Feed for W2HRO folding dish

 

 

During 2023 to 2024years, a number of folding dishes manufactured and supplied by Paul W2HRO came into use. This is a very successful portable antenna design that has great applications for EME DX expeditions from rare sites and DXCCs. The antenna is very easy to assemble and works very well. Tested on many DX expeditions. A disc patch feed is used to iluminate the antenna and a 90°hybrid is used to provide circular polarization. However, to switch between LHCP and RHCP, a power relay and a set of cables are required. So I have made a proto-type feed which will be tested by Alex EA8DBM and Gene KB7Q stations. The results will be evaluated and I wonder if using this feed will improve the efficiency of the system. The feed is based on the principle of a septum baffle, which however does not have steps but only an inclined plane according to the original work published in IEEE. The original paper is also available for download here on the web. The total weight of the feed is 980g. Details in the pictures.

Measurements achieved in the lab SWR -30dB and better, broadband for -20dB is 112 MHz,  isolation between RX and TX port of -24dB for both prtotypes. Thus, a small SMA relay will be sufficient to provide LNA protection.

First prototype using Alex EA8DBM

Septum slope transformer

Second prototype using and testing by Gene KB7Q

New design of holder

First practical experience by Gene KB7Q

23cm HRO patch feed with relay and preamp ready to go is 1.57 kg. 
DFC septum feed with same relay and preamp is 1.19 kg  
Initial receiver test showed via sky noise and echo testing showed about a 1 dB improvement in RX.
SWR was excellent 450 watts forward, 10 watts reflected (Bird wattmeter). 1.3:1
My automatic tracking broke a drive shaft, so I had to set up manual tracking, but no visible moon. Heard my 2.4 Meter dish best -24, but my aiming wasn't very good.
Gene KB7Q

Another test of Gene:

Hello Zdenek,

Your feed is a winner! It out performed calculated expectation. I had visual moon today, so manually aiming was good. My motor tracking is broken. I'm seeing echoes around -20.5 now! Before I never, ever saw better than -24 to -26. Average -25. I did see echoes of -17.5 at one point, but -20.5 average was easy to duplicate at will.

For me the septum seems to be 4dB better on RX and maybe 1.5 to 2 dB on TX. Here some info from contacts I made today. 

 

KB2SA - Bill was 400 watts on his 1.9 meter dish, I heard him -20 and my best to him was -18. I was running 400 W at the feed.

 

W1FKF - 2M dish, 400 watts heard -21

N5TM - 3M dish 600 watts received here at -16! He heard me best -18 

KG5CHG 3.2M dish just 100 watts heard -23,  I complete QSO with him easily. 

It finally got too cold for how I was dressed so I went QRT. It was -18°C when I stopped. Two pictures attached.

Gene KB7Q

 

New LNA setup on the feed

Echo test

First series of feeds for those who want to replace their existing feeds.

For the feedy, which are produced in the first series of 25 pieces, a new laser head welding technology was used. I hope that the owners of the new irradiators will be satisfied with the quality of workmanship.

 

 

The next step in the development is the 2304 - 2320 MHz feed. On the picture is a prototype with serial production expected during April. Now tests and measurements will follow.

2304 - 2320 MHz feed

Another user of light feed, Douh K6JEY