Homemade 49:1 Impedance Transformer For An EFHW Antenna

[@orlandoluscombe3008]

Great video, why do the capacitors need to be such high voltage?

[@dxexplorer]

Hi Orlando... A capacitator of 100 pF can be placed over the primary side of the transformer, so you can compensate any (unwanted) secondary capacity. This is only relevant if you use the 15 -12 - 10 meter band. If you don’t use this, the capactitator isn’t necessary. 73

[@dxexplorer]

P. S. The high voltage is needed because of the high current you get into the antenna and also the transformer if you transmit... at least that's what I know so far )

[@warplanner8852]

Orlando, to add to DX's responses, voltage at the end of a half wave antenna is highest there while current is highest at the center. Using a cap with a lower voltage invites destruction. It's the same reason you use high voltage caps when making traps (tuned LC circuits) for multi-band antennas. de k6whp

[@dxexplorer]

Thank you for this ) 73

[@sv2tcb]

Made it with whatever parts I found but It still worked and I was surprised. The propagation lately is very bad and I only get few locals and some operators from Italy. However I have completed the first version of the sputnik and I made it as compact as I could in order to fit in my hands. Actually some of my amateur Greek friends were surprised for how well they were heard through my receiver in my last video.

[@dxexplorer]

I'm really happy to hear that. I also want to remake the first version too to use it as portable and keep the second version for home use.

[@BastHoen]

Nice video, thank you! With all this nice building, make sure you are passing your license exam! Maybe we meet someday on the airwaves! 73 Bas PA5BAS

[@dxexplorer]

Thank you as well for watching. Ohh yes I hope I can finally go for the exam soon. I just have to wait a little for things to calm down with the "craziness" of the certificates )) I'd be glad to hear each other on the radio waves. 73 and Thank you one more time.

[@theDaftman]

Seen loads of youtubers/ham are using the FT114-43 i don't understand why as the Frequency range (Broadband Frequencies) is 25-300 MHz (43 material) not much use for 40 meters. it will work bit its not the correct one for 40m, now a FT240-31 is a Lower Broadband Frequencies 1-300 MHz that's what i will be using now I've built my own version of your SPUTNIK thanks to all you info. Thanks

[@dxexplorer]

That I don't really know... but even in my old amateur radio books they are also using the 43 material. Must be a reason so I won't ask more.... I'm sure they have better knowledge than I do. But to be honest the antenna performs really well. This Sunday.... I will come with another video on the receiver.... to talk about a few details and answer a few questions that most people ask. Glad you like it and I hope it turns out well. 73 my friend. Sorry I reply slow.... really busy this week.

[@theDaftman]

@@dxexplorerI appreciate any reply thank you for your time looking forward to next video. couldn't find a way to post you some pictures of mine, my PCB is smaller than yours only 100mm x 70mm

[@dxexplorer]

@@theDaftman The PCB is smaller because you wanted it that way ? Or because of the way it was printed ? I also added the PDF file in the folder as many people told me that printing the regular JPG may end in different size printing. 73. You can email me photos at [e-mail]

[@gravestonemyth]

The 25-300 MHz spec you mention is the RFI suppression for the 43 mix. The wideband transformer range is more like .5-500, though realistically, it becomes inefficient after 25 MHz or so.

[@dxexplorer]

@gravestonemyth I don't remember the video to be honest. But for sure it was some mistake. If I say 300 for sure I thought of 30 MHz. I did not tested it on any other frequencies. Is ok as I spent a lot of time making many tests this year... and I want to replace the video with the new one. Thank you for letting me know. Is late now but I will watch it again tomorrow. It's been a while since I made it )). Ohh and yes is true... in my case from 26 MHz up to 30 MHz the efficiency was going down. Not drastically as it was still efficient enough... but it was going down a bit.

[@jorgerodriguez-wp6en]

Hello there sir. Excellent your video of Un-Un 49:1 A question. I have very small Amidon 50-43 toroids. They are really small. I want them only for a Un-Un receiving antenna (SWL). Do I have to put the capacitor 100pf too? .. Thanks for reply. 73 George

[@dxexplorer]

Hi Jorge... send me an email please... you have the email in the video description... I will explain you a little more. 73 hermanito.

[@Radionut63]

Awesome

[@dxexplorer]

Thanks so much Darrell.... I see a difference in the signal... clearly it works better than what I had before. And I also have less noise :) 73 and have a great weekend buddy.

[@x_CrossHair_x]

Do I need the "100pf Capacitor" if I am not Transmitting ?? (I just want to use my EFHW for Shortwave listening)..

[@dxexplorer]

If not transmitting not really. Is good practice to have it though. It brings the SWR lower on bands like 20m, 15m etc. But if just receiving I don't think is such a big deal if there is no capacitor 😁.

[@x_CrossHair_x]

Thanks!. And 73s.

[@dxexplorer]

Always a pleasure. 73, YO6DXE.

[@theDaftman]

the board you shown us right is not the same as the one in your download? new diagram please. also more info please on the multi turn pot (main tune)

[@dxexplorer]

The PCB is just a little different as I improved the position of some of the parts, but the schematic didn't changed. Everything it's in the download folder. I have there a document saying that I will continue to try to improve it.... and I will always have there the latest design. The multiturn pot... the one I use is from SR PASSIVES - Model POT2218P-10K. You can also use a simple 10k potentiometer as well singe there is also a fine tuning. But the multiturn helps a little. 73

[@TheAntonymer]

You have no outtake for ground. Is this not needed?

