 11:05 PM
On a tube & fabric airplane, the metal groundplane that is mentioned late in the thread is essential. If you have a metal belly plate already, there you go.

Tom Downey
12-14-2011, 12:17 AM
I used one of these in a All wooden aircraft and it has been working great for about 10 years http://www.aircraftspruce.com/catalog/avpages/antennasystems.php

Mike Switzer
12-14-2011, 01:36 PM
Tom, did you use that in the Fairchild? Where did you mount it?

Tom Downey
12-14-2011, 03:59 PM
Tom, did you use that in the Fairchild? Where did you mount it? Yes, it is mounted (glued) to the under surface of the turtle back fabric. 12:00 high on the fuselage. lots of choices on the 24. and the VAL-Com 2000c broadcasts like a louden boomer on it.