If you don't have one already, use this as an excuse to get some sort of antenna analyzer. NanoVNA, MFJ, Rigexpert, whatever you end up buying, they have one for just about every budget. In the end, I think just experimenting with different configurations to see what works and what works better is time well spent. Might be a good time to try out WSPR as well. Personally, I have an EFHW for 10m about a half wavelength off the ground, parallel to the ground and added a tuning stub to get a slightly better SWR. I've only relied on my radio's SWR meter and generally run QRP and occasionally up to maybe 20 watts. I've worked Asia, Canada, Mexico - South America, Western Europe and almost have all 50 states. I realize not everyone has room or trees that high to do that so I've also run it vertical or sloper from the top of a mast. All work pretty well. In the end, it's all about results. Make a contact and feel successful.
The answer is no. 1:47 Please test a small transmitter located at the transformer feed of the EFHW without coax or any additional wire. The EFHW dipole will radiate the same power as a center fed dipole less a bit of loss (~1 dB) caused by the transformer. I've done this test several times confirming no need for a counterpoise of any sort.
The correct answer is that it needs to match the impedance of your impedance transformer. If you use a 49:1, you need enough on the opposing side of the long portion of your antenna to be long enough to match 2450 ohms. If you have a 64:1, you will need enough to match 3200 ohms. YMMV based on your specific situation.
My EFHW is from myantennas It is 6 feet off ground at feed point and 40 feet off ground at far end. My coax runs from feed point 6 feet towards ground and then the remaining coax runs along ground 60 feet (like Dave said). I've made over 500 Q's during 2023 already. 80m @1:1.5 and the remaining bands (40 - 30 - 20 - 17 - 15 - 10) are close to 1:1.2 except 17 which is 1:1.8. Greet antenna.
To Dave's question about lower vs higher feed point height and how it works with regards to a counterpoise, I do not have a choke on my coax and do not have a counterpoise in place, the feed point is over 20' in the air with the far end about 30' up and it plays really really nice.
I was curious about why I was getting erratic results when I was doing FT8 on WSJT-X with my EFHW antenna. Receive worked just fine and I could hear / decode traffic from all over. As soon as I enabled transmit, everything got very garbled and messy on the waterfall. I figured I was getting RF on my rig somewhere but wasn't sure where / how. This explains it. Choke ordered from DXE and we'll see how FT8 works now! Thank you so much!
I run an EF that is 289' from end to choke on the coax and a common mode choke at the receiver. The wire is 203' long. Very quiet, tunes all bands from 120 to 6 end to end and SWR is less than 3:1 down to 1:1.. I've worked 99% of all stations I can hear on 100W. From APAC, SA, South Africa, Tasmania, Japan, eastern europe, russia,etc... It is a very tall Z shape when viewed from below and 45' down to 15'... I started with a 155' Palomar Bullet kit and modified it. Love this antenna. The choke was moved around to tune it and I don't have anything dropping down until after the choke into the shack. The transformer is 40' up in the air. And the choke is about 20' in the air about 25' from the shack.
From doing portable for many years going place to place .I can say the counterpoise can change. also the length of end fed half can change from location to location. wet ground vs dry ground vs snow on ground. how high up is the unun . all can change loading of a antenna . even the weather can . some times adding more counterpoise can broadband SWR more. so the answer is whatever works well for your location of you EFHW . same goes for the 9:1 . some have 49:1 and a 1:1 bult in. that will need a counterpoise. I use the off set center fed dipole. 40 to 6 meter. that has both transformers in it. the short element is the counterpoise. harder to set up in a park. EFHW is quite easy for quick set up. I had the 49:1 near or on ground and going straight up or sloper . just lean DX commander pole into a tree. done. any fiberglass pole. MFJ has a nice one. just bring a counterpoise wire . you may need it. and may vary on different bands. sometimes a counterpoise can bring down the noise and can increase it. try both ways whatever works better go with that. 73's
RF in the shack can manifest itself in a few ways. The most extreme is getting a shock or RF burn when you touch the ground side of the transmitter chassis. Other symptoms are poor audio quality (distortion) on your transmitted signal, distortion coming through unshielded speakers, and electronic devices randomly shutting off. I'll have to think about how that can be demonstrated in a video.
