Author Topic: Winding an Un-Un  (Read 9525 times)

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Online iMo

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Re: Winding an Un-Un
« Reply #100 on: June 10, 2022, 09:22:50 am »
Long time back I had 41m off center dipole on the very roof, worked nice. Then I had to remove it and used a 6m long wire, it worked "somehow" 20m up across Europe.

Then I made myself the EFHW8010, from my balcony across the street to the opposite building (had to negotiate a permission..) and after some time w/ finetunig of the transformer I finished with 3 taps on the unun and I work all bands without ATU (warc bands with a little bit higher swr).

The EFHW works, but you have to consider many factors and nuances in practice. I've been regularly helping local ham friends with their endfeds and I do finetune their endfeds too, so I can see that it is not easy to make a good EFHW performing, even an experienced homebrewer/ham may cope with issues.

The classic design - 1:49 on 43 material, and 110uH coil for 80m with 22m long antenna is just a "base to start", it is a pretty compromise, imho.

You have to experiment with the transformer ratio as well, as the impedance of a real "tuned" wire mounted somewhere is NOT around 2500-3500ohm across all bands as people say. It starts at something around 5000-6000ohm at 80m, and drops continuously up to 450-1000ohm at 10m. The exact Z at the specific band depends on many factors, but it follows that principle (I saw that on all endfeds I messed with).

Thus the higher the band the lower transformation ratio you would need. Therefore a multitap unun is the best solution, it almost eliminates the need for the 100-150pF capacitor at the primary (the capacitor is basically not good to have there, of course).

Also mind the tuning of the 80m band with the 110uH coil and 22m long antenna is pretty difficult, as the tuning sensitivity at the aprox 2m long part after the coil is about 5kHz/cm (from my experiments). The BW of the 80m is also pretty narrow (like 40kHz) in this setup, thus you have to decide before the tuning where to place your 80m frequency segment of choice exactly.
The positive part is the 80m band is tuned independently from other bands in this specific setup.

The 40m long EFHW have other issues handy - the minima of swr do not fit the bands, thus you have to apply tricks - like 1uH coil at the beginning of the wire and a capacitor in the middle of the wire.

EFHW basically works, but to master a good performing one is not easy..
« Last Edit: June 10, 2022, 10:21:21 am by imo »
 

Online bingo600

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Re: Winding an Un-Un
« Reply #101 on: June 10, 2022, 10:33:44 am »
@all
Thank you for your tips and experiences.
Invaluable to a HF newbie ...

Please keep it comming  :-+ :-+

@Hamlec
Yepp . Forgot to mention the 15m band.

@A.Z
The FT-991A built in antenna tuner will only do 3:1 , not good enough for a "Random wire" , i am considering to get a MFJ-939Y Ant. tuner though.
But for a start i'll go with the HyendFeed , as it should do all the mentioned bands with a nice swr.  But it also comes with a steep price.
I'm a bit worried about the counterpoise ... Does that carry any noticable RF energy. ?  - Grand children playing around the trees.
And i'm not even sure i can get the antenna 17' up in the air.


@imo
Your experiences are excactly why i'll get a HyendFeed for starters, as it "should be" mount & run.
Later on i would like to build something that can take the full Yaesu power.

@all
I have ordered one of the new 4" 4GHz NanoVNA's from Ali to help in testing the antenna(s).
But i have to learn to use it ... Ie. Smith-chart looks a "Childs doodling" to me ... or an Alien Vortex.
I'm a IP Network guy , not an EE or RF engineer , who got his license some 40+ years ago.

I'll do some googling when i get the VNA , else i'll cry for help


The radio is for a bit of "Cosy Chat" , not DX'ing , and i never learned CW  :-X
That might also affect my choice of the 80M band center ...
I'll be using it in the summerhouse in Sweden, expected the bands to be "EU alligned" , but i don't think ie. 70MHz is allowed there . It is in DK.


