Re: Calculating the impedance of a dielectric rod in free space to get a match to 377 ohms?

Neil Smith G4DBN

Simulation is working fine, but I had a feeling there was an analytical solution to calculate the characteristic impedance of a dielectric rod waveguide in air. Intellectual curiosity getting the better of me in late-night modelling sessions....

The extension rod does seem to reduce the sidelobes a little when it is about 6mm diameter.  I'm more interested in getting the edge taper right, and by adjusting the cone angle, I can get a nicely flattened lobe with a slight dip in the middle.  This is  in a 22 mm diameter tube but with a narrower lobe and no dip. It will be amusing to see if the real thing is anything close to the models

Neil G4DBN

Re: Calculating the impedance of a dielectric rod in free space to get a match to 377 ohms?

Mike Willis

Simulate it perhaps? E.g. the HB9PZK design lens in 22mm circular waveguide.

--
Mike G0MJW

Re: Calculating the impedance of a dielectric rod in free space to get a match to 377 ohms?

Dominique Dehays

Hi Matti ,

thx very much for this interesting report , it gives me some ideas...

73

Dom/F6DRO

Re: Wavelab 2W 24Ghz TRV

Neil Smith G4DBN

I haven't had mine under the microscope yet. Hope to have a close look for any polarity bumps tomorrow night. I think I have a suitable collet crimper so any individual-wire connector will do. I might look for one that is pre-terminated with pigtails, because laziness...

Neil G4DBN

On 10/03/2021 22:55, Steve G4KNZ wrote:
I ordered one, which arrived today (just arrived, no fee or VAT to pay at least so far).
The PCB connectors appear to be 20-way (2x10way) 1.27mm pitch female, does anyone happen to know the correct or an appropriate part to mate with these?

S

Re: Wavelab 2W 24Ghz TRV

Steve G4KNZ

I ordered one, which arrived today (just arrived, no fee or VAT to pay at least so far).
The PCB connectors appear to be 20-way (2x10way) 1.27mm pitch female, does anyone happen to know the correct or an appropriate part to mate with these?

Steve G4KNZ

GB3VHF

ian hope (2E0IJH)

Have sent Chris a email and a friend has sent him a text, but if any has contact with Chris FDZ, GB3VHF seems ill, its very low on output and sometimes just keys dead carrier, GB3UHF seems ok

There was a Major power outage in Meopham/Vigo with flickering power and overhead line arcing

Ian
M5IJH

Re: Calculating the impedance of a dielectric rod in free space to get a match to 377 ohms?

Neil Smith G4DBN

Hi Matti! Very interesting document, many thanks.  I need to read it thoroughly, but it is late and I need to sleep.

Neil G4DBN

On 10/03/2021 21:30, Matti Lukkarinen,OH1DB wrote:
HI Neil!

Here you get some information. With this document, i have done my own polyrod antenna
https://hamwaves.com/dielectric.rod/doc/dielectric_rod_antenna.pdf

de. Matti oh1b

On Wed, 10 Mar 2021 at 21:22, Neil Smith G4DBN <neil@...> wrote:

I'm doing some simulations of dielrod/dielspike horns using a simple taper from a round waveguide down to a round rod.  The plan is to set the diameter of the round rod extension such that it has the same impedance as free space, so there is no discontinuity at the end of the taper, and hopefully to minimise reflections.

Can anyone point me at a way to calculate the diameter of a dielectric rod guide to get the impedance of the terminal extension close to 377 ohms?  At the moment, I'm just fiddling with the diameter to see if I can reduce the sidelobes a little, but I'd prefer to set the rod to a known size, then adjust the length of the rod and the taper angle.

The dielectric plastic is Rexolite 1422, with a dielectric "constant"  of 2.53.

