Hi Manuel, thanks a lot for the interesting video! I also found out that the Chinese metric system measures usually a bit less than in Europe 😉. Two years ago, I also did hundreds of measurements with efficient EFHW transformers and radiators on many different summits and realized that depending on the setup, the environment and even how the coax or "counterpoise" is laid, you'll get different results. Like you, I also realized that the higher the band, the lower the impedance of the EFHW seems to be. Therefore, 1:64 or 1:81 ratios usually work better on lower bands than e.g. 1:49 and visa versa. This and many more conclusion are contained in my 50+ page PDF document that you'll easily find on the web. 73 Stephan
Hi Stephan, easy to find in deed, when you know what to look for. In fact, allow me to share it with the community: hb9sota.ch/wp-content/uploads/2021/08/Portable-7-Band-EFHW_HB9EAJ-V1.2.pdf Thanks for your work presented in your document. I did not know, it existed..... I wIll definately read it and get some inspiration from it ! 73 Manuel; DL2MAN
Interesting to proof that the 49:1 performs better on the harmonics (higher bands) and the 64:1 better on the fundamental in this setup. You could also see that with the 64:1 transformer, the antenna wire must be shortened to increase resonance frequency on 40m. But then at a good SWR. For my portable activities I usually use 64:1 transformers for a 40m EFHW (20m wire). The resonance point of the 1st harmonic (14 MHz) will be in the SSB portion, i.e it is higher. This is what you see. To bring the SWR on the higher bands down to the CW portion on 14 MHz, you can use a short stub (e.g 30- 50cm wire with croco clamp) and connect it at the feeding point with the antenna wire. It adds capacity and brings down SWR of the harmonics. 73 de Chris DL1GKC
This a great video, in my own testing i have found the ground, the height of the mast and height of the feed point all play a role on the swr, for now i have settled on using a 49:1 auto-wound (on 40m EFHW) with a links for 30m, 20m and 17m you many think the 20m link is redundant because 20m is harmonic but i found on occasions that i can lower the swr on 20m by making it into a 20m EFHW (20m as the fundamental). It testing antennas is good fun. 73
I use the cheap fishing pole. I epoxied three loops around the top of the bottom section. With some stakes and four-foot guys, it is free standing. Thanks for the videos and info.
Hi Manuel, many thanks for your video. In my tests I noticed that changing height where transformer is will change SWR. Usually, having transformer low 30-50cm will improve SWR. However, when you model such setup we can see that antenna gain is also reduced. Another method to find optimal ratio is to measure resistive part of impedance at resonance points for preferred frequencies. From that measurement you can see what ratio is optimal for that band. However, this method is good only for permanent setup, as you know working portable gives different results every time. I am looking forward to next episode. Good health and look after yourself 73 Marek
A few years ago, I found an article that a solution can be adding a capacitor about 1-1.5m from the further end of the radiator. I can't remember the exact value. It electrically shortens the antenna, but impedance changes with frequency; therefore, it shortens more on lower bands than on higher ones.
Interessante Messungen, Manuel. Einen Hinweis möchte ich hier in Erinnerung rufen: für die Resonanzpunkte spielt auch der Teil des Antennengebildes eine Rolle, der noch "Mantelwellen" trägt. Auch auf die Impedanz wird es einen Einfluss haben. Bei deiner nächsten Messung wäre es interessant den Einfluss durch eine in Antennendrahtrichtung am Massepunkt des Übertrages angeschlossenes kurze Drahtstück (40m-Band x o,o2 lamda) zu untersuchen. Damit wird der Einfluss der Mantelwelle auf dem Koax geringer. Vielleicht zeigt sich auch ein Effekt für die harmonischen Bänder! 73/DJ8CY
Take good care of yourself Manuel! I am in week #1 after a bog standard cold - at least 3 tests were negative - and oh boy am I still exhausted and tired. 😉
Hi Manuel, thank for the sharing of your experimentations. Regarding the SWR changing when you touch the connector, that might be due to common mode current, a choke balun at the output of the TX may helps so the coax shield will act as counterpoise or maybe put it before the transformer and add a separate counterpoise ? Based on your findings, i understand that fundamental frequency resonance doesn't change so much by changing the transformation ratio but that changes harmonics. In your case, you can reduce the wire length to be closer of the 40, 20 ant 10m ham bands. If the wire diameter is thin, a 1:64 transformer performs better regarding the SWR (but has more losses). As a 20m wire is quite long in portable, i've mainly experimented EFHW as you on a fishing pole but only 6 to 7 m, in inverted V and with the feeding point at the ground and it produces a quite good SWR curve but i nerver tried with the antenna highly elevated from the ground. 73s
Totally understand why you're out of breath. Just got over COVID a few days ago myself. I had the vaccination took the antiviral and still it was rough.
