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Re: nanoVNA-H no boot screen flickers then black
On Sat, Sep 25, 2021 at 07:57 AM, William Smith wrote:
Thanks for the suggestion. I tried it, but all I get is a more dramatic flickering of the display at a slower rate. --Al |
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Re: nanoVNA-H no boot screen flickers then black
William Smith
Try disconnecting the battery, disconnecting the USB cable, powering it on to discharge any caps, and then boot it with just the USB as power supply? Battery might be getting soft...
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73, Willie N1JBJ On Sep 25, 2021, at 7:24 AM, Al Holt <grovekid2@...> wrote: |
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nanoVNA-H no boot screen flickers then black
Hello all,
I'd had this nanoVNA-H for a few years, h/w v.3.4, and it's had this startup trouble for a long time. At power on, the screen lights up, a blank screen flickers as if trying to boot and after ~30 seconds goes dark. For a long time I've been able to get it to boot by repeatedly flicking power switch off and on. Researching the trouble on this forum I have found I can attach external power to USB port and then after ~30 seconds pull the connector and it will boot. Symptoms were there with the original firmware. I've updated it to v.1.0.64. Battery voltage is 4.16 volts. I've read about a troublesome IC or cap, but I can't find those on my board, a blue PCB that looks official. When it does boot, it works well enough. What the best course of action? I wouldn't mind a larger screen, but I'm reluctant about purchasing a -H4 model if I can get this one to reliably start. Thanks! --Al WD4AH |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
circle is the series circle" .... or is that back-to-front??The right/constant resistance circle is the shunt circle, and the left/constant conductance I've read it exactly this way in another article too. And in some other article I found it the other way around. IMHO I think it's just a naming issue / point of view looking at it. It is important that you know how it works. But, however, I'm not an expert in this area, still learning and playing with Smith charts. Thank you very much for this link, Dave !SimSmith is a very powerful application. It's free and can be accessed at: I just tested this, very nice ! I can add another link: This is an online tool, you can build your circuit and see the result. Similar, but not so powerful as the mentioned SimSmith. Best regards / 73 Rainer, DK2ZR |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
Hi,
Re this article is Point 3, Page 3 correct ?? ie "The right/constant resistance circle is the shunt circle, and the left/constant conductance circle is the series circle" .... or is that back-to-front?? Secondly, I have been following all the 'Antenna sweeping/matching' Threads and playing with a test antenna also ... (folded dipole) and reading heaps of articles etc.. But one point eludes me, and that is, a bit of overview. Most of the stuff I read goes into L/C impedance matching (as per this article) OR concentrates on Voltage transformer/Ferrite core matching of feedline to antennae. I am missing the link here. Specifically, the L/C Network approach focusses on matching reactances, whereas the Voltage/Ferrite Core matching seems to me to be focussed on the resistances eg 300ohm antenna to a 50 ohm coax ... antenna reactance?? My gut feel here is that the link I am missing is to do with the resonant frequency or bandwidth or .... ??? Can some-one expand on this or point me to a relevant article??? Thanks, Ian -- Cheers, Ian Melbourne, Australia |
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Re: PC Boards for QEX Step Attenuator Available
Hi Miro,
Yes, you need 2 jumpers to engage a section, but only 1 to bypass it. It is more convenient to keep the 2 jumpers together, this way you switch the section with a single motion of turning the pair. Not as good as a single button push, but I think it is a good tradeoff between cost, performance, and convenience. 73, Mike AF7KR |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
SimSmith is a very powerful application. It's free and can be accessed at:
and an excellent tutorial specifically addressing SimSmith: <> Dave - W?LEV On Fri, Sep 24, 2021 at 12:35 PM chris_group_mail via groups.io <chris_group_mail@...> wrote: I have read it and as a complete beginner to this it looks very useful.-- *Dave - W?LEV* *Just Let Darwin Work* |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
A nice document with a lot of good information.? The restrictions on impedance matching range in Figures 4 and 5 of the Abracon white paper are shown in more detail in Figures 5.57 and 5.58 of the 2021 ARRL Handbook and in similar figures in earlier editions.
