It`s worth saying here that the main reason for these things heating up, is trying to couple into, (match), an antenna that is excessively reactive. If the antenna is purely resistive, the ferrite core can be very small. Type 43 1in diam carrying 100 watts without heating. Also, once the ferrite core has reached a certain high temperature, it will saturate and begin heating up even faster! (Curie temperature). Great work, this channel needs more subs!!
Thanks very much Chris. That's very helpful information. I'm guessing in a random length wire antenna which is not resonant on any one band then there will be a fair bit of reactance encountered (either inductive or capacitive). There are a lot of variables at play aren't there? It is certainly fascinating stuff. Thanks again. 73 Nick
@@M0NTVHomebrewing Yes, that is so very true. These things are ok to use with reactive SWR up to around 3 to 4 but with resistive coupling, can easily couple into the end of a half wave wire (2000 to 3500 ohms). The wire has to be resonant though and a suitable balun will give a good coupling (match) to 50ohms. I use one for a halfwave kite antenna, with good result.
Thanks Alan! Yeah, I've had the FT8 RX working a few times now. It certainly does the job very well and decodes signals from all over the world. See you soon!
Good video on 1:9 UNUN, thanks. It may be helpful to mention that, although people say to use these 1:9's with long wires or random wires, some care is advisable with the length if the wire to avoid 1/4 or 1/2 wave resonance. There are many articles online and books that advise on appropriate "random" lengths for the band/s you want to operate on. KJ7DJR's site is just one example of what appears to be a good guide.
You are quite correct Steve. I remember when I made an inverted L with 9:1 UnUn some years ago I had a big list of lengths to avoid! Thanks for watching. 73 Nick
Be interesting to know how efficient a random long wire would be compared to an EFHW on 20 and 40. Obviously there's the hassle of requiring an ATU, but if your rig has one built in, no problem. Also I believe the random long wire needs to be grounded an the balun... Must try it!
I would go for an EFHW every time having used both types of antenna. For me the only advantage of a random wire with 9:1 UnUn is that you can tune it up to pretty much any band. I used to be able to put FT8 out on top band with mine - though I shudder to think how little signal was actually making it out of my antenna! But it did work. 73 Nick.
Howdy. Really nice walkthrough. I might suggest a larger impedance ratio. The end impedance could be as high as 2k - 3k closer to antenna resonance. Also I would suggest tapping the secondary to provide a rough matching and taking some of the work off the tuner. Finally I suggest using glass fibre silicone flexible tubing for the enamelled wires. This tubing is highly heat tolerant. Regards.
@@M0NTVHomebrewing Howdy again. Yeah. Some more suggestions about the tapping. Let's say one winds the toroid with 4 or 5 parallel wires. Only one winding needs to tapped. Just leave the tapped winding free floating. Then use a banana plug jumper to connect the low end of the tap winding to 1:1, 1:2, 1:3 or 1:4. Whichever comes closest to swr 1:1. Finally connect the dipole to the best tap to come even closer. In high regards.
I really don't understand why these are so popular! first, the 9:1 unun is designed to feed a 450 ohm load and once you stray from that 450 ohms, the efficiency decreases quite a bit, especially if you are feeding a load that is less than 450 ohms where it cause the current in the balun to skyrocket and really heat things up! A random wire will only be 450 ohms by chance and then only on a few frequencies because any length of wire's impedance changes as the frequency changes. The impedance of a single piece of wire can vary from just a few ohms to several hundred ohms. and maybe even over 2500 ohms ! So, if the antenna doesn't produce a 450 ohm load signified by a high swr, the losses in the unun increase, and since coax is most efficient when feeding a matched load, the losses on the coax feedline also increase ! So, you have losses in the unun and in the coax feeding it, and then there are losses in the tuner itself. Remember, very low impedance load increases current in the system that cause wasted power in the form of heat and not radiated by the antenna. And if the load is less than 450 ohms, remember that the 9:1 unun is down converting that to something even lower ! For example, lets say the load presented by the wire is 50 ohms, then the unun converts that down by a factor of 9, so you have 50/9 = 5.55 ohms, or a mismatch of 9:1. This causes the losses in the unun, the coax and the tuner to increase. Also, the longer the coax is, the higher those losses are too ! Now, if you happen to be operating QRP, 5 watts or less and only a fraction of you power is actually making it to the antenna to be radiated. Lets say you are using 50 feet of RG58 coax and with a mismatch of 9:1, the loss at 14 mhz is 2.427db - almost half your power ! With 5 watts in, you get 2.859 watts presented to the 9:1 unun which also has losses due to the mismatch, and a 5.5 ohm load to the tuner also increases losses there, and lets say that adds another 2 db of loss or so, you are now below 2 watts to the antenna to be radiated. Yes, you will make contacts with it, I have made many with less power than that, but just think how many more contacts you can make with a more efficient antenna system !