@@KB9VBRAntennas Right, how do you replicate it without risk. I see lots of videos on equipment and features but almost no before and after videos. Do you have any that start with a poor reception then apply the various filters and adjustments to tweak the signal to the best audio output? Knowing what a feature does is one thing, knowing when and how to use it is another. Your videos are great, your doing a great service. Thank you.
:D a friend of mine was surprised I use a coax shield as one of radials when using my center loaded vertical :D having "only" 8 5 m radials, adding another one is usually measurable (well, today, after a week of raining = good ground conductivity it is not visible). My idea originated from using coax braid as a counterpoise of EFHW antennas.
20-25’ on a 40 m efhw. 40-50’ on a 80 m efhw. Then a common mode choke. Then any length to your radio. Palomar and PackTenna both support these measurements
Is an end feed antenna with a counterpoise really an off-center fed antenna? Or does the counterpoise function just to serve as a ground and not as a radiator?
Even without a coax shield connected to the secondary winding, it will still work thanks to the DISPLACEMENT current and capacitance between the primary and secondary winding. So whatever we do the antenna will always find a way not to violate Kirchhoff's law, BTW KCL does not apply entirely to RF circuits. See the test without any connection to the second port of the secondary winding. ua-cam.com/video/7bm0c_CNtVU/v-deo.htmlsi=gsvkeJz7wdy2uEz3
Might also be noteworthy that at qrp levels (5-10 watts) a choke isn't usually necessary. At higher power, that RF gets more nasty coming back to your transceiver, so a choke becomes more of a necessity.
If you run it to a stake in the ground, ,it's not nearly an endfed anymore. It's more like a centerfed and your feedpoint impedance will drop. If you start thinking of the antenna as an antenna and not an antenna with a counterpoise, you will begin to understand the theory more. Because there never is any "counterpoise". The antenna has 2 connections to it. On an endfed, it can be a tiny stub on one side and a long stretch on the other. There's capacitance that can be measured distributed across the element to the other side of the element. There's inductance distributed along the element. The collective values are the XL and the Xc which make up the "X" in the R+/-jX equation. So if you make one side of the feedpoint really small, the Xc and XL will be really small because the tiny inductance is in series with the large inductance on the other side and small inductance in series with the large inductance is a small inductance. The small capacitance on one side is in parallel with the larger portion on the other side. That capacitance will be very small. The outer conductor of the feedline does not become any "counterpoise". It's a feedline. The feedline feeds to the feedpoint. When it feeds to the feedpoint, current will flow into the antenna. If it's not a match, some current will reflect back to the transmitter. That reflection is on both conductors of the feedline. Current always is flowing on the outside of your coax. This is something you want. It's a part of the design. What you don't want is reflected currents. You avoid reflected currents by matching the feedline impedance to the antenna feedpoint impedance. It's the only option. An "isolation transformer" is a real thing in electronics. It's something to remover the DC flowing in the primary from flowing in the secondary. I don't have any DC in my transmission line. But you could if you are powering something at the other end of your transmission line, I guess. The more small side antenna you have, the lower your feedpoint radiation resistance. That's all it is. The smaller you make the small side, the closer to infinity the feedpoint radiation resistance becomes. You know you have a 9:1, 49:1, or a 64:1 transformer. The small side has to match whatever your transformer is really needing to see. If you want to choke the heck out of your signal, fer crissakes, choke the signal. Lower your output power. Opinions don't matter here. Only facts. Please learn the topic. You don't know what "common mode currents" are. Look at Mark Smith's video between 3:00-5:00 minutes. He slips up and uses stuff he learned in school during these 2 minutes and panders to pseudo-science the rest of the video. He can't figure out how it all fits together because real science is not congruent with pseudo-science. But he does give a pretty good view of the facts for 2 minutes here ua-cam.com/video/3ReRu7Yt4Ao/v-deo.html . According to him in these 2 minutes, there is current flowing in both conductors and when it is a differential current, it is a good thing. But what "common mode currents" is not, it's not "current flowing in the outside of the coax". You're welcome for the feedback.
