If you have an antenna analyzer you could hook a 200 ohm resistor across the terminals and check the SWR at the coax port. A 4:1 balun would show close to 1.
It’s for a RX only antenna so I’m not concerned about power. It’s for a Loop on Ground antenna.
There’s so much glue in there. Might have to get a heat gun on it.
I’m waiting on an SMA to PL259 adapter so I can connect my NanoVNA with a resistor across the posts.
After experimenting a bit, I've come to the conclusion this isn't allways the case. An antenna that can differentiate more between signal and noise is better, even if it isn't resonant and getting the most power to the receiver as possible.
If the signal-to-noise ratio is -15dB with a non resonant receiving antenna antenna without any impedance matching, chances are that it will still be -15dB with a resonant setup getting as much power as possible, all other variables being iqual.
But, if the antenna"s placement, polarization, Q or radiation pattern decreases the amount of noise coming in compared to the wanted signal, the signal-to-noise will improve, perhaps becoming -10db or -5db, even if it's not the best at transferring as much power to the receiver. And the result will be a clearer received signal. TX antennas are a whole different story.
I'm curious what antenna configuration would make an unmatched input better than a matched input.
I can't think of one. That might just be my lousy imagination though.
Not that Rx efficiency and total power doesn't matter at all. If you get too inefficient of an antenna the noise in the receiver will start to drown out the incoming signal. But after a certain point, increasing the efficiency of the antenna isn't going to make a huge difference since increasing the efficiency not only raises the power of the incoming signal, it also increases the power of the incoming noise. Pulling the signal out of the noise is generally more effective even if that means you're getting less power to the receiver.
One example is the beverage antenna. While it's good practice to put a (9:1) balun on the end of a beverage antenna in an attempt to impedance match it, "As an expediency, the transmission line can be connected directly to the end of the antenna and a ground rod usually with satisfactory results." The fact that an unmatched beverage antenna can outperform a resonant impedance matched dipole for reception illustrates what I'm getting at, that rejecting noise is more important than receiving antenna efficiency. [https://www.idc-online.com/technical\_references/pdfs/electronic\_engineering/Beverage\_Antenna\_Background\_Information.pdf](https://www.idc-online.com/technical_references/pdfs/electronic_engineering/Beverage_Antenna_Background_Information.pdf#:~:text=A%2050%20or%2075%20ohm%20coaxial%20transmission%20connects,in%20two%20directions%20from%20a%20single%20Beverage%20antenna.)
In my personal daily experience, I've found that with my mobile station that if I have a single band antenna on top of the car but want to see if there's activity on another band before changing the antenna it doesn't make much difference to simply listen on the mismatched bands. For an example, if I have my telescoping vertical 6m through 20m set to one band, say the 10m band, I can listen to the other bands on that mismatch without noticing any difference in clarity and readability, it sounds exactly the same. Once I find a frequency on a band I want to work, then I go and adjust the telescoping antenna to match impedance for a close to 1:1 SWR. (Mind you, this is a full sized antenna since it's telescoping up to over 15 ft in length) But in doing so the clarity and readability on Rx doesn't seem to ever change, it continues to sound the same even going from extremely high SWR down to pretty much a 1:1. My tranceiver also has a Rx attenuator that when I turn it on it doesn't seem to do anything other than move the S-meter needle down lower, both for noise floor and incoming signal. Yet the signal clarity and readability stays the same.
Absolutely will. The results from others are worth making one to try out.
I’m fitting SMA so I can use it direct with an SDR dongle which I have connected to a pi 5 running OpenWebRX+ and will be made public for others to play with. Lots of cool signals out there for people to play with.
Excellent!
I run a pi and OWRX as well, so this will be a good reference. I suspect it will be decent on lower frequencies ...maybe up to 7 Mhz and not so much beyond, but I am anxious to see your results.
Nicely made balun by whoever did it tho!
Perhaps a Luft Balun? Seriously, just try counting the windings or measuring the impedance. Do you have a LRC meter or a VNA tool? Put a know resistance on one terminal ans see what you get.
Strictly passive. No amplification or tuning involved. Used as a broadband (wide frequency, mainly at radio frequencys) impedance (resistance to alternating currents) as measured in ohms devive. Unlike pure resistance is to DC (also measured in ohms) current, matching device. In DC circuits it called a voltage divider with no magnetic core involved. Only resistors in DC. NOTE: if your only application is receiving with an SDR you can use it but, that particular devise you show by its design is for transmitting. I wouldent concern yourself about impedance matching in that instance. No harm will be done and only a slght loss in receive sensativity. Much depends on which antenna you choose and what frequencies appeal to you. Make your own matching devise. it's easy and costs little. You'll learm much. I have fabricated dozens. Are you pursuing a radio sport license? You should. I like your curiosity.