/Bingo

« Last Edit: June 10, 2022, 11:00:40 am by bingo600 »
 

Offline A.Z.

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Re: Winding an Un-Un
« Reply #102 on: June 10, 2022, 10:53:05 am »
@A.Z
The FT-991A built in antenna tuner will only do 3:1 , not good enough for a "Random wire" , i am considering to get a MFJ-939Y Ant. tuner though.
But for a start i'll go with the HyendFeed , as it should do all the mentioned bands with a nice swr.  But it also comes with a steep price.
I'm a bit worried about the counterpoise ... Does that carry any noticable RF energy. ?  - Grand children playing around the trees.
And i'm not even sure i can get the antenna 17' up in the air.

As for the "17' up in the air.", while the higher the better (as usual), the counterpoise may just come down from the feedpoint for whatever lenght and the remainder may just lay down on ground, no need for it to be "suspended", just use insulated wire and insulate the end of the counterpoise so nobody will get hurt touching it; as for the ATU and the "random", well, up to you
 

Online iMo

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Re: Winding an Un-Un
« Reply #103 on: June 10, 2022, 10:59:42 am »
@bingo600: welcome to the club  ;)
HyendFed: I saw "real in-situ" measurements of those off the shelf antennas - they need a finetunig too (they are somehow "pre-tuned", but not perfectly, afaik). Those are usually based on the classic design. Except that a DIY one would cost you say 10% of that price  :D
Long wire: there are specific lengths listed where you get an swr (with the 1:9 unun) <= 1:3 such your ATU can tune it well..
NanoVna: this site is your friend: https://groups.io/g/nanovna-users
« Last Edit: June 10, 2022, 11:06:31 am by imo »
 

Online bingo600

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Re: Winding an Un-Un
« Reply #104 on: June 10, 2022, 11:14:51 am »
Just for my understanding...

Counterpoise:
How much RF energy is approx. going down such a wire ?
A.Z says i can use an isolated wire , but i have grandchildren ....
Enough to get even a light Zap ?

Chances are that i won't use the station when they're visiting , but then again .. Their Dad might want to see the station in use ... There is trouble

/Bingo
 

Offline A.Z.

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Re: Winding an Un-Un
« Reply #105 on: June 10, 2022, 12:38:49 pm »
Just for my understanding...

Counterpoise:
How much RF energy is approx. going down such a wire ?
A.Z says i can use an isolated wire , but i have grandchildren ....
Enough to get even a light Zap ?

Chances are that i won't use the station when they're visiting , but then again .. Their Dad might want to see the station in use ... There is trouble

/Bingo

As long as the FAR END of the counterpoise wire is properly insulated you won't have any problems with that; and in any case you will NEED it even with the EFHW, don't fall for the poor folks saying that an endfed won't need the counterpoise "because it's half wave", in such a case your coax will work as the counterpoise and while it's acceptable for SOTA/POTA or in any case portable and QRP operation, running more than a few watts through such a "no counterpoise" setup won't be a good idea


 
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Online iMo

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Re: Winding an Un-Un
« Reply #106 on: June 11, 2022, 10:39:52 am »
With well designed EFHW antennas you do not need any counterpoise. The coax itself running from the transformer to your TRX works as the counterpoise (even though the counterpoise is theoretically not needed with end fed half wave antennas)..
« Last Edit: June 11, 2022, 11:15:36 am by imo »
 

Offline A.Z.

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Re: Winding an Un-Un
« Reply #107 on: June 11, 2022, 12:02:08 pm »
With well designed EFHW antennas you do not need any counterpoise. The coax itself running from the transformer to your TRX works as the counterpoise (even though the counterpoise is theoretically not needed with end fed half wave antennas)..

and the coax acting as the counterpoise will cause "RF in the shack" in TX and noise in RX, bad idea, also, would you please explain me how should an EFHW work w/o a counterpoise ? Is it some kind of miracle antenna violating the laws of physics ?
 

