@@M0XYM They gave it to me when I haggled the purchase of the spec an. It was £1500 as they hadnt been out long when I bought it. I think you can buy the basic spec an for 3 bob and a conker now :-)
Thanks for sharing this Mark, very interesting. I've been doing similar to test some baluns (UnUns actually) I built for SWL, mainly MW and the lower SW broadcast bands. As I don't have a vast array of test equipment, I'm just using a NanoVNA-F. Port 1 (S11) is connected to the balun input (hi-Z) via a 20dB resistor pi network that matches (for a 9:1) 450R to 50R. Port 2 (S21) is connected directly to the balun output (50R). This method allows me to see the frequency response/loss versus frequency and the return loss. If I reverse the connections then I can see the return loss presented to the RX. 73, Nick
I have a Nano-VNA but have never really used its full capabilities; probably because I have all the other fancy test gear. This demo shows how the return loss varies to the TX/RX on the unbalanced side of the balun by varying the match on the balanced side.
I have a 2 element multi band quad. 2 of my bands are 1.25 to 1 SWR. I would like them to be perfect. Can you imagine anyone wanting that? Yes, I can cut a new piece of 75 ohm stub, put on a connector, strip the other end so I can connect it to the element, measure my specs, trim the end I just stripped, rinse, repeat, until it's right where I want it. Phew, lots of work. ( I'm using a crank up so I have to take it all the way up to know what my changes have done.) I would like a gamma match I can attach that will handle full power. Or something that will bring my "R" from 62 to 50 without having to do all the 75 ohm coax stub match stuff. At this point, ( I have NO experience with this kind of thing ) I'm thinking of a copper rod that will slide inside of a copper tube with a set screw threaded in the side to lock it in place. I'm getting the impression that each bit of antenna detail, like folded dipole, or loop, or quad, will change drastically how my matching network has to be configured. There must be an easier way to tune this how I'd like without having to do the stub match thing. If I could figure how to use my current reading of "R" to know exactly how much 75 ohm coax to snip off to get me what I'm after that would be good, but so far I haven't figured out how to do that. Non destructive tuning would be very nice. Thank you in advance if you ever see this.
If your SWR is 1.2:1 then that is more than good enough. Anything below 1.5:1 isnt worth the effort of improving as the gains in radiated RF are almost non existent.
@@MarkG0MGXThank you very much for that. I've been beating my brains out with this. I think it's my profession. I program CNC machinery. For four decades I MUST get "The numbers" right. For the most part, there is always a way to make an adjustment to bring a parameter closer to, or further away from nominal. So, my point is that I virtully always have a way to bring a parameter closer to my goal. Yes I know antenna radiation is not the same thing as a bore in a piece of steel. But my instinct tells me it must be closer to perfect. So I am stubborn and at times will really waste a lot of time and money to "improve" things that don't need improving. Maybe this is my way of taking my mind off the fact that the radio I want is really taking it's time coming out. I'm using a KX3 which is actually a very capable radio. But I want that dang K4 sitting on my desktop. I may just have to get a 7610, or TS890 or a FTDX 101 instead. I know, what a terrible problem to have huh? If I knew it would be two or three months more that's one thing. But if it's going to be ten or twelve........I don't know if I can wait that long. And as usual I can't shut up. Sorry! Thanks again.
@@smartazz61 If you can make it all the way through, I tried very hard to explain the concept of SWR and why less than 1.5:1 is pointless here:: g0mgx.blogspot.com/2017/12/swr-transmission-lines-and-terminations.html
Interesting. Could you provide some info on the return loss bridge you used?
Hi Kevin, its the Rigol bridge - matched to the spec an. A "Rigol VB1020"
Aha! Slick gear. Thanks Mark - Kevin M0XYM
@@M0XYM They gave it to me when I haggled the purchase of the spec an. It was £1500 as they hadnt been out long when I bought it. I think you can buy the basic spec an for 3 bob and a conker now :-)
Interesting Mark.. Good job :)
Thanks! 😃
Thanks for sharing this Mark, very interesting. I've been doing similar to test some baluns (UnUns actually) I built for SWL, mainly MW and the lower SW broadcast bands. As I don't have a vast array of test equipment, I'm just using a NanoVNA-F.
Port 1 (S11) is connected to the balun input (hi-Z) via a 20dB resistor pi network that matches (for a 9:1) 450R to 50R. Port 2 (S21) is connected directly to the balun output (50R). This method allows me to see the frequency response/loss versus frequency and the return loss. If I reverse the connections then I can see the return loss presented to the RX. 73, Nick
I have a Nano-VNA but have never really used its full capabilities; probably because I have all the other fancy test gear. This demo shows how the return loss varies to the TX/RX on the unbalanced side of the balun by varying the match on the balanced side.
I have a 2 element multi band quad. 2 of my bands are 1.25 to 1 SWR. I would like them to be perfect. Can you imagine anyone wanting that?
Yes, I can cut a new piece of 75 ohm stub, put on a connector, strip the other end so I can connect it to the element, measure my specs, trim the end I just stripped, rinse, repeat, until it's right where I want it. Phew, lots of work. ( I'm using a crank up so I have to take it all the way up to know what my changes have done.)
I would like a gamma match I can attach that will handle full power. Or something that will bring my "R" from 62 to 50 without having to do all the 75 ohm coax stub match stuff.
At this point, ( I have NO experience with this kind of thing ) I'm thinking of a copper rod that will slide inside of a copper tube with a set screw threaded in the side to lock it in place.
I'm getting the impression that each bit of antenna detail, like folded dipole, or loop, or quad, will change drastically how my matching network has to be configured.
There must be an easier way to tune this how I'd like without having to do the stub match thing. If I could figure how to use my current reading of "R" to know exactly how much 75 ohm coax to snip off to get me what I'm after that would be good, but so far I haven't figured out how to do that.
Non destructive tuning would be very nice.
Thank you in advance if you ever see this.
If your SWR is 1.2:1 then that is more than good enough. Anything below 1.5:1 isnt worth the effort of improving as the gains in radiated RF are almost non existent.
@@MarkG0MGXThank you very much for that. I've been beating my brains out with this. I think it's my profession. I program CNC machinery. For four decades I MUST get "The numbers" right. For the most part, there is always a way to make an adjustment to bring a parameter closer to, or further away from nominal. So, my point is that I virtully always have a way to bring a parameter closer to my goal.
Yes I know antenna radiation is not the same thing as a bore in a piece of steel. But my instinct tells me it must be closer to perfect.
So I am stubborn and at times will really waste a lot of time and money to "improve" things that don't need improving. Maybe this is my way of taking my mind off the fact that the radio I want is really taking it's time coming out.
I'm using a KX3 which is actually a very capable radio. But I want that dang K4 sitting on my desktop. I may just have to get a 7610, or TS890 or a FTDX 101 instead. I know, what a terrible problem to have huh?
If I knew it would be two or three months more that's one thing. But if it's going to be ten or twelve........I don't know if I can wait that long.
And as usual I can't shut up. Sorry!
Thanks again.
@@smartazz61 If you can make it all the way through, I tried very hard to explain the concept of SWR and why less than 1.5:1 is pointless here:: g0mgx.blogspot.com/2017/12/swr-transmission-lines-and-terminations.html