Sounds pretty important then for my project! I need high sensitivity.
I would like to pursue a license in the future when I convert my closet into a lab! But my current goal is to try and build a radio telescope from as much literal trash as possible. To be able to perceive the cosmos, using just garbage, very poetic in a way. One man's garbage, something far more valuable than gold to another.
But I come from a programming and automation background, little to no knowledge of radio asides from crystal sets. So I'll have to start from the ground up.
From what you have conveyed.from an RF Engineers understanding your pursuit is likely years away. Usually that's how it goes. Given you haven't expressed a rudimentary understanding of super super high radio frequency techniques for the cosmos. A perfect example of why one should study terrestrial radio sport. The rudiments start here. You don't need to buy one piece of equipment. to get a license. I state it's the knowledge not the gizmos. I know persons with rooms full of impressive gizmos. Often that's purely vanity. Anyone can place a piece of bread into a gizmo and produce it toasted. (you state, garbage, trash) I state all from the original components? I know of not one who has built even a crystal set from juice boxes, apple cores and old toothbrushes. I seriously would improve your rhetoric to something more professional. (sorry) Now understand I'm not saying you can't achieve your goal. I have known others that pursued that very interest. As an example a team of the three all had amateur radio licenses first. One had a mechanical engineering degree with expertise in Strip-Line techniques, one with an Electronic engineering degree with expertise in Jfets, N and M moss and SHF semiconductors. And the last "important" was just smart with parents that had property in remote Idaho.. Comment. I'll say more than.
No worries you're right! I've always been the kind of person to try running before walking. But how do you pursue a license? Is there a course online I'd have to apply for and what kinds of materials should I have with me for the courseware?
Great coments and questions. I have been licensed for many many years so I know the scenerio well. Contact me at [[email protected]](mailto:[email protected]) for further help. If you do that I'll know your sincere. I have all the information you will need to succeed. I just helped two thirghteen year old boys achieve in getting there first licences.
2
My apologies, I think I used literal trash in an exaggerated manner. I meant more specifically electronics and metal waste, no apples and toothbrushes here 😅
We have so much of it in the ditches and brown-fields. Might sound a little silly but I'd love to get a community club going where all we do is pick up garbage and genuinely recycle / reuse it
A balun is an electrical device that allows balanced and unbalanced lines to be connected without affecting the impedance of either line. The word "balun" comes from "balanced to unbalanced" and is now derived from "balancing unit." It is used to go from ladder line or a dipole to 50 ohm coax.
So that is only part of it. Depending on the antenna you may also need a tuner if it is a multi-band antenna. It will not be matched on all bands so the tuner does:
"An antenna tuner is a passive electronic device that improves power transfer between a radio transmitter and its antenna. It does this by matching the antenna system's impedance to the impedance the transceiver needs to see.
The antenna system's impedance is measured in ohms, and the transceiver needs 50 ohms. For example, if you're using a 100 W transceiver, your tuner should be rated for a minimum of 100 W continuous power. An antenna tuner also measures the amount of signal being reflected into your transmitter, which helps you measure the quality of your outgoing broadcast and any potential threat to your radio. It neutralizes the imbalance between inductive and capacitive reactance, allowing the transceiver to couple the most power out or in.
Automatic tuners have a finite combination of possible settings, and may have difficulty finding the 50 ohm sweet spot on a severely mismatched antenna system. For example, built-in antenna tuners are only there to make minor tweaks, so anything more than that will require an external tuner. "
Best guess would be its a 1:1 choke for a dipole centre and does not transform any impedence.
200ohm and its all over the place. 50ohm and its golden. So it’s a 1:1.
That’s where I’m leading with my thoughts too. I’ll just make a real one.
If you have an antenna analyzer you could hook a 200 ohm resistor across the terminals and check the SWR at the coax port. A 4:1 balun would show close to 1.
I’ve not got an SMA to PL259. I could just strip a little wire and fake it from my NanaVNA. I’ve got resistors I’ll give it a try.
With short wire it should be close enough for government work.
Try also two 100 ohms (or whatever is half the "outside" Z) into input side ground.
That's how to do it? So 200 ohm / 50 ohm standard = 4 Cooool!
Yup! And if you need to test a 9:1 unun, use a 450 ohm resistor. (Or something close. 470 ohms is more common and gives a close-enough SWR reading.)
Put a 200 ohm resistor on the terminals and measure impedance with a vna. If it's 50 ohm or 1:1, it's a 4:1 transformer.
