Monthly Archives: September 2014

Cheap and easy to build 1296MHz EME feedhorn for offset dishes

Recently I build a circular polarization feedhorn to try to do EME in 1296 MHz. The hint was that it have very easy to build and cheap. I was looking some designs based in ual mode septum designs from N2UO and RA3AQ but they not are easy to build for me. My idea has been use fireplace pipeย and a dielectric depolarizer.

1296 Dual mode feedhorn

1296 Dual mode feedhorn

To build the feehorn I have used fireplace inox pipe of 150mm and a galvanized reduction from 250 to 150mm. The dielectric depolarizer is a piece of Rogers Duriod 5880. To try to minimize the number of sma connectors, I used a small piece of Suhner .141 as a probe that will connect directly to the LNA saver switch.

Building the RX probe

Building the RX probe

RX port probe

RX port probe

Feedhorn inside

Feedhorn inside

In the TX port I used a standard N connector. I measured the RL in the lab, but have to measure the RL in the dish for this reason the bottom plate not is soldered yet, it is glued using metalic tape, until the RL is adjusted on the dish.

Measuring return loss

Measuring return loss

Feedhon on the dish

Feedhon on the dish

Detected meteor that has crossed tonight over Catalonia

Tonight, I was recording the Graves radar frequency (143.050 MHZ) to see I can detect the 2014 RC asteroid without success. But over a nice meteor has crossed Catalonia at the 04:56:50 UTCย  and has ben detected ๐Ÿ™‚

bolid

Meteor detected

The signal not is specially strong, because the target was very near from me. Using the Graves radar is more easy see meteors that are impacting from more remote locations of France or Italy

Other meteors can be observer before and after the target

Graves radar to UTC correlation

The Graves radar uses a multibeam antenna system that is switched every 0.8 seconds. When a meteor is detected and prints a large trace, is easy to see the beam switching after the meteor.

Graves beam switching

Graves beam switching

As the Graves radar system uses the transmitter and receiver in different geographic locations, is easy to think that they are synchronized the the UTC.

To check if it is true Miguel EA4EOZ and me are doing stereo recordings stereo of the Graves radar in one channel and a 1PPS signal from a GPS receiver in the other channel. And efectively they areย  locked to the UTC ๐Ÿ™‚

Graves radar 1PPS correlation

Graves radar 1PPS correlation

The coincidences to UTC are in the second 0,4,8,12,16,etc.. of every minute.

Some usefull info can be readed on the PE1ITR website.

PE1ITR, Greaves beam diagram

PE1ITR, Greaves beam diagram