Very basic antenna question

[cdev]

first walk, then run; start from window, go to a corner, along the fence to the other corner, up to window, the result will be a triangular loop, feed it with the balun or the mla preamp and test it for some days, then we may discuss modifications, don't jump the gun; also, try keeping the loop (all or most part of it as high as you can)

This is why I haven't done this. Some telescoping fiberglass poles for the corners would be super helpful in preventing it from becoming an NVIS antenna.

[cdev]

I will give it a try. I'll pick up some speaker wire as it is cheap and can get long lengths. This is what I was thinking, $5.95 for 25ft (which I can split up into 2 pieces for 50 ft total length):

https://secure.sayal.com/STORE2/View_SHOP.php?SKU=144048



Speaker wire isnt very durable in the weather, it develops holes and stretches and then snaps. When water gets in there it tarnishes to a black color. It really will look like a mess in just a few years..

I don't have much room for more than 25 ft anyways, and I figure I can connect 2 wires together to get 50 ft. Some lengths are particularly good for use on multiple bands with tuners because tghey are non-resonant on any of them. Hopefully the connection won't affect it much. I can either hang a big loop from my window or make a diamond (see attached photo), or just run as long a length as I can from the window to the fence as I did in the past.

If I have a loop, then I can connect to the two sides of the MLA-30 junction box, or to the suggested 1:9  balun (see below) , but if I have a single wire, how do I interface it with my Tecsun or SDR? I assume it would just go to central conductor of the coax, or the "tip" of the 1/8" mono male antenna plug? And what, if anything, do I connect the outer part of the SMA (e.g. external shield) to or the outer ring of the 1/8" mono male antenna plug?
(stuff about commercial unun deleted)

Don't pay money for a unun you can make for pennies with two #43 material  ferrite cores and wire you probably already own. .. Justtwist three equal length pieces together and circle it though both of them.

"Any reason why 1:9 should be used and not 1:4 or 1:1 or other ratios?"
https://antenna-theory.com/basics/impedance.php
It depends on what length of wire you use, its orientation and what frequency range you are targeting.

I am planning this purely as a Rx antenna and I've seen lots of articles talking about Tx antenna baluns which talk about making sure you don't lose power or heat up your transmission/feed lines. I'm not sure how and whether the same thing applies with receiving but perhaps the signal also gets eaten up in the feed lines if things aren't balanced.

I'm still very much not understanding any of this. I just got past a couple of chapters taking about complex impedance/admittance for the first time and learning about current/voltage not being in phase, standing waves, loss, etc. But actually putting that into practice is a different story. For now I am at a level of just duplicating what others have done and seem to work.

[A.Z.]

first walk, then run; start from window, go to a corner, along the fence to the other corner, up to window, the result will be a triangular loop, feed it with the balun or the mla preamp and test it for some days, then we may discuss modifications, don't jump the gun; also, try keeping the loop (all or most part of it as high as you can)

This is why I haven't done this. Some telescoping fiberglass poles for the corners would be super helpful in preventing it from becoming an NVIS antenna.

which part of "first walk, then run" was unclear to you ?

[cdev]

I think he means "just do it" which is always good advice for people like me who ruminate endlessly.

[edy]

So part of the problem is that my home is in suburbia with houses packed next to each other like sardines as in the attached picture!

If I could erect some poles on fences without upsetting the neighbors, wife, or both, it would be nice. If I even had some trees around that I could run wires to, that would be nice. We don't even have any mature trees around at this point.

I feel like my only way around this is to eventually crawl up through the attic opening and try to run some various lengths of wires along the inside of my roof (access permitting). Alternatively, I may have to carry something portable to a park nearby and string it up between two trees, but that will be very inconvenient.

If I do use anything like a vertical antenna it will have to be temporary, taken down each time I use it. There is no way I can mount anything permanently for now.

I may try what is suggested here:

https://www.hamradiosecrets.com/shortwave-antenna.html

They show a "sloper antenna" that is basically what I was doing before from my window to the fence. The only difference being, I didn't have a connection box outside the window, I was running the wire directly into the house through my window. I also didn't have a balun, I just alligator-clipped it to the end of my Tecsun antenna. Also, the lengths required I am unable to get anywhere close to. I max out around 25-30 ft tops... the backyard is just too small. They suggest not making any bends sharper than 90-degrees so even if I used a longer wire I would need to keep the angles less.

