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APRS Antenna Test Flight - Delta Pop Aviation

Pat Hatch

Well Known Member
Advertiser
I am flight testing a couple of new APRS antennas for Don at Delta Pop Aviation. I received the first one yesterday and mounted it today on the belly of my RV-6 where my original antenna was mounted. Just had to drill a couple of additional holes for the new antenna mount and re-connect the antenna coax. Here are a couple of pictures of the installation:

021.jpg


029.jpg


I will be flight testing the antenna tomorrow, Wednesday, at 11 a.m. eastern for anyone who might might want to track the flight. The plan is to stay low and fly out to the boonies in order to see how the antenna handles it.

Full disclosure: I volunteered to help Don run the tests and he in turn has offered to let me keep both antennas. Otherwise I have no connection with his enterprise.

Don is going to have a few different versions of the antenna, I believe, please contact Don if you have any questions.
 
Ground Clearance

Vlad,

Good eye! ;)

The ground clearance on this antenna is 1.25", due primarily to its location pretty far aft on the fuselage. I have much better ground clearance with the original Comant antenna, which I located as far aft as I could to maximize the distance from the comm antennas up front. Also the Comant is a little shorter and the bend a bit more severe, so there's about 4" of ground clearance with that one. However, Don's second antenna, which has a different impedance matching circuit, is quite a bit shorter. As soon as I get it installed in a couple of days, I'll put up a photo so you can see the difference. I'll let Don explain the technical differences between the two.

We'll see how it works today on the test flight!
 
I will be flight testing the antenna tomorrow, Wednesday, at 11 a.m. eastern for anyone who might might want to track the flight. The plan is to stay low and fly out to the boonies in order to see how the antenna handles it.

Excellent track, Pat. Looked like an enjoyable flight as well. :)
 
Excellent track, Pat. Looked like an enjoyable flight as well. :)

Thanks, Sam. Yes, makes me feel a little guilty, especially as I was talking to Don and he tells me there's 20" of snow and the temp is 15? in Wisconsin! :D

I'll post today's track and the original track with the Comant antenna about a year ago. I tried to fly the identical profile of the first flight so there would be a basis for comparison, and as you can see, both tracks are pretty much the same. On today's flight the tower asked me to make a 360? on final, so that's the only difference really.

Here's the original Comant track on Feb 10, 2010:

aprstrack2-10-10.png


And today's track:

aprstrack1-12-11.png


I noticed that my i-Gate picked up quite a few of the beacons from Don's antenna! (The black diamond near the 360? turn on final). :)

Brantel nailed it: Don's got a winner!
 
Pat,

That is a nice track. What is your tracking interval timing set for? Also what are you using for the smart tracking settings for turns? I haven't enabled smart tracking for turns on mine yet but need to so curious what settings to put in.

Thanks
 
Pat,

That is a nice track. What is your tracking interval timing set for? Also what are you using for the smart tracking settings for turns? I haven't enabled smart tracking for turns on mine yet but need to so curious what settings to put in.

Thanks

Mark,

Credit goes to Don at Delta Pop, this is a very nice antenna!

I used Sam's standard configuration for our trackers... just go to the first thread on the APRS forum, or click here:

http://www.vansairforce.com/community/showthread.php?t=31660

Should be all you need.
 
Pat,
Thanks for your test flight time today, happy to hear the antenna performed well for you.
 
Don sent me one of his antennas to test with my APRS setup, which I received today. I'm very impressed with the quality of the antenna. I'm going to install it this weekend and do some VSWR measurements with a MFJ-259 antenna analyzer.
 
pat, that is one........

nice looking RV! it would be nice to meet up some day. have you been flying much? i was up at c j cannons last night for some great food. is your hanger on the east side of approach to runway 4? turbo
 
nice looking RV! it would be nice to meet up some day. have you been flying much? i was up at c j cannons last night for some great food. is your hanger on the east side of approach to runway 4? turbo

Turbo, sent you a PM. :)
 
2nd Delta Pop Antenna

I installed Don's alternate antenna for APRS today. This one is a couple of inches shorter than the first one and consequently ground clearance is now about 2?". As soon as I get a chance to test fly it, I'll post the results.

027.jpg
 
Transponder Antenna?

Is the transponder antenna in the photo one of Don's by any chance?