Both the proximity to the ground and the ground conductivity affect the SWR, because the ground is part of the antenna system until the antenna gets multiple wavelengths above the ground. This also implies that each band will respond differently to a given height above the ground because it is at a different fraction of a wavelength above the ground. Because of this it makes sense to use a transformer with multiple taps, which is what you will see in antenna tuners that lack a roller inductor. I am always amused at arguments about whether a 49 to 1 or a 64 to 1 is a better transformer for an EFHW antenna. I would put multiple taps on any such transformer. I don't understand those who build them with only 1 impedance output option. Why? It's just an inch or 2 of wire and connectors to add more outputs at other impedances.
The fishing pole is not a fail as it has a bend that will keep the antenna away from the pole. I found this is important as carbon fiber interacts with wire--crazy, right! The practical transformer experience is valuable regardless! But you have to repeat future experiments at the same exact configuration and location. Does the presence of the car affect the measurements? I had some big swings in my experiments with counterpoise plus ground wire interaction--EFHW aren't supposed to be affected by counterpoise radials! Keep testing, my friend! KG5WHQ
Jetzt noch eine Anleitung zum Balun mit den Abgriffen wäre der Hammer. Pass auf dich auf, das grösste Risiko auf Longcovid isr zu schneller und heftger Einstieg in das vorheIge "leisten". Gehe es möglicht lange langsam wieder an.
Hi Manuel, Did you connect a capacitor for the higher band (10m)? Is it possible to connect a capacitor and see if you can lower the SWR on the bands from 20 meters to 10 meters? Maybe a 100 to 200 pF adjustable capacitor. Very interesting to see what the altitude does. I previously had my EFHW hanging almost horizontally and the SWR was reasonable at the time. now it hangs at a height of 12 meters (transformer) and then diagonally downwards to a height of 2 meters. everywhere the SWR is now 1:1.1 and on the 10 meter band 1:1.4. After changing the position from almost horizontal to diagonal, I had to shorten the antenna by 50 cm Keep posting this video's, I love them.
Are there alternatives to EFHW that exhibit more stable performance and less susceptible to environment changes such as height above ground? I've built a couple of EFHWs and they all seem extremely sensitive to the height and the orientation of the counterpoise.
Hi Manuel, thanks a lot for the interesting video!
I also found out that the Chinese metric system measures usually a bit less than in Europe 😉.
Two years ago, I also did hundreds of measurements with efficient EFHW transformers and radiators on many different summits and realized that depending on the setup, the environment and even how the coax or "counterpoise" is laid, you'll get different results.
Like you, I also realized that the higher the band, the lower the impedance of the EFHW seems to be. Therefore, 1:64 or 1:81 ratios usually work better on lower bands than e.g. 1:49 and visa versa.
This and many more conclusion are contained in my 50+ page PDF document that you'll easily find on the web.
73 Stephan
Hi Stephan, easy to find in deed, when you know what to look for. In fact, allow me to share it with the community: hb9sota.ch/wp-content/uploads/2021/08/Portable-7-Band-EFHW_HB9EAJ-V1.2.pdf Thanks for your work presented in your document. I did not know, it existed..... I wIll definately read it and get some inspiration from it ! 73 Manuel; DL2MAN
@@dl2man @PortableRadio thank you for sharing this out
Interesting to proof that the 49:1 performs better on the harmonics (higher bands) and the 64:1 better on the fundamental in this setup. You could also see that with the 64:1 transformer, the antenna wire must be shortened to increase resonance frequency on 40m. But then at a good SWR.
For my portable activities I usually use 64:1 transformers for a 40m EFHW (20m wire). The resonance point of the 1st harmonic (14 MHz) will be in the SSB portion, i.e it is higher. This is what you see. To bring the SWR on the higher bands down to the CW portion on 14 MHz, you can use a short stub (e.g 30- 50cm wire with croco clamp) and connect it at the feeding point with the antenna wire. It adds capacity and brings down SWR of the harmonics.
73 de Chris DL1GKC
This a great video, in my own testing i have found the ground, the height of the mast and height of the feed point all play a role on the swr, for now i have settled on using a 49:1 auto-wound (on 40m EFHW) with a links for 30m, 20m and 17m you many think the 20m link is redundant because 20m is harmonic but i found on occasions that i can lower the swr on 20m by making it into a 20m EFHW (20m as the fundamental). It testing antennas is good fun. 73
I use the cheap fishing pole. I epoxied three loops around the top of the bottom section. With some stakes and four-foot guys, it is free standing. Thanks for the videos and info.
Hi Manuel, many thanks for your video. In my tests I noticed that changing height where transformer is will change SWR. Usually, having transformer low 30-50cm will improve SWR. However, when you model such setup we can see that antenna gain is also reduced. Another method to find optimal ratio is to measure resistive part of impedance at resonance points for preferred frequencies. From that measurement you can see what ratio is optimal for that band. However, this method is good only for permanent setup, as you know working portable gives different results every time. I am looking forward to next episode. Good health and look after yourself 73 Marek
Please take good care of your health, Manuel. COVID is a very strange disease and I have lost friends and family to it.
