Thanks Randy, I built this project for my ATU based on your info and Dan's, ND6T's info and built mine on scrap PCB, the 1/4 "pads I supaglued onto a 2 " * 2 " PCB.I had a 100Ua meter calibrated for swr which I wanted to use. I also have a Kenwood TS2000 which does 5 watts to 100 watts. I wanted to use the 100Ua meter, however a variable pot in series with this meter needed to be 120K ohms, and far too touchy. I had a 20K ohm 10 turn pot, and I shunted the 100 Ua meter ( 1.8K ohm Internal resistance) with a 150 Ohm resistor. This made the meter movement 1.3ma, and gave a very smooth adjustment from 0.5 watts to 200 watts. The project performed excellantly over 1.3mhz to 30 mhz, (didn't work on 6m, probably the toroid wouldn't handle 6 m) Can you please explain how you entered the swr formula into excel? Thanks so much, Barry, VK2FP/AG7VC
@@K7AGE Thanks Randy, I rebuilt an old ATU I built 30 years ago, but was shaken up while 4 wheel driving, so I decided to do a re-build, the original swr bridge never worked properly, but yours/ND6T's design worked great. I had a beautiful ex-commercial/military 100 ua meter calibrated for SWR, and using your design & shunting the 100Ua meter with 150 ohms did a marvelous job, mind you I tried for hours various meter shunts, etc and found a 1.3 ma meter movement did the best results, Thanks so much for sharing, Barry, VK2FP/AG7VC
I am from Pakistan ...Thank you soooo much sir ..It helps me a lot .I will try this at home.You have done a great job .Keep it up .Stay blessed .I am a wirless technician in police demartment .I hope you will help me in any other difficulty .Once again Thanks a lot .
Randy, way late to the dance here but a couple of comments are in order. Firstly, this series is a wonderful effort to get new hams into building and understanding basic circuit theory. But I believe that your Triplett meter already has a shunt in it to make it read FS for the scale values. Most times the surplus/swap meet meters have much smaller FS sensitivity - often 50 uA. Running anything over that could ruin the meter movement. To make the meter work for the SWR device, you need to calculate the internal resistance of the meter and then run it in parallel with an appropriately calculated shunt IN ADDITION to the series resistance. There are plenty of RUclips videos that show how that can be done. Thanks again for your fine efforts! de k6whp dit dit
Thanks for this great video series. Understand things much more than before! Which brings me to a question. If I was going to create an SWR meter for a 1000W Linear amp, I can imagine the wire size and the toroids would change, but what about the rest of it? Would it be possible to increase the pot resistance to bring down the current for the 1 mA meter or just usea 1 A meter. Since the voltages in the rest of the circuit are indirect how many amps and volts would the rest of the circuit have to handle. Considering the 1:10 toroid, what is the voltage range on a 1000W amplifier antenna line? This toroid would multiply that voltage by 10? Seems unreasonable and impossible with this setup. How do Hi W SWR meters deal with this concern? Thanks again for your great videos.
Awesome project, I will try this to test my FPV antennas! ;) Will this work from 900Mhz to 5.8Ghz? Any special considerations based on the frequency to test? I will want to test SWR for antennas working at 900Mhz, 1.2Ghz, 2.4Ghz, and 5.8Ghz
I wouldn’t trust it above 28MHz. The open wiring with long lead lengths makes use at the higher frequencies just about impossible. A bridge for those frequencies would be built using surface mount devices on a pcb. Checkout a NanoVNA.
Randy, Echoing HamRadioJoe's comment above, it's great to hear from you again! I have a really dumb question for you. At 6:10 or so, you add another 50 ohm dummy load "in series," which I assumed meant the two resistances would be additive, hence a total load of 100 ohms, but the total resistance seems instead to be 25 ohms, which suggests parallel, not series. Forgive my slowness, but what obvious fact am I missing? Thanks again, and keep up the good work. Mark N5CBF
I connected the two terminators in series, one connected to the other. But, inside each is the 50 ohms to ground. So, the two in series place the two 50 ohm resistors in parallel, 25 ohms. You were paying attention.
Probably not. The component lead length will degrade operation at 433. It would be best to use a printed circuit board for the construction. Google around for UHF SWR meter plans.Thanks for watching
Thanks Randy, I built this project for my ATU based on your info and Dan's, ND6T's info and built mine on scrap PCB, the 1/4 "pads I supaglued onto a 2 " * 2 " PCB.I had a 100Ua meter calibrated for swr which I wanted to use. I also have a Kenwood TS2000 which does 5 watts to 100 watts. I wanted to use the 100Ua meter, however a variable pot in series with this meter needed to be 120K ohms, and far too touchy. I had a 20K ohm 10 turn pot, and I shunted the 100 Ua meter ( 1.8K ohm Internal resistance) with a 150 Ohm resistor. This made the meter movement 1.3ma, and gave a very smooth adjustment from 0.5 watts to 200 watts. The project performed excellantly over 1.3mhz to 30 mhz, (didn't work on 6m, probably the toroid wouldn't handle 6 m) Can you please explain how you entered the swr formula into excel? Thanks so much, Barry, VK2FP/AG7VC
Barry, you really dig into this project. Don’t know if I have excel anymore.
