VE4MA Feed Horn 1296 MHz

VK2KRR · Post by **VK2KRR** » Fri Sep 09, 2005 7:27 am

Slowly working away at getting a dish running on 1296 MHz for tropo work.

Just wondering about the VE4MA style feed horns.

I have seen articles with measurements for building one of these feeds, but they all seem to be circularly polarised.

In relation to the physical measurements of the feed horn itself (waveguide diameter and length etc), would there be any difference in these measurements if the feed was set up to be linear polarised rather than circular? I can't see that there would be, but am not 100% sure.

I'm hoping to use a 0.4 f/D ratio dish. If anyone has suggestions as to physical measurements to use for the horn, let me know.

Thanks

VK4JAM · Post by **VK4JAM** » Wed Nov 02, 2005 1:35 pm

Why not use 4NEC2 or similar to design your own feed. You can then get a feed that best illuminates your reflector, and gives you the desired polarisation. I've used 4NEC2 to do feed designs at 2.4 Ghz and it works well.
73
Andrew

VK2KRR · Post by **VK2KRR** » Tue Dec 27, 2005 3:35 pm

12 foot dish now built, but have to build the feed horn.

Anyone know where I can get some copper sheet from for this purpose?

I have not looked anywhere yet.

VK2JDS · Post by **VK2JDS** » Thu Oct 26, 2006 9:35 pm

this is an old thread, but worth regenerating.
i tried a copper tube feed, big heavy and awkward and it underilluminated my 4.6m dish, best results came from a doublequad feed with a brass plate reflector
i have now built a dual circular feed for eme with preamp at the feedpoint etc.
hoping to install this weekend (bushfires here , so mightnt get the chance)
have heard ssb off the moon with the doublequad feed, it was unreadable but that was on old gear now replaced.
cheers

VK4KKD · Post by **VK4KKD** » Wed Jul 04, 2007 5:27 pm

VK2KRR wrote:12 foot dish now built, but have to build the feed horn.

Anyone know where I can get some copper sheet from for this purpose?

I have not looked anywhere yet.

G'day leigh - a lot of water has gone under the bridge since you started this thread and I think you would have all the feed system sorted by now.

If Not contact Trevor (VK4AFL) - he is running a VE4MA feedhorn (waveguide) on his 3.7m dish on 1296.

All the construction details are on the web for building and running either CP or linear - it really is a very simple procedure to do.

The VE4MA unit works fine - why re invent the wheel when someone has already done all the hard yards?

I am trying to clear my back orders for towers then I will be setting up my dish for 1296 - but seeing as my main aim is portable work (the dish will be trailer mounted) I am going to opt for a "patch feed" - super simple to construct and far less bulky than the waveguide feedhorn style. Plus I will probably go for the dual band patch feed and run 70cm as well as 1296 from the dish. I will still get a reasonable gain from the 2.3m dish on 70cm - reasonable enough for portable work anyway.