G4DGU Skobelev Derived Feed


Chris Bartram G4DGU
 

Hello John,

The G4DGU Skoboloff dual flare works very nicely .
Thanks for that nice comment!

However, being the pedant I am :-) the Skobelev derived feed which I used to make is a dual-mode feed which in which two circular waveguide propagation modes are excited in such a way as to ensure that they cancel at the mouth of the horn. This results in the sidelobe generating  currents which would otherwise be induced in the rim of the horn being (effectively) cancelled. Thus improving the efficiency of the dish/feed combination.

The horn works on the same principle as the better known W2IMU dual-mode feed, but the waveguide flare which results in the generation of the higher-order mode in that design has been replaced by a step change in the 'guide diameter. The step does much the same thing, but is easier to make.

The feed was designed as a part of the 10GHz transverter system I designed and sold back a decade or so ago. It was specifically designed to work well with TV offset dishes, and I have recently been using one modified for WG17 input with a 1m dish as I stagger back onto 10GHz EME.  I'm sorry to say that they are no longer available. I'm trying to make a bit more space in my life to do some microwaving ... However, if someone were to be interested in making the horn under some form of licence, and can convince me that they are capable of doing it properly, I'd be happy to talk.

73

Chris G4DGU


John Fell
 

Has it been that long Chris ......

Good to know you are moving towards 10GHz EME again , Julian G3YGF and I and the rest of the G4RFR team look forward to the QSO and of course Paul M0EYT also has his own 10GHz EME system , so you can work IO90 and IO80 .

Oddly enough I got my eldest Son in Law G1MXD , who was then running his own CNC firm , to do a quote for the 10GHz horn .
However he decided to sell up and go back into Management , so a chance to licence manufacture did not materialise .
I will see if his contacts are interested .....

Our EME nearly terminated back in January thanks to a burst 15mm copper waterpipe that turned our club Microwave room into a small swimming pool. The large TWT and PSU were on one side of the room on a bench and luckily survived the 3 day long dunking .

Due to C19 we have not been able to test all the components till a couple of weeks ago , but so far so good and we have tested on Sun,Moon and echoes within last week .Normal operations will resume as soon as the club is allowed to re-open .

Off on hols to Kernow next weekend - a week near Helston and a week in N Devon to follow .

73
John
G0API

On Sat, 19 Jun 2021 at 19:58, Chris Bartram G4DGU <chris@...> wrote:
Hello John,

> The G4DGU Skoboloff dual flare works very nicely .
Thanks for that nice comment!

However, being the pedant I am :-) the Skobelev derived feed which I
used to make is a dual-mode feed which in which two circular waveguide
propagation modes are excited in such a way as to ensure that they
cancel at the mouth of the horn. This results in the sidelobe
generating  currents which would otherwise be induced in the rim of the
horn being (effectively) cancelled. Thus improving the efficiency of the
dish/feed combination.

The horn works on the same principle as the better known W2IMU dual-mode
feed, but the waveguide flare which results in the generation of the
higher-order mode in that design has been replaced by a step change in
the 'guide diameter. The step does much the same thing, but is easier to
make.

The feed was designed as a part of the 10GHz transverter system I
designed and sold back a decade or so ago. It was specifically designed
to work well with TV offset dishes, and I have recently been using one
modified for WG17 input with a 1m dish as I stagger back onto 10GHz
EME.  I'm sorry to say that they are no longer available. I'm trying to
make a bit more space in my life to do some microwaving ... However, if
someone were to be interested in making the horn under some form of
licence, and can convince me that they are capable of doing it properly,
I'd be happy to talk.

73

Chris G4DGU