Date   

Re: WIMO SHF 2328 23cm-Yagi 28 Element ?

alwyn.seeds1
 

Dear Chris,

Thanks for the note about the “Pawsey Stub”.

Like Uda, White did not receive the recognition due to him, although at least in Uda’s case Yagi’s involvement in the work was considerable.

I have a number of the ‘30s patents from Blumlein’s group- their innovations were absolutely remarkable- and the patents easier to read than subsequent textbook descriptions.

Regards,

Alwyn


_____________________________________________________

Alwyn Seeds, Director
114 Beaufort Street (Management) Company Ltd.,
114 Beaufort Street,
London,
SW3 6BU

114 Beaufort Street (Management) Company Ltd., Registered in England and Wales: No. 02797775 Registered Office Address: 114 Beaufort Street, London, SW3 6BU
______________________________________________________


Re: Yagi- more

Robin Szemeti - G1YFG
 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)


On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:
I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .
Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

73
John
G0API

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:
Interesting ...

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...



On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:
Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


Re: Microwave oven test

Neil Smith G4DBN
 

It will probably be uPVC then, which is not a great dielectric, but for this application, and if the sections are thin, you should get away with it.  Losses vary, but the figures I've seen are something like a tan delta of 0.02 at 1GHz for uPVC, about the same as polycarbonate, compared with 0.0003 or so for polystyrene, polypropylene, PTFE and polystyrene.  Just because the loss tangent is 70 times as bad isn't necessarily serious, seventy times a tiny amount is still a tiny amount. You wouldn't use it in a tuned cavity or as the dielectric in a capacitor or a microwave lens though.

I've seen lemonade bottles used to cover helicals, but there is always a problem with condensation if it is too enclosed, so think umbrella rather than wetsuit. PET loss tangent is something around 0.008 at 1GHz, and being thin, any loss would be very small unless you are also running 10GHz through the bottom of the bottle and it is one of those with a heavily moulded base, where you might get some weirdness.

Do the oven test and see if you detect any warming. If the material has unusual fillers or plasticisers, it could be radically different from raw uPVC

Neil G4DBN

On 23/09/2020 21:48, G8TZJ via groups.io wrote:
 Neil Smith G4DBN

It is going to be outside and probably subject to rain. (I'm unsure about a covering, as I want to limit the wind loading). The plastic type is unknown. Its the off cuts from soffits and bargeboards etc. from when the roof was done some time back.

73 Andrew G8TZJ
-- 
Neil
http://g4dbn.uk


Tropo opening reports

John Quarmby
 

I would be pleased to receive any reports of DX worked and interesting observations on propagation from the opening earlier this week, which I can then summarise for DUBUS 4/20, and I can also copy reports onto John G4BAO for RadCom & Scatterpoint.

73

John G3XDY


--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus


Re: Microwave oven test

G8TZJ
 

 Neil Smith G4DBN

It is going to be outside and probably subject to rain. (I'm unsure about a covering, as I want to limit the wind loading). The plastic type is unknown. Its the off cuts from soffits and bargeboards etc. from when the roof was done some time back.

73 Andrew G8TZJ


Re: WIMO SHF 2328 23cm-Yagi 28 Element ?

Robin Szemeti - G1YFG
 

My current 70cm antenna is a "Pawsey stub" balanced dipole feed, I tried replicating it at 1296, but the mount above the boom when all the directors are through boom messes it up.   I will be cutting away a section of boom and fitting a bracing piece, maybe that will solve it.

On Wed, 23 Sep 2020 at 14:18, Chris Bartram G4DGU <chris@...> wrote:
Hello Robin,

I looked at the problems with folded dipoles (or loops as most of them
become at >1GHz) some years ago using a proper E-M analysis tool (not
NEC derived software) when designing antennas for my old QTH in SW
Wales. While folded dipoles/loops with a half-wave balun could be made
to work with some fiddling, I decided to use simple split dipoles with
driven by a so-called Pawsey Stub(1) balun. That showed good balance,
despite a friend suggesting that the structure was unbalanced 'by
inspection'. The losses were very low indeed when measured on my HP net.
an. at that time. I've come to the conclusion that favouring the 'folded
dipole' feed has no real engineering validity.