In the broad sense, there isn't much of a difference. They perform similar functions. We typically speak of vertical antennas using radials and horizontal wire antennas needing a counterpoise.
5% of a wavelength at the LOWEST frequency is pretty universally accepted as the minimum length when utilizing the coax shield as the counterpoise. So for a 40-10 EFHW, 5% of 40 meters = 2 meters (aprox 7 ft.). I've been known to slip a 110uh coil extension on my 67 ft. wire and run the EFHW on 80 meters, so I always use the same 15 ft. coax between my 49:1 UNUN and the coax choke. KZ9V
We sometimes call an end fed halfwave an end fed dipole, because it acts as a dipole at the lowest frequency, and multiple dipoles at harmonic frequencies. Furthermore, modeling shows that the radiation pattern is that of a dipole. So....I wonder why a counterpoise is needed? Does a counterpoise make it an off-center fed dipole and not a true end fed halfwave??? Did the original end fed "zep" halfwave wire antennas require a counterpoise?
End fed half wave on the fundamental frequency gives a pattern like the traditional dipole. however you can work multiple harmonics with this antenna with a low SWR depending on how high it is placed above ground with just your radio tuner. counterpoise is needed if you choke the antenna at the feedpoint. if not it will use the outer shield braid as the counterpoise
I wonder if the original 'Zeps' were more of the non-resonant variety and not the end fed half wave style we are accustomed to today. A 450ohm impedance would be easier to match with transmitters of the day than a 4000 ohm one. I need to find a really old copy of the Antenna Guide to see if my hunch is correct, though. But to your other point, adding a counterpoise to an EFHW doesn't turn the antenna to an OCF dipole. A true OCF is a half wave with the feed point roughly at the 2/3 point of the radiator. With the EFHW, the entire 1/2 wave of the antenna is being end-fed. Little, if any, forward power should be going to the counterpoise.
Is a counterpoise needed for an EHFW? Simulation and experiments suggest no. Search "Of end-feds and feed-lines" for a link to the receipts backing up this statement and revelation of certain counterpoise lengths that will certainly draw unwanted current away from the radiator. The original zepp as popularly described has the 1/2 wave wire radiator with 1/4 wave stub for a total electrical length of 1 wavelength. This length is complete and requires no counterpoise to function and may well be compromised by certain lengths of feedline or mounting structure. This is analogous to the J antenna of course and a simple trick tames this tendency. Search for "the j pole is herewith fixed" for one solution.
Interesting question. An EFHW is a special case of an OCFD (off center fed dipole) where the 2nd leg is extremely short. The key is that you are deliberately feeding a EFHW at the high impedance (low current) point through a 49:1 or similar impedance transformer. As I understand it the short leg of an OCFD is usually wired differently from the counterpoise of an EFHW such that it is not directly attached to the coax shield. Not all OCFDs use the same design so the details may vary. OCFDs also experience common mode currents that can make the outside of the coax act like part of the antenna. I now use an OCFD with a choke at both the antenna feed point and the transceiver. Without any chokes the whole house smoke alarms would sound every time I transmitted and the SWR was a little higher than I liked. I added the 2nd choke to reduce the receiver noise floor. I was stunned how much the noise floor dropped with two chokes (from myantennas.com). It's now usually around S1. Of course every installation is different. For QRP in the field the choke isn't needed because the power is low and there are few noise sources nearby. This makes the EFHW extremely practical as a field antenna (which I use). For home use with 100 watts or more it needs to be tamed. An OCFD is slightly more efficient and able to handle more power than a EFHW because the impedance transformer (4:1 unun) losses are lower.
No. Lightning arrestors consist of a gas discharge tube which is kind of like a circuit breaker. It will let RF energy pass, but large impulses like lightning cause the tube to fail, breaking the flow of energy which then is shunted to ground. Common mode chokes use inductance, either from a coiled cable or a ferrite choke, to block RF energy, but electrical fields are allowed to pass through.
