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Re: Tuning a Firestick NGP antenna
Sure sounds like the length of coax is part of the antenna matching.Especially true for an antenna without radials or a ground plane.
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So that extra length of coax between the radio and the SWR meterchanges the tuning of the antenna 'system'. Good luck with your tweaking.? Kent On Sunday, November 10, 2024 at 06:12:31 AM CST, Andrew Harman via groups.io <nexus9d9@...> wrote:
I have a Firestick No Ground Plane antenna on order that I'm going to install for a friend.? Reading through the reviews there are comments that you cannot use an external SWR meter to tune it.? That you use the radio's internal SWR meter.? I'm not sure why this would be or if that also means I cannot use either my NanoVNA or MFJ259.? Does anyone have any background with these? Thanks again, /A |
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Tuning a Firestick NGP antenna
I have a Firestick No Ground Plane antenna on order that I'm going to install for a friend. Reading through the reviews there are comments that you cannot use an external SWR meter to tune it. That you use the radio's internal SWR meter. I'm not sure why this would be or if that also means I cannot use either my NanoVNA or MFJ259. Does anyone have any background with these?
Thanks again, /A |
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Re: Dipole antenna with Low Z0 feed point Impedance
Dave,
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You're onto something, but to match 25 ohms to 50 ohms you need 1/4 wavelength (electrical length) of 37 ohm (not 75 ohm) coax. This is easily achieved with two 75 ohm coaxes in parallel. I've used this many times and works great! A word to the wise: if you use foam dielectric coax the velocity factor may be wildly different than the published value Good luck! 73 Frank W3LP ----- Original Message -----
From: "Dave Robinson via groups.io" <kb7gp@...> To: [email protected] Sent: Saturday, November 9, 2024 5:33:30 PM Subject: Re: [nanovna-users] Dipole antenna with Low Z0 feed point Impedance One thought would be to use a 1/4 wavelength of RG59 for example at the frequency your dipole is cut for. I did not notice that reference in your original message. This should perform the proper transition from a 50 Ohm feedline to the 25 Ohme impedance at your dipole center. DaveR KB7GP |
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Re: Dipole antenna with Low Z0 feed point Impedance
On Sat, Nov 9, 2024 at 08:06 AM, Bill WA2WIO wrote:
Back to your question: no, you can't just turn around a 2:1 balun - that is, unless you re-wire it. If it is in a box that is easy to get to the internals, you may be able to flip the coil around - but you need to wire it properly such that it stays being a balun, i.e. the shield terminal from your coax connection has to be on the leg of the transformer that is not directly connected to one of the balanced terminals. The other 1:2 balun you found is a very nicely done design, but made for 3kW it is expensive. You don't need 3kW: a 100W version of that same balun should be much more reasonably priced - or you could make your own on a FT240-43 core. |
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Re: Dipole antenna with Low Z0 feed point Impedance
One thought would be to use a 1/4 wavelength of RG59 for example at the frequency your dipole is cut for. I did not notice that reference in your original message. This should perform the proper transition from a 50 Ohm feedline to the 25 Ohme impedance at your dipole center.
DaveR KB7GP |
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Re: Dipole antenna with Low Z0 feed point Impedance
I use 1:2 transformers on all bands in my stackmatches similar to this one:
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I use it also on my 40m yagi with its 27 ohm impedance. On the high bands I use just 5 trifilar windings with the stackmatch. 73 Peter, DJ7WW -----Original-Nachricht----- Betreff: Re: [nanovna-users] Dipole antenna with Low Z0 feed point Impedance Datum: 2024-11-09T01:08:27+0100 Von: "Kirk Kleinschmidt, NT0Z via groups.io" <sohosources@...> An: "[email protected]" <[email protected]> Bill, Single band or multi? Because the 1:2 transformer (also use a ferrite choke) only matches the feed point essentially on one band (there will likely be some higher-order sorta-matches in there, too), I always just put up the attic loop or dipole and put an LDG RT-100 (or similar) at the feed point. Then, DC to Daylight. Interesting question, though. I want to know the answer as well. :) Regards, Kirk, NT0Z My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon) On Friday, November 8, 2024 at 11:54:24 AM CST, Bill WA2WIO <sla@...> wrote:
Using a VNA to measure dipole antenna feed point characteristics has been discussed. I believe this is a little different twist. I have an attic mounted 1/2 wave dipole antenna with a 20-25 ohm Z0 at the feed point. I expected this because of the 12 foot attic mounting height, non-linear non-symmetric shape, near by structures, poor ground effect, other constraints, etc. Having confirmed this, how to best match this dipole's Z0 of 25 Ohms to a 50 ohm coax line is now the challenge. Would a 1:2 UnUn be appropriate? 1:2 BalUn? If so, what would this UnUn / BalUn look like? I have seen 2:1 commercial units available. The input and output connectors are for 2:1. I have not seen one with the connections setup for 1:2. If this is a viable are there any recommended commercial sources for it? I would then use the VNA to verify results. Thoughts and suggestions? Thank you. Bill WA2WIO ? |
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Re: Dipole antenna with Low Z0 feed point Impedance
40m and 20m. Anything else is a gift.