Hi Rick, thanks for your very detailed response. I don't doubt anything you say but would just make the point that any antenna (even a highly compromised one) is better than no antenna. My first HF antenna was an end fed wire with a 9:1 UnUn and whilst certainly not brilliant it did get me out on most bands. I have now converted to the End-Fed Half-Wave and have never looked back. But the UnUn in the video was built for a friend at my radio club who wanted one - so I made him one! Thanks for taking the time to reply. 73 Nick
If, after about 36.7 MHz, the impedance is heading back up towards 50 ohms, should the VSWR not be heading down towards 1:1 again at the same time? Presumably, your load resistors are changing impedance at higher frequencies.
Hi! That's an interesting question. I no longer have that UnUn because I built it for a bloke at my radio club but I did do a similar test with an older one I had built and used. That was even worse! Whilst it is tempting to blame it on the resistors I fear the issue is closer to home i.e. the windings of the UnUn. I suspect that inductive reactance in the windings will be playing a part. The truth is that the Random Wire + 9:1 UnUn is a compromise antenna which has to be used with a tuner. The nominal value of 450Ω is guesswork really because it depends on how long your antenna is and how high it is etc. But it doesn't need to be a brilliant SWR reading - just one that is reasonably do-able for your tuner. How efficient it is at radiating your signal is another matter though! But as I replied to another poster: any antenna is better than no antenna and mine served me pretty well until I discovered the End Fed Half Wave. 73 Nick
I think that for the turns it is not simply more is better, and the reason is that, for a given core and current through the coil, at some point you will saturate the core if you add enough turns, and then the core quickly overheats and everything fails. I think for some high-power ununs/baluns this enters into the design. I like the mechanics of your unun except for the banana jacks. I honestly am puzzled about why I see those on these devices sometimes. I use baluns with dipoles, and use spade lugs that I solder onto and then that screws onto the connection. It's designed for this. A banana plug is designed for plugging into things on your bench. I just don't see how the banana plugs would even stand up to the tension of the wires if it were hanging in the middle. I am really puzzled by this. I can see maybe for field operation or something like that? Very odd.
Hi Todd, thanks for watching and commenting. Really there shouldn't be any tension on the connections going in to the UnUn. It's not like a BalUn which can be suspended high up between the two legs of a dipole. The 9:1 UnUn is usually employed in an end-fed wire at close to ground level so strain relief shouldn't be an issue. When I've used these in the past I haven't even plugged anything into the actual banana sockets - just wrapped the wires around them and tightened them. Ultimately it is a compromise antenna option but it can work pretty well and as they say, any antenna is better than no antenna! Thanks again, 73 Nick
BalUns and UnUns are a big topic and sadly there is a lot of misinformation around - as you've probably gathered if you do a bit of googling! For the UnUn I made the main concern is to preserve the correct phasing of the turns and twisting the wires would therefore be a bad idea. In some transformers however you want a very tight coupling and so you will deliberately twist the wires e.g. in a trifilar transformer in a diode ring mixer. It's a subject that needs careful consideration because not all BalUns, UnUns & transformers are alike. Incidentally if you want a great explanation of a common mode choke (often incorrectly called a BalUn) then check out Mark Smith's excellent video: th-cam.com/video/SW34Z4JPK_o/w-d-xo.html All the Best, Nick
Put it in the Roofspace and connect the black connector to ground via the copper pipe and the Red through a hole in the bargeboards to a tree 1 Mile from the house.
Thanks very much Kevin! No the 17m rig is just something I've been playing with over the last few months. It's my own design but as usual borrows from lots of other people. 73 Nick
@@M0NTVHomebrewing Oh ok. It's just that I'm (attempting!) building a scratch build rig under the guidance of the G-QRP club. I'm a couple of months away from finishing though (at least). Maybe I'll get lucky and have a QSO in the late summer? 73 Kevin M0XYM
That sounds fantastic Kevin. I wish you every success. The hardest bit I find is not building it but fault-finding when it doesn't work as expected. You need to strongly resist the urge to throw the whole thing in the skip! I seriously feel that way about every rig I've ever built - but if you can stay doggedly persistent then you WILL get it working in the end. All of mine do (eventually!). Don't be afraid to shout if you need some advice (or counselling!!!). 73 Nick
It`s worth saying here that the main reason for these things heating up, is trying to couple into, (match), an antenna that is excessively reactive. If the antenna is purely resistive, the ferrite core can be very small. Type 43 1in diam carrying 100 watts without heating. Also, once the ferrite core has reached a certain high temperature, it will saturate and begin heating up even faster! (Curie temperature). Great work, this channel needs more subs!!