Nothing is obligated, but performance will vary by the implementation method. I personally would never bring a long wire into the shack, but set it up, properly terminated as an external antenna and use coax to enter the shack.
Could I use a 1:1 unun for an RF choke? I'm pretty new to this, so I'm really struggling with the choke idea. (I'm thinking something like the LDG RU 1:1.) Thanks!
You could. Adding a 1:1 choke is common in the construction of 4:1 transformers. This is done because 4:1 transformers are usually of the voltage design, so choking is a necessity. 9:1 and 49:1 designs are typically current transformers so a typical coaxial choke or ferrite is enough. But using a 1:1 current choke wouldn't hurt.
Great video. As what was stated, one can choose between using their coax as the counterpoise but to prevent RFI must be choked off either at the antenna balun/unun feed. If you use a counterpoise, choke the feedline right at the balun. I use a donut-type ferrite with a few turns of coax. They work great on preventing RFI. Folks do well to remember that any antenna whether vertical or end fed is essentially a dipole that needs the other half of the antenna to come from somewhere. It's up to the op to determine where. 73 de Scott W1AL
Dave did answer - either counter poise OR coax with transformer at right end - and Michael confirmed. Watch again - but yet, Not a clear YES/NO - cause the answer is a bit more complex.
Good video. There definitely is controversies regarding a counterpoise or not. I feel like Dave was very well spoken about this topic.
If you don't have one already, use this as an excuse to get some sort of antenna analyzer. NanoVNA, MFJ, Rigexpert, whatever you end up buying, they have one for just about every budget. In the end, I think just experimenting with different configurations to see what works and what works better is time well spent. Might be a good time to try out WSPR as well.
Personally, I have an EFHW for 10m about a half wavelength off the ground, parallel to the ground and added a tuning stub to get a slightly better SWR. I've only relied on my radio's SWR meter and generally run QRP and occasionally up to maybe 20 watts. I've worked Asia, Canada, Mexico - South America, Western Europe and almost have all 50 states.
I realize not everyone has room or trees that high to do that so I've also run it vertical or sloper from the top of a mast. All work pretty well.
In the end, it's all about results. Make a contact and feel successful.
The answer is no.
1:47 Please test a small transmitter located at the transformer feed of the EFHW without coax or any additional wire. The EFHW dipole will radiate the same power as a center fed dipole less a bit of loss (~1 dB) caused by the transformer. I've done this test several times confirming no need for a counterpoise of any sort.
The correct answer is that it needs to match the impedance of your impedance transformer. If you use a 49:1, you need enough on the opposing side of the long portion of your antenna to be long enough to match 2450 ohms. If you have a 64:1, you will need enough to match 3200 ohms. YMMV based on your specific situation.
My EFHW is from myantennas It is 6 feet off ground at feed point and 40 feet off ground at far end. My coax runs from feed point 6 feet towards ground and then the remaining coax runs along ground 60 feet (like Dave said). I've made over 500 Q's during 2023 already. 80m @1:1.5 and the remaining bands (40 - 30 - 20 - 17 - 15 - 10) are close to 1:1.2 except 17 which is 1:1.8. Greet antenna.
To Dave's question about lower vs higher feed point height and how it works with regards to a counterpoise, I do not have a choke on my coax and do not have a counterpoise in place, the feed point is over 20' in the air with the far end about 30' up and it plays really really nice.
ABP - Always Be 'Poisen Great Explanation of why/why not to use a counterpoise!
I was curious about why I was getting erratic results when I was doing FT8 on WSJT-X with my EFHW antenna. Receive worked just fine and I could hear / decode traffic from all over. As soon as I enabled transmit, everything got very garbled and messy on the waterfall. I figured I was getting RF on my rig somewhere but wasn't sure where / how. This explains it. Choke ordered from DXE and we'll see how FT8 works now! Thank you so much!