By the way, is a 9:1 the same as a 1:9? Also I saw YouTube review of the noelec 1:9 balun and they didn't mention anything about turning it into a unun. So am I using it as a balun or unun? They seem to just connect it out of the box, no modifying of the resistor, straight into the SDR and it worked. 

[cdev]

Here is how to make a 9:1 unun that will work better than a commercial one, I suspect, for almost nothing.
Find two identical noise suppression split cores and enough thin insulated wire to make approximately ten to twelve turns trough the core three times. fold it into three equal portions, cut the ends so you have three parallel wires. Twist them around one another gently so they are held together tightly. These will be your coils. Notethat the way the coils will be wound around half of the wire will be enclosed completely by the split cores. Look at the image below. Obviously because yoiou are using two identical split beads (the heaviest you can find, it will be different but dont worry, you'll find that this way of winding this makes a better unun. Make sure the wires are close together and twisted, like the twisted pairs in Ethernet cables, in fact that kind of wire would be a great choice to use.


Resistor? Ive never used resistors in ununs . All my 9:1 ununs are grounded so provide a DC path to ground. Dont use them with a bias tee, that could burn something out.

[A.Z.]

The other option, at least for now, is to string a 25 ft length of speaker wire out my upstairs window and tie it to the fence at either corners of the back yard.

Look at the attached pic, the idea is to use some ropes at the three corners to suspend the triangular loop at some distance (e.g. 19") from the building and from the fence, the two ends of the wire will then be connected to the MLA-30 preamp or to the BalUn with the coax coming in and feeding the SDR, if possible, before entering the building with the coax, wrap the coax in some turns to form a coil and apply some snap-on ferrite chokes over the coil (as much as you can) and cover them with tape to both protect them and keep them in place, the whole setup will take quite little time

[edit]

An alternative may be putting the MLA-30 in the yard, but in such a case you'll need to add a connector to it (see here) so that you'll be able to feed it using a longer run of coax, the latter may just be some cheap TV/sat coax running all the way to your listening post, that way your loop will be outside and possibly won't cause problems with "SWMBO"  another alternative may be the antenna described here it's totally INVISIBLE and works pretty well up to around 14MHz, chech this for an idea about its performance, to feed this latter antenna you may use the 9:1 balun you already have and I do really doubt that it will cause any reaction from SWMBO

[edit #2]

Forgot, the PL-330 has a 3.5mm socket to connect an external antenna, so to connect it to the coax feeding your antenna you'll just need an adapter with a 3.5mm jack at one end and a connector matching the one used for the coax at the other end

[A.Z.]

Here is how to make a 9:1 unun that will work better than a commercial one

That's the same UnUn described here https://vk6ysf.com/unun_9-1_v2.htm it will work, but the frequency response will depend from the kind of material used for the core  and then you will also want to place a choke at the output, since, as is, it has no common mode current blocking, so it would be a good idea placing something like this https://vk6ysf.com/balun_guanella_current_1-1.htm at the output of the UnUn and then connect the output of the choke to the coax plug, that UnUn will work ok with unbalanced antennas like a random wire or the like, but while such antennas do work, I doubt it will fit well given the location of the OP, which being surrounded by other building is probably quite RFI "dense", so I believe a loop may serve him better and in that case we'll need a balun, the OP already owns a NooElec (or similar) balun, so he may just use it, as for the "resistor" it isn't a resistor but it's marked as "R1" in the balun schematic (see my other post with link to the schematic) and it goes between the transformer center tap and ground

[cdev]

Thats the picture I was looking for, its much clearer to understand.

One thing about the 9:1 unun and its important. A huge part of the improvement it offers is from the decoupling of the vertically polarized noise due to the grounding. The grounding is very important. Otherwise you wont get the full benefit of a good unun and it may even make things worse. Because the signal will be working againat the coax shield and the AC power system connected to your radio, which could mean the elusive DX signal is crapified. . Suppose you intend to use it with a vertical antenna. The ground will give you a very marked quieting and it has the effect of decoupling your feedline from the noise in the environment (in both of our cases a back yard) I live in a similar neighborhood with houses fairly close to one another. My back yard arrangement is quite similar to the picture. I have more space and I would guess, taller trees .. so its not so bad.. Problem is, I live close to light industrial that I suspects injects a lot of noise into my picture. I have some very modest grounding. Not much of a ground rod at all, and it was pushed into the ground by hand, with a hose's assistance. but it helps a lot. And it definitely does help decouple common mode junk. Thats one of the biggest benefits of a 9:1 unun. If its a decent ground, it will help a lot.The ground lead should be as short as possible.