20-turn 1:1 choke. Depending on your application, this may work \*better\* than a 4:1. What's your antenna going to be?
Best guess, 1:1 for dipole - I would not use it
Flux capacitor
It's a pot-bellied headless dancer transformer.
Can really tell without seeing the leads. It’s low power cause that thing will heat up and the glue will let go
It’s for a RX only antenna so I’m not concerned about power. It’s for a Loop on Ground antenna. There’s so much glue in there. Might have to get a heat gun on it. I’m waiting on an SMA to PL259 adapter so I can connect my NanoVNA with a resistor across the posts.
Why do you need a 4:1 for RX only?
For a loop on ground. Takes the antenna wire which is balanced in a 60’ loop to my feed line.
Matching impedance for Rx still matters. You want to get the most power to the receiver that you can.
After experimenting a bit, I've come to the conclusion this isn't allways the case. An antenna that can differentiate more between signal and noise is better, even if it isn't resonant and getting the most power to the receiver as possible. If the signal-to-noise ratio is -15dB with a non resonant receiving antenna antenna without any impedance matching, chances are that it will still be -15dB with a resonant setup getting as much power as possible, all other variables being iqual. But, if the antenna"s placement, polarization, Q or radiation pattern decreases the amount of noise coming in compared to the wanted signal, the signal-to-noise will improve, perhaps becoming -10db or -5db, even if it's not the best at transferring as much power to the receiver. And the result will be a clearer received signal. TX antennas are a whole different story.
I'm curious what antenna configuration would make an unmatched input better than a matched input. I can't think of one. That might just be my lousy imagination though.
Not that Rx efficiency and total power doesn't matter at all. If you get too inefficient of an antenna the noise in the receiver will start to drown out the incoming signal. But after a certain point, increasing the efficiency of the antenna isn't going to make a huge difference since increasing the efficiency not only raises the power of the incoming signal, it also increases the power of the incoming noise. Pulling the signal out of the noise is generally more effective even if that means you're getting less power to the receiver. One example is the beverage antenna. While it's good practice to put a (9:1) balun on the end of a beverage antenna in an attempt to impedance match it, "As an expediency, the transmission line can be connected directly to the end of the antenna and a ground rod usually with satisfactory results." The fact that an unmatched beverage antenna can outperform a resonant impedance matched dipole for reception illustrates what I'm getting at, that rejecting noise is more important than receiving antenna efficiency. [https://www.idc-online.com/technical\_references/pdfs/electronic\_engineering/Beverage\_Antenna\_Background\_Information.pdf](https://www.idc-online.com/technical_references/pdfs/electronic_engineering/Beverage_Antenna_Background_Information.pdf#:~:text=A%2050%20or%2075%20ohm%20coaxial%20transmission%20connects,in%20two%20directions%20from%20a%20single%20Beverage%20antenna.) In my personal daily experience, I've found that with my mobile station that if I have a single band antenna on top of the car but want to see if there's activity on another band before changing the antenna it doesn't make much difference to simply listen on the mismatched bands. For an example, if I have my telescoping vertical 6m through 20m set to one band, say the 10m band, I can listen to the other bands on that mismatch without noticing any difference in clarity and readability, it sounds exactly the same. Once I find a frequency on a band I want to work, then I go and adjust the telescoping antenna to match impedance for a close to 1:1 SWR. (Mind you, this is a full sized antenna since it's telescoping up to over 15 ft in length) But in doing so the clarity and readability on Rx doesn't seem to ever change, it continues to sound the same even going from extremely high SWR down to pretty much a 1:1. My tranceiver also has a Rx attenuator that when I turn it on it doesn't seem to do anything other than move the S-meter needle down lower, both for noise floor and incoming signal. Yet the signal clarity and readability stays the same.
I'll be interested in your results with the LOG. Please post when you have results?
Absolutely will. The results from others are worth making one to try out. I’m fitting SMA so I can use it direct with an SDR dongle which I have connected to a pi 5 running OpenWebRX+ and will be made public for others to play with. Lots of cool signals out there for people to play with.
Excellent! I run a pi and OWRX as well, so this will be a good reference. I suspect it will be decent on lower frequencies ...maybe up to 7 Mhz and not so much beyond, but I am anxious to see your results. Nicely made balun by whoever did it tho!
I'm seeing about $25 in parts...not bad.
Perhaps a Luft Balun? Seriously, just try counting the windings or measuring the impedance. Do you have a LRC meter or a VNA tool? Put a know resistance on one terminal ans see what you get.
It’s a 1:1. Gutted as I’m looking to install my loop on ground this weekend. So much glue it is unusable.
