Construction of the feed horn for the 432 MHz band continues. Today I made a box for LNA and relay. The work on the design of the feed, its placement in the feed point and rotation in V and H polarization is completed. Today I will install the feed into the dish and try how the unit works. If everything works as I hope, I will QRV in ARI EME contest on 432 and 1296 MHz bands
Finally I also got around to making a feed for the 432 MHz band.
I chose the proven loop feed design described
and used a power relay to switch the RX and TX paths. Next, I used the miniature
SMA isolation relay and VLNA described
Now I need to align the ALU box with placement on a KR400 rotator to
change polarization vertically and horizontally, with the ability to
continuously adjust the angle of rotation.
I originally wanted to participate in the DUBUS contest on 432 MHz, but because
I had not finished the LNA and feed and because the EME expedition on KH6 was coming
up, I decided to spend the nice weather to finish the work on the new offset
was necessary to make a jig for precise alignment of the feed in the focus. I
hadn't had time to do this in the autumn 2021, so I waited until the weather had
calmed down a bit and I could work on the metal parts with my bare hands. The
antenna with the feed installed "by eye" did somehow work, I had 14dB of sun
noise, but it was still 7dB behind the assumption I should have had.
|Septum feed with collar W2IMU for offset F/D 0,457. VLNA G4DDK 0,2dB N/F and 36dB gain. Feed in feed point. So far I'm still 4dB short of the expected maximum Sun noise level, but the weather is not good for outdoor work and measurements. Today it is already snowing and we have 0°C outside. I now need to accurately measure the focal point and place the feed in the correct position. Looks like I'll be busy enough for next spring again.|
|I finished production of septum feed with collar W2IMU for offset F/D 0,457. VLNA G4DDK 0,2dB N/F and 36dB gain. This weekend I will install the feed into the dish and test the antenna finally properly illuminated. It's just a shame that the sun is at a very low declination this time of year.|
|Today I brought the W2IMU copper collars for feedhorns in 2320 and 1296 MHz bands. Now I have to finish the feeds for F/D 0,457 and make measurements and final antenna calibration.|
For the new offset antenna it is necessary to produce new
W2IMU collars to the currently used feeds for 1296 and 2320 MHz bands. I first
calculated the collar dimensions and then designed a square-circle transition
for the actual implementation of the 1296 and 2320 MHz feeds. The material used
was copper 0,6mm thick.
The lower images show the calculated values for the dish with F/D 0.457 and the upper copies of the DXF files for the laser burning machine.
I expect the final semi-finished products for feed production on November 2nd.