Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
MiniCircuits uses one inductor.? ?Common ground on the bottom, 75 Ohms at the top, and a tap for the 50 Ohm port.
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On Thursday, July 1, 2021, 09:02:36 AM CDT, Gert Gremmen <cetest@...> wrote: Normally the difference between 50 and 70 is neglectable. If you really know that the source/load is exactly 50 Ohm (that means you have measured that) and you really know the other side is exactly 70 Ohm, only then it's worth do do the effort. build a transformer on ferrite material suitable for the frequency. You have to know that? the impedance increases with the square of the winding ratio. A 2 winding to 4 winding transforms your 50 into 200 Ohm. you will need a winding ratio of 1.25 for 50-70 ohm. At low frequency you may want a lot of windings, at high frequencies you need much less. Using whole windings that means that the lowest number of windings is 4 :5 This seems suitable up to 250 MHz approx with the right ferrite. But at these high frequencies parasitic? and L may jeopardize the impedances at both side, normally not a big problem, but you wantend to be accurate isn't it ? If it is narrow band, within the resonance band of an LC, you may use a capacitor step up construction?? (C1- C2 and L back to C1) If you connect 50 ohm over C2 you will have 70 ohm over C1+C2 if C2 = 0,25 x C1.? And the loop needs to be in resonance too. And your caps need to be 5% or better. Quite a challenge. Other may have even better suggestions. Gert On 1-7-2021 15:41, Zack Widup wrote: I know. That's a problem in this application. Another possibility is a
broadband impedance matching transformer with the appropriate ferrite
toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm
side as close enough.
73. Zack W9SZ
On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote:
? Quarter wave transformer for what frequency????
54 MHz or 600 MHz.? ? Can't have both!
73? Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
? ? ? On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
? The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
? ? ? ? ? ? ? ? ? ? Mikek
-- Independent Expert on CE marking EMC Consultant Electrical Safety Consultant
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Joe, yes you are correct. All he needs is a 75 ohm resistor or 75 ohm load to re-calibrate his NanoVna to 75 ohms.
Thanks Joe.
Larry, K4LED
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On Jul 1, 2021, at 10:14 AM, Joe WB9SBD <nss@...> wrote:
?I do not understand why a good 75 ohm calibration load would not make the thing be a 75 ohm test.
Isn't that what the 50 ohm one is doing when you calibrate the dead short and the 50 ohms load?
Joe WB9SBD
On 7/1/2021 8:41 AM, Zack Widup wrote:
I know. That's a problem in this application. Another possibility is a
broadband impedance matching transformer with the appropriate ferrite
toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm
side as close enough.
73. Zack W9SZ
On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote:
Quarter wave transformer for what frequency????
54 MHz or 600 MHz. Can't have both!
73 Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote: Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Yes building or buying a 75 to 50 ohm matching transformer if that¡¯s what you need (MiniCircuts sells them) is possible but it will cause a small insertion loss that needs to be accounted for if a precision measurement is needed. You didn¡¯t say if precision is necessary or just a comparison is the goal.
Larry
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On Jul 1, 2021, at 10:03 AM, Gert Gremmen <cetest@...> wrote:
?Normally the difference between 50 and 70 is neglectable. If you really know that
the source/load is exactly 50 Ohm (that means you have measured that) and you
really know the other side is exactly 70 Ohm, only then it's worth do do the effort.
build a transformer on ferrite material suitable for the frequency.
You have to know that the impedance increases with the square of the winding ratio.
A 2 winding to 4 winding transforms your 50 into 200 Ohm.
you will need a winding ratio of 1.25 for 50-70 ohm.
At low frequency you may want a lot of windings, at high frequencies you need much less.
Using whole windings that means that the lowest number of windings is 4 :5
This seems suitable up to 250 MHz approx with the right ferrite.
But at these high frequencies parasitic and L may jeopardize the impedances at both side,
normally not a big problem, but you wantend to be accurate isn't it ?
If it is narrow band, within the resonance band of an LC, you may use
a capacitor step up construction (C1- C2 and L back to C1)
If you connect 50 ohm over C2 you will have 70 ohm over C1+C2
if C2 = 0,25 x C1. And the loop needs to be in resonance too.
And your caps need to be 5% or better. Quite a challenge.
Other may have even better suggestions.
Gert
On 1-7-2021 15:41, Zack Widup wrote:
I know. That's a problem in this application. Another possibility is a
broadband impedance matching transformer with the appropriate ferrite
toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm
side as close enough.
73. Zack W9SZ
On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote:
Quarter wave transformer for what frequency????