Neil G4DBN

```--
Neil
http://g4dbn.uk```

Re: Calculating the impedance of a dielectric rod in free space to get a match to 377 ohms?

Matti Lukkarinen,OH1DB

HI Neil!

Here you get some information. With this document, i have done my own polyrod antenna
https://hamwaves.com/dielectric.rod/doc/dielectric_rod_antenna.pdf

de. Matti oh1b

On Wed, 10 Mar 2021 at 21:22, Neil Smith G4DBN <neil@...> wrote:

I'm doing some simulations of dielrod/dielspike horns using a simple taper from a round waveguide down to a round rod.  The plan is to set the diameter of the round rod extension such that it has the same impedance as free space, so there is no discontinuity at the end of the taper, and hopefully to minimise reflections.

Can anyone point me at a way to calculate the diameter of a dielectric rod guide to get the impedance of the terminal extension close to 377 ohms?  At the moment, I'm just fiddling with the diameter to see if I can reduce the sidelobes a little, but I'd prefer to set the rod to a known size, then adjust the length of the rod and the taper angle.

The dielectric plastic is Rexolite 1422, with a dielectric "constant"  of 2.53.

Neil G4DBN

Calculating the impedance of a dielectric rod in free space to get a match to 377 ohms?

Neil Smith G4DBN

I'm doing some simulations of dielrod/dielspike horns using a simple taper from a round waveguide down to a round rod.  The plan is to set the diameter of the round rod extension such that it has the same impedance as free space, so there is no discontinuity at the end of the taper, and hopefully to minimise reflections.

Can anyone point me at a way to calculate the diameter of a dielectric rod guide to get the impedance of the terminal extension close to 377 ohms?  At the moment, I'm just fiddling with the diameter to see if I can reduce the sidelobes a little, but I'd prefer to set the rod to a known size, then adjust the length of the rod and the taper angle.

The dielectric plastic is Rexolite 1422, with a dielectric "constant"  of 2.53.

Neil G4DBN

Re: Feedthrough capacitor wanted

G4WIM KT6UK

Andy,

I had the same problem when building my 13cm PA - I had the feed thru's but they were an American thread, landed up buying a tap from China to match the thread pitch / size.

Worked out a lot cheaper than buying new metric feed thru's.

73 Tim

Re: New 241 GHz record (via F1VL)

militaryoperator

I can usually work into netherlands/france/Jersey with 50W on 70cm from my location, and I have to beam through the hill that you sit on ... I was otherwise occupied on Tuesday, will be on 6m on Thursday though.

Fantastic.

Best last night here in 432FMAC was just 62Km, with 50W to X5000 colinear at 50ft.

Mind you, someone got 112Km with 25W and a dipole......... apparently!.
I wonder how high the dipole was?

Seems I'm wasting my time and efforts in some respects.

Ben G4BXD

--
Robin Szemeti - G1YFG
_._,_._,_

Re: New 241 GHz record (via F1VL)

Neil Smith G4DBN

On 10/03/2021 11:22, militaryoperator via groups.io wrote:

Seems I'm wasting my time and efforts in some respects.
Hi Ben, time spent playing on the radio is never wasted though. It is far better than time spent NOT playing on the radio...

I often struggled to make 50 km in the 432 FMAC using an 18-ele beam and my handheld, even with it vertical, so you are doing better than I was.

There is a lot of chat around how the 20 mW at 241 GHz was generated. With 57 dBi gain, that is a mighty EIRP, and then the little matter of climbing a mountain and having an optical path does tend to add a shedload of dBs to the signal!

Nel G4DBN

Re: New 241 GHz record (via F1VL)

Robin Szemeti - G1YFG

I can usually work into netherlands/france/Jersey with 50W on 70cm from my location, and I have to beam through the hill that you sit on ... I was otherwise occupied on Tuesday, will be on 6m on Thursday though.

On Wed, 10 Mar 2021 at 11:22, militaryoperator via groups.io <Military1944=aol.com@groups.io> wrote:
New IARU R1 record on 241 GHz. QSO 6 March 2020, 17.10 UTC between:
DK5NJ at JO50TI29JN 690m ASL Schwedenwache (DK0NA) and DB6NT at JO60GJ03MN 896m ASL Aschberg (Saxe).
Distance 63.987 km.
--------------------------------

Fantastic.

Best last night here in 432FMAC was just 62Km, with 50W to X5000 colinear at 50ft.

Mind you, someone got 112Km with 25W and a dipole......... apparently!.
I wonder how high the dipole was?

Seems I'm wasting my time and efforts in some respects.

Ben G4BXD

--
Robin Szemeti - G1YFG

Re: New 241 GHz record (via F1VL)

militaryoperator

New IARU R1 record on 241 GHz. QSO 6 March 2020, 17.10 UTC between:
DK5NJ at JO50TI29JN 690m ASL Schwedenwache (DK0NA) and DB6NT at JO60GJ03MN 896m ASL Aschberg (Saxe).
Distance 63.987 km.
--------------------------------

Fantastic.

Best last night here in 432FMAC was just 62Km, with 50W to X5000 colinear at 50ft.

Mind you, someone got 112Km with 25W and a dipole......... apparently!.
I wonder how high the dipole was?

Seems I'm wasting my time and efforts in some respects.

Ben G4BXD

New 241 GHz record (via F1VL)

Neil Smith G4DBN