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Note that the restriction on the geometry of L-networks (Rs < Rl) in Figure 5.58 applies to all combinations of impedances only when the impedances on both sides are real.? The impedances on either side may be complex in practical installations, especially when electrically short antennas are to be matched. Figure 5.58 of the Handbook shows only two L-network geometries that conform to the restriction, both of which place the parallel element across the higher of the two impedances.? For some combinations of impedances, it is possible to reverse the network, yielding four possible geometries instead of two.? In "More Octave for L-Networks," QEX, May/Jun, 2012, a GNU Octave procedure is given for determining whether or not an L-network may be reversed and, if so, what other geometries result from that reversal.? The Octave code gives values for the elements of either two or four L-networks as appropriate. 73, Maynard Wright W6PAP On 9/23/21 4:29 PM, John Slaughter wrote:
I did not read it either, however here is the link: |
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Re: PC Boards for QEX Step Attenuator Available
On Thu, Sep 23, 2021 at 09:31 AM, vbifyz wrote:
Nicely done Mike! Just a quick question - why do you need "dual" jumpers? Would it work if you have a single jumper per attenuator, so either you have attenuator engaged (jumper off) or shorted "jumper on"? If I see it correctly, in your design, in order to "engage" the attenuator u must remove one "bridge" (horizontal) and put two (vertical) in, right? THANKS for the work put in! |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
On Fri, Sep 24, 2021 at 07:35 AM, <chris_group_mail@...> wrote:
... Somebody must have an app for that, which starts with an impedance and generates the L and C values needed to match itAnd to answer to the google search string with another - "impedance matching lc calculator" :) Here are some I use the first one often |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
I have read it and as a complete beginner to this it looks very useful. It's increased my understanding of the matching process.
Intriguing that for a simple single frequency all that's involved is rotating the point about various circles so what is needed is to determine the intersection between two circles. Somebody must have an app for that, which starts with an impedance and generates the L and C values needed to match it to a transmission line. Have looked but can't find anything, maybe I'm not using the correct terms. Chris |
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Re: Stripping Coax
ALL- I never saved the link and I looked at Banggood.com and do not see any like the ones I had. Frankly that purchase was pre-pandemic and Banggood is like Amazon.. A collaboration of individual sellers that use the common website for advertising..
This is not the only thing I saw come and go on Banggood, Same with shipping time and is today's price what it was pre-pandemic.. Also pre-pandemic they had free shipping, then free shipping on orders over $49.. Now.. It's all different.. So- it is what it is.. Frankly at $1.65 I think the guy figured out he wasn't making money ---or-- the product was some sort of blow out sale to get rid of what he had.. |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
Yes and thank you for posting the link. At the time of my post I was on a computer interface that was very minimal!!!
However, again thanks and that is the correct location. Enjoy. |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
I did not read it either, however here is the link:
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John -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of AB6BT Sent: Thursday, September 23, 2021 5:35 PM To: [email protected] Subject: Re: [nanovna-users] #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED Actually he stated: "Antenna Impedance Matching Simplified authored by company Abracon" "Type the above into your search engine. " |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
Plug in the search phrase: Antenna Impedance Matching Simplified
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authored by company Abracon It will get you there. Dave - W?LEV On Thu, Sep 23, 2021 at 10:05 PM Larry Rothman <nlroth@...> wrote:
Uh.....Alan, you forgot the link..... --
*Dave - W?LEV* *Just Let Darwin Work* |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
Sigh.? It's been a long day :(
On Thu., 23 Sep. 2021 at 6:35 p.m., AB6BT<AB6BT@...> wrote: Actually he stated: "Antenna Impedance Matching Simplified? authored by company Abracon" "Type the above into your search engine. " |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
Actually he stated:
"Antenna Impedance Matching Simplified authored by company Abracon" "Type the above into your search engine. " |
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Re: #tutorials ANTENNA IMPEDANCE MATCHING SIMPLIFIED
#tutorials
Uh.....Alan, you forgot the link.....?
On Thu., 23 Sep. 2021 at 4:14 p.m., alan victor<avictor73@...> wrote: Here is a well written short 5 page pdf on the topic. Written and illustrated very nicely. Antenna Impedance Matching Simplified? authored by company Abracon Type the above into your search engine. Alan |
Larry Macionski
John Slaughter
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