Re: Topband: The Magic-T

[Richard (Rick) Karlquist]

The 90 degree hybrid is a third type of hybrid combiner,
distinct from the 0 degree and 180 degree types.  It
is typically used for 4 square phasing.  All 3 combiners
basically have a 3 dB insertion loss for signals having
appropriate phase conditions.

What you say is true to the extent that using a 90
degree combiner for two signals that are in phase
will result in a 3 dB loss.  You would not normally
want to do that.

Rick N6RK



On 2/10/2021 2:25 PM, P H via Topband wrote:

My impression is that a hybrid combiner, which introduces 90 degree shift 
(hence two identical signals of amplitude A fed to its inputs will give in 
total a signal with the amplitude of 1.41*A) is 3dB less efficient in 
comparison to a simple combiner where A+A gives 2*A at the output.
Do you have any thoughts on this?
A loss of 3 dB may be like "to be or not to be" of a QSO on 160 meters.
Regards
Piotr, SP2BPD
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Re: Topband: UA9BA Spitfire antenna

[John Kaufmann via Topband]

This antenna was clearly working well at UA2FW in the recent CQ 160 contest.
When I listened on the band, UA2FW was, by far, the strongest signal coming
out of Europe in mediocre conditions.  Normally northern Europe, including
UA2, is at a disadvantage in terms of propagation to the US.  Also, UA2FW
has the highest claimed multi-op score in the CQ 160 contest, so it's a
remarkable achievement.

73, John W1FV

-Original Message-
From: Topband
[mailto:topband-bounces+john.kaufmann=verizon@contesting.com] On Behalf
Of Alexander Teimurazov
Sent: Wednesday, February 10, 2021 10:44 AM
To: 'TopBand List'
Subject: Topband: UA9BA Spitfire antenna

https://dxnews.com/ua9ba-spitfire-160m/

 

 73   Al 4L5A

 

 






 

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Re: Topband: KM5KG network designer

[Jim Brown]

On 2/10/2021 9:16 AM, Eric Scace K3NA wrote:

More generally, is there a modern software tool available


Hi Eric,

Many of us are using SimSmith for modeling anything that can fit on a 
Smith Chart. Freeware, mature, runs in Java, imports Touchstone files 
from measurements and antenna models (in EZNEC, the result of a 
computation of complex Z and SWR over a user chosen bandwidth). It can, 
for example, take an antenna measurement made in the shack, subtract out 
the feedline, then put it back in with a matching network that we 
design, compute and plot loss from fundamental models of >50 common coax 
lines. Lots of optimization tools.


73, Jim K9YC
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Re: Topband: The Magic-T

[Joe Subich, W4TV]

On 2021-02-10 5:25 PM, P H via Topband wrote:


A loss of 3 dB may be like "to be or not to be" of a QSO on 160
meters.


That is extremely unlikely.  The limiting factor on 160 meters is
signal to noise ratio, not absolute signal levels.  Most amateur
receivers have absolute sensitivities of -130 dBm or greater while
the background noise is as much as 20 dB higher than that.

Since 3 dB loss in a splitter applies to both the signal and the
noise component, there is no net loss in signal to noise ratio.
In fact one may want to apply attenuation at the receiver input to
reduce strong adjacent (broadcast) signals and prevent receiver
overload.

73,

   ... Joe, W4TV


On 2021-02-10 5:25 PM, P H via Topband wrote:

My impression is that a hybrid combiner, which introduces 90 degree shift 
(hence two identical signals of amplitude A fed to its inputs will give in 
total a signal with the amplitude of 1.41*A) is 3dB less efficient in 
comparison to a simple combiner where A+A gives 2*A at the output.
Do you have any thoughts on this?
A loss of 3 dB may be like "to be or not to be" of a QSO on 160 meters.
Regards
Piotr, SP2BPD


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Re: Topband: The "Magic-T" vs 0 degree and 180 degree hybrid combiner/splitters

[Lee STRAHAN]

Hi All,
Rick I have to agree with you up to a point. Your 9 circle and other 8 
circle receiving arrays except mine are on wide footprints and only use 4 
active antennas at a time. All of my antennas are reduced footprint antenna 
arrays which require much more phasing accuracy for optimum performance. In a 
small array such as a 4-square there is a need for at least 2 combining 
channels before a final combination. Many more in the all active 8 element 
array. Some with delay lines and some without. If you accurately measure a 
Magic Tee or an inverting transformer or even a 2:1 impedance matching 
transformer at 160 meters you will find that each one of these has a finite 
degree or 2 of phase shift. Fortunately this phase shift closely scales with 
frequency. I have not tried to fully understand why except they do indeed have 
line length. What is important is I have learned to use various combinations of 
the Magic Tee and the matching transformers, or inverters to my advantage in 
balancing the
  intrinsic phase shift between the inputs and delay lines improving the 
accuracy of the phasing over a broad range of frequencies. Sometimes the 
transformers are introduced into a phasing channel where one is not necessarily 
needed just to balance the phasing. Past conventional thinking about antennas 
was that if you could get 20 dB of front to back ratio on any array you were 
doing good. In my arrays with lots of front to back ratio (not all models)  
this attention to detail of phasing almost always produces 30 dB of front to 
back ratio and when combined with new version more accurate element amplifiers 
I am getting reports of 40 dB front to back 
 So sometimes what looks unneeded and out of place may not be just because it 
looks out of place.
  Lee  K7TJR  OR



