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Re: What is the resonate frequency of this?
On Tue, 8 Sep 2020 at 19:31, Roger Need via groups.io <sailtamarack=
[email protected]> wrote:
The circuit is more a curiosity than anything else. But it hopefully gets people away from the belief that the resonant frequency of a parallel turned is independent of the losses of components. That¡¯s only true for series, not parallel network Dave -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom |
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Re: What is the resonate frequency of this?
On Tue, 8 Sep 2020 at 15:11, Jerry Gaffke via groups.io <jgaffke=
[email protected]> wrote: Yes, the R's have no effect on resonant frequency. The resonant frequency of a parallel tuned circuit does depend on the resistive losses, but for a series tuned circuit it does not. I believe that all the books aimed at passing amateur radio exams make the assumption that R doesn¡¯t matter. For modest losses, the effect is minimal, but for high losses it is not. G8WRB Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom |
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Re: What is the resonate frequency of this?
On Tue, 8 Sep 2020 at 15:00, Rich NE1EE <73.de.NE1EE@...> wrote:
On 2020-09-08 14:41:+0100, you wrote:This will be difficult to draw in an email, so I will describe it, too I don¡¯t know how to do it on my iPhone. I use the gmail app. Someone worked it out. The result is that the impedance is real at all frequencies, so you could argue it¡¯s resonate at all frequencies. ???
Dave, G8WRB -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom |
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Re: What is the resonate frequency of this?
On Tue, 8 Sep 2020 at 14:55, John Baines via groups.io <jbaines=
[email protected]> wrote: My first guess was that the resonant frequency is unchanged by any value That¡¯s true for series connected devices, not parallel. As someone has shown, the impedance is purely real at all frequencies.
G8WRB --Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom |
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Re: NanoVNA vs. MFJ-259B Antenna Analyzer
Hi Larry,
Yes, I've used that page from Tom. It is more complicated that the NanoVNA for sure....He was an MFJ contract employee for years but stepped away just a few years ago. I used his guide to create a false RF ground in my 2nd floor shack when building our house 9 years ago. His site has a lot of theoretically sound and practical info! Take a look at his antenna farm via Google Earth. Local broadcast stations in Barnesville GA are envious, LOL. 73, Frank K4FMH |
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NanoVNA vs. MFJ-225 Antenna Analyzer
On 10.09.2020 20:38, Larry Rothman wrote:
The NanoVNA is an incredible price point. It is not an "antenna analyzer" in the way that most hams approach such a device. There are many other brands of A-As but MFJ established the market for such a device. I have several others besides the MFJ 269 (and the 259b before it). But the 269 is a small RF lab in a box. The NanoVNA, even with the A-A firmware, is much more challenging to use in the field as many other posters here have stated. The intended use case often drives what is satisfactory. The NanoVNA has stupified many purchasers who jumped at the price tag and the buzz about it when what they wanted was a "cheap" (single port) A-A. Do you have experience with MFJ-225. How is it compared to NanoVNA? -- 73, Pedja YT9TP Checkout: |
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Re: NanoVNA vs. MFJ-259B Antenna Analyzer
Hi Bob,
Very well articulated statement on why the NanoVNA is the preferred tool for you. I'm delighted that you've learned what it can do for you. It's clear though that only a smaller share of hams have the technical appreciation for what the NanoVNA will do than you do. I've seen several hams who jumped on the NanoVNA instead of an A-A (MFJ or otherwise) because of the price, only to become very disappointed to just not understand how to use it effectively. Moreover, they were ticked off at the learning curve. Well, that's basically their fault, to buy something that you have no motivation to learn how to use properly. But what that says is what Pierre posted in this thread too. Many hams really want a "good" single-port A-A and not a two port device. They would never read, for instance, Bob Witte's book on test equipment or Joe Carr's books on test and measurements equipment. And would never want to. That's why I commented on 10f11's "peed off" comment: it does not place in context what the single port A-A is most useful for and the market that can best appreciate it! To couch the distinction in terms of a particular manufacturer's "anger" assumes that one knows the motivations of that manufacturer. I communicate with Martin Jue every week and have a lunch meeting with him every quarter. I do not work for the company. We are just close friends. So I can speak with some authority as I know Martin has a NanoVNA himself. But he's not upset in the least at such