Dave, I think Jon is right using a 9:1 unun with a NON resonant EF - which is a 'random' wire. A 49:1 unun is used with resonant EF's. Thanks for the video!
A "random length" antenna fed with a 9:1 unun is essentially either a non-resonant monopole, if the counterpoise wire is on the ground; or a non-resonant off-center fed dipole, if counterpoise wire is high and parallel to ground, sloped or vertical. Whatever the configuration, it requires a wide-range antenna tuner (matchbox) to provide an impedance match/transformation between the antenna system (i.e., feedline + unun + antenna) and your 50 ohm, 20 watt transmitter. If feedline loss is relatively low (either via short moderate-loss feedline or long low loss feedline) and impedance matching devices (matchbox and unun) fairly efficient, the antenna will perform well. As Dave said, the size of the 9:1 unun doesn't matter much as long as its rated for at least the power applied to it. Also, as Dave suggested, consider using an end-fed half-wave (i.e., resonant antenna) with a 49:1 or 64:1 unun. Ken WA8FCI
Dave, thank you for your helpful answers to my question about baluns and ununs! I have enough loaned and gifted equipment to get back on HF with 20 watts after many years of being inactive. Before I invest in a 100 watt rig I wanted to setup different stealth HF antennas (that can fit in my very limited space) and test those antennas real time by checking into HF nets that listen for QRP stations and by using the Reverse Beacon Network. The icom 7300 is my first choice for a 100 watt rig, so I'm glad you recommend it for someone getting back into HF, and also have it for your reference station. Thanks again! Jon, K3MAH.
In my opinion, the best radio to use is the one you already have. Once you gain experience, you will have a much better idea of what you want and enjoy as well as what works for you.
I would say given your space limitation beyond repurposed mobile antennas you will not see much difference between designs on the bands below 20m. Being so close to the ground in terms of wavelength most of the radiation is projected up and omnidirectional. This is great for contacts in the medium range (probably most of the USA) but the higher radiation angle will hurt DX performance. For longer range work from a small area some sort of ground mounted vertical is going to do the job better with it's lower angle of radiation. In light of these comments I think you will find one of the multistage fiberglass poles a useful item. Use it to support many simple configurations for example vertical, inverted V and inverted L. Perhaps not the best for long term fixed installations but certainly light, non conductive and deployable for portable work.
The ferrite cores used in HF baluns, tranformers, auto transformers, ununs etc. can have losses of a Db or so. Those measurements were made at the low power milliwatt level from analyzers. At high power levels the losses increase dramatically. Ferrites and other magnetic materials are nonlinear devices. They saturate. So, using higher power ferrites helps keep losses down and will also reduce splatter, harmonics and inter-modulation distortion which cause interference.
Nice channel, Dave. In the Netherlands, Novices can use certain HF bands (10, 20 & 40) with 25W. We are in the proces of letting Novices use 100W on the HF bands (it will almost be certain this year, 2021). On VHF & UHF (2M & 70 cm) it will still be 25Watts. A 1:9 UnUn is used for an EFLW antenna, where the lenghth of the antenna wire isn't critical (usually about 50 ft). A 1:49 or 1:64 UnUn is used for a EFHW , where the antenna lenghth must be a half wave.
KN4ZLH: In my opinion the higher watt rated balun has less resistance (DC). They run cooler and are usually more efficient. They should pass low wattage better than the cheaper low wattage units. I run a 4:1 balun on a 40 meter loop with 1.5Kw rating. I only have a 100 watt radio, no amp.
I have an end fed, it has been up for quite a long time. It still "works" For sure not my first choice in antennas. The add in the handicap of 20 watts.. I am afraid he is going to get disappointed and give up. There are a lot of rigs even new that are in that same price range... the IC-718 for example. If you want to try 20 watts, just turn the power down to 20 watts. Been at this over 50 years... don't handicap yourself! Even a good used 100 watt radio and a simple dipole are going to do you a much better service.
My EFHW 4010 is rated for a kilowatt, but works extremely well with my 817nd 5 watts, 2.5 watts and 500 milliwatts. Made so many DX contacts also. 73s.
