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What is it?

petehowell

petehowell

Well Known Member
DDRR%20005.jpg


Even my wife called me a geek after fabbing this up in the office tonight. Details tomorrow after flight testing if the WX allows.........
 
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wait, wait, don't tell me!!

I have no idea, but let me venture a guess.
Some kind of device for a DF steer; direction finding device?
or someone's first attempt at modern art:D
or a plumber's practice project:p
 
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Coffee warmer

As you transmit on your 2 meter, you place a cup of coffee in the middle of this antenna so you can use the RF to heat the cup up.

Not being one to step on other hams, the coffee is used to make this a dummy load.

After using the coffee for tuning up the radio, you drink it, reduce the power, and then use the antenna for the radio.

What's the directionality of it?
 
Its a seat warmer

You put it in the foam in your seat bottom, the circle part is what you put the boys in to keep um warm on those really cold flights.
 
Its one of them free thingies near the front door at Axe man surplus.
I made a GPS antenna that looked somthin like that once:confused:
 
Modified double square antenna. Lots of theory over there. Good luck with your research Pete.
 
FrankK90989 said:
Its one of them free thingies near the front door at Axe man surplus.
Click to expand...

Ahhh....good memories! I LOVED going to the Axeman when I was a teenager. my rule was to never go in looking for something particular - you'd never find it! Just wander in with ten bucks though...and see what weird stuff came to your attention! I still have some high speed drogue chutes somewhere in a box.....

Paul
 
DDRR

Well, Paige nailed it right off the bat. It is a 1/4 wave 2M DDRR(DirectionalDiscontinuity Ring Radiator). I tuned it up for 144.39 and the SWR is close to 1. When I finally got the tuning right, this thing was buzzing the computer speakers like crazy.

The DDRR is interesting in that it is a short, flat antenna that has vertically polarized signal - to un-geek that - it means that it is better for transmitting APRS signals from the plane. The knock against the j-poles(that work pretty darn well) is that laying in the wingtip, most of their signal is horizontally polarized.

Here is the quick and dirty install:
DDRR%20006.jpg


I did not get to flight test tonight, but the taxi to the fuel pump looks pretty good:

DDRR.JPG


Hope to flight test it tomorrow.......
 
Quit dancing around the question.

Alright,
So who is going to be the first flying RV to make a DDRR 13.6% bigger than the APRS unit being tested by Pete. (so that the center freq is 127 Mhz :rolleyes:). I am too far away from flying to do testing.

Since this is the first time I have seen a DDRR, the quick reading on the web makes me believe this type of antenna has a quick preformance dropoff as one goes away from the designed frequency (hence the original need for a tunable capacator at the "free" end of the loop.) I am curious if the hams would comment on that aspect.

Dang, I miss my dad. This is right down his alley. :(
 
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rzbill said:
Alright,
So who is going to be the first flying RV to make a DDRR 13.6% bigger than the APRS unit being tested by Pete. (so that the center freq is 127 Mhz :rolleyes:). I am too far away from flying to do testing.
Click to expand...

Ahh Bill,

The stealth Comm antenna......I made one already for my handheld, and the problem was as you mention - this style antenna is very narrow banded. It would require re-tuning when you change freqs. There might be ways to make it more broadbanded, but I am already beyond my intelligence level here.

The one freq nature of APRS let me tune it dead on - and I hope it will work well in the air. It was cheap, fun, and easy to make in an evening - and I learned a bunch along the way
 
We Might Have a Winner!!

OK- I am almost ready to declare the DDRR a winner. Here is the ground coverage at Anoka County. This thing tracks like a hound dog!

DDRR1.JPG


Here is the entire flight - mostly at 1000-1500 AGL - good tracking in the turns and very few missed packets.

DDRR2.JPG


I'll take it up to altitude later this week to see how it works up high .

Pros
- seems to work really well
- looks like something out of Star Trek
- your hangar mate does not have one (yet)

Cons
- harder to make and tune
- costs more
- bit harder to install
 
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