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Right now, system is: 1/2 wave Dp antenna to about 40ft of RG58 coax to 15T coax wound CMC on a 4" PVC form to ATU10 to rig (SDR QRP for now, eventual 200w). Without ATU SWR 5-6. With ATU SWR 1.2-2.5. Also, S4-5 noise level. LDG is cool but expensive (may be worth it). I am using the ATU at the xmtr to keep the rig happy. I am using the VNA looking to make the antenna itself work better. I found these products: 1:2 1-56MHz 200W Balun HAM Shortwave Antenna Balun 50 ohm to 100 ohm Unbalanced Balance SKU: 1741737 (looking into this one) Model 1213 - 1:2 Balun (25 to 50 ohms) 3kW This is a unique design by Dr. Jerry Sevick (W2FMI) that combines a 25 ohm balun with a 1:2 unun for final transformation to 50 ohms. Used anywhere there is a need to transform 25 ohms balanced to 50 ohms unbalanced. Big price difference (again, might be worth it). ¡¤ Would I be correct that a 2:1 and a 1:2 are very different animals? You can't just turn around a 2:1?? Thoughts? Bill WA2WIO -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Kirk Kleinschmidt, NT0Z via groups.io Sent: Friday, November 8, 2024 7:08 PM To: [email protected] Subject: Re: [nanovna-users] Dipole antenna with Low Z0 feed point Impedance Bill, Single band or multi? Because the 1:2 transformer (also use a ferrite choke) only matches the feed point essentially on one band (there will likely be some higher-order sorta-matches in there, too), I always just put up the attic loop or dipole and put an LDG RT-100 (or similar) at the feed point. Then, DC to Daylight. Interesting question, though. I want to know the answer as well. :) Regards, Kirk, NT0Z My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon) On Friday, November 8, 2024 at 11:54:24 AM CST, Bill WA2WIO <sla@...> wrote: Using a VNA to measure dipole antenna feed point characteristics has been discussed. I believe this is a little different twist. I have an attic mounted 1/2 wave dipole antenna with a 20-25 ohm Z0 at the feed point. I expected this because of the 12 foot attic mounting height, non-linear non-symmetric shape, near by structures, poor ground effect, other constraints, etc. Having confirmed this, how to best match this dipole's Z0 of 25 Ohms to a 50 ohm coax line is now the challenge. Would a 1:2 UnUn be appropriate? 1:2 BalUn? If so, what would this UnUn / BalUn look like? I have seen 2:1 commercial units available. The input and output connectors are for 2:1. I have not seen one with the connections setup for 1:2. If this is a viable are there any recommended commercial sources for it? I would then use the VNA to verify results. Thoughts and suggestions? Thank you. Bill WA2WIO |
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Default Color dump TinySA Ultra
Could someone get the default color dump with the hex codes of the TinySA Ultra for me.