I run an EF that is 289' from end to choke on the coax and a common mode choke at the receiver. The wire is 203' long. Very quiet, tunes all bands from 120 to 6 end to end and SWR is less than 3:1 down to 1:1.. I've worked 99% of all stations I can hear on 100W. From APAC, SA, South Africa, Tasmania, Japan, eastern europe, russia,etc... It is a very tall Z shape when viewed from below and 45' down to 15'... I started with a 155' Palomar Bullet kit and modified it. Love this antenna. The choke was moved around to tune it and I don't have anything dropping down until after the choke into the shack. The transformer is 40' up in the air. And the choke is about 20' in the air about 25' from the shack.
From doing portable for many years going place to place .I can say the counterpoise can change. also the length of end fed half can change from location to location. wet ground vs dry ground vs snow on ground. how high up is the unun . all can change loading of a antenna . even the weather can . some times adding more counterpoise can broadband SWR more. so the answer is whatever works well for your location of you EFHW . same goes for the 9:1 . some have 49:1 and a 1:1 bult in. that will need a counterpoise. I use the off set center fed dipole. 40 to 6 meter. that has both transformers in it. the short element is the counterpoise. harder to set up in a park. EFHW is quite easy for quick set up. I had the 49:1 near or on ground and going straight up or sloper . just lean DX commander pole into a tree. done. any fiberglass pole. MFJ has a nice one. just bring a counterpoise wire . you may need it. and may vary on different bands. sometimes a counterpoise can bring down the noise and can increase it. try both ways whatever works better go with that. 73's
Great topic. Thanks for the information.
What would be helpful is showing us what it looks like when rf is coming back in the shack. Then demonstrate remedy options and the results
That's a good suggestion.
KZ9V
RF in the shack can manifest itself in a few ways. The most extreme is getting a shock or RF burn when you touch the ground side of the transmitter chassis. Other symptoms are poor audio quality (distortion) on your transmitted signal, distortion coming through unshielded speakers, and electronic devices randomly shutting off. I'll have to think about how that can be demonstrated in a video.
@@KB9VBRAntennas Right, how do you replicate it without risk. I see lots of videos on equipment and features but almost no before and after videos. Do you have any that start with a poor reception then apply the various filters and adjustments to tweak the signal to the best audio output? Knowing what a feature does is one thing, knowing when and how to use it is another. Your videos are great, your doing a great service. Thank you.
Good advice all around.
Great video, Michael, I'm glad I found this! 73, K7KS
:D a friend of mine was surprised I use a coax shield as one of radials when using my center loaded vertical :D
having "only" 8 5 m radials, adding another one is usually measurable (well, today, after a week of raining = good ground conductivity it is not visible).
My idea originated from using coax braid as a counterpoise of EFHW antennas.
I run a choke at both ends of the coax with a counterpoise
20-25’ on a 40 m efhw. 40-50’ on a 80 m efhw. Then a common mode choke. Then any length to your radio. Palomar and PackTenna both support these measurements
Is an end feed antenna with a counterpoise really an off-center fed antenna? Or does the counterpoise function just to serve as a ground and not as a radiator?
Se agradece usar medidas en "metros" 73
Even without a coax shield connected to the secondary winding, it will still work thanks to the DISPLACEMENT current and capacitance between the primary and secondary winding. So whatever we do the antenna will always find a way not to violate Kirchhoff's law, BTW KCL does not apply entirely to RF circuits. See the test without any connection to the second port of the secondary winding. ua-cam.com/video/7bm0c_CNtVU/v-deo.htmlsi=gsvkeJz7wdy2uEz3
Might also be noteworthy that at qrp levels (5-10 watts) a choke isn't usually necessary. At higher power, that RF gets more nasty coming back to your transceiver, so a choke becomes more of a necessity.
Still good for noise reduction. Nowadays, the receivers are very sensitive.
At QRP power levels, transceivers can be more tolerant of common mode currents, so choking isn't as much of an issue.
If you run it to a stake in the ground, ,it's not nearly an endfed anymore. It's more like a centerfed and your feedpoint impedance will drop.