A few years ago, I found an article that a solution can be adding a capacitor about 1-1.5m from the further end of the radiator. I can't remember the exact value. It electrically shortens the antenna, but impedance changes with frequency; therefore, it shortens more on lower bands than on higher ones.
Interessante Messungen, Manuel. Einen Hinweis möchte ich hier in Erinnerung rufen: für die Resonanzpunkte spielt auch der Teil des Antennengebildes eine Rolle, der noch "Mantelwellen" trägt. Auch auf die Impedanz wird es einen Einfluss haben. Bei deiner nächsten Messung wäre es interessant den Einfluss durch eine in Antennendrahtrichtung am Massepunkt des Übertrages angeschlossenes kurze Drahtstück (40m-Band x o,o2 lamda) zu untersuchen. Damit wird der Einfluss der Mantelwelle auf dem Koax geringer. Vielleicht zeigt sich auch ein Effekt für die harmonischen Bänder! 73/DJ8CY
Take good care of yourself Manuel!
I am in week #1 after a bog standard cold - at least 3 tests were negative - and oh boy am I still exhausted and tired. 😉
Hi Manuel, thank for the sharing of your experimentations. Regarding the SWR changing when you touch the connector, that might be due to common mode current, a choke balun at the output of the TX may helps so the coax shield will act as counterpoise or maybe put it before the transformer and add a separate counterpoise ?
Based on your findings, i understand that fundamental frequency resonance doesn't change so much by changing the transformation ratio but that changes harmonics. In your case, you can reduce the wire length to be closer of the 40, 20 ant 10m ham bands. If the wire diameter is thin, a 1:64 transformer performs better regarding the SWR (but has more losses).
As a 20m wire is quite long in portable, i've mainly experimented EFHW as you on a fishing pole but only 6 to 7 m, in inverted V and with the feeding point at the ground and it produces a quite good SWR curve but i nerver tried with the antenna highly elevated from the ground. 73s
Totally understand why you're out of breath. Just got over COVID a few days ago myself. I had the vaccination took the antiviral and still it was rough.
Both the proximity to the ground and the ground conductivity affect the SWR, because the ground is part of the antenna system until the antenna gets multiple wavelengths above the ground. This also implies that each band will respond differently to a given height above the ground because it is at a different fraction of a wavelength above the ground. Because of this it makes sense to use a transformer with multiple taps, which is what you will see in antenna tuners that lack a roller inductor. I am always amused at arguments about whether a 49 to 1 or a 64 to 1 is a better transformer for an EFHW antenna. I would put multiple taps on any such transformer. I don't understand those who build them with only 1 impedance output option. Why? It's just an inch or 2 of wire and connectors to add more outputs at other impedances.
You *MIGHT* try experimenting with the value of that capacitor on your transformer board.
*73 de AF6AS*
The fishing pole is not a fail as it has a bend that will keep the antenna away from the pole. I found this is important as carbon fiber interacts with wire--crazy, right! The practical transformer experience is valuable regardless! But you have to repeat future experiments at the same exact configuration and location.
Does the presence of the car affect the measurements?
I had some big swings in my experiments with counterpoise plus ground wire interaction--EFHW aren't supposed to be affected by counterpoise radials!
Keep testing, my friend!
KG5WHQ
Jetzt noch eine Anleitung zum Balun mit den Abgriffen wäre der Hammer.
Pass auf dich auf, das grösste Risiko auf Longcovid isr zu schneller und heftger Einstieg in das vorheIge "leisten". Gehe es möglicht lange langsam wieder an.
Can you do a video on how to setup the built in automatic CW thing?
Hi Manuel, Did you connect a capacitor for the higher band (10m)?
Is it possible to connect a capacitor and see if you can lower the SWR on the bands from 20 meters to 10 meters?
Maybe a 100 to 200 pF adjustable capacitor.
Very interesting to see what the altitude does.
I previously had my EFHW hanging almost horizontally and the SWR was reasonable at the time.
now it hangs at a height of 12 meters (transformer) and then diagonally downwards to a height of 2 meters.
everywhere the SWR is now 1:1.1 and on the 10 meter band 1:1.4.
After changing the position from almost horizontal to diagonal, I had to shorten the antenna by 50 cm
Keep posting this video's, I love them.
Are there alternatives to EFHW that exhibit more stable performance and less susceptible to environment changes such as height above ground? I've built a couple of EFHWs and they all seem extremely sensitive to the height and the orientation of the counterpoise.
How do we program the automatic cW part?
Me too. Covid post 3 days. VE6KBI Canada. Dana