FWIW, my VHF/UHF yagi antennas were designed around 4m lengths of 20mm
od, 1.5mm wall alloy tube - I forget the alloy type, maybe 6082. These
were self-supporting at 20m agl even in the windy conditions of NW
Carmarthenshire. I used polyprop. standoff insulators manufactured for
supporting a commercial garden trellis. Unfortunately, these are no
longer available. I have used the simple dipole/'Pawsey' stub balun
arrangement very sucessfully on various antennas from 82 - 1296MHz.


73

Chris G4DGU

(1) Pawsey was a pioneer Australian radio astronomer working from the
mid-1940s. He described the balun structure which carries his name
sometime around 1950, however, the idea was patented by EMI in 1936, in
the name of an engineer named White who was working with Alan Blumlein
on the development of high power TV transmitters.


On 23/09/2020 10:15, Robin Szemeti - G1YFG wrote:
> The problem with the DL6WU dipole is that it is very difficult to fit
> over the boom on 1296 and above.
>
> Most articles recommend 50mm  between the top and bottom of the folded
> dipole as the maximum for 144MHz,  and if you scale that to 1296 you
> get about 6mm ... if you make the gap too big, it begins to behave
> like some sort of resonant full wave loop, not a folded dipole.
>
> Most 1296 booms are around 15mm and the "over boom" diploles I see
> have a height of around 25 to 30mm .. this is far too big in my
> opinion.  I've spent some time playing with a coupler and a variety
> of  lengths, I was unable to get an acceptable match and get it to fit
> over the boom ...
>






--
Robin Szemeti - G1YFG


Re: Microwave oven test

Colin Ranson
 

Out of interest – my microwave oven does not have a turntable. The antenna(s) are under the floor. Somehow they are electronically steered ?

 

I found it very weird first few times I used it.

 

Regards

 

Colin de ‘LBS.

 

Sent from Mail for Windows 10

 

From: Andy G4JNT
Sent: 23 September 2020 14:35
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Microwave oven test

 

And while we're on the subject of microwave ovens, I stumbled on this simple demonstration of the effectiveness of silver plating.

Put both a stainless steel and EPNS piece of cutlery into the uWave oven (along with the obligatory glass of water) and power on for 30 seconds or so.

 

The stainless steel cutlery will end up hot, possibly even too hot to touch, while the Electroplated Silver will remain cold

 

I discovered this quite by accident when making my regular deluxe Hot Choc in the evening which involves first melting chocolate buttons in a small amount of milk before topping-up.    Burnt my finger on the S-Steel teaspoon, whereas the EPNS one stays cold.

Fully recommend https://www.chococo.co.uk/  BTW :-)

 

 

Andy

 

 

 

On Wed, 23 Sep 2020 at 14:25, Clint Sharp <cjaysharp@...> wrote:

A glass tray or plate of thinly spread egg whites is a good way to test radiation pattern in a microwave because they turn white with a little energy

 

On Wed, 23 Sep 2020, 13:31 Neil Smith G4DBN, <neil@...> wrote:

If you do it with chocolate and don't rotate the turntable, you get a pattern of melting.  I'd suggest something over a half-wave at 2.6 GHz and support it so there is air around it, to prevent conductive heat loss. The cup of water will boil after a minute or so, and the steam will make your plastic hot, so 30-40 seconds is probably a practical limit.

If it's going to be outside, avoid nylon as it soaks up water. ABS, acrylics and polycarb are sort-of OK, PTFE/HDPE/PU/polystyrene are very good. Acetal/POM and PEEK are less than brilliant, but great mechanically. Small bore tubing is good for stiffness and light weight, or strips of Styrene modelmakers sheet (actually polystyrene) drilled and then thread two or three on to the helix and fix with polystyene cement.

If it is going inside a radome, then just use closed-cell polystyrene foam blocks as the support

Neil G4DBN

On 23/09/2020 12:32, G8TZJ via groups.io wrote:

I have heard that to test if a plastic is suitable for a microwave project, you put it in a microwave oven. I'm making a helix for 2.4 GHz and it will need some supports. So my questions are;
How big a piece do I put in the oven to test?
How long do I run the microwave oven for?
Its an 800W oven.
I know you have to put a cup of water in as well.

Any suggestions?