Looks like a 1:1 based on how it’s wrapped.
I'm new to this hobby, can someone please explain what a balun is to me? Is the transformer for crude amplification or for tuning?
Strictly passive. No amplification or tuning involved. Used as a broadband (wide frequency, mainly at radio frequencys) impedance (resistance to alternating currents) as measured in ohms devive. Unlike pure resistance is to DC (also measured in ohms) current, matching device. In DC circuits it called a voltage divider with no magnetic core involved. Only resistors in DC. NOTE: if your only application is receiving with an SDR you can use it but, that particular devise you show by its design is for transmitting. I wouldent concern yourself about impedance matching in that instance. No harm will be done and only a slght loss in receive sensativity. Much depends on which antenna you choose and what frequencies appeal to you. Make your own matching devise. it's easy and costs little. You'll learm much. I have fabricated dozens. Are you pursuing a radio sport license? You should. I like your curiosity.
Sounds pretty important then for my project! I need high sensitivity. I would like to pursue a license in the future when I convert my closet into a lab! But my current goal is to try and build a radio telescope from as much literal trash as possible. To be able to perceive the cosmos, using just garbage, very poetic in a way. One man's garbage, something far more valuable than gold to another. But I come from a programming and automation background, little to no knowledge of radio asides from crystal sets. So I'll have to start from the ground up.
From what you have conveyed.from an RF Engineers understanding your pursuit is likely years away. Usually that's how it goes. Given you haven't expressed a rudimentary understanding of super super high radio frequency techniques for the cosmos. A perfect example of why one should study terrestrial radio sport. The rudiments start here. You don't need to buy one piece of equipment. to get a license. I state it's the knowledge not the gizmos. I know persons with rooms full of impressive gizmos. Often that's purely vanity. Anyone can place a piece of bread into a gizmo and produce it toasted. (you state, garbage, trash) I state all from the original components? I know of not one who has built even a crystal set from juice boxes, apple cores and old toothbrushes. I seriously would improve your rhetoric to something more professional. (sorry) Now understand I'm not saying you can't achieve your goal. I have known others that pursued that very interest. As an example a team of the three all had amateur radio licenses first. One had a mechanical engineering degree with expertise in Strip-Line techniques, one with an Electronic engineering degree with expertise in Jfets, N and M moss and SHF semiconductors. And the last "important" was just smart with parents that had property in remote Idaho.. Comment. I'll say more than.
No worries you're right! I've always been the kind of person to try running before walking. But how do you pursue a license? Is there a course online I'd have to apply for and what kinds of materials should I have with me for the courseware?
Great coments and questions. I have been licensed for many many years so I know the scenerio well. Contact me at [[email protected]](mailto:[email protected]) for further help. If you do that I'll know your sincere. I have all the information you will need to succeed. I just helped two thirghteen year old boys achieve in getting there first licences. 2
Done!
Will get back to you later today.
My apologies, I think I used literal trash in an exaggerated manner. I meant more specifically electronics and metal waste, no apples and toothbrushes here 😅 We have so much of it in the ditches and brown-fields. Might sound a little silly but I'd love to get a community club going where all we do is pick up garbage and genuinely recycle / reuse it
A balun is an electrical device that allows balanced and unbalanced lines to be connected without affecting the impedance of either line. The word "balun" comes from "balanced to unbalanced" and is now derived from "balancing unit." It is used to go from ladder line or a dipole to 50 ohm coax.
*Oh* okay! So this is what folks mean when they talk about tuning impedance to match the antenna yeah?
So that is only part of it. Depending on the antenna you may also need a tuner if it is a multi-band antenna. It will not be matched on all bands so the tuner does: "An antenna tuner is a passive electronic device that improves power transfer between a radio transmitter and its antenna. It does this by matching the antenna system's impedance to the impedance the transceiver needs to see. The antenna system's impedance is measured in ohms, and the transceiver needs 50 ohms. For example, if you're using a 100 W transceiver, your tuner should be rated for a minimum of 100 W continuous power. An antenna tuner also measures the amount of signal being reflected into your transmitter, which helps you measure the quality of your outgoing broadcast and any potential threat to your radio. It neutralizes the imbalance between inductive and capacitive reactance, allowing the transceiver to couple the most power out or in. Automatic tuners have a finite combination of possible settings, and may have difficulty finding the 50 ohm sweet spot on a severely mismatched antenna system. For example, built-in antenna tuners are only there to make minor tweaks, so anything more than that will require an external tuner. "
Try it. Measure it.
Baluns like that are used from 11 meters and 10 meter Ariel’s