innovation for he built his company on the same principle with a CW filter kit that undercut the major rig manufacturers at the time! So this is all good...I have tools on my workbench that I like better than a similar tool where each can make the measurements at a give time. I love my Tek 2465a 4-chan scope...and my Rigol 1054z, too. But the Rigol gets the serious work where I want the measurement data on my PC for further analysis..especially when I'm using a dual chan sig gen with phase control for the DUT. Still love the Tek for general testing. Still love the MFJ-269. But the NanoVNA (all 5 of them) will get the measurements over to my PC for further analysis whereas the 269 will not. I'm certainly not "peed off" that it won't. Neither is MFJ over the rise of the NanoVNA. 73, Frank K4FMH |
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Re: NanoVNA vs. MFJ-259B Antenna Analyzer
Hi Dave,
Did you calibrate your 259 and did you buy it new? I can tell you from many customer service calls to MFJ that many complaints arrive from customers who purchased the 259/269 units used. The buyer never RTM, never cal'd the A-A. MFJ sells cal kits for them and discusses that need in the manual. Now, from my experience on my workbench, most test equipment errs more on the extremes, whether it's voltage, capacitance, resistance or RF. I have no clue why how how your got the "20%" error measurements. What were you comparing the MFJ 259's readings to? On your statement, "And MFJ misleads on being capable of reading the complex portion of the impedance. Most don't. Only a few at the high end of their pricing do, with bad tolerance. Not so with the NANOVNA's!", how does the MFJ reading mislead in ways that Martin himself has not told users how to add the sign of the j to the 259/269's readings? e.g., see . High end of whose pricing? MFJ's on the 259? Not sure what you're saying here. Please explain. The NanoVNA is an incredible price point. It is not an "antenna analyzer" in the way that most hams approach such a device. There are many other brands of A-As but MFJ established the market for such a device. I have several others besides the MFJ 269 (and the 259b before it). But the 269 is a small RF lab in a box. The NanoVNA, even with the A-A firmware, is much more challenging to use in the field as many other posters here have stated. The intended use case often drives what is satisfactory. The NanoVNA has stupified many purchasers who jumped at the price tag and the buzz about it when what they wanted was a "cheap" (single port) A-A. I'm not posting this to argue nor was I when I called out 1of11's "MFJ must be peed-off" statement which I know directly to be false (love or not, 1of11). I'm posting this to articulate that there is a context in which we all evaluate gear. You have yours regarding yoru new or used 259. MFJ can't keep up production to fill orders for their A-As and have the next-gen on the design board. Their market for antenna analyzers is reasonably secure as they've diversified their product line in this niche. I have 5 versions of the NanoVNA besides my 269. I'll calibrate it from time to time but it will be in my field gear bag for some time to come. 73, Frank K4FMH |
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Anritsu 22N50 open/short definitions
#calibration
I picked up a cheap Anritsu 22N50 male N-type open/short recently. Apparently these were meant to be used mainly with the Site Master (scalar) antenna analyzers, but they are listed as an accessory for some VNAs as well. It looks like a decent design, with precision 18GHz N connectors and an open with an extender pin (instead of just a shield). Unfortunately, there doesn't seem to be a datasheet with standard definitions.
When you select the predefined N (m) calibration kit on an Anritsu VNA, it will use the following definitions: Open: offset 17.83mm, C0=4e-15 F, C1=200e-27 F/Hz, C2=0 F/Hz^2, C3=1.1e-45 F/Hz^3 Short: offset 17.83mm, L0=0, L1=0, L2=0, L3=0 This will probably give reasonable results, but I wonder if anyone here has actually measured one of these? |
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Re: Serious question
Wow! Great response. I will attempt to answer your questions in order.
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1. 135¡¯ was one of the recommended lengths to avoid being a 1/2 wave. The 9:1 has 75¡¯ of LM400 connected to it. I have no idea what the ohms are going into the auto tuner. 2. The wire is #12 copper clad steel from Wireman and insulated. 3. The only thing I have to tell me SWR is my NanoVNA H4 and the SWR meters on my MFJ 993B auto tuner and 991A radio. I was unsure about putting another SWR meter inline but sounds like I maybe should. 4. My counterpoise is on the other side of my matchbox, in the trees, same type wire, insulated, at the same height. Thanks Darrell N5FTW Sent from my over-rated IPhone 7 Plus. Any Mis-spellings or grammar errors are due to my IPhone auto correct feature. On Sep 10, 2020, at 06:39, DougVL <K8RFTradio@...> wrote: |
Dr. David Kirkby, Kirkby Microwave Ltd
K4FMH
YT9TP - Pedja
Roger Need
Darrell Carothers