I often see 8 circle phasing networks that use a 3 piece ensemble of separate 
magnetic parts, consisting of:

1.  A 1:1 transformer wired for a 180 degree phase shift 2.  A 0 degree hybrid 
("magic-tee"), and 3.  A 37.5 ohm to 75 ohm transformer.

A single 180 degree hybrid replaces all 3 of the above.
(There is nothing "incorrect" about the 3 piece ensemble; it's just needlessly 
complicated).

My 9 circle array uses this very successfully.

73
Rick N6RK
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Topband: The Magic-T

[P H via Topband]

My impression is that a hybrid combiner, which introduces 90 degree shift 
(hence two identical signals of amplitude A fed to its inputs will give in 
total a signal with the amplitude of 1.41*A) is 3dB less efficient in 
comparison to a simple combiner where A+A gives 2*A at the output.
Do you have any thoughts on this?
A loss of 3 dB may be like "to be or not to be" of a QSO on 160 meters.
Regards
Piotr, SP2BPD
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Topband: The "Magic-T" vs 0 degree and 180 degree hybrid combiner/splitters

[Richard (Rick) Karlquist]

Ham radio literature often IMHO misuses the term
"magic tee" to refer to a transformer-based
0 degree hybrid combiner/splitter.

AFAIK, a magic tee is a WAVEGUIDE device as explained here:

https://www.tutorialspoint.com/microwave_engineering/microwave_engineering_eh_plane_tee.htm

and here:

https://blog.pasternack.com/uncategorized/magic-tee-magical/?gclid=Cj0KCQiApY6BBhCsARIsAOI_GjZHPm6HGT9O06rgnjXBXyc_xUD1aezOCcrNMuSrA4yrSjWqE-r3uFcaAotvEALw_wcB

In some loose sense, what hams talk about as a magic tee
is a lumped element equivalent of the waveguide magic tee.
Outside of ham radio, it is referred to simply as a 0 degree
hybrid.

The 0 degree hybrid circuit has a dual version called a 180 degree 
hybrid combiner/splitter that seems to be less well-known in ham

circles.  It is also a sort of lumped element equivalent
of the magic tee, as explained here:

https://electronics.stackexchange.com/questions/483616/what-does-the-25-%CE%A9-termination-resistor-do-in-a-0-180-degree-hybrid-power-splitt

The 180 degree hybrid has several advantages over the 0 degree hybrid:

1.  The input vs output impedance level is a function of
the turns ratio and therefore is not confined to a value
of 1:2.

2.  It happens to provide so-called "Galvanic Isolation" which
is sometimes helpful

3.  It inherently provides a 180 degree phase shift.

I often see 8 circle phasing networks that use a 3 piece
ensemble of separate magnetic parts, consisting of:

1.  A 1:1 transformer wired for a 180 degree phase shift
2.  A 0 degree hybrid ("magic-tee"), and
3.  A 37.5 ohm to 75 ohm transformer.

A single 180 degree hybrid replaces all 3 of the above.
(There is nothing "incorrect" about the 3 piece ensemble;
it's just needlessly complicated).

My 9 circle array uses this very successfully.

73
Rick N6RK
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Re: Topband: KM5KG network designer

[Chris G3SVL]

Hi Eric,

Long time no speak - hope you are well.

Have you looked at SimSmith? It appears to do some of the things you are 
looking for. Plenty of videos on YouTube or start here perhaps: 
https://www.w0qe.com/SimSmith.html


73 Chris, G3SVL


On 10/02/2021 17:16, Eric Scace K3NA wrote:

Grant KM5KG (SK) had a Windows program for impedance matching network 
design that provided current and voltage levels for each component in the 
system, based on the power passing through the network to the load, as well as 
many other useful features for reducing a theoretical design into a practical 
implementation. I had a copy at one time, but it seems to have disappeared.

Does anyone have a copy?