73 Andrew G8TZJ

-- 
Neil
http://g4dbn.uk

 


Re: Yagi- more

John Fell
 

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .
Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

73
John
G0API

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:
Interesting ...

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...



On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:
Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


--
Robin Szemeti - G1YFG


Re: Tropo

John Fell
 

Thanks Nick.
Overland duct linkages (200km+) into Sea ducts are still quite rare down this way , so if we see more this year I will be very pleased to report them.Linkage it the local duct was at low dish elevation and was narrow tolerance - some bent AZ paths noted , all to the East.
In the late 1970's October was a banker for VHF /UHF ducting into LA/SM etc - often on a small vertical with a couple of Watts ....

73
John
G0API

On Wed, 23 Sep 2020 at 13:04, Nicholas Shaxted <nick@...> wrote:

HI John,

I have not seen any data that provides statistically significant correlation one way or the other so the short answer is no.

 

It is a very difficult question to answer though and it will require the spectacles of hindsight to gain a considered view. The global wildfires of course will add confusion as they are seeding huge amounts of aerosols and Carbon Dioxide into the upper tropospheric region and may end being responsible for an increase in rainfall.

What does appear to be significant is that this year we have reached either a peak or a tipping point in extreme weather

 

Tropical cyclones forming off the North African coast / Azores and zipping northwards are unusual and it will only be a matter of time before some shift slightly eastwards (latest one is Paulette)

 

Southern North Sea sea surface temperature reached a peak of 20 deg C this year which is about normal. I will check back on the data I started to collect about 25 years ago to be sure.

Simple analysis of DX cluster information has not really shown a change – one has to be careful as the use of such resources has changed significantly with so many adopting digimodes on the low bands.

This has an effect that distorts the overall picture and I have yet to work out a way to normalize such reporting.

 

When I lived in GM-land in the 1982-2006 I got used to hearing SK6MHI (~1000km) on 23cm everyday between May – September, SK6UHI was not far behind. DB0GHZ on 3cm appeared 20% of the same timeframe.  Here in south-east England on 3cm DB0GHZ (~560km) appears nearly every day between August/September (2019/2020). PI7ALK and PI7RTD are always present (~300km).

So I can fall back on that data to provide a long baseline with a slight adjustments.

 

Certainly this recent tropo event gave John G3XDY and me a chance to improve our ODX on 3cm to beyond 1300km.

 

It shows that reliable reporting across the whole of Europe allows the collection and analysis of propagation data. From my perspective it is clear more sophisticated tools are required but this has always been the case.

 

My thanks go to all who contributed by being active or reporting activity.

 

John G4BAO and John G3XDY should be busy over the next few weeks collecting and correlating all your reports 😊

 

 

73

Nick – g4ogi

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of John Fell via groups.io
Sent: 23 September 2020 10:10
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tropo

 

Hi Nick,

Thank you for your usual high standard input analysis of the recent Tropo conditions .

 

From reports on this Reflector and BeaconSpot.UK it is apparent that it was a significant event for all Microwave bands .

My original comment mentioned the influence of reduced airborne pollution due to the current situation and if it would prove to be of benefit to this season's Tropo .

 

Would appreciate your thoughts 

 

73

John

G0API

 

On Tue, 22 Sep 2020 at 19:30, Nicholas Shaxted <nick@...> wrote:

There are multiple contributing factors that have made for some interesting propagation conditions this autumn.

The main highlights from an amateur radio perspective is that a relatively stable High pressure region formed consistently of multiple High pressure systems. Their dissipation allowing elevated temperature inversions to occur and also existed opportunity underneath for an almost contiguous surface duct to form.

 

If you look at the appropriate data (Skew-T Charts) across a number of cities across Europe you will quickly see that these temperature inversions were at 950 (~500m asl)  and 750hPa (~2500m asl). The low level inversion has been present from Manchester to Warsaw and from Stockholm to Stuttgart and provided microwavers with decent opportunities for contacts. The higher level one has been a little patchier and from the data I have collected seems more confined more to northern areas of Europe (Copenhagen and northern Germany) and thus probably confused many VHFers

 

I have said on this reflector before that skewed propagation are the result of refraction through an air mass body. This mass will be subject to changes in temperature, humidity, local pressure and wind which will contribute to a swirling (slow moving) mixing blob with variable refraction properties. The speed of mixing takes place over hours and can produce strong localised refraction in any plane (it is a 3D body). At microwave frequencies it is not unusual to see angles of arrival varying a number of degrees in azimuth over a short time.

