woensdag 20 mei 2015

Red Bull Test Antenna

When I putted the  Red Bull  antenna into use, during the ARI DX 2015, I was aware of the controversial nature of short antennas. But I had absolutely NO doubt about this short antenna, with it's "wingspan" of just 12 inch.
I was convinced that I could make QSO's with QRP or even QRPp from the shack.

I was curious, whether the  Red Bull  antenna  could be used on 14 MHz, although it was tuned at 26 MHz, in stead of 14 MHz.
Further I was curious, whether the symmetrical tuner could be used to get a SWR of 1:1

I clamped the PVC tube of the antenna between  the bookshelf and connected a 300 ohm twin-lead between the symmetrical tuner and the coil of the antenna. 
The coil had 14 turns on a 40 mm coil former. I did not bother to change the coil to lower the operating frequency, which was 26 MHz and thus much higher than 14 MHz, on which I would operate. The 300 ohm ribbon is is equipped with two alligator clips, which are connected to two connection points on the coil one turn apart.

Red Bull test antenna May 2015 PA1B
The tuning runs smoothly. It's very easy to get a accurate SWR of 1:1 So I could transmit with the antenna. I only tried 14 MHz, because that was, where the action was and I wanted to make QSO's immediately. I did not try 21 MHz or 28 MHz.. 

Does it work? Yes.
I convinced myself with 360 milliwatt, with the antenna indoor, at a height of 4 meter above the ground.  Is it not amazing.
The first QSO that I made with this 12 inch antenna, was a more than 1000 Miles per Watt QSO.

On the air
After adjusting the SWR, I heard the station II6T
I could easily make a QSO, using a power of just 360 milliwatt. I tried to work them, earlier in the contest, on the damaged inverted V. But they could not copy my RST on the cracking inverted V.
I am very pleased, with this first QSO on the  Red Bull  antenna. Later I realized that this QSO is a more than 1000 Miles per Watt QSO.
I made QSO's with EA, YU, SM, YL and LZ with 3.6 W
With 800 mW I managed to make a QSO with HA and a QSO with UR.
Further I made a QSO with 360 mW with an other station from Italy.
IK0YVV copied my call immediately, when I answered his CQ. His signal was strong, it was over S9.

On receive
There a large difference between wire antennas, like the half wave dipole or inverted V and the short Cylinder dipole. The signals that are received on this short antenna, are much weaker. But also the short antenna picks up less noise. I noticed that it takes some time to got used to the weaker signals. 

ARI DX contest 2015  -  Red Bull test antenna  - May 2015  -  PA1B
Improvements and Next steps
  • The next step is building the same antenna with larger cans and a larger coil former, so the antenna will resonate at 14 MHz and therefor has a good efficiency.
  • Test the antenna on 28 MHz. This frequency is near the actual resonance frequency.
From one moment to the other
I decided to put up this antenna this antenna in the ARI DX contest 2015, when my inverted V let my down. I constructed the  Red Bull  antenna to test the properties of symmetrical feeding, a few months before. The test showed that the cable, which is connected at the middle of the coil,
has no hand effect on the cable.  The antenna lay around in the shack.

Tuning and SWR are not critical
Was it properly tuned to the operating frequency? NO.
But I am very happy with the fact that the cylinder dipole is NOT critical in tuning and that the SWR is easily to adjust.

Red Bull antenna - May 2015  PA1B
Connecting the twin-lead.
One turn apart 

4 opmerkingen:

  1. Very interesting test Bert tks. Enjoy milliwatt qso's 73 de SV1GRN

    1. Hello Panagiotis, thank you for your nice comment and the nice remarks on your interesting Blog. The best thing of being a HAM is the possibility to run a test on the air. hi. I like: Ενδιαφέρον. 73, Bert

  2. Hallo Bert, dat is wel een heel aparte antenne. Toch kun je met allerlei dingen die stralen werken. Zo heb ik ooit de gordijnrail gebruikt voor een verbinding op 160 meter. 73 Paul

    1. Hallo Paul, it is unbelievable to make a 1000 Miles per Watt QSO on a 12" antenna in the shack, with a height of 4 m above the ground. hi. Klopt, alles straalt, maar hier komt het op het rendement aan. 73, Bert