Re: 10GHz WG transition


Alan Beard
 

Hi all,

I asked about the "T" bar transition a while back, has anybody tried a flat strip replacing the round cross bar?

Could somebody do a simulation to give use guidelines for a "simple to build" transition?

Alan VK2ZIW

On Fri, 11 Jun 2021 09:57:23 +0100, John Fell wrote
> Hi Alan,
> Probably but I have no data .
> At the low frequencies you quote I would use a conventional 1/4 wave dipole structure mounted on a suitable coaxial socket .For no tune expand the dipole diameter and it should give a wideband performance .
> Material mix could give you long term intermetallic issues in a damp environment .
>
> 73
> John
> G0API   
>
> On Fri, 11 Jun 2021 at 06:45, Alan Beard <beardal@...> wrote:
>

> Hi John,
>
>

> "T" bar, can the bar be replaced by a flat strip?
>
>

> Are there any simulations to give us some guidelines?
>
>

> I'm looking for "no tune" transitions for 1, 2 and 3GHz.
> Where the waveguide will be extruded aluminium and
> all the added bits will be brass with the coax soldered to them. 
> Also, to reduce the inductance where the "inner goes to the bar",
> bring the coax right into the waveguide, the coax outer being a larger
> diameter.
>
>

> I have a 3.5GHz "T" bar transition here from 1950 perhaps, beautifully made
> but a custom, never seen anywhere, coax connector.
> WG 2 3/8" x 1 1/8" or 60mm x 29mm and the bar 1/2" or 12.5mm 5/8" or 16mm
> from the back-short, 3/8 " or 10mm centre up from the WG broad face. 
> Thus the gap down to the broad face is about 4mm.
>
>

> Alan VK2ZIW
>
>

> On Thu, 10 Jun 2021 11:06:27 +0100, John Fell wrote
> > Fairy snuff .
> > It was based on one you made and I swopped for a T bar , rear of guide socket based thingy - long time ago .
> >
> > I also like the 3 stub /screw design using brass or copper plated brass screws for a more defined bandwidth .
> >
> > 73
> > John
> > G0API
> >
> > On Thu, 10 Jun 2021 at 10:48, Andy G4JNT <andy.g4jnt@...> wrote:
> >

> >
> > 'snot my design.    If I gave it to you,  'twould have been nicked from somewhere else. 
> > Remember decades ago hearing a rule of thumb along the lines of  "a fifth of a wavelength probe at a fifth of a wavelength from the back short".
> >
> > Andy
> > www.g4jnt.com
> >
> > On Thu, 10 Jun 2021 at 10:33, John Fell <john.g0api@...> wrote:
> >

> > Found this design by G4JNT just now .(see attached)
> > I have made several and they are easy to adjust using cross coupler and diode detector .
> >
> > The back short was milled from 1"x 1/2" Brass bar into a T section length and then cut into 1/2" lengths , providing a solid contact around the inner guide faces .
> >
> > The short is inserted partially and return loss measured - if required the short is squeezed further into the guide using a vice or thumped with a hammer and measurement repeated .
> >
> > As shown the socket is based on a flanged N type with extended spill.An SMA version is fine , with the spill extended using the outer of solid jacket cable to within a mm of the inner guide wall .
> >
> > 73
> > John
> > G0API
> >
> >

> >
> >

>
> ---------------------------------------------------
> Alan VK2ZIW
> Before the Big Bang, God, Sela.
> OpenWebMail 2.53, nothing in the cloud.
>
>
>
>


---------------------------------------------------
Alan VK2ZIW
Before the Big Bang, God, Sela.
OpenWebMail 2.53, nothing in the cloud.

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