 

Local signals here tended to remain anchored to the horizon (0 deg) elevation) but significant  (3dB or so) improvement to some long haul signals were measured (SK1SHH at 1306km, OZ1UHF at 915km) with the dish elevated by between 0.2 – 0.4 degrees.

 

Nick – g4ogi

 

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of SAM JEWELL via groups.io
Sent: 22 September 2020 16:10
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tropo

 

Although we are probably agreed it was predominantly an elevated duct for the real DX, the number and strength of Dutch stations on 2 and 70 (maybe a few on 23cm but activity is lower) seems to indicate a low level surface duct was also present.

Reflections from single ships and builds are not likely to result in much of a reflection, but we are talking about hundreds, if not thousands of significant buildings/ structures along the coast and within the common volume beamwidth of the antennas.

On 2m there was some evidence of multipath on some of the stronger FT8 signals in the UK, who were, presumably, beaming east towards the continent.

I have, over the years, worked a number of northern England and Scotland stations by beaming eastish from here in Suffolk. This mainly on 23cm, back when there was more activity. Skew paths on 10GHz are quite common and again it may be reflection or refraction. The Galloper and Great Gabbard wind farms are the biggest contributors here.

I might add that the Belgian radar on 23cm was really strong the last few days. The noise blanker really was unable to take it out on any setting. Not just every eight seconds of rotation, but continuous, as it rotated and reflected from every object it illuminated!

 

73 de Sam, G4DDK

 

 

 





------ Original Message ------
From: "Marcus Walden" <marcus.g0ijz@...>
To: UKMicrowaves@groups.io
Sent: Tuesday, 22 Sep, 20 At 14:57
Subject: Re: [UKMicrowaves] Tropo

I don't think there will be any tropospheric propagation via 'vertical incidence'. However, we are interested in the vertical refractive index profile because that provides an indication of whether or not ducting is likely. Is there a mix-up in terminology in an earlier posting?

Looking at radiosonde data for Schleswig (Northern Germany for Sunday 20 September at 1200 UTC and Monday 21 September at 0000 UTC, there is evidence of a very strong elevated duct - sufficiently strong to support VHF and UHF. Was there tropo activity on 2 m and 70 cm this weekend? I don't know because I'm HF QRP and currently without an antenna.

The elevated duct and inland stations might be an indication that the off-great-circle paths are not caused by reflections from ships. Hills/mountains?

With HF propagation, there can be horizontal gradients in the electron density in the ionosphere, which results in bearings that are not great-circle. Could a similar effect be happening within the troposphere? In other words, there is refraction in the horizontal plane (or at least not vertical), as well as in the vertical plane.

Perhaps anomalous bearings could be collected from multiple stations to see if there is a common characteristic or focal point on a map? What about weather conditions in this region, if one is identified?

73 Marcus G0IJZ


Re: Yagi- more

Robin Szemeti - G1YFG
 

Interesting ...

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...



On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:
Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


--
Robin Szemeti - G1YFG


Yagi- more

John Fell
 

Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


Re: Tropo

Neil Smith G4DBN
 

Perhaps we need to ask Philip Gladstone if it is possible to add bands above 23cm into PSKReporter, as then all reception reports will be collated from any station with uploads enabled.  I don't know for sure if WSJT-X uploads on microwave bands, but it is easy enough to check. It does on 23cm for sure.  The other aspect is to ask Philip if it is possible to run extract queries over a longer timespan for V/U/SHF bands.  I see only Opera and FT8 on 23cm for the last 24 hours, and trying to cheat by extending from 86400 in the permalink has no effect, so I guess that only the last 24 hours are available for query via the web interface.

https://pskreporter.info/pskmap.html?preset&callsign=ZZZZZ&what=all&band=480000000-1400000000&timerange=86400

It does need a pinch of salt now and then, where someone is pointed at their IF instead of transverter and you find that EI8xxx has heard PY on 70cm FT8.

https://pskreporter.info/pskmap.html?preset&callsign=ZZZZZ&what=all&band=300000000-480000000&timerange=86400

If Philip can't help with longer-term database entries, perhaps a scraper could slurp up each day's worth of reports from the table fields and collate them for analysis?

