Re: orders for 122


I get "Not Found" for the link.

73,  Zack W9SZ

On Thu, Nov 7, 2019 at 6:44 PM Paul Wade W1GHZ <w1ghz.q@...> wrote:
for those who want to play with IMU feed dimensions
and other stuff, yesterday I updated the HDL_ANT program
to run on 32 bit systems:

please let me know if you find any problems


On Thu, Nov 7, 2019 at 7:36 PM Neil Smith G4DBN <neil@...> wrote:
Hi Mike, for the IMU, I just used the raw calculations on the W1GHZ site
and just picked 0.68 f/d out of the aether as a nice-sounding number.
The rest of the dimensions just come from the equation for the taper and
outer diameter for the 3/4 wave phase match for the TE11 and  TM11
modes. Very easy to pop in a different F/D and get the correct
dimensions in the model.

Barry G8AGN also did a model for a W2IMU and pointed out that his
version could be made using a 2.0 and 3.5mm drill bit in a bit of 6mm bar.

My 5.7GHz Super-VE4MAs use a 0.71 wavelength aluminium tube with a
TIG-welded backshort and choke ring 0.3 wavelengths deep and 0.4 wide. 
I used the same proportions for the choke on the 122GHz version, but the
bore is 1.80mm instead of the 1.74mm it should be.  The wall of the
inside bore is about 0.15mm, the choke is 0.73mm deep and 0.98mm wide
and with a 0.15mm outer wall, so about 4.4mm diameter overall.  It was
designed for an f/d 0.55 dish.  I haven't run a model for this one, but
it is really too small and delicate to be practical. Nice as ear-rings

I'm going to take a bespoke approach and make horns to specific f/d for
those who want to experiment.  I haven't modelled my three-groove
Chaparral yet. Too many other jobs to do, and the day job as well. If I
ever get any spare time I want to try electroforming horns so I can do
corrugations and non-linear tapers.

Barry's model for the Skobelev looks good. My hope is that I can use a
3mm end mill in a toolpost spindle to cut the internal taper using the
compound slide on the lathe.

For additional giggles, I'm trying to model a 3/4 wave oval-iris-plate
round guide to WR-08 narrowband transition to fit between two UG387/U
style flanges to see whether it is feasible to machine it on my ancient
Bridgeport.  Certainly looks possible with perhaps a 1.2mm end mill if I
can spin it at ten times the RPM the old lump of iron can manage.

Way past my bedtime, I have work tomorrow, I'll post my .m files in the

Neil G4DBN

On 07/11/2019 23:33, Mike Lavelle K6ML wrote:
> Hi Neil ...
> For the scaled IMU, do you know what f/D the orginal ('scaled from')
> design was designed for?
> Similarly, for the second feed you're working on, what f/D?

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