He could also be referring to the Xeigu G90, which is 20 warts and is less than five hundred dollars. During a POTA activation that was featured in three different videos during the latest Thursday Night Ham Radio ( " Life at Terminal Velocity", "Temporarily Offline", and "Astro Leah") they made contact from Chain of Lakes state park in Indiana to California with Leah's G90 running a KM4ACK EFHW set up in an NVIS configuration (two to three feet off the ground).
You should not bother too much about upgrading to 100W. Remember, your signal strength will only increase by 1 (in words: one) S-unit. If other stations can hear you, your output power is sufficient. But you should use resonant antennas. If the internal tuner has to do a heavy job, the transmitter reduces the output power automatically. That can ruin your day... I operate my G90 with an endfed halfwave wire and a 49:1 balun. With these resonant endfeds (a 40m long wire for 80/40 and a 30m long wire for 30/60) I can work a radius of about 1000km in SSB on 40m or 80m from my QTH in Germany with 20W PEP. In FT8 I already managed to work Rhode Island and Massachusetts on 30m with only 15W.
Hi Dave, I got a question that really grinds my gears, and I can't find an answer to it. What happens if you use a random wire antenna with a 1:9 unun or a quarter wave vertical without any radials but with an 1:1 unun or other wave blocker before the feedline to the radio. In order to prevent the coax from radiating and being the counterpoise. Is it true that you "choke the antenna" this way? Pse help and 73 from DL
These are two very different antennas you mention. An additional 1:1 choke is advisable for any EF antenna, resonant or not, especially when there is no counterpoise. Best placement would usually be in the shack just before the radio or tuner (whichever comes first) or at least 6m/20ft from the antenna. This way the feedline between the choke and the antenna acts as a controlled counterpoise, which is no problem and actually what you want. If you place the choke right at the antenna, the common mode currents will look for other and unpredictable paths. This means the antenna system will not work as efficiently and you will probably end up with unwanted RF issues. I would say the same for the vertical setup, but I have no experience of my own with that one... Curious what others have to say on your question.
@@erpece thanks for the answer. To explain the situation a little bit better : The question results in my experiment with a 25m long random wire for 80m (matched with an old VCI manual tuner). The SWR was quite OK but I got so much RF from the coax in my shack that the oven started beepin' and also my electric kettle started to act weirdly, with only about 30W RF power. Now I ordered a Moonraker AmPro 80 to play around with, but I see the same problems coming up with that antenna. It has no counterpoise and will probably rely on the coax feedline to act als counterpoise. I don't have the possibility to set up a bunch of radials, due to the confined space here in the city. And I can't use 20m of feedline to provide enough length to act as counterpoise (which will also not solve the problem of HF inside the house). Furthermore the radials for 80m must be quite long to function correctly. The idea is now just to block out the common mode, but I don't know how the antenna will behave when doing so.
He said 20 watts, that tells me G-90, an inexpensive and feature rich radio in the $450 range. Right now FT-8 is the premiere mode while sunspots are down and 20 watts will do fine. Perhaps by the time the SFI climbs over 100 he will be able to buy a higher power radio. The gain from 20 to 100 watts is far less than it sounds.
Dave, my Elmer is a silent key many years ago. I wish that I had him back to share the new technologies we have today. Elmers are one of the greatest aspects of ham radio. Thank you You Tube content creaters!
Dave, I think Jon is right using a 9:1 unun with a NON resonant EF - which is a 'random' wire. A 49:1 unun is used with resonant EF's. Thanks for the video!
