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Re: At which point do we take the value of impedance to tune an antenna?
On both charts, 25+j0 and 100+j0 need to be swapped. They are wrong as labeled.
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On Wednesday, August 3, 2022, 06:42:32 PM EDT, Roger Need via groups.io <sailtamarack@...> wrote:
Time is well spent learning a bit about the Smith Chart. You can plot a complex? impedance and then draw a circle that intersects the point and get the SWR.? You can also measure the distance and get the reflection coefficient and gamma. A picture is worth a thousand words so here is a plot on a Smith Chart of several complex impedances that all result in a SWR of 2 and a reflection coefficient of 0.333 ( a Reflection Loss of 9.54 dB).? The 40 + j30 from the earlier discussion is one of these. Roger |
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Re: New owner of nanovna-H and H4, However pondering the next step in precision
Hi John
Good guess at both my range of interest(indeed below 900MHz) and the education side... I have very limited techniques as im new to it all. Im going to try and find that article you mention, if not il try to buy an old hard copy of the mag on ebay. Re the loads, you are referring to the three calibration connectors provided correct? Would making my own finer tuned ones be a realistic task? as in components, pricing, and skill? If not if you know anywhere to buy some finer tuned I would appreciate the link Thanks for the help! |
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Re: Launch of a new product by Deepelec (DeepSDR 101)!
Doug
I, for one, really appreciated hearing about this new product although it may have been in the wrong forum.
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I don't know where else Kadir might have announced it that I would have seen it. Perhaps there is an SDR forum for such news. Doug. On 03/08/2022 21:13, Kadir Mari?o Abreu wrote:
I apologize for the inconvenience caused, it will not be repeated, thank you.-- */If you forward this email, please delete the forwarding history which also includes my email address. When sending emails, please BCC so as to hide all addresses. Thanks for helping to prevent Scammers and Spammers from mining addresses and spreading viruses./ 73 Doug Kearney VA3DKA * *Ottawa, ON * --
This email has been checked for viruses by Avast antivirus software. |
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Re: New owner of nanovna-H and H4, However pondering the next step in precision
Oroot,
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Assuming the frequency range of interest is 900MHz and below, your best investment for better accuracy in RL/VSWR and attenuation is probably educating yourself in best technique. As an example, the recent QEX magazine (July/Aug 2022) has an article on using the NanoVNA to accurately measure low loss devices like short cables and RF relays. Another investment might be in a better Load standard for the connector type you use most. The supplied standard load is fine for most purposes, but for measuring very high RL the NanoVNA is capable of taking advantage of a better load. You can probably make your own Short and Open for any connector type you use at HF/VHF/UHF frequencies. --John Gord On Wed, Aug 3, 2022 at 04:55 PM, 0root wrote:
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Re: At which point do we take the value of impedance to tune an antenna?
An excellent learning tool by just jumping in is SimSmith:
There is also an excellent tutorial (and a lot more) by W?QE at: Dave - W?LEV On Wed, Aug 3, 2022 at 10:42 PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: Time is well spent learning a bit about the Smith Chart.-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV |
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New owner of nanovna-H and H4, However pondering the next step in precision
Hey all, first post here.
I currently own and love the nanovna-h and h4, I was sure to buy them from the alibaba store zeenko as this is apparantly hugens chosen manufacturer. However, if I wanted to get more precision - specifically in the areas of Return Loss / VSWR and attenuation readings - what would be the next device up to get - within the region of $100 - $2000 and no higher... I see alot of siglent stuff, but the reviews are not too appetizing |
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Re: At which point do we take the value of impedance to tune an antenna?
Time is well spent learning a bit about the Smith Chart.
You can plot a complex impedance and then draw a circle that intersects the point and get the SWR. You can also measure the distance and get the reflection coefficient and gamma. A picture is worth a thousand words so here is a plot on a Smith Chart of several complex impedances that all result in a SWR of 2 and a reflection coefficient of 0.333 ( a Reflection Loss of 9.54 dB). The 40 + j30 from the earlier discussion is one of these. Roger |
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Re: Launch of a new product by Deepelec (DeepSDR 101)!
As long as it is free and open source, I don't mind the announcements for related projects.
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If it is a product you have to pay for, I am all for every bit of censorship. On Wednesday, August 3, 2022, 03:48:35 PM EDT, Dave Daniel <kc0wjn@...> wrote:
Kadir, Please do not post messages on this forum that contain only marketing information that is not specifically related to the NanoVNA product concerned with this particular group. I have deleted the message. DaveD, co-owner On Aug 3, 2022, at 14:55, Kadir Mari?o Abreu <cm3kma@...> wrote: |
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Re: Launch of a new product by Deepelec (DeepSDR 101)!