If you start thinking of the antenna as an antenna and not an antenna with a counterpoise, you will begin to understand the theory more. Because there never is any "counterpoise". The antenna has 2 connections to it. On an endfed, it can be a tiny stub on one side and a long stretch on the other. There's capacitance that can be measured distributed across the element to the other side of the element. There's inductance distributed along the element. The collective values are the XL and the Xc which make up the "X" in the R+/-jX equation. So if you make one side of the feedpoint really small, the Xc and XL will be really small because the tiny inductance is in series with the large inductance on the other side and small inductance in series with the large inductance is a small inductance. The small capacitance on one side is in parallel with the larger portion on the other side. That capacitance will be very small.
The outer conductor of the feedline does not become any "counterpoise". It's a feedline. The feedline feeds to the feedpoint. When it feeds to the feedpoint, current will flow into the antenna. If it's not a match, some current will reflect back to the transmitter. That reflection is on both conductors of the feedline.
Current always is flowing on the outside of your coax. This is something you want. It's a part of the design. What you don't want is reflected currents. You avoid reflected currents by matching the feedline impedance to the antenna feedpoint impedance. It's the only option.
An "isolation transformer" is a real thing in electronics. It's something to remover the DC flowing in the primary from flowing in the secondary. I don't have any DC in my transmission line. But you could if you are powering something at the other end of your transmission line, I guess.
The more small side antenna you have, the lower your feedpoint radiation resistance. That's all it is. The smaller you make the small side, the closer to infinity the feedpoint radiation resistance becomes. You know you have a 9:1, 49:1, or a 64:1 transformer. The small side has to match whatever your transformer is really needing to see. If you want to choke the heck out of your signal, fer crissakes, choke the signal. Lower your output power.
Opinions don't matter here. Only facts. Please learn the topic. You don't know what "common mode currents" are. Look at Mark Smith's video between 3:00-5:00 minutes. He slips up and uses stuff he learned in school during these 2 minutes and panders to pseudo-science the rest of the video. He can't figure out how it all fits together because real science is not congruent with pseudo-science. But he does give a pretty good view of the facts for 2 minutes here ua-cam.com/video/3ReRu7Yt4Ao/v-deo.html . According to him in these 2 minutes, there is current flowing in both conductors and when it is a differential current, it is a good thing. But what "common mode currents" is not, it's not "current flowing in the outside of the coax".
You're welcome for the feedback.
Good info. Thanks 😊 WG7D
What's the difference between a counter poise and a radial?
A rose by any other name...
In the broad sense, there isn't much of a difference. They perform similar functions. We typically speak of vertical antennas using radials and horizontal wire antennas needing a counterpoise.
I keep hearing 5% for the counterpoise length.
5% seems awful short.
For an EFHW, consider 5% of the fundamental wave-length as the minimum length for a counterpoise -- it works for me...
5% of a wavelength at the LOWEST frequency is pretty universally accepted as the minimum length when utilizing the coax shield as the counterpoise. So for a 40-10 EFHW, 5% of 40 meters = 2 meters (aprox 7 ft.). I've been known to slip a 110uh coil extension on my 67 ft. wire and run the EFHW on 80 meters, so I always use the same 15 ft. coax between my 49:1 UNUN and the coax choke.
KZ9V
We sometimes call an end fed halfwave an end fed dipole, because it acts as a dipole at the lowest frequency, and multiple dipoles at harmonic frequencies. Furthermore, modeling shows that the radiation pattern is that of a dipole. So....I wonder why a counterpoise is needed? Does a counterpoise make it an off-center fed dipole and not a true end fed halfwave??? Did the original end fed "zep" halfwave wire antennas require a counterpoise?
End fed half wave on the fundamental frequency gives a pattern like the traditional dipole. however you can work multiple harmonics with this antenna with a low SWR depending on how high it is placed above ground with just your radio tuner. counterpoise is needed if you choke the antenna at the feedpoint. if not it will use the outer shield braid as the counterpoise
@@wildbill1 Was this a response to any of my questions or comment???
I wonder if the original 'Zeps' were more of the non-resonant variety and not the end fed half wave style we are accustomed to today. A 450ohm impedance would be easier to match with transmitters of the day than a 4000 ohm one. I need to find a really old copy of the Antenna Guide to see if my hunch is correct, though.