Thanks very much Chris. That's very helpful information. I'm guessing in a random length wire antenna which is not resonant on any one band then there will be a fair bit of reactance encountered (either inductive or capacitive). There are a lot of variables at play aren't there? It is certainly fascinating stuff. Thanks again. 73 Nick
@@M0NTVHomebrewing Yes, that is so very true. These things are ok to use with reactive SWR up to around 3 to 4 but with resistive coupling, can easily couple into the end of a half wave wire (2000 to 3500 ohms). The wire has to be resonant though and a suitable balun will give a good coupling (match) to 50ohms. I use one for a halfwave kite antenna, with good result.
Yes, good point. If the antenna is not resistive, that power is going to have to be dissipated somewhere (like balun or coax).
Thanks for this Nick, I learn something every time I watch one of your videos 73
Thanks Bob. That's very kind of you. Thanks for watching another one! 73
Nicely explained Nick - as always. Spot the FT8 20m RX!
Thanks Alan! Yeah, I've had the FT8 RX working a few times now. It certainly does the job very well and decodes signals from all over the world. See you soon!
Good video on 1:9 UNUN, thanks. It may be helpful to mention that, although people say to use these 1:9's with long wires or random wires, some care is advisable with the length if the wire to avoid 1/4 or 1/2 wave resonance. There are many articles online and books that advise on appropriate "random" lengths for the band/s you want to operate on. KJ7DJR's site is just one example of what appears to be a good guide.
You are quite correct Steve. I remember when I made an inverted L with 9:1 UnUn some years ago I had a big list of lengths to avoid! Thanks for watching. 73 Nick
Be interesting to know how efficient a random long wire would be compared to an EFHW on 20 and 40. Obviously there's the hassle of requiring an ATU, but if your rig has one built in, no problem. Also I believe the random long wire needs to be grounded an the balun... Must try it!
I would go for an EFHW every time having used both types of antenna. For me the only advantage of a random wire with 9:1 UnUn is that you can tune it up to pretty much any band. I used to be able to put FT8 out on top band with mine - though I shudder to think how little signal was actually making it out of my antenna! But it did work. 73 Nick.
Howdy. Really nice walkthrough.
I might suggest a larger impedance ratio. The end impedance could be as high as 2k - 3k closer to antenna resonance.
Also I would suggest tapping the secondary to provide a rough matching and taking some of the work off the tuner.
Finally I suggest using glass fibre silicone flexible tubing for the enamelled wires. This tubing is highly heat tolerant.
Regards.
Hi Eugene. Thanks for watching and for sharing your suggestions. 73 Nick
@@M0NTVHomebrewing Howdy again. Yeah.
Some more suggestions about the tapping.
Let's say one winds the toroid with 4 or 5 parallel wires. Only one winding needs to tapped. Just leave the tapped winding free floating. Then use a banana plug jumper to connect the low end of the tap winding to 1:1, 1:2, 1:3 or 1:4. Whichever comes closest to swr 1:1. Finally connect the dipole to the best tap to come even closer.
In high regards.
I really don't understand why these are so popular! first, the 9:1 unun is designed to feed a 450 ohm load and once you stray from that 450 ohms, the efficiency decreases quite a bit, especially if you are feeding a load that is less than 450 ohms where it cause the current in the balun to skyrocket and really heat things up! A random wire will only be 450 ohms by chance and then only on a few frequencies because any length of wire's impedance changes as the frequency changes. The impedance of a single piece of wire can vary from just a few ohms to several hundred ohms. and maybe even over 2500 ohms ! So, if the antenna doesn't produce a 450 ohm load signified by a high swr, the losses in the unun increase, and since coax is most efficient when feeding a matched load, the losses on the coax feedline also increase ! So, you have losses in the unun and in the coax feeding it, and then there are losses in the tuner itself. Remember, very low impedance load increases current in the system that cause wasted power in the form of heat and not radiated by the antenna. And if the load is less than 450 ohms, remember that the 9:1 unun is down converting that to something even lower ! For example, lets say the load presented by the wire is 50 ohms, then the unun converts that down by a factor of 9, so you have 50/9 = 5.55 ohms, or a mismatch of 9:1. This causes the losses in the unun, the coax and the tuner to increase. Also, the longer the coax is, the higher those losses are too ! Now, if you happen to be operating QRP, 5 watts or less and only a fraction of you power is actually making it to the antenna to be radiated. Lets say you are using 50 feet of RG58 coax and with a mismatch of 9:1, the loss at 14 mhz is 2.427db - almost half your power ! With 5 watts in, you get 2.859 watts presented to the 9:1 unun which also has losses due to the mismatch, and a 5.5 ohm load to the tuner also increases losses there, and lets say that adds another 2 db of loss or so, you are now below 2 watts to the antenna to be radiated. Yes, you will make contacts with it, I have made many with less power than that, but just think how many more contacts you can make with a more efficient antenna system !