I installed Don's alternate antenna for APRS today. This one is a couple of inches shorter than the first one and consequently ground clearance is now about 2?". As soon as I get a chance to test fly it, I'll post the results.

027.jpg
 
Dan,
The transponder antenna in Pat's photo is a Comant antenna, the Delta Pop Antenna looks identical.
 
Pat, your aircraft is a testing bed anyway. :) Why not to test the antenna installed on the top of the turtle deck and fly directly over or close to a digipiter/iGate? You may not want to make swiss cheese airframe, maybe just tape it over and run cable on top?



Added: I installed Don's transponder antenna. That's the look.

Donantenna.jpg
 
Last edited:
Hey Vlad,

There's no doubt in my mind that Don's straight antenna mounted on the top will work just as well as the belly mounts! You could mount one on your Morris and test it on your way down here to Florida for another visit! :D

You need a break from building right? Come down and see us! Turbo is nearby. How soon before you're flying?
 
You need a break from building right? Come down and see us! Turbo is nearby. How soon before you're flying?

Pat,
I need a break from idling! :)For about a year I am not working on my plane. What could be done at home is done, will move to an airport soon I hope. Thanks for the invitation I will surface in your area in couple months. :D
 
Finally got around to flying Don's second tracker antenna yesterday afternoon. I am posting a couple of screen shots of the flight, but was particularly impressed with the amount of ground hits that I got. I guess the true test of any antenna will be its performance on the ground, so by all indications both of Don's antennas seem to be great performers.

Glad to have a couple of more excellent choices in the APRS antenna arena! :)

This screen shot shows the taxi out, takeoff, landing and taxi back in. Notice that every beacon transmission was picked up by an i-Gate. A lot of times on the ground the beacons are missed and the track cuts corners, but not here:

aprstrack1-19-11b.png


aprstrack1-19-11a.png
 
Do Don's antennas require a ground plane? What would be the proper mounting technique for fiberglass?

Thanks,

-Dj
 
Regarding Delta Pop Antennas:

All the antennas I manufacture are quarter wave and require a ground plane for optimum performance.
A ground plane can be added to a composite aircraft using a thin sheet of aluminum, painting the interior with a copper conducting paint or a radial arrangement of
wires or thin metal connected like the spokes of a wheel.
The ground plane should have a radius of 1/4 wave at the antenna design frequency. The Com frequency requires a radius about 25", the APRS frequency about 20.5" and the UAT / Transponder frequency require about 3".
The antenna base must make good electrical contact with the ground plane for the best performance.

Other antenna designs exist that do not require a ground plane, example 1/2 wave and 5/8 wave. The disadvantage is at the APRS frequency they are 40" and 51"long and difficult to totally enclose vertically in the aircraft.

Pete's "J Pole" APRS antenna may be ideal for a your glass aircraft, it could be total enclosed in the tail section or wingtip and provide great range.
 
Ground Plane

Self-adhesive aluminum tape makes a pretty good ground plane. Just make sure to "stiple" the area between overlapped strips, since the sticky side is non-conductive, and a pick tapped down through both sides of the tape (lots of times) will make a good connection. If you are doing an "X" Try to get radials about 5 % longer than the driven element.

Allen
VHS
 
Pete's "J Pole" APRS antenna may be ideal for a your glass aircraft, it could be total enclosed in the tail section or wingtip and provide great range.

Thanks, Don. I think you are right that this would be my best approach. I'm building a Glastar Sportsman and I already have an aircraft band COM antenna bonded into the fiberglass vertical tail section. Ideally I am trying to minimize external antennas if possible, so the wingtip would be the ideal location for me if I can make that happen.

I'll probably put an MT-RTG and antenna in one wingtip and have the 144/440 radio wired to an antenna in the other wingtip. That will give me maximum separation between the two, and will allow me to maintain APRS use while also using the dual band ham radio for AM aircraft receive in addition to two way voice comms. At least, that is my working theory at the moment... :) GPS antenna centered on top inside of the fiberglass fuselage (above the metal cage), and transponder antenna on the bottom external to the fuselage. Not sure of the NAV receive antenna yet, but will probably have to put a "Y" one at the top of the rudder if I can't figure out how to get it internally.

-Dj
 
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