[A.Z.]

Thats the picture I was looking for, its much clearer to understand.

One thing about the 9:1 unun and its important. A huge part of the improvement it offers is from the decoupling of the vertically polarized noise due to the grounding. The grounding is very important. Otherwise you wont get the full benefit of a good unun and it may even make things worse. Because the signal will be working againat the coax shield and the AC power system connected to your radio, which could mean the elusive DX signal is crapified. . Suppose you intend to use it with a vertical antenna. The ground will give you a very marked quieting and it has the effect of decoupling your feedline from the noise in the environment (in both of our cases a back yard) I live in a similar neighborhood with houses fairly close to one another. My back yard arrangement is quite similar to the picture. I have more space and I would guess, taller trees .. so its not so bad.. Problem is, I live close to light industrial that I suspects injects a lot of noise into my picture. I have some very modest grounding. Not much of a ground rod at all, and it was pushed into the ground by hand, with a hose's assistance. but it helps a lot. And it definitely does help decouple common mode junk. Thats one of the biggest benefits of a 9:1 unun. If its a decent ground, it will help a lot.The ground lead should be as short as possible.

You seem pretty confused to me; when it comes to an unbalanced antenna, it needs the "missing half", otherwise it will use the coax feeder as part of the antenna, and we don't want that, so in those cases, we use counterpoise and/or ground systems; the UnUn described at that link does nothing to stop common mode current flowing toward the antenna and then back to the receiving system, so you may want to add some decent choke(s), a good one can be built by winding about 18 turns of RG174 around an FT140-43 toroidal core and connecting it between the UnUn and the coax feedline (and then you may add more chokes along the feedline, if needed); that said, if you live in a quite (RF) noisy location, a "random wire" antenna like the one you described won't exactly be the best choice, you may achieve lower noise levels by using a dipole or a loop, for the latter you may consider either this design or, if you have the room for it, this one, both antennas offer pretty good performance on the HF bands (and below) and help a lot with noise, the transformer used for both is simple to put together or, not willing to build it, a NooElec 9:1 will work as well

[edit]

As for the NooElec, please refer to this schematic for the V1 and notice that the trace marked as "R1" in the schematic is just a "zero Ohm" resistor running from the transformer (a coilcraft one) center tap to the circuit ground, now, to use the V1 with the two suggested loops you'll need to cut the "R1" trace (it's easy to see, on the back of the PCB); if instead you'll go for the V2 (from NooElec too), that one has no tap, so it can be used "as is"; in either case, you will probably also want to add a decent choke between the BalUn and the coax feedline, also, regarding the latter, since you're in a noisy spot, it would be a good idea using some run of TV/sat cable (the so-called "RG6"), since not only it's cheap, but it also offers better shielding and lower loss when compared to the "garden variety" thin RG-174; the latter may still be useful to wind very effective common mode chokes, which, in your case, I highly recommend

[A.Z.]

@Edy

Just to expand the idea a bit, let's start from the triangular loop design I proposed



now, willing to artificially increase the antenna length, we may consider the idea of turning that single wire loop into a linear loaded one, to do so, instead of using a single wire to form the loop we may use some length of 3-conductors cable which may be flat or round, something like this



now, just run the cable around to form the loop, then connect the ends of the conductors in series as shown in the image and  then connect the two endpoints marked "A" and "B" to the balun (or the MLA-30 preamp box), the result will be a loop with the same total physical length but with a longer "electrical" length which may help obtaining better reception at lower frequencies; again, it's just an idea, but may be worth a try

[edy]

Thanks for all the help. I found this video which I will try to copy and make a 9:1 unun. Seems like it is a staple for longwire antennas, there are quite a few similar videos around all showing the same thing:



And here: https://m0ukd.com/homebrew/baluns-and-ununs/91-magnetic-longwire-balun-unun/

Seems like one lead goes to the longwire, one goes to the coax that leads to the radio, and one connects to a ground. For grounding, can I connect it to the ground wire of a 3-prong outlet? That's my best bet if I'm inside, as the plumbing in the house these days is all plastic.