Hi Rick, thanks for your very detailed response. I don't doubt anything you say but would just make the point that any antenna (even a highly compromised one) is better than no antenna. My first HF antenna was an end fed wire with a 9:1 UnUn and whilst certainly not brilliant it did get me out on most bands. I have now converted to the End-Fed Half-Wave and have never looked back. But the UnUn in the video was built for a friend at my radio club who wanted one - so I made him one! Thanks for taking the time to reply. 73 Nick
If, after about 36.7 MHz, the impedance is heading back up towards 50 ohms, should the VSWR not be heading down towards 1:1 again at the same time? Presumably, your load resistors are changing impedance at higher frequencies.
Hi! That's an interesting question. I no longer have that UnUn because I built it for a bloke at my radio club but I did do a similar test with an older one I had built and used. That was even worse! Whilst it is tempting to blame it on the resistors I fear the issue is closer to home i.e. the windings of the UnUn. I suspect that inductive reactance in the windings will be playing a part.
The truth is that the Random Wire + 9:1 UnUn is a compromise antenna which has to be used with a tuner. The nominal value of 450Ω is guesswork really because it depends on how long your antenna is and how high it is etc. But it doesn't need to be a brilliant SWR reading - just one that is reasonably do-able for your tuner. How efficient it is at radiating your signal is another matter though! But as I replied to another poster: any antenna is better than no antenna and mine served me pretty well until I discovered the End Fed Half Wave. 73 Nick
I think that for the turns it is not simply more is better, and the reason is that, for a given core and current through the coil, at some point you will saturate the core if you add enough turns, and then the core quickly overheats and everything fails. I think for some high-power ununs/baluns this enters into the design.
I like the mechanics of your unun except for the banana jacks. I honestly am puzzled about why I see those on these devices sometimes. I use baluns with dipoles, and use spade lugs that I solder onto and then that screws onto the connection. It's designed for this. A banana plug is designed for plugging into things on your bench. I just don't see how the banana plugs would even stand up to the tension of the wires if it were hanging in the middle. I am really puzzled by this. I can see maybe for field operation or something like that? Very odd.
Hi Todd, thanks for watching and commenting. Really there shouldn't be any tension on the connections going in to the UnUn. It's not like a BalUn which can be suspended high up between the two legs of a dipole. The 9:1 UnUn is usually employed in an end-fed wire at close to ground level so strain relief shouldn't be an issue. When I've used these in the past I haven't even plugged anything into the actual banana sockets - just wrapped the wires around them and tightened them. Ultimately it is a compromise antenna option but it can work pretty well and as they say, any antenna is better than no antenna! Thanks again, 73 Nick
Hi, can someone advise me on baluns. I have read that twisting the wires is bad as it causes capacitance.?
BalUns and UnUns are a big topic and sadly there is a lot of misinformation around - as you've probably gathered if you do a bit of googling! For the UnUn I made the main concern is to preserve the correct phasing of the turns and twisting the wires would therefore be a bad idea. In some transformers however you want a very tight coupling and so you will deliberately twist the wires e.g. in a trifilar transformer in a diode ring mixer. It's a subject that needs careful consideration because not all BalUns, UnUns & transformers are alike. Incidentally if you want a great explanation of a common mode choke (often incorrectly called a BalUn) then check out Mark Smith's excellent video: th-cam.com/video/SW34Z4JPK_o/w-d-xo.html
All the Best, Nick
Put it in the Roofspace and connect the black connector to ground via the copper pipe and the Red through a hole in the bargeboards to a tree 1 Mile from the house.
As usual - so well explained. Suddenly I thought - the 17m rig; is that a G-QRP project?
Thanks very much Kevin! No the 17m rig is just something I've been playing with over the last few months. It's my own design but as usual borrows from lots of other people. 73 Nick
@@M0NTVHomebrewing Oh ok. It's just that I'm (attempting!) building a scratch build rig under the guidance of the G-QRP club. I'm a couple of months away from finishing though (at least). Maybe I'll get lucky and have a QSO in the late summer? 73 Kevin M0XYM
That sounds fantastic Kevin. I wish you every success. The hardest bit I find is not building it but fault-finding when it doesn't work as expected. You need to strongly resist the urge to throw the whole thing in the skip! I seriously feel that way about every rig I've ever built - but if you can stay doggedly persistent then you WILL get it working in the end. All of mine do (eventually!). Don't be afraid to shout if you need some advice (or counselling!!!). 73 Nick
What about using tape to keep the three wires like a flat tape.
It's alright so long as your tape doesn't melt! Thanks for watching.
👍👏👏
Sir, it will be better if you put any design for Ground penetrating radar (GPR). Sir I will eager to see it in your channel.
Sorry, that's not really my thing! I'm sure there's someone doing it somewhere though. Best Wishes.