More generally, is there a modern software tool available that:
supports an arbitrary placement of inductors, capacitors, stubs and line 
segments between generator and load
calculates the peak V and I on each element
calculates Z at the input of each stage in the network
nice to have:
Smith chart overview
multiple frequencies; i.e.:
load characterized by Z at several frequencies
Smith chart display of Z with those frequencies at each stage

I’ve hand-built Excel spreadsheets for specific networks to do the above, 
but it’s very easy to make programming errors on a complex spreadsheet…

Thanks for any suggestions.

— Eric K3NA
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Topband: KM5KG network designer

[Eric Scace K3NA]

   Grant KM5KG (SK) had a Windows program for impedance matching network design 
that provided current and voltage levels for each component in the system, 
based on the power passing through the network to the load, as well as many 
other useful features for reducing a theoretical design into a practical 
implementation. I had a copy at one time, but it seems to have disappeared.

   Does anyone have a copy?

   More generally, is there a modern software tool available that:
supports an arbitrary placement of inductors, capacitors, stubs and line 
segments between generator and load
calculates the peak V and I on each element
calculates Z at the input of each stage in the network
nice to have:
Smith chart overview
multiple frequencies; i.e.:
load characterized by Z at several frequencies
Smith chart display of Z with those frequencies at each stage

   I’ve hand-built Excel spreadsheets for specific networks to do the above, 
but it’s very easy to make programming errors on a complex spreadsheet…

   Thanks for any suggestions.

— Eric K3NA
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Topband: UA9BA Spitfire antenna

[Alexander Teimurazov]

https://dxnews.com/ua9ba-spitfire-160m/

 

 73   Al 4L5A

 

 






 

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Re: Topband: The Magic-T

[Jorge Diez - CX6VM]

Hello

KD9SV made a great Magic T

https://www.dxengineering.com/parts/svp-sv-rsc

73,
Jorge
CX6VM/CW5W

El mar, 9 feb 2021 a las 23:02, Lee STRAHAN () escribió:

> Hi Low Band people,
>Nice presentation Steve. I would like to point out that Beverage users
> or even other phased antenna users should not use paralleling two 75 ohm
> coaxes and then matching them back to 75 for the receiver. While on the
> surface that all sounds good there is a little problem for the individual
> antennas. If you look from the wire through the Beverage transformer to the
> parallel junction the antenna transformer actually sees the other antenna
> at 75 ohms in parallel with the rig matching transformers 75 ohms. This
> causes the real load impedance on the Beverage transformer to be 37.5 ohms
> and not 75. This may cause the Beverage to not have the anticipated
> impedance flat curve or possible performance problems. This could also make
> the end load resistor not be an anticipated value. If you use a delay line
> in one antenna for stagger, the following should be noted. It has been my
> experience that although theoretically you only need to match at least one
> end of a coax for the phase delay in circuit to match the proper terminated
> value, I have found that terminating both ends reduces problems from
> component tolerances not terminating the proper coax impedance causing
> unwanted phase shifts. Using a Magic Tee will help terminating the coaxes
> with their proper impedance keeping the phase delay where you expect it.
> Early designers of passive 4 or more element receiving arrays missed this
> point when making combiners for arrays using paralleled transmission lines.
>Bottom line is to yes yes, use a Magic Tee or some version of a hybrid
> combiner for combining which will isolate between  antennas.. Then the
> antennas as well as the receiver will see the 75 ohm load as likely
> designed.
>  Here is a nice technical tutorial on the Magic Tee.
> https://michaelgellis.tripod.com/magict.html
> Lee  K7TJR  OR
>
> -Original Message-
> From: Topband  On Behalf Of
> donov...@erols.com
> Sent: Tuesday, February 9, 2021 3:28 PM
> To: topband 
> Subject: Re: Topband: The Magic-T
>
>
> This is the corrected URL for Steve's Magic-T video
>
>
> www.youtube.com/watch?v=_Bbt1IcC4bk
>
>
> 73
> Frank
> W3LPL
> - Original Message -
>
> From: "VE6WZ_Steve" 
> To: "topband" 
> Sent: Tuesday, February 9, 2021 10:29:54 PM
> Subject: Topband: The Magic-T
>
> Today I uploaded a video to my RX series which explains the Magic-T
> combiner.
> I have received a few emails asking me “how do I make the magic-T”? so I
> thought a video would be helpful.
>
> I show the method for winding and building the Magic-T combiner and I
> explain how it is used in phased RX antennas.
> The associated 2:1 impedance transformer is discussed, and I show the
> difference between an isolated and auto-transformer architecture.
>
> I also discuss an error that can be made when building phased RX antennas
> if care is not taken to avoid an unintentional 180 phase shift at one of
> the elements, especially if using home-brew matching boxes.
>
> YouTube video: https://youtu.be/_Bbt1IcC4b -
>
> 73, de steve ve6wz
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> Reflector
>


-- 
73,
Jorge
CX6VM/CW5W
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