@@K7AGE Thanks Randy, I rebuilt an old ATU I built 30 years ago, but was shaken up while 4 wheel driving, so I decided to do a re-build, the original swr bridge never worked properly, but yours/ND6T's design worked great. I had a beautiful ex-commercial/military 100 ua meter calibrated for SWR, and using your design & shunting the 100Ua meter with 150 ohms did a marvelous job, mind you I tried for hours various meter shunts, etc and found a 1.3 ma meter movement did the best results, Thanks so much for sharing, Barry, VK2FP/AG7VC
I am from Pakistan ...Thank you soooo much sir ..It helps me a lot .I will try this at home.You have done a great job .Keep it up .Stay blessed .I am a wirless technician in police demartment .I hope you will help me in any other difficulty .Once again Thanks a lot .
Randy, way late to the dance here but a couple of comments are in order. Firstly, this series is a wonderful effort to get new hams into building and understanding basic circuit theory. But I believe that your Triplett meter already has a shunt in it to make it read FS for the scale values. Most times the surplus/swap meet meters have much smaller FS sensitivity - often 50 uA. Running anything over that could ruin the meter movement.
To make the meter work for the SWR device, you need to calculate the internal resistance of the meter and then run it in parallel with an appropriately calculated shunt IN ADDITION to the series resistance. There are plenty of RUclips videos that show how that can be done.
Thanks again for your fine efforts!
de k6whp
dit dit
Thanks for this great video series. Understand things much more than before! Which brings me to a question. If I was going to create an SWR meter for a 1000W Linear amp, I can imagine the wire size and the toroids would change, but what about the rest of it? Would it be possible to increase the pot resistance to bring down the current for the 1 mA meter or just usea 1 A meter. Since the voltages in the rest of the circuit are indirect how many amps and volts would the rest of the circuit have to handle. Considering the 1:10 toroid, what is the voltage range on a 1000W amplifier antenna line? This toroid would multiply that voltage by 10? Seems unreasonable and impossible with this setup. How do Hi W SWR meters deal with this concern? Thanks again for your great videos.
Brilliant series. Thanks so much. This noobie has learnt a great deal from this.
Awesome project, I will try this to test my FPV antennas! ;)
Will this work from 900Mhz to 5.8Ghz? Any special considerations based on the frequency to test? I will want to test SWR for antennas working at 900Mhz, 1.2Ghz, 2.4Ghz, and 5.8Ghz
I wouldn’t trust it above 28MHz. The open wiring with long lead lengths makes use at the higher frequencies just about impossible. A bridge for those frequencies would be built using surface mount devices on a pcb. Checkout a NanoVNA.
Randy,
Echoing HamRadioJoe's comment above, it's great to hear from you again!
I have a really dumb question for you. At 6:10 or so, you add another 50 ohm dummy load "in series," which I assumed meant the two resistances would be additive, hence a total load of 100 ohms, but the total resistance seems instead to be 25 ohms, which suggests parallel, not series. Forgive my slowness, but what obvious fact am I missing?
Thanks again, and keep up the good work.
Mark
N5CBF
I connected the two terminators in series, one connected to the other. But, inside each is the 50 ohms to ground. So, the two in series place the two 50 ohm resistors in parallel, 25 ohms. You were paying attention.
I know this video is a couple of years old, but man it really makes you wonder why we pay so much for a commercially made VSWR bridge. Cheers VK4IM
Thank you ever so much for this video...putting the maths in there was just what I was lookig for. 73 from mw7gib
MERRY CHRISTMAS AND HAPPY NEW YEAR TO YOU AND YOUR FAMILY..............
Hi Randy. Is your full video of building a balanced tuner online?
I don’t have a tuner build video, sorry.
Hi Sir, can i apply this bridge design to the 433mhz frequency? but i plan to use 1N60 or bat42 didode, i waiting for your answer
thanks
Probably not. The component lead length will degrade operation at 433. It would be best to use a printed circuit board for the construction. Google around for UHF SWR meter plans.Thanks for watching
How many watts of RF power could you run through that?
It is basically for QRP. I have not tried 100 watts. Not sure it the toroid saturate.
I Have been looking for an explanation of how to build A SWR Meter. And now A have found it
That was fantastic....Thanks
RANDY, WHERE YOU BEEN ? I MISS YOU.... DO MORE VIDEOS, MAYBE DO ONE ON A 160 WIRE ANTENNA OR AN END FED..
Relaxing. Probably no 160 meter antenna. I'll need to do some reseach on end fed antennas.
Thanks
can you show us how to make such a thing for UHF
Not sure. The sampler becomes more difficult at the higher frequencies. Ill have to google around to see what is out there.
Here is a good plan
vk5ajl.com/projects/swrmeter.php
thanks very much.
Great stuff, as usual! de KEØOG
i was looking for a circuit like that to put inside of my homemade antenna tunner thank´s for sharing ...my call sing YV5-JAU
man ! i wish i had a brain