Dave the magic of radio you described is exactly what hooked me and why I am interested in HF. 73 from Moose Jaw. Tim
A "random length" antenna fed with a 9:1 unun is essentially either a non-resonant monopole, if the counterpoise wire is on the ground; or a non-resonant off-center fed dipole, if counterpoise wire is high and parallel to ground, sloped or vertical. Whatever the configuration, it requires a wide-range antenna tuner (matchbox) to provide an impedance match/transformation between the antenna system (i.e., feedline + unun + antenna) and your 50 ohm, 20 watt transmitter. If feedline loss is relatively low (either via short moderate-loss feedline or long low loss feedline) and impedance matching devices (matchbox and unun) fairly efficient, the antenna will perform well. As Dave said, the size of the 9:1 unun doesn't matter much as long as its rated for at least the power applied to it. Also, as Dave suggested, consider using an end-fed half-wave (i.e., resonant antenna) with a 49:1 or 64:1 unun. Ken WA8FCI
Dave, thank you for your helpful answers to my question about baluns and ununs! I have enough loaned and gifted equipment to get back on HF with 20 watts after many years of being inactive. Before I invest in a 100 watt rig I wanted to setup different stealth HF antennas (that can fit in my very limited space) and test those antennas real time by checking into HF nets that listen for QRP stations and by using the Reverse Beacon Network. The icom 7300 is my first choice for a 100 watt rig, so I'm glad you recommend it for someone getting back into HF, and also have it for your reference station. Thanks again! Jon, K3MAH.
In my opinion, the best radio to use is the one you already have. Once you gain experience, you will have a much better idea of what you want and enjoy as well as what works for you.
I would say given your space limitation beyond repurposed mobile antennas you will not see much difference between designs on the bands below 20m. Being so close to the ground in terms of wavelength most of the radiation is projected up and omnidirectional. This is great for contacts in the medium range (probably most of the USA) but the higher radiation angle will hurt DX performance. For longer range work from a small area some sort of ground mounted vertical is going to do the job better with it's lower angle of radiation. In light of these comments I think you will find one of the multistage fiberglass poles a useful item. Use it to support many simple configurations for example vertical, inverted V and inverted L. Perhaps not the best for long term fixed installations but certainly light, non conductive and deployable for portable work.
The ferrite cores used in HF baluns, tranformers, auto transformers, ununs etc. can have losses
of a Db or so. Those measurements were made at the low power milliwatt level from analyzers.
At high power levels the losses increase dramatically. Ferrites and other magnetic materials are
nonlinear devices. They saturate. So, using higher power ferrites helps keep losses down and
will also reduce splatter, harmonics and inter-modulation distortion which cause interference.
Nice channel, Dave. In the Netherlands, Novices can use certain HF bands (10, 20 & 40) with 25W. We are in the proces of letting Novices use 100W on the HF bands (it will almost be certain this year, 2021). On VHF & UHF (2M & 70 cm) it will still be 25Watts.
A 1:9 UnUn is used for an EFLW antenna, where the lenghth of the antenna wire isn't critical (usually about 50 ft). A 1:49 or 1:64 UnUn is used for a EFHW , where the antenna lenghth must be a half wave.
KN4ZLH:
In my opinion the higher watt rated balun has less resistance (DC). They run cooler and are usually more efficient. They should pass low wattage better than the cheaper low wattage units. I run a 4:1 balun on a 40 meter loop with 1.5Kw rating. I only have a 100 watt radio, no amp.
Very informative. Thanks.
I have an end fed, it has been up for quite a long time. It still "works" For sure not my first choice in antennas. The add in the handicap of 20 watts.. I am afraid he is going to get disappointed and give up. There are a lot of rigs even new that are in that same price range... the IC-718 for example. If you want to try 20 watts, just turn the power down to 20 watts. Been at this over 50 years... don't handicap yourself! Even a good used 100 watt radio and a simple dipole are going to do you a much better service.
Good advice.
But you can use the 7300 for QRP ops. You do hot have to use all if the 100 w output.
My EFHW 4010 is rated for a kilowatt, but works extremely well with my 817nd 5 watts, 2.5 watts and 500 milliwatts. Made so many DX contacts also. 73s.
He could also be referring to the Xeigu G90, which is 20 warts and is less than five hundred dollars. During a POTA activation that was featured in three different videos during the latest Thursday Night Ham Radio ( " Life at Terminal Velocity", "Temporarily Offline", and "Astro Leah") they made contact from Chain of Lakes state park in Indiana to California with Leah's G90 running a KM4ACK EFHW set up in an NVIS configuration (two to three feet off the ground).