Neil G4DBN


On 23/09/2020 13:04, Nicholas Shaxted wrote:

 

It shows that reliable reporting across the whole of Europe allows the collection and analysis of propagation data. From my perspective it is clear more sophisticated tools are required but this has always been the case.

 



Re: Activity List for the final session of the UKuG 5.7/10GHz Contests 2021 - Sunday 27th September

John Lemay
 

Hi John and all

I plan to be QRV ...........

Callsign: G4ZTR
Locator: JO01KW
Band: 10GHz, 10w, 1m dish
Talkback: ON4KST and 144MHz
Times: Various to suit activity

Regards

John G4ZTR

-----Original Message-----
From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of John Quarmby via groups.io
Sent: 21 September 2020 15:59
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] Activity List for the final session of the UKuG 5.7/10GHz Contests 2021 - Sunday 27th September

Next Sunday sees the final session of the UK Microwave Group 5.7 and
10GHz contest series. This takes place between 0600 and 1800 GMT (0700 -
1900 BST), entrants can operate for a maximum of 8 hours during the
period. Full rules can be found here:

https://www.microwavers.org/files/2020-mwrules_v6.pdf

Unfortunately i don't think weather and conditions will be quite as good
as the weekend we have just had, but let us see what happens.

Please send your plans in the usual format (as below) and I will issue a
collated list on the 26th September.


Callsign: G3XDY
Locator: JO02OB
Bands: 5.7GHz 15W, 60cm dish
10GHz 10W, 60cm dish
Talkback: ON4KST, Zello SHF Chat
Times: Various throughout.

73

John G3XDY
UKuG Contest Manager


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Re: Microwave oven test

Andy G4JNT
 

And while we're on the subject of microwave ovens, I stumbled on this simple demonstration of the effectiveness of silver plating.
Put both a stainless steel and EPNS piece of cutlery into the uWave oven (along with the obligatory glass of water) and power on for 30 seconds or so.

The stainless steel cutlery will end up hot, possibly even too hot to touch, while the Electroplated Silver will remain cold

I discovered this quite by accident when making my regular deluxe Hot Choc in the evening which involves first melting chocolate buttons in a small amount of milk before topping-up.    Burnt my finger on the S-Steel teaspoon, whereas the EPNS one stays cold.
Fully recommend https://www.chococo.co.uk/  BTW :-)




On Wed, 23 Sep 2020 at 14:25, Clint Sharp <cjaysharp@...> wrote:
A glass tray or plate of thinly spread egg whites is a good way to test radiation pattern in a microwave because they turn white with a little energy

On Wed, 23 Sep 2020, 13:31 Neil Smith G4DBN, <neil@...> wrote:

If you do it with chocolate and don't rotate the turntable, you get a pattern of melting.  I'd suggest something over a half-wave at 2.6 GHz and support it so there is air around it, to prevent conductive heat loss. The cup of water will boil after a minute or so, and the steam will make your plastic hot, so 30-40 seconds is probably a practical limit.

If it's going to be outside, avoid nylon as it soaks up water. ABS, acrylics and polycarb are sort-of OK, PTFE/HDPE/PU/polystyrene are very good. Acetal/POM and PEEK are less than brilliant, but great mechanically. Small bore tubing is good for stiffness and light weight, or strips of Styrene modelmakers sheet (actually polystyrene) drilled and then thread two or three on to the helix and fix with polystyene cement.

If it is going inside a radome, then just use closed-cell polystyrene foam blocks as the support

Neil G4DBN

On 23/09/2020 12:32, G8TZJ via groups.io wrote:
I have heard that to test if a plastic is suitable for a microwave project, you put it in a microwave oven. I'm making a helix for 2.4 GHz and it will need some supports. So my questions are;
How big a piece do I put in the oven to test?
How long do I run the microwave oven for?
Its an 800W oven.
I know you have to put a cup of water in as well.

Any suggestions?