I understand for a longwire, I will have 1 terminal in the house and the other end outside tied to the fence. But if I loop it around back I'll have both ends available, I can't use an unun like the one described above. I would instead have to join the ends of the wire-loop to the 2 terminals on my MLA-30. On the other hand, the 1:1 Guanella balun you linked  here (https://vk6ysf.com/balun_guanella_current_1-1.htm) has 2 terminals on the left, which I presume connect to each side of a loop wire, and 1 terminal on the right, which I guess connects to the coax feedline that leads off to my radio input (I don't see any "ground" connection unless I'm supposed to ground the outer sleeve of the coax):


 
Perhaps I need to build both and try them out?

Another confusing part is I'm not sure how much of the videos and builds I see are talking about Rx vs Tx antennas. My understanding is that with Tx you will need to use larger toroids, thicker wires, etc... to be able to handle the power of the transmitter. However, for simply a receiving antenna application, do I need such big toroid sizes and wire gauges? I have smaller ferrite toroids scavenged from devices and stranded insulated wire that will be easier to thread through and wrap around the toroid. It will not be able to handle Tx power levels but for Rx should it not be ok?

[A.Z.]

no need to wind that, the balun you already have will work, but if you're going for a "random wire" then layout one wire to the fence and connect a second shorter piece of wire to the balun, just leave it dangling down, that will be your counterpoise, but, sincerely, given your QTH location, I don't think a random will be a good choice

[edy]

I'm wondering for now if I should try and make myself another loop antenna, based on the YouLoop linked below. It seems simple enough. At the top, you cross over the conductors so essentially the loop becomes 2 loops of wire (by using the outer shielding as another conductor on the second pass around the loop).

Based on the diagram is appears the loop itself continuous (one big loop just folded into 2 "windings") that at the bottom (the blue and yellow wires) runs through one side of a 1:1 transformer. However, on the other side (right) of the transformer (that heads to the radio receiver) it appears there is a "tap" (vertical black line) that connects part of the loop shielding to the radio shield, which I don't understand. However, it is easy enough to build with the materials I have at hand.

YouLoop: https://airspy.com/wp-content/uploads/2020/03/YouLoop-2T.png

Or something like this:



The 1:1 balun/choke in the above photo appears to have continuity for the red wire coming out of the loop and going to the BCN connector, same goes for the black wire. Whereas the schematic seems to show the two sides being "isolated" electrically from each other... that is, more like a 1:1 transformer using a toroid to wind around like this:



So I'm confused.    One seems to allow direct continuity between the loop and the connector, and the other seems to allow each side to wrap around the toroid so they are magnetically coupled so that the loop current causes it's toroidal windings to induce current in the windings that go to the connector.

I'm not exactly sure what the application of this one is:

http://www.arcticpeak.com/images/antenne/Balun/Balun5.gif

And here is a transformer for a ground-loop antenna mentioned at https://www.kk5jy.net/LoG/:



As far as the 9:1 balun or unun goes (again I'm confused as I see various comments on what to call it), I could try to build one of these:



So I assume the 9:1 seems to be used more for long-wire antennas because there is a bigger difference in the ohm value for the wire (especially if it is very long) as compared to a smaller loop? Intuitively the way the 9:1 is drawn feels like it should be a 3:1... the "tap" taken out of the toroid to the receiver seems to be at about the 1/3rd of the way along the full winding, yet it's called a 9:1? Here's another view:



One answer I have found seems to be the 1:3 turns ratio leads to a 1:9 impedance ratio... that is, the square.    At this point it all seems like voodoo to me.

[A.Z.]

... At this point it all seems like voodoo to me.

Edy, before digging down into UnUns, BalUns and other antenna ideas, I believe you may use what you already have and try putting together an antenna; in your case, the NooElec 9:1 (or clone) will fit, start by looking at its schematic (which hopefully will be the same even if you have a clone and not the original thing)



now, if you cut that "0 Ohm" resistor marked R1 in the schematic (it's on the back of the board) you'll obtain a 9:1 transformer just like the one used by KK5JY for his loops, at this point it would be easy putting up a simple wire loop (see my other post, please) and testing it.