Blind Assumption: that isn't picking 20 watts because he wants or needs a small portable station. Maybe the 20 he wants, is wanted for a reason.
Xiegu g90 is cheap, has a built in tuner, and is 20w. That's my guess.
I’m sure he got the Xiegu G90. Maybe he can use it for digital after moving up to a 100w rig.
You should not bother too much about upgrading to 100W. Remember, your signal strength will only increase by 1 (in words: one) S-unit. If other stations can hear you, your output power is sufficient. But you should use resonant antennas. If the internal tuner has to do a heavy job, the transmitter reduces the output power automatically. That can ruin your day... I operate my G90 with an endfed halfwave wire and a 49:1 balun. With these resonant endfeds (a 40m long wire for 80/40 and a 30m long wire for 30/60) I can work a radius of about 1000km in SSB on 40m or 80m from my QTH in Germany with 20W PEP. In FT8 I already managed to work Rhode Island and Massachusetts on 30m with only 15W.
GREAT advice Dave! QRP is an "acquired" taste for sure... All great videos...
73' de K4WRF
Hi Dave,
I got a question that really grinds my gears, and I can't find an answer to it.
What happens if you use a random wire antenna with a 1:9 unun or a quarter wave vertical without any radials but with an 1:1 unun or other wave blocker before the feedline to the radio. In order to prevent the coax from radiating and being the counterpoise.
Is it true that you "choke the antenna" this way?
Pse help and 73 from DL
These are two very different antennas you mention. An additional 1:1 choke is advisable for any EF antenna, resonant or not, especially when there is no counterpoise. Best placement would usually be in the shack just before the radio or tuner (whichever comes first) or at least 6m/20ft from the antenna. This way the feedline between the choke and the antenna acts as a controlled counterpoise, which is no problem and actually what you want. If you place the choke right at the antenna, the common mode currents will look for other and unpredictable paths. This means the antenna system will not work as efficiently and you will probably end up with unwanted RF issues.
I would say the same for the vertical setup, but I have no experience of my own with that one... Curious what others have to say on your question.
@@erpece thanks for the answer.
To explain the situation a little bit better :
The question results in my experiment with a 25m long random wire for 80m (matched with an old VCI manual tuner).
The SWR was quite OK but I got so much RF from the coax in my shack that the oven started beepin' and also my electric kettle started to act weirdly, with only about 30W RF power.
Now I ordered a Moonraker AmPro 80 to play around with, but I see the same problems coming up with that antenna.
It has no counterpoise and will probably rely on the coax feedline to act als counterpoise. I don't have the possibility to set up a bunch of radials, due to the confined space here in the city. And I can't use 20m of feedline to provide enough length to act as counterpoise (which will also not solve the problem of HF inside the house).
Furthermore the radials for 80m must be quite long to function correctly.
The idea is now just to block out the common mode, but I don't know how the antenna will behave when doing so.
He said 20 watts, that tells me G-90, an inexpensive and feature rich radio in the $450 range. Right now FT-8 is the premiere mode while sunspots are down and 20 watts will do fine. Perhaps by the time the SFI climbs over 100 he will be able to buy a higher power radio. The gain from 20 to 100 watts is far less than it sounds.
I’m curious about the little visitor walking across the screen in your videos. 😂
His name is Elmer and he often drops by during video production.
@@davecasler that’s so neat
Dave, my Elmer is a silent key many years ago. I wish that I had him back to share the new technologies we have today. Elmers are one of the greatest aspects of ham radio. Thank you You Tube content creaters!
If your not doing portable you could always just turn the 7300 down to 10 watts
Thank you, Dave. I had wondered about this. N0QFT
What about the EFHW created by K6ARK
RG 400 not LMR
For what you get with the 7300, the 705 is a waste of money.
5W standard
All of 10 and 12m should be tech. Why? 11m taken away and made into CB band.
Good question and great answer! 73 de N2MXX
100w definitely not needed. 20 is plenty, as they say
If you want to operate on HF, get a General license.