73 Andrew G8TZJ
-- 
Neil
http://g4dbn.uk


Re: Unsure what these are called

Dave G8KHU
 

Hi Mike
Further to John's reply the flange in your picture is choked (deep groove inside the O ring) ands should be mated to a plain flange.
The guide does look to be WG16 (aka WR90 / R100), if so the inside dimensions of the guide are 0.9" x 0.4" and O/D will be 1" x 1/2".
I can't help you with rings I'm afraid, but I can let you have a couple of WG16 plain round flanges with pleasure. Send me your address off relector and I'll post them to you.
73
Dave
G8KHU


Re: Microwave oven test

Clint Sharp <cjaysharp@...>
 

A glass tray or plate of thinly spread egg whites is a good way to test radiation pattern in a microwave because they turn white with a little energy


On Wed, 23 Sep 2020, 13:31 Neil Smith G4DBN, <neil@...> wrote:

If you do it with chocolate and don't rotate the turntable, you get a pattern of melting.  I'd suggest something over a half-wave at 2.6 GHz and support it so there is air around it, to prevent conductive heat loss. The cup of water will boil after a minute or so, and the steam will make your plastic hot, so 30-40 seconds is probably a practical limit.

If it's going to be outside, avoid nylon as it soaks up water. ABS, acrylics and polycarb are sort-of OK, PTFE/HDPE/PU/polystyrene are very good. Acetal/POM and PEEK are less than brilliant, but great mechanically. Small bore tubing is good for stiffness and light weight, or strips of Styrene modelmakers sheet (actually polystyrene) drilled and then thread two or three on to the helix and fix with polystyene cement.

If it is going inside a radome, then just use closed-cell polystyrene foam blocks as the support

Neil G4DBN

On 23/09/2020 12:32, G8TZJ via groups.io wrote:
I have heard that to test if a plastic is suitable for a microwave project, you put it in a microwave oven. I'm making a helix for 2.4 GHz and it will need some supports. So my questions are;
How big a piece do I put in the oven to test?
How long do I run the microwave oven for?
Its an 800W oven.
I know you have to put a cup of water in as well.

Any suggestions?

73 Andrew G8TZJ
-- 
Neil
http://g4dbn.uk


Re: WIMO SHF 2328 23cm-Yagi 28 Element ?

Chris Bartram G4DGU
 

Hello Robin,

I looked at the problems with folded dipoles (or loops as most of them become at >1GHz) some years ago using a proper E-M analysis tool (not NEC derived software) when designing antennas for my old QTH in SW Wales. While folded dipoles/loops with a half-wave balun could be made to work with some fiddling, I decided to use simple split dipoles with driven by a so-called Pawsey Stub(1) balun. That showed good balance, despite a friend suggesting that the structure was unbalanced 'by inspection'. The losses were very low indeed when measured on my HP net. an. at that time. I've come to the conclusion that favouring the 'folded dipole' feed has no real engineering validity.

FWIW, my VHF/UHF yagi antennas were designed around 4m lengths of 20mm od, 1.5mm wall alloy tube - I forget the alloy type, maybe 6082. These were self-supporting at 20m agl even in the windy conditions of NW Carmarthenshire. I used polyprop. standoff insulators manufactured for supporting a commercial garden trellis. Unfortunately, these are no longer available. I have used the simple dipole/'Pawsey' stub balun arrangement very sucessfully on various antennas from 82 - 1296MHz.


73

Chris G4DGU

(1) Pawsey was a pioneer Australian radio astronomer working from the mid-1940s. He described the balun structure which carries his name sometime around 1950, however, the idea was patented by EMI in 1936, in the name of an engineer named White who was working with Alan Blumlein on the development of high power TV transmitters.

On 23/09/2020 10:15, Robin Szemeti - G1YFG wrote:
The problem with the DL6WU dipole is that it is very difficult to fit over the boom on 1296 and above.

Most articles recommend 50mm  between the top and bottom of the folded dipole as the maximum for 144MHz,  and if you scale that to 1296 you get about 6mm ... if you make the gap too big, it begins to behave like some sort of resonant full wave loop, not a folded dipole.

Most 1296 booms are around 15mm and the "over boom" diploles I see have a height of around 25 to 30mm .. this is far too big in my opinion.  I've spent some time playing with a coupler and a variety of  lengths, I was unable to get an acceptable match and get it to fit over the boom ...


