[NLRS] [Mw] Boradwall Waveguide slots for antennas

[Dr. Gerald N. Johnson]

Some of the literature I have calls them dumbells. Just seems they are 
easier to make than straight slots because of drilling the end holes. 
And then the endmlll doesn't have to drill too to get the slot started. 
But many a two flute endmill can drill, though it will want to wander 
because there's nothing pointy to fit in a center punch mark. A four 
flute endmill cuts a smoother surface but not when cutting a slot and 
often won't drill. A two flute endmill should always be used for cutting 
a slot because it makes a smoother wall. The mid flute on the leading 
face of a four flute endmill in a slot kicks the cutter sideways and 
makes it dig into the wall cutting a slot wider than the cutter where a 
two flute endmill can cut a slot the same width as the endmill diameter. 
I think a saw will do better than both. I'll learn more soon making a 
slotted line for waveguide measurements.

73, Jerry, K0CQ

On 12/3/2015 4:20 PM, KENT BRITAIN wrote:
> I am talking about where the slots end with a larger hole.
> Sort of a dumbbell configuration.
>
> ------------------------------------------------------------------------
> *From:* Dr. Gerald N. Johnson <geraldj at netins.net>
> *To:* KENT BRITAIN <wa5vjb at flash.net>
> *Cc:* Microwave list <microwave at lists.eclectechs.com>; NLRS Reflector
> <NLRS at mailman.qth.net>
> *Sent:* Thursday, December 3, 2015 4:12 PM
> *Subject:* Re: [Mw] Boradwall Waveguide slots for antennas
>
> And for the convenience of cutting with a vertical mill.
>
> 73, Jerry, K0CQ
>
> On 12/3/2015 4:05 PM, KENT BRITAIN wrote:
>  > The round ends are usually for high power applications. WA5VJB
>  >
>  > ------------------------------------------------------------------------
>  > *From:* Dr. Gerald N. Johnson <geraldj at netins.net
> <mailto:geraldj at netins.net>>
>  > *To:* Microwave list <microwave at lists.eclectechs.com
> <mailto:microwave at lists.eclectechs.com>>; NLRS Reflector
>  > <NLRS at mailman.qth.net <mailto:NLRS at mailman.qth.net>>
>  > *Sent:* Thursday, December 3, 2015 3:55 PM
>  > *Subject:* [Mw] Boradwall Waveguide slots for antennas
>  >
>  > I know there has been some mention in references I have about round ends
>  > vs square ended slots, though most of the computation appear to be based
>  > on square ends to the slots and no thickness to the waveguide walls. Is
>  > there any literature showing a difference between the resonances and
>  > radiation of round vs square ended slots?
>  >
>  > Then is there any that allows for the slot in the inside of the guide
>  > being a different length than on the outside, as it would naturally be
>  > from cutting the slots with a metal circular saw blade? Or does all the
>  > literature presume all slots will be squared up by hand after the
>  > milling operations. With copper not a fun material to cut slots in with
>  > an end mill because its so gummy and grabby, I'm thinking cutting with a
>  > fine toothed saw blade would make much smoother slot walls and destroy
>  > way fewer cutting tools. Filing isn't much fun either with a file small
>  > enough to fit in a 10 GHz slot. The stroke can't be very long and the
>  > file has to be thin and weak. I have a large supply of 3" and 4"
>  > diameter metal saw blades that I can use, if the slot resonance and
>  > radiation aren't messed up by sloping ends on the slots. I also have
>  > collected a few 3/4" and 1" diameter but those won't get the ends
>  > perfectly perpendicular to the surface and have very coarse teeth
>  > compared to the bigger ones.
>  >
>  > 73, Jerry, K0CQ
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