[@dxexplorer]

It depends on the antenna. The one in the video was mostly for RX... and also it was for the 40 to 10m bands... so the ground or counterpoise are not so necessarly. On the 80m band for example the common mode current is much more accentuated so it needs a connection to ground or a counterpoise. It can work just as well with none of those... but you need the 1 to 1 common mode current choke to make sure there is no RF going back in the transceiver. At least this is what I discovered so far since I keep playing with different designs. 73, YO6DXE.

[@ishsnikaishsnika2066]

I have good news my friend :)...Sputnik is working finally, since I add 1 mega resistor between base of Q2 and ground.. I want to build this end-fed antena as I already have wire 21m long...I want to ask you something, whether this transformer has any influence about receiver preformance or it is important just in case of transmiting(SWR, power loses etc)...?

[@dxexplorer]

The receiver was designed initially to work with any antenna... either a proper 40m band half wave antenna ... or just a simple wire you hang somewhere up thats at least 6-8m long. It should work with both nearly the same, with no much difference in receiving quality. Of course with a proper 40m half wave end fed antenna.. you will probably get better reception as its properly turned on 40m. I used it like that just because I wanted to be able to have an antenna to use on 40m to also transmit after I get my license. But in the past... I just had 6m of wire hanged around the ceiling in the room and I was still happy with it ))) Very happy the receiver is working. Not sure why it needs that resistor though. I just built another one and it seems to work like a charm from the first power up... no adjustments needed.

[@ishsnikaishsnika2066]

​@@dxexplorer ok, I got it..Only to mention, in my ham radio experience, for transceiver performances most important is height of antenna, better to say, it is best to be higher than any other spot in the neighborhood..with simple 40m dipole and Yaesu ft-901 (100w), I managed to collect qsl cards from all continents as very young teenager, but it was good home-made(thanks to my older coleague from the club) 40m dipole elevated on high spot, oriented to west-east, so I could do qsos with whole world without problems..About the resistor, I dont have a clue really, but I was thinking why my receiver works only in case when I hook-up the probe of the oscilloscope to the base of Q2..so, I got the idea to add that resistor, considering that the resistance of the probe is exactly 1megaom...before that, I tried all what came to my mind, I changed almost the half of elements from pcb, but without succes...I suppose that resistor has to do with offset point of Q2 transistor which is very important in case of regen receivers as I read somewhere.. Its about final version of my Sputnik on PCB, but in version before that, which I built on proto board, there wasnt any problem..So I think that is no matter of construction at all, than it is something about my realisation, which is not perfect for some reason...I am glad, that you are going to get your license and that you wil be able to enjoy in ham-radio, my friend..

[@dxexplorer]

Thank you so much my friend. Yes is very strange with that resistor... but as far as I have been building... I've always ended up with strange things and solutions that happened to me too hahaha. Its good that it works and you found a way around. About the antenna.. ohh yes its true. Mine also is about 6m high. I forgot to mention that. But just to have fun and receive some dx stations in the evening for a beginner.... a few meters of wire would do just fine. Especially that many don't have the space to run a proper antenna outside... especially in the city. I was staying at my sister's apartment a little while ago.. and I was lucky I found a tree around. So I ended up using the tree to make my self an antenna from the balcony... but I guess not all may have that tree around ))) 73

[@ishsnikaishsnika2066]

@@dxexplorer exactly, in the electronics, specially in the field of telecomunications, 2+2 is not always 4 :-))...73

[@dxexplorer]

Yes yes yes... it took me a while to realize that hahaha )))

[@oliverfranklypartolesen9882]

I have a t50 2 toroid how many turns i have 0.5 mm and 1 mm wires

[@dxexplorer]

Hi Oliver... the T50-2 will not be good for this transformer. Hmmmm this is a video idea. I will make one for this weekend. The T50-2 could be used for a 9:1 unun.... This one is great for a random wire antenna... other than half wave... quarter wave and so on. So for the 40m band for example... instead of using a 20m wire... you will have to use 25 for example. But the windings and the connections are a little different than the one in this video. For this particular transformer you do need a 43 material in order to work properly. I'll make a video and post it this Sunday so you can make a proper 9:1 unun with what you have. 73

[@infotech-malayalam4857]

Can you make Transistor FM VHF superegenarative receiver like GR 21 A

[@dxexplorer]

I will make one that is also solar powered and mostly made out of trash parts. I don't know how soon but it's for mom as she requested me to make her one.... and I will post the video as well :)

[@gravestonemyth]

It seems you have 15 turns instead of 14. The crossover counts as one turn.

[@dxexplorer]

It depends.. usually it counts as half turn not a full turn. Some people count it as a turn, some not. To be honest I tried both ways... and didn't notice major differences. So you can make it both ways. Now I usually build the transformers with more turns in the secondary... 14, 16, 18... with taps. This way I have more options depending on the antenna wire I use and the bands used. 73, YO6DXE.

[@gravestonemyth]

@@dxexplorer I agree on it making little difference. I have been experimenting with several variations of windings and cores. If I can get a low SWR across the desired bandwidth, it's impossible to measure a difference in practice. But the "recognized" way to count windings is to only consider passes through the center of toroidal core, with the Riesert crossover counting as one passing (or turn).

[@madalinbetea9871]

If i use FT 140-43 winding its same ???.

[@dxexplorer]

Salut Madalin. Da da nu e bai pastreaza acelasi numar de spire. Am facut la fel la antena asta: kzbin.info/www/bejne/en3IXqWBnrWGi6c La fel si daca folosesti toroid mai mare gen FT240-43. 73 si o saptamana frumoasa.

[@thomashorsten835]

Nice work, you should easily be able to pass the test and get a license :) 73 de OZ5TN (aka M0TRN, AF7BE)

[@dxexplorer]

Thank you Thomas. Meanwhile I did it finally hehehe. 73, YO6DXE.