Re: Microwave oven test

Neil Smith G4DBN
 

If you do it with chocolate and don't rotate the turntable, you get a pattern of melting.  I'd suggest something over a half-wave at 2.6 GHz and support it so there is air around it, to prevent conductive heat loss. The cup of water will boil after a minute or so, and the steam will make your plastic hot, so 30-40 seconds is probably a practical limit.

If it's going to be outside, avoid nylon as it soaks up water. ABS, acrylics and polycarb are sort-of OK, PTFE/HDPE/PU/polystyrene are very good. Acetal/POM and PEEK are less than brilliant, but great mechanically. Small bore tubing is good for stiffness and light weight, or strips of Styrene modelmakers sheet (actually polystyrene) drilled and then thread two or three on to the helix and fix with polystyene cement.

If it is going inside a radome, then just use closed-cell polystyrene foam blocks as the support

Neil G4DBN

On 23/09/2020 12:32, G8TZJ via groups.io wrote:
I have heard that to test if a plastic is suitable for a microwave project, you put it in a microwave oven. I'm making a helix for 2.4 GHz and it will need some supports. So my questions are;
How big a piece do I put in the oven to test?
How long do I run the microwave oven for?
Its an 800W oven.
I know you have to put a cup of water in as well.

Any suggestions?

73 Andrew G8TZJ
-- 
Neil
http://g4dbn.uk


Re: Tropo

Neil Smith G4DBN
 

Need more sleep (or more coffee). Unable to re-read my own posts with any degree of accuracy. Beyond hope....

On 23/09/2020 11:11, Dave Brown wrote:

Neil

Actually- you did.

From your post in reply to my query---“ Image from the excellent path profile software from Mike Willis.”

73 (from one who also forgets-often!!)

ZL3FJ

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Neil Smith G4DBN
Sent: Wednesday, September 23, 2020 20:56
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tropo

 

Very remiss of me not to give my usual acknowledgement when I use screen grabs from Mike's software. I have administered a self-slap to the wrist.

Neil G4DBN

On 23/09/2020 09:43, Andy G4JNT wrote:

 

-- 
Neil
http://g4dbn.uk


Re: Tropo

Nicholas Shaxted
 

HI John,

I have not seen any data that provides statistically significant correlation one way or the other so the short answer is no.

 

It is a very difficult question to answer though and it will require the spectacles of hindsight to gain a considered view. The global wildfires of course will add confusion as they are seeding huge amounts of aerosols and Carbon Dioxide into the upper tropospheric region and may end being responsible for an increase in rainfall.

What does appear to be significant is that this year we have reached either a peak or a tipping point in extreme weather

 

Tropical cyclones forming off the North African coast / Azores and zipping northwards are unusual and it will only be a matter of time before some shift slightly eastwards (latest one is Paulette)

 

Southern North Sea sea surface temperature reached a peak of 20 deg C this year which is about normal. I will check back on the data I started to collect about 25 years ago to be sure.

Simple analysis of DX cluster information has not really shown a change – one has to be careful as the use of such resources has changed significantly with so many adopting digimodes on the low bands.

This has an effect that distorts the overall picture and I have yet to work out a way to normalize such reporting.

 

When I lived in GM-land in the 1982-2006 I got used to hearing SK6MHI (~1000km) on 23cm everyday between May – September, SK6UHI was not far behind. DB0GHZ on 3cm appeared 20% of the same timeframe.  Here in south-east England on 3cm DB0GHZ (~560km) appears nearly every day between August/September (2019/2020). PI7ALK and PI7RTD are always present (~300km).

So I can fall back on that data to provide a long baseline with a slight adjustments.

 

Certainly this recent tropo event gave John G3XDY and me a chance to improve our ODX on 3cm to beyond 1300km.

 

It shows that reliable reporting across the whole of Europe allows the collection and analysis of propagation data. From my perspective it is clear more sophisticated tools are required but this has always been the case.

 

My thanks go to all who contributed by being active or reporting activity.

 

John G4BAO and John G3XDY should be busy over the next few weeks collecting and correlating all your reports 😊

 

 

73

Nick – g4ogi

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of John Fell via groups.io
Sent: 23 September 2020 10:10
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tropo

 

Hi Nick,

Thank you for your usual high standard input analysis of the recent Tropo conditions .

 

From reports on this Reflector and BeaconSpot.UK it is apparent that it was a significant event for all Microwave bands .