54 MHz or 600 MHz. Can't have both!
73 Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote: Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
--
Independent Expert on CE marking
EMC Consultant
Electrical Safety Consultant
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Or $2, plus shipping, from Minicircuits.
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On Thursday, July 1, 2021, 08:42:02 AM CDT, Zack Widup <w9sz.zack@...> wrote: I know. That's a problem in this application. Another possibility is a broadband impedance matching transformer with the appropriate ferrite toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm side as close enough. 73. Zack W9SZ On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote: ? Quarter wave transformer for what frequency????
54 MHz or 600 MHz.? ? Can't have both!
73? Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
? ? On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
? The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
? ? ? ? ? ? ? ? ? ? Mikek
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
On 7/1/21 7:13 AM, Joe WB9SBD wrote: I do not understand why a good 75 ohm calibration load would not make the thing be a 75 ohm test.
Isn't that what the 50 ohm one is doing when you calibrate the dead short and the 50 ohms load? exactly. I'd do the cal at the end of the coax, too.
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Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
On 7/1/21 6:41 AM, Zack Widup wrote:
I wouldn't sweat all these matching transformers, etc.? 75 isn't far from 50, so you're not going to have a "math and measurement" precision issue.
What I would do is get your 75 ohm cable, Calibrate using 50 ohm load, short, and open at the *end* of the cable and the fact that it's a 75 ohm cable is absorbed into the calibration.
Then, if you want to know VSWR or S11 for a 75 ohm system, convert your 50 ohm data to a 75 ohm reference impedance using math.
OR - get a 75 ohm termination, do the cal using 75, short and open, and your data will all be with reference to a 75 ohm system.? S11 and VSWR will be correct. What might not be correct is the resistance in the .s1p file and the reference impedance at the center of the Smith chart.
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Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
I do not understand why a good 75 ohm calibration load would not make the thing be a 75 ohm test.
Isn't that what the 50 ohm one is doing when you calibrate the dead short and the 50 ohms load?
Joe WB9SBD
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On 7/1/2021 8:41 AM, Zack Widup wrote: I know. That's a problem in this application. Another possibility is a
broadband impedance matching transformer with the appropriate ferrite
toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm
side as close enough.
73. Zack W9SZ
On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote:
Quarter wave transformer for what frequency????
54 MHz or 600 MHz. Can't have both!
73 Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Zack,
12/10 turns is 2% off - certainly close enough as you say, but 11/9 turns is even better at 0.2% off.
73/72
John
M0JBA
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On 1 Jul 2021, at 14:41, Zack Widup <w9sz.zack@...> wrote:
I know. That's a problem in this application. Another possibility is a
broadband impedance matching transformer with the appropriate ferrite
toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm
side as close enough.
73. Zack W9SZ
On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote:
Quarter wave transformer for what frequency????
54 MHz or 600 MHz. Can't have both!
73 Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Normally the difference between 50 and 70 is neglectable. If you really know that
the source/load is exactly 50 Ohm (that means you have measured that) and you
really know the other side is exactly 70 Ohm, only then it's worth do do the effort.
build a transformer on ferrite material suitable for the frequency.
You have to know that? the impedance increases with the square of the winding ratio.
A 2 winding to 4 winding transforms your 50 into 200 Ohm.
you will need a winding ratio of 1.25 for 50-70 ohm.
At low frequency you may want a lot of windings, at high frequencies you need much less.
Using whole windings that means that the lowest number of windings is 4 :5
This seems suitable up to 250 MHz approx with the right ferrite.
But at these high frequencies parasitic? and L may jeopardize the impedances at both side,
normally not a big problem, but you wantend to be accurate isn't it ?
If it is narrow band, within the resonance band of an LC, you may use
a capacitor step up construction?? (C1- C2 and L back to C1)
If you connect 50 ohm over C2 you will have 70 ohm over C1+C2
if C2 = 0,25 x C1.? And the loop needs to be in resonance too.
And your caps need to be 5% or better. Quite a challenge.
Other may have even better suggestions.
Gert
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Show quoted text
On 1-7-2021 15:41, Zack Widup wrote: I know. That's a problem in this application. Another possibility is a
broadband impedance matching transformer with the appropriate ferrite
toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm
side as close enough.
73. Zack W9SZ
On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote:
Quarter wave transformer for what frequency????
54 MHz or 600 MHz. Can't have both!
73 Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
--
Independent Expert on CE marking
EMC Consultant
Electrical Safety Consultant
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
I know. That's a problem in this application. Another possibility is a
broadband impedance matching transformer with the appropriate ferrite
toroid. I calculate 12 turns on the 75 ohm side to 10 turns on the 50 ohm
side as close enough.
