Electronics > RF, Microwave, Ham Radio

Winding an Un-Un

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Hamelec:

--- Quote from: imo on June 12, 2022, 06:30:00 am ---The losses with EFHW come mainly from the ferrites we use. Especially the 43 is lossy and definately not the optimal one, but the best we have for 2-30MHz range. We would need a new material, something with mu' close to 1000 till 30MHz and with mu'' similar to the material 61..  ;)
But the losses should not be higher than 15% in the transformer (ie. with SSB and 100W the loss is less than 3W in an average).

--- End quote ---
I would not say mainly.
I measured some different sizes and brands of 43 toroids, beginning with FT140-43, FT240-43, WÜRTH 74270097 and endet up with a WÜRTH 74270191.
Measured TWO of it as 1:49 connected face to face and got around 3.5dB at 160m, better 1.5dB between 80 and 20m, 2.5 at 10m and 4.7dB at 6m.
(Note that the loss is for two UnUn).

A.Z.:

--- Quote from: Hamelec on June 12, 2022, 09:42:25 am ---
--- Quote from: imo on June 12, 2022, 06:30:00 am ---The losses with EFHW come mainly from the ferrites we use. Especially the 43 is lossy and definately not the optimal one, but the best we have for 2-30MHz range. We would need a new material, something with mu' close to 1000 till 30MHz and with mu'' similar to the material 61..  ;)
But the losses should not be higher than 15% in the transformer (ie. with SSB and 100W the loss is less than 3W in an average).

--- End quote ---
I would not say mainly.
I measured some different sizes and brands of 43 toroids, beginning with FT140-43, FT240-43, WÜRTH 74270097 and endet up with a WÜRTH 74270191.
Measured TWO of it as 1:49 connected face to face and got around 3.5dB at 160m, better 1.5dB between 80 and 20m, 2.5 at 10m and 4.7dB at 6m.
(Note that the loss is for two UnUn).

--- End quote ---

at this point, it would be interesting to run the same test on some 1:9; plus, the same tests would become very interesting when it comes to a real antenna, presenting quite a wide range of R+X combinations ; and that's where a simulation and optimization SW would come handy, since it would allow to run "virtual" sweeps and optimize the lenght, giving a starting size for both antenna and counterpoise (yes, you will want it too) which will be in the ballpark for real, on field, tests

Hamelec:
No, i don't want it..  :)
for me it was enough to see the losses of the 1:49 UnUn, put it to my Endfed and measure again s11 to see the resonant frequencies (and trimming the wire lenght).
Not really interested on simulation, more on the actual antenna performance and  QSO..  ;D
73

imo:
There is a lot information re EFHW 1:XX ununs available, with measurements and never ending discussions on winding style, material, toroid form, stacking, wire used, etc.. Most people do not care whether there is a 15% loss in the transformer as they want to make QSOs on all HF bands without an ATU (ie SOTA) and with an easy and quick to mount antenna (fed from the end), and the difference between a perfect transformer and a real one (ie with 10-15% loss) is not measurable long distance. People are more concerned about their SWR - such the TRX does not lower the output power (most TRX do from SWR 1:2 up). Also QTH and antenna installation (ie. its height over ground) play a bigger role than the loss in the ferrite, imho.

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