I have done the upgrade, but something went wrong with the colors. The background is white, the spectrum line is blue, etc. I like to have the original colors to maybe I can adjust this via the terminal emulator. Thanks in advance. Jouke van de Merwe PH1A |
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Re: Dipole antenna with Low Z0 feed point Impedance
Bill,
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Single band or multi? Because the 1:2 transformer (also use a ferrite choke) only matches the feed point essentially on one band (there will likely be some higher-order sorta-matches in there, too), I always just put up the attic loop or dipole and put an LDG RT-100 (or similar) at the feed point. Then, DC to Daylight. Interesting question, though. I want to know the answer as well. :) Regards, Kirk, NT0Z My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon) On Friday, November 8, 2024 at 11:54:24 AM CST, Bill WA2WIO <sla@...> wrote:
Using a VNA to measure dipole antenna feed point characteristics has been discussed. I believe this is a little different twist. I have an attic mounted 1/2 wave dipole antenna with a 20-25 ohm Z0 at the feed point. I expected this because of the 12 foot attic mounting height, non-linear non-symmetric shape, near by structures, poor ground effect, other constraints, etc. Having confirmed this, how to best match this dipole's Z0 of 25 Ohms to a 50 ohm coax line is now the challenge. Would a 1:2 UnUn be appropriate? 1:2 BalUn? If so, what would this UnUn / BalUn look like? I have seen 2:1 commercial units available. The input and output connectors are for 2:1. I have not seen one with the connections setup for 1:2. If this is a viable are there any recommended commercial sources for it? I would then use the VNA to verify results. Thoughts and suggestions? Thank you. Bill WA2WIO |
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Re: Dipole antenna with Low Z0 feed point Impedance
Michael Robinson
Greetings.
I had a 40 meter dipole at 12' above ground with fair ground conductivity and had a feed point Z of 22 ohms and very little reactive component. I went to Balun Designs and bought a balun that was 25 to 50 (or 1:2 Z match) and it fixed the problem. Worked very well at full legal limit for power, also. Balun Designs is my recommendation. Best Regards, Michael L Robinson, KC0TA ¡°In the beginning of a change the Patriot is a scarce man, and brave, and hated and scorned. When his cause succeeds, the timid join him, for then it costs nothing to be a Patriot.¡± ¨D Mark Twain When Tyranny becomes Law, Revolution becomes Duty! On Fri, Nov 8, 2024 at 11:54?AM Bill WA2WIO via groups.io <sla= [email protected]> wrote: Using a VNA to measure dipole antenna feed point characteristics has been |
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Dipole antenna with Low Z0 feed point Impedance
Using a VNA to measure dipole antenna feed point characteristics has been discussed. I believe this is a little different twist.
I have an attic mounted 1/2 wave dipole antenna with a 20-25 ohm Z0 at the feed point. I expected this because of the 12 foot attic mounting height, non-linear non-symmetric shape, near by structures, poor ground effect, other constraints, etc. Having confirmed this, how to best match this dipole's Z0 of 25 Ohms to a 50 ohm coax line is now the challenge. Would a 1:2 UnUn be appropriate? 1:2 BalUn? If so, what would this UnUn / BalUn look like? I have seen 2:1 commercial units available. The input and output connectors are for 2:1. I have not seen one with the connections setup for 1:2. If this is a viable are there any recommended commercial sources for it? I would then use the VNA to verify results. Thoughts and suggestions? Thank you. Bill WA2WIO |
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Re: Measure transformers, inductors and trap filters
Gervais:
I have good news--- I've had similar difficulties getting to understand what to do with my NanoVNA-H4. I came upon a very informative book that I bought on Amazon to read on my Kindle app in this laptop. It's called "NanoVNAs Explained for the Radio Amateur: The author is Mike Richards, G4WNC. It's copyright 2022, and the price is about USD 20, as I recall. The great thing is that he starts out explaining what VNA's are, how & when invented. And then he moves on to the NanoVNA, explaining what the two ports are, and why they are called "S11" or "S21"---- etc. Then he moves on to examples and limitations of these inexpensive units [mostly bandwidth and sensitivity at VHF and above.] Finally, he tells about a freeware program called "NanoVNA-saver"---where to download it, and what it lets you do. The examples in that section are worth the price of the book! The entire Part 2 of the book is a series of sections on topics like "antenna feeder loss", "Passive filter measurement" and "Cable checker" to name a few. Oh! He also has a very clear explanation of how a Smith Chart works. 73 Bill, K2TNO On Thu, Nov 7, 2024 at 7:08?AM Gervail Antoine via groups.io <gervail.antoine@...> wrote: Hello guys, |
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Re: Measure transformers, inductors and trap filters
Here is another fixture idea. The connectors are Pomona BNC female #2451 and the contacts are a Phoenix Contact #1190363. In the photos the "short" is installed. You can see that there is an easy match between the BNC center conductor and the pin of the Phoenix contact. Three #4 standoffs 9/16" are used and it is epoxied after assembly and soldering.
/g/nanovna-users/album?id=298861 Mouser link to Phoenix Contact: Mouser link to Pomona BNC: |
Dave Robinson
Kirk Kleinschmidt, NT0Z
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