Kadir,
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Please do not post messages on this forum that contain only marketing information that is not specifically related to the NanoVNA product concerned with this particular group. I have deleted the message. DaveD, co-owner On Aug 3, 2022, at 14:55, Kadir Mari?o Abreu <cm3kma@...> wrote: |
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Re: At which point do we take the value of impedance to tune an antenna?
Yes!!! Learn the Smith Chart!!!! Also, learn and internalize Ohm's
Law!!!! Both will serve you well with all things RF. SWR can be measured as current, or voltage standing wave ratios. A good test for all this confusion is to establish a system which measures 1:1 SWR at a known frequency. Then add an electrical 1/8 to 1/4-wavelength of transmission line to the system. If the SWR remains 1:1 with the added transmission line in place, indeed, the SWR is 1:1. If the measurement with the additional line length measures something other than 1:1, the original 1:1 measurement is in error. This is the primary reason S-parameters deal strictly with power, the product of voltage and current for a sine wave. With SWR on the transmission line, voltage and current along the line changes as measured at single points along the line. However, power remains the same along the line - it's just Ohm's law with a little very simple algebra. Dave - W?LEV On Wed, Aug 3, 2022 at 4:10 PM Kenneth Hendrickson via groups.io <dsp_stap= [email protected]> wrote: Russ,-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV |
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Re: At which point do we take the value of impedance to tune an antenna?
Helpful document:
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On 8/3/2022 9:10 AM, Kenneth Hendrickson via groups.io wrote:
Russ, |
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Re: At which point do we take the value of impedance to tune an antenna?
Russ,
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If the load is not perfectly matched to the source, there will be a voltage standing wave ratio (VSWR) because of the mismatch. Learn the Smith chart. On Wednesday, August 3, 2022, 11:52:31 AM EDT, Russ <u.rusty@...> wrote:
On Tue, Aug? 2, 2022 at 05:26 PM, Jerry Stuckle wrote: Can you explain this in more detail. I thought VSWR was based on voltage. |
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Re: At which point do we take the value of impedance to tune an antenna?
SWR = Zt / Zo applies only when both impedances are resistive. When Zt = 40 +
j30 ohms, the load is highly reactive. The coefficient of reflection rho is: rho = (Zt - Zo) / (Zt + Zo) = 0 + j0.3333 ... SWR = (1 + abs(rho)) / (1 - abs(rho)) = 2.0 73, Maynard W6PAP On Tuesday, August 02, 2022 05:26:38 PM Jerry Stuckle wrote: Incorrect. The VSWR is based on impedance - which is a combination of----------------------------------------- |
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Re: At which point do we take the value of impedance to tune an antenna?
40+j30 is a Z of 50 ohms. In this case, this is an SWR 1:2 !!! Not 1:1 .
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Only swr 1:1 is 50 ohms resistive load (and then again, using a 50 ohm cable ;-) ). 73 Arie PA3A Op 3-8-2022 om 02:26 schreef Jerry Stuckle: Incorrect. The VSWR is based on impedance - which is a combination of resistance and reactance. A vertical at resonance will have an impedance of about 35 + 0j ohms or an impedance of 35 ohms and a 50/35 or 1.43:1 SWR. However, slightly off resonance it could have an impedance of say 40 + 30j ohms, which would have a total impedance of 50 ohms (just an example for ease of calculations) and an SWR of 1:1. The antenna is non-resonant at the lowest SWR reading. |
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Re: At which point do we take the value of impedance to tune an antenna?
Incorrect. The VSWR is based on impedance - which is a combination of resistance and reactance. A vertical at resonance will have an impedance of about 35 + 0j ohms or an impedance of 35 ohms and a 50/35 or 1.43:1 SWR. However, slightly off resonance it could have an impedance of say 40 + 30j ohms, which would have a total impedance of 50 ohms (just an example for ease of calculations) and an SWR of 1:1. The antenna is non-resonant at the lowest SWR reading.
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Re: At which point do we take the value of impedance to tune an antenna?
Note that when the load looks resistive the VSWR versus frequency is at a minimum.
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On August 2, 2022 4:38:51 PM MDT, W0LEV <davearea51a@...> wrote:
And please remember resonance is not necessarily at 1:1 SWR. It may or may |
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Re: At which point do we take the value of impedance to tune an antenna?
And please remember resonance is not necessarily at 1:1 SWR. It may or may
not be. Resonance is *defined* by (consult the complex portion of the measured impedance): +jX = -jX. The resistance term is purely resistive (consisting "mostly" of the radiation resistance) while the reactive component is strictly reactive: capacitive or inductive. Dave - W?LEV On Mon, Aug 1, 2022 at 10:01 AM Diane BONKOUNGOU <dianebonk2@...> wrote: Hello Roger,-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV |
Roger Need
Arie Kleingeld PA3A
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