73. Zack W9SZ
toggle quoted message
Show quoted text
On Thu, Jul 1, 2021 at 8:15 AM KENT BRITAIN <WA5VJB@...> wrote: Quarter wave transformer for what frequency????
54 MHz or 600 MHz. Can't have both!
73 Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <
w9sz.zack@...> wrote:
The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
If your just making comparisons between antennas any mismatch would reduce the actual signal strength of both equally so a relative comparison could still be made.
Larry, K4LED
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On Jul 1, 2021, at 8:26 AM, William Smith <w_smith@...> wrote:
?Good question, I'm sure part of it involves no 50-ohm cables, and probably calibration with a 75-ohm load termination, but there may be some other corrections to VSWR, etc.
Let us know!
73, Willie N1JBJ
On Jul 1, 2021, at 8:13 AM, Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
Re: Modify Original Nanovna for easy DFU mode like the H4
#dfu
#mods
change the resistor R5 from 1K (original) to 5K (as H4) Sorry, my mistake - I just detected that your picture shows already the H4, so I should change _from_ 5K to _1K_ But nevertheless it works well without the swap; the HI voltage is 2.2V - according to the data sheet the high level voltage for BOOT0 shall be 0.2 x VDDIOx + 0.95V = 1.61V
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Re: Measuring 49:1 ferrite transformers
thats all very interesting ... I'll need to read it a few times to 'digest' all your findings. thanks.
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Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Quarter wave transformer for what frequency????
54 MHz or 600 MHz.? ? ?Can't have both!
73? Kent WA5VJB
Minicircuits does sell broad band 50-75 Ohm transformers.
toggle quoted message
Show quoted text
On Thursday, July 1, 2021, 07:39:00 AM CDT, Zack Widup <w9sz.zack@...> wrote: The best way would be to use a quarter-wave section of 62 ohm cable. Lacking that, you may have to build some sort of antenna tuner. 73, Zack W9SZ On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote: Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
? ? ? ? ? ? ? ? ? ? Mikek
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.
73, Zack W9SZ
toggle quoted message
Show quoted text
On Thu, Jul 1, 2021 at 7:13 AM Mikek <amdx@...> wrote: Testing a couple of TV antennas for Signal strength and just curious about
what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
Re: impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Good question, I'm sure part of it involves no 50-ohm cables, and probably calibration with a 75-ohm load termination, but there may be some other corrections to VSWR, etc.
Let us know!
73, Willie N1JBJ
toggle quoted message
Show quoted text
On Jul 1, 2021, at 8:13 AM, Mikek <amdx@...> wrote:
Testing a couple of TV antennas for Signal strength and just curious about what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
impedance test of a TV antenna, How do I adjust 50 ohm to 75 ohm
Testing a couple of TV antennas for Signal strength and just curious about what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek
|
Re: Measuring 49:1 ferrite transformers
An excellent piece of work Gary.
|
The other hams have good ideas but I am older now and climbing up the hatch and into a HOT attic is not going to happen! I just set the nanovna to cover 3MHz to 30MHz and scanned SWR of each to find which were HF or not. From those that were HF I checked each band for SWR then did the same for the non HF. Worked well.
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Re: New to NanoVna - Newest version?
Just be sure not to deal with Nooelec.
WL
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-----Original Message----- From: Roy <roy@...> To: nanovna-users < [email protected]> Date: Wednesday, 30 June 2021 2:02 PM EDT Subject: Re: [nanovna-users] New to NanoVna - Newest version? On Tuesday 29 June 2021 10:51:25 pm Bill K wrote: Hello, I've been considering purchasing one of these for some time. I'm not an engineer or anything even close, but I am an amateur radio operator who enjoys experimenting with antennas, and this seems like a really useful tool. However, I am unsure of which model is most current. I understand that the latest is the NanoVna-H4, but none of the vendors listed on nanovna.con have this model in stock. It appears that Aursinc has the F version in stock on Amazon, I am not sure if there is much difference for my purposes, or if I should wait for the H4 to come back in stock. Also, is it safe to assume that the vendors listed through nanovna.com are selling good quality items? I'm a bit leery of buying a cheap clone from an unknown source. I bought my H4 from R&L, along with adapters to PL259 and BNC, and am quite happy with what I ended up with... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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Larry Dodd
Ho-Ro
Jon-G0MYW
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Richard Clemens
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