Online iMo

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Re: Winding an Un-Un
« Reply #108 on: June 11, 2022, 06:25:02 pm »
The EFHW antenna does not require a counterpoise from principle of its operation.
"EFHW" means you feed the antenna in the point of highest impedance, the currents are pretty low there.

The "counterpoise" with EFHW works like "grounding" - the coax on the ground is coupled via its shielding capacitance to the ground.

I've never seen an issue with RF going to the hamshack or into the TRX with EFHW here - with many hams using it at their local QTH or portable. Also people usually use a choke on the coax to avoid RF..
 

Offline A.Z.

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Re: Winding an Un-Un
« Reply #109 on: June 11, 2022, 06:56:58 pm »
The EFHW antenna does not require a counterpoise from principle of its operation.
"EFHW" means you feed the antenna in the point of highest impedance, the currents are pretty low there.

The "counterpoise" with EFHW works like "grounding" - the coax on the ground is coupled via its shielding capacitance to the ground.

I've never seen an issue with RF going to the hamshack or into the TRX with EFHW here - with many hams using it at their local QTH or portable. Also people usually use a choke on the coax to avoid RF..

interesting, so current flows through an EFWH without an equal and opposite current flowing elsewhere; man, you just found an antenna violating the laws of physics !

how cool :P

 

Offline A.Z.

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Re: Winding an Un-Un
« Reply #110 on: June 11, 2022, 07:01:00 pm »
 

Online iMo

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Re: Winding an Un-Un
« Reply #111 on: June 11, 2022, 07:26:48 pm »
@A.Z.: EFHW antenna IS a dipole. The exactly same antenna as a "traditional" dipole fed in the middle.
Some people call it "end fed dipole" too..
Try to spend some time with EFHW topic and you will certainly learn how it works..
 

Offline A.Z.

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Re: Winding an Un-Un
« Reply #112 on: June 11, 2022, 09:11:06 pm »
@A.Z.: EFHW antenna IS a dipole. The exactly same antenna as a "traditional" dipole fed in the middle.
Some people call it "end fed dipole" too..
Try to spend some time with EFHW topic and you will certainly learn how it works..

oh, a dipole; interesting, did you even read the doc at the URL in my last post ?
 

Offline Hamelec

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Re: Winding an Un-Un
« Reply #113 on: June 11, 2022, 10:37:34 pm »
For me is the EFHW the solution, using it with the classic design - a UnUn 1:49 on a FT240-43 and a <110uH coil for 80m, all ~22m long.
But it needs some tuning especially for 80 with a HP8753.. - possible with any other VNA or SWR Analyzer.
I have only limited space for a antenna but with the Endfed i am QRV from 10-80m. Also working DX (in SSB, not FT8 or CW) is possible with 100W PEP.
I know that the design has losses, but say ~3dB - who cares, that is only half a S-Unit.
And of course, i am using an counterpoise and also a common mode coil on the RG58.
I also have a Vertical quarter wave for 10m, but it is so noisy that it is not of use.
 

Online iMo

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Re: Winding an Un-Un
« Reply #114 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).
« Last Edit: June 12, 2022, 06:35:00 am by imo »
 

Offline Hamelec

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Re: Winding an Un-Un
« Reply #115 on: June 12, 2022, 09:42:25 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).
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).
 

Offline A.Z.

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Re: Winding an Un-Un
« Reply #116 on: June 12, 2022, 05:25:26 pm »
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).
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).

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

« Last Edit: June 12, 2022, 10:18:29 pm by A.Z. »
 

Offline Hamelec

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Re: Winding an Un-Un
« Reply #117 on: June 13, 2022, 10:23:17 am »
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
 

Online iMo

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Re: Winding an Un-Un
« Reply #118 on: June 13, 2022, 12:47:12 pm »
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.
« Last Edit: June 13, 2022, 12:52:48 pm by imo »
 


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