Tks F1VL on hyperfr-ref for this news snippet from DB6NT and DK5NJ. Marvellous stuff

Neil G4DBN

New IARU R1 record on 241 GHz. QSO 6 March 2020, 17.10 UTC between:

DK5NJ at JO50TI29JN 690m ASL Schwedenwache (DK0NA) and DB6NT at JO60GJ03MN 896m ASL Aschberg (Saxe).
Distance 63.987 km.
Reports 559/599.
Temp -1C, RH 45%.
Both receivers used a sub-harmonic mixer drive by a 120 GHz LO
Transmit power 20 mW
Both ends used 40 cm dishes with a gain of 57 dB and a beasmwidth of less than 0.25°
This was a line of sight path, and alignment was done using riflescopes
Signal strength was around 30dB over noise, suggesting the possibility that 100 km could have been achieved under those conditions.

Re: Feedthrough capacitor wanted

Andy G4JNT

I have dozens, nay hundreds possibly,  of second-hand feedthroughs of all sizes.   They are one of the items worth recovering above all else from scrap rally-purchases, being so expensive bought new.
However, having said that, there aren't many in there with a thread diameter of 4mm.  Some measure at 4.5mm and many 5.5 or 6mm

I was going to say  PM me your address, but Roger's message just-now popped up to say he had loads of that size, so better off there.
But if anyone else needs larger feed throughs, I do have a wide selection...   See photo attached ...

Actually it's damned annoying.   Most of them have coarse American threads and I have no or very few nuts suitable, so quite often end up soldering in threaded types - which sometimes damages them and always looks untidy.    The only metric threaded feedthroughs have generally come from Eu built ex mob phone etc kit - which is usually too good in itself to just rip apart from the components.

Andy

On Wed, 10 Mar 2021 at 07:59, John Lemay <john@...> wrote:
I'm looking for just one feedthrough capacitor, to replace a failed item:

The most important feature is the screw-in thread, which needs to be 8-32,
to fit the tapped hole in my case. Overall length about 20mm. Capacitance
value is unimportant and the working voltage only needs to be 24v.

Anyone got one tucked away in the spare component drawer ?

Tip: 8-32 thread looks like M4 at first glance.

Thanks

John G4ZTR

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Re: Feedthrough capacitor wanted

John Lemay

Roger

That would be brilliant thanks !

I'll drop you my address on a PM.

John

-----Original Message-----
From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Roger Ray via groups.io
Sent: 10 March 2021 08:17
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Feedthrough capacitor wanted

Hi John,

I have got a few hundred 1000pF. I believe are 8/32. ie same size but will not fit a 4mm nut. I can send you a few.

Roger
On 10 Mar 2021, at 07:59, John Lemay <john@carltonhouse.eclipse.co.uk> wrote:

﻿I'm looking for just one feedthrough capacitor, to replace a failed item:

The most important feature is the screw-in thread, which needs to be 8-32,
to fit the tapped hole in my case. Overall length about 20mm. Capacitance
value is unimportant and the working voltage only needs to be 24v.

Anyone got one tucked away in the spare component drawer ?

Tip: 8-32 thread looks like M4 at first glance.

Thanks

John G4ZTR

--
This email has been checked for viruses by AVG.
https://www.avg.com

Re: Feedthrough capacitor wanted

Roger Ray

Hi John,

I have got a few hundred 1000pF. I believe are 8/32. ie same size but will not fit a 4mm nut. I can send you a few.

Roger

On 10 Mar 2021, at 07:59, John Lemay <john@carltonhouse.eclipse.co.uk> wrote:

﻿I'm looking for just one feedthrough capacitor, to replace a failed item:

The most important feature is the screw-in thread, which needs to be 8-32,
to fit the tapped hole in my case. Overall length about 20mm. Capacitance
value is unimportant and the working voltage only needs to be 24v.

Anyone got one tucked away in the spare component drawer ?

Tip: 8-32 thread looks like M4 at first glance.

Thanks

John G4ZTR

--
This email has been checked for viruses by AVG.
https://www.avg.com

Re: DB6NT sequencer

John Lemay

Hi Pete

Very long time no speak ! Hope you’re well.

Yes, checked the diode and it was OK, but replaced it anyway, being cheap and easy to do.

Regards

John G4ZTR

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Peter Burgess via groups.io
Sent: 09 March 2021 21:45
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] DB6NT sequencer

Hi John

Check that the protection diode across the relay has not gone open circuit.

Peter
G4BCH

 Virus-free. www.avg.com

Feedthrough capacitor wanted

John Lemay

I'm looking for just one feedthrough capacitor, to replace a failed item:

The most important feature is the screw-in thread, which needs to be 8-32,
to fit the tapped hole in my case. Overall length about 20mm. Capacitance
value is unimportant and the working voltage only needs to be 24v.

Anyone got one tucked away in the spare component drawer ?

Tip: 8-32 thread looks like M4 at first glance.

Thanks

John G4ZTR

--
This email has been checked for viruses by AVG.
https://www.avg.com

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