As for the impedance transformation ratio, the "square rule" is correct; if you look at the KK5JY transformer you'll see that we have two turns on a side and 6 turns on the other, now if we divide 6 by 2 we obtain 3 and 3^2 will give us 9, which is the impedance transformation ratio; in the case of the UnUn, let's say we have a trifilar winding made with 4 turns and connected (in series) as an "autotransformer", now, in this case we consider the number of turns for the primary (4) and the total number of turns for all windings (12) and if we divide 12 by 4 we obtain 3 and, again, 3^2 gives us 9, that is the transformation ratio

Let me make another example, let's say we want a 16:1 UnUn, we wind it quadrifilar (4 wires) and make 9 turns, the total number of turns will now be 36, and the primary will have 9 turns, now, if we divide 36 by 9 we obtain 4 and 4^2 = 16 which is our UnUn transformation ratio

As for the coax loop, sincerely I don't like it so much and I don't like the way it's connected to the coax, I'd probably use a tapped 1:1 transformer, say 5+5 turns with a tap at 3 turns on the secondary, the untapped winding would then go to the coax while the tapped one will be connected to the loop ends with the loop shield connected to the center tap, such a config would allow to mantain the loop balance; notice that you can do that with your NooElec balun, once you cut "R1" you just connect the coax loop braid to the center tap and you'll have exactly such a config

But again, just try the loop idea at my previous post, also since a random wire will probably be "too noisy" for your location

[edy]

Thanks, I guess part of my confusion with the toroid construction is whether they are "isolation" or provide electrical continuity. Most of the toroid constructions show the wires wrapped around the toroid 3 times, and you basically "tap" off one of the windings that only goes around once. So you get a 1:3 voltage ratio and 1:9 impedance ratio. But if you put a continuity meter at one end of the first winding let's say (your antenna input) and one at the furthest other end of the entire set of windings (the one going to the shild of your coax) they are electrically connected. You are just "tapping" off from the 1/3rd way mark into the center of the coax. Technically you could just wrap one wire around the toroid and splice in a point 1/3rd way around it (at 0 and  120 degree mark apart) and use that connection.

On the other hand, if you want to electrically isolate them (only magnetically couple) then I would have the wires never actually soldered to each other. One wire would wrap around the toroid 3 times, another wire would wrap around the same toroid 1 time. This would transform the voltage by a factor of 3, and the current by a factor of 1/3rd, so VI is same on both sides more or less. I'm not sure if this is the idea of the transformer used for radio antenna or not, and whether there is even enough "signal" strength to allow such a transformer to have enough magnetic coupling to even let a signal through. Perhaps for a transmitting situation, but for receiving it will probably be too low.

So perhaps that's why I'm confused, and I should construct one that actually has electrical continuity and not isolating, like most of those 9:1 baluns show.

[A.Z.]

why ? I mean, each design has advantages and disadvantages (set aside the difference between UnUn and BalUn), and sincerely, for some antennas (e.g. loops) I prefer using the "insulated design" (as you call it), possibly followed by a vanilla 1:1 guanella choke

[cdev]

And the improvement in signal is often really dramatic (or it appeared to me to really be when I tried one the first time. It was the design I posted the image of, implemented in enameled wire, on a diminutive FT-50-43 toroid ferrite core (shiny black) I still have it and it still performs very well with any old length of wire. its currently attached to my radiator for grounding. with a long wire going out my window to a tree in the back yard. Its my backup HF antenna.

Another useful balun that I have now is made of two square binocular cores, its basically a copy of a popular Elecraft balun kit and its switchable from 1:1 to 4:1 with a toggle switch. It is wound using clear speaker wire, 18 gauge, and it works very well, always. With any balanced antenna. Yes, it works with loops. Its housed in a plastic box with vent holes on the side and banana plugs on the top. It uses a BNC jack for its connection. I built it in anticipation of getting a ham license and transmitting with it. It would probably handle 100 watts but not much more.

why ? I mean, each design has advantages and disadvantages (set aside the difference between UnUn and BalUn), and sincerely, for some antennas (e.g. loops) I prefer using the "insulated design" (as you call it), possibly followed by a vanilla 1:1 guanella choke

[A.Z.]

The elecraft is a good balun, it's a guanella with a switch allowing to connect the secondary windings either in parallel (1:1) or in serier (4:1), it can be easily built using a couple of toroids as shown here

http://www.m0pzt.com/blog/4to1-current-balun/

as for the unun, it's ok for an unbalanced antenna like an EFHW, a random and the like, but for sure not for balanced antennas

and, in both cases the balun and the unun have almost no effect on common mode currents, so it will be a good idea adding a good guanella choke between the balun and the coax

or better said, the unun has no effect, the guanella in 1:1 config has good choking, the guanella in 4:1 config has about 1/2 of the 1:1 CMC impedance, so for both the unun and the 4:1 it will be a good idea adding a choke

Forgot; if going to build that M0PZT design, use #43 material for the cores and increase the turns to 17; that is 16 for the toroid (8+8) plus one for the "crossing"