During last weekend I was playing with a temporary setup of an old Cushcraft 13B2 145MHz yagi that I had lying around. The aim was to try and decode some EME traffic with a simple station setup, but the old 13B2 did not yield any result. Then I decided to build a more efficient antenna by myself.
After considering many design options I decided to build a 12-El.-Yagi EF2012B modified for 50 Ohm-V and optimized by DK7ZB. Here is a preliminary progress report:
Antenna ready for the first VNA test on a stub, abt. 1 meter above ground.
VNA results on a stub, abt. 1 meter above ground looks very promising.
Antenna mounted in my temporary setup, ready for new VNA test.
VNA results not so good. I suspect that the elevation rotor is to close to the boom. I have to make a new rotor arm to get the rotor out of the way. …………….to be continued
Been working on the matching problem all evening and it has nothing to do with the proximity to the rotor.
It’s all about fine tuning this part, the radiator. Trimming the V-dipole length and bending angle did the trick.
Now it looks very close to the EZNEC simulation.
I think there may be potential for better return-loss by some more fine tuning, but it is not going to happen tonight!
From the rear.
It is not easy to find room for all this airborne metal in a small back yard. 🙂
After over nine years with the DK7ZB 4-Element-28-Ohm-OWA-Yagi with 2,20m-Boom I decided to do an upgrade. During about 7 hours work on August 19, 2016 I dismantled the old 2,2m boomer, recycled a lot of its parts and build a new DK7ZB 6-Element-50-Ohm-Yagi with 6,00m-Boom
Here are some pictures:
08:00 hour, boom lift in place.
Working on the new 6-meter boom, old 2,2-meter on the floor.
Antenna recipe 🙂
Radiator is from the old antenna, but as this is a 50-ohm antenna the old DK7ZB match is replaced with a choke. Here I have 4 ½ turns, ID approx. 50mm. I threw in some surplus ferrite beads to, but I don’t know if they will do any good.
Preliminary test to check if everything seems sane. MFJ-meter is happy.
Antenna in place, about 2 meters below the HF-yagi. Not a perfect location, but it is the best I can do for the time being.
VNA-check & the operator is happy with the results.
Next is real on the air performance tests.
Testing the AE20401 5.8 GHz Frequency Counter / RF Power Meter kit from Ascel-Electronics.
Here testing a dummy-load for return loss @ 2,2GHz generated by the MiniVNA (old style) and the Extender. I measure 29.5 dB which equals about 1.07 in VSWR. Pretty good for this kind of equipment at these frequencies.
Meter hooked up the computer. The meter has a type A female USB jack so I had to make an odd Type A male to Type A male cable to get it connected. I have no idea why they have chosen to use this kind of jack in the instrument.
I have just ordered one of these pneumatic towers from Mr. Hero Ba’s company PHT in China.
The plan is to put my new 3m EME dish on it, but it may take a while because it is shipped by the sea.