But to your other point, adding a counterpoise to an EFHW doesn't turn the antenna to an OCF dipole. A true OCF is a half wave with the feed point roughly at the 2/3 point of the radiator. With the EFHW, the entire 1/2 wave of the antenna is being end-fed. Little, if any, forward power should be going to the counterpoise.
Is a counterpoise needed for an EHFW? Simulation and experiments suggest no. Search "Of end-feds and feed-lines" for a link to the receipts backing up this statement and revelation of certain counterpoise lengths that will certainly draw unwanted current away from the radiator.
The original zepp as popularly described has the 1/2 wave wire radiator with 1/4 wave stub for a total electrical length of 1 wavelength. This length is complete and requires no counterpoise to function and may well be compromised by certain lengths of feedline or mounting structure. This is analogous to the J antenna of course and a simple trick tames this tendency. Search for "the j pole is herewith fixed" for one solution.
Interesting question. An EFHW is a special case of an OCFD (off center fed dipole) where the 2nd leg is extremely short. The key is that you are deliberately feeding a EFHW at the high impedance (low current) point through a 49:1 or similar impedance transformer. As I understand it the short leg of an OCFD is usually wired differently from the counterpoise of an EFHW such that it is not directly attached to the coax shield. Not all OCFDs use the same design so the details may vary. OCFDs also experience common mode currents that can make the outside of the coax act like part of the antenna. I now use an OCFD with a choke at both the antenna feed point and the transceiver. Without any chokes the whole house smoke alarms would sound every time I transmitted and the SWR was a little higher than I liked. I added the 2nd choke to reduce the receiver noise floor. I was stunned how much the noise floor dropped with two chokes (from myantennas.com). It's now usually around S1. Of course every installation is different. For QRP in the field the choke isn't needed because the power is low and there are few noise sources nearby. This makes the EFHW extremely practical as a field antenna (which I use). For home use with 100 watts or more it needs to be tamed. An OCFD is slightly more efficient and able to handle more power than a EFHW because the impedance transformer (4:1 unun) losses are lower.
Doesn't the lightning arrestor, since it is grounded act to remove cmc before hitting your transceiver?
No. Lightning arrestors consist of a gas discharge tube which is kind of like a circuit breaker. It will let RF energy pass, but large impulses like lightning cause the tube to fail, breaking the flow of energy which then is shunted to ground. Common mode chokes use inductance, either from a coiled cable or a ferrite choke, to block RF energy, but electrical fields are allowed to pass through.
Is COAX Obligate For Long Wire ANtenna?
Nothing is obligated, but performance will vary by the implementation method. I personally would never bring a long wire into the shack, but set it up, properly terminated as an external antenna and use coax to enter the shack.
Could I use a 1:1 unun for an RF choke? I'm pretty new to this, so I'm really struggling with the choke idea. (I'm thinking something like the LDG RU 1:1.) Thanks!
You could. Adding a 1:1 choke is common in the construction of 4:1 transformers. This is done because 4:1 transformers are usually of the voltage design, so choking is a necessity. 9:1 and 49:1 designs are typically current transformers so a typical coaxial choke or ferrite is enough. But using a 1:1 current choke wouldn't hurt.
Um...won't an unun be connected like a transformer? A choke is connected differently? Maybe I do not understand Marty's question.
Great video. As what was stated, one can choose between using their coax as the counterpoise but to prevent RFI must be choked off either at the antenna balun/unun feed. If you use a counterpoise, choke the feedline right at the balun. I use a donut-type ferrite with a few turns of coax. They work great on preventing RFI. Folks do well to remember that any antenna whether vertical or end fed is essentially a dipole that needs the other half of the antenna to come from somewhere. It's up to the op to determine where. 73 de Scott W1AL
anyone notice how they did not answer the question? The entire video did not answer the question.
Dave did answer - either counter poise OR coax with transformer at right end - and Michael confirmed. Watch again - but yet, Not a clear YES/NO - cause the answer is a bit more complex.
ABC, always be counterpoising 👍