My original comment mentioned the influence of reduced airborne pollution due to the current situation and if it would prove to be of benefit to this season's Tropo .

 

Would appreciate your thoughts 

 

73

John

G0API

 

On Tue, 22 Sep 2020 at 19:30, Nicholas Shaxted <nick@...> wrote:

There are multiple contributing factors that have made for some interesting propagation conditions this autumn.

The main highlights from an amateur radio perspective is that a relatively stable High pressure region formed consistently of multiple High pressure systems. Their dissipation allowing elevated temperature inversions to occur and also existed opportunity underneath for an almost contiguous surface duct to form.

 

If you look at the appropriate data (Skew-T Charts) across a number of cities across Europe you will quickly see that these temperature inversions were at 950 (~500m asl)  and 750hPa (~2500m asl). The low level inversion has been present from Manchester to Warsaw and from Stockholm to Stuttgart and provided microwavers with decent opportunities for contacts. The higher level one has been a little patchier and from the data I have collected seems more confined more to northern areas of Europe (Copenhagen and northern Germany) and thus probably confused many VHFers

 

I have said on this reflector before that skewed propagation are the result of refraction through an air mass body. This mass will be subject to changes in temperature, humidity, local pressure and wind which will contribute to a swirling (slow moving) mixing blob with variable refraction properties. The speed of mixing takes place over hours and can produce strong localised refraction in any plane (it is a 3D body). At microwave frequencies it is not unusual to see angles of arrival varying a number of degrees in azimuth over a short time.

 

Local signals here tended to remain anchored to the horizon (0 deg) elevation) but significant  (3dB or so) improvement to some long haul signals were measured (SK1SHH at 1306km, OZ1UHF at 915km) with the dish elevated by between 0.2 – 0.4 degrees.

 

Nick – g4ogi

 

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of SAM JEWELL via groups.io
Sent: 22 September 2020 16:10
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tropo

 

Although we are probably agreed it was predominantly an elevated duct for the real DX, the number and strength of Dutch stations on 2 and 70 (maybe a few on 23cm but activity is lower) seems to indicate a low level surface duct was also present.

Reflections from single ships and builds are not likely to result in much of a reflection, but we are talking about hundreds, if not thousands of significant buildings/ structures along the coast and within the common volume beamwidth of the antennas.

On 2m there was some evidence of multipath on some of the stronger FT8 signals in the UK, who were, presumably, beaming east towards the continent.

I have, over the years, worked a number of northern England and Scotland stations by beaming eastish from here in Suffolk. This mainly on 23cm, back when there was more activity. Skew paths on 10GHz are quite common and again it may be reflection or refraction. The Galloper and Great Gabbard wind farms are the biggest contributors here.

I might add that the Belgian radar on 23cm was really strong the last few days. The noise blanker really was unable to take it out on any setting. Not just every eight seconds of rotation, but continuous, as it rotated and reflected from every object it illuminated!

 

73 de Sam, G4DDK

 

 

 





------ Original Message ------
From: "Marcus Walden" <marcus.g0ijz@...>
To: UKMicrowaves@groups.io
Sent: Tuesday, 22 Sep, 20 At 14:57
Subject: Re: [UKMicrowaves] Tropo

I don't think there will be any tropospheric propagation via 'vertical incidence'. However, we are interested in the vertical refractive index profile because that provides an indication of whether or not ducting is likely. Is there a mix-up in terminology in an earlier posting?

Looking at radiosonde data for Schleswig (Northern Germany for Sunday 20 September at 1200 UTC and Monday 21 September at 0000 UTC, there is evidence of a very strong elevated duct - sufficiently strong to support VHF and UHF. Was there tropo activity on 2 m and 70 cm this weekend? I don't know because I'm HF QRP and currently without an antenna.

The elevated duct and inland stations might be an indication that the off-great-circle paths are not caused by reflections from ships. Hills/mountains?

With HF propagation, there can be horizontal gradients in the electron density in the ionosphere, which results in bearings that are not great-circle. Could a similar effect be happening within the troposphere? In other words, there is refraction in the horizontal plane (or at least not vertical), as well as in the vertical plane.

Perhaps anomalous bearings could be collected from multiple stations to see if there is a common characteristic or focal point on a map? What about weather conditions in this region, if one is identified?

73 Marcus G0IJZ

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