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Re: Mini-Whip recommendation?
Thank you all for the replies! Sorry for being quiet.
Yes, I contacted Roelof a few days ago. He is building one of his MiniWhip designs for me right now (he has 3 versions right now!). His pricing is also very reasonable! Martin (G8JNJ), thank you for the links about proper installation of Mini-Whip! Yes, I'm aware of some of these things... Will need to experiment in my small Urban garden. Direct grounding below the antenna might be a problematic in my case without violating NEC codes but I can experiment and maybe do some bonding to the main electric ground in the future (was in my plan anyway). Right now some of my other antennas are grounded directly to the main electric panel GND rod but they are on another side of the building where my electric panel is located. Garden is on opposite side and I need to figure out how to do it properly. By NEC all auxiliary GND rods needs to be bonded to the main one with at least 16mm2 (6 AWG) line. It's not complicated, just time and effort. And yes, I could definitely build miniWhip myself. Being an RF R&D/Applications Engineer I have no problem working with SMD components down to 0201 size. It's just time and effort that I'm not sure I want to spend right now on this project (aside from experimenting with already built antenna). And I strongly believe that sometimes its just better and easier to order from someone who already done many of those assemblies and know all the ins and outs of his designs. Especially if pricing is about the same. I'm not even sure if I will spend less money building it myself. Don't get me wrong - I like building stuff myself, just not always and not this time. Thank you all! Regards, Simon |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
¿ªÔÆÌåÓýHi Chin-leong Lim, ? There is nothing wrong with the suggested Laudet's model. Besides, other sources support the same model for unshielded SMA. ?You may use Levkov's model but it represents Norton's layout with a current source.?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? I looked at the graphs of your article. Your presented a graph of S21 frequency ?response of 2nd order LPF which is unrealistic ¨C to much attenuation starting ?already ?at low frequencies, however the selected cutoff frequency of your dummy antenna elements is correct about 28 MHz. I do not whether ?you selected correctly source and load impedances for this dummy antenna. How well they match with ?realistic SMA ? Your point is ?how come your measurements do not coincide with Ehrenfried's loop measurement. Well, probably you have been ?comparing apples with oranges¡ ? Raphael
From: [email protected] <[email protected]> On Behalf Of biastee via groups.io
Sent: Monday, September 30, 2024 2:50 AM To: [email protected] Subject: Re: [loopantennas] Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos ?
Hi Raphael, Actually, the low pass was the first topology I considered, if only for the reason it agrees with , which will then add legitimacy to my work. Unfortunately, the low pass dummy results in a modelled impedance (see the bottom right graph in ) that is totally incongruent with Ehrenfried's loop measurement. Moreover, the low pass dummy exhibits decreasing sensitivity with frequency, which is the opposite of observed small loop behaviour. Link to modelled gain of low pass dummy with LZ1AQ preamp below: ? It is not hard to understand why a low pass network will have the opposite gain / sensitivity response from the real loop. ?
Since you did not respond, I will assume that your concern has been addressed by the above statement. ?
Hi Martin, I just realized that I haven't answered this question. I agree with the statement. I have added a paragraph before fig. 5 to explain the balun placement trade-off. :-) Moving on, there will be a side-by-side performance comparison in version 2, either by me or someone else! ? Thanks again to all reviewers who have unstintingly given their time. ? 73, Chin-leong Lim, 9W2LC ? |
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Re: Mini-Whip recommendation?
Original PA0RDT Mini-Whips are the way to go!? Been using them for years. 73, Bill, WA2DVU Cape May, NJ
On Monday, September 30, 2024 at 04:16:24 AM GMT-4, Johan Bodin <jbodin@...> wrote:
Simon, You can buy an original Mini-Whip from PA0RDT Roelof Bakker himself. Contact information here: Johan SM6LKM rfsam wrote:
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Re: Mini-Whip recommendation?
¿ªÔÆÌåÓýSimon, You can buy an original Mini-Whip from PA0RDT Roelof Bakker himself. Contact information here: Johan SM6LKM rfsam wrote:
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Re: Mini-Whip recommendation?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> on behalf of rfsam <1rfsam@...>
Sent: Monday, September 23, 2024 12:54 PM To: [email protected] <[email protected]> Subject: Re: [loopantennas] Mini-Whip recommendation? ?
Thank you!
Simon
On Mon, Sep 23, 2024, 11:53?AM Oyster Town (G0IFS) via
<nigel_clayton=[email protected]> wrote:
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Re: Mini-Whip recommendation?
Hi Simon, roelofndb?(at)Regards, Jari On Mon, Sep 23, 2024 at 9:54?PM rfsam via <1rfsam=[email protected]> wrote:
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Re: Noise-Cancelling Passive Loop (NCPL)
Hi Gary and Martin and group,
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Gary - I am glad to try and answer any questions on your Shared Apex Loop project.
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Martin - thanks for the reference to the Shared Apex Group.
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Also, just would like to take the opportunity to thank this group for the excellent discussion and information on loop antennas and amplifiers. This is one of the few forums that I follow.
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73,
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Mark KB7GF |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Hi Chin-leong Lim,
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Understood about the switch, but I think the location of the balun is causing problems.
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Either build a separate balun, or obtain a switch.
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If you can't easily obtain a switch, email me with your address, and I'll post one to you for free, as I've got some in my junk box.
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Regards,
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Martin
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On Mon, Sep 30, 2024 at 07:45 AM, <biastee@...> wrote:
On the other hand, a the balun before dummy, it will require a 4PDT which is not readily available. |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Hi Martin,
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There is another compelling reason for my not choosing the balun before dummy configuration, but I have forgotten all about it.
I want to be able to re-use the balun for P1dB & OIP3 testing without involving the dummy. In the existing balun after dummy arrangement, a DPDT switch is all it takes to bypass the dummy:
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On the other hand, a the balun before dummy, it will require a 4PDT which is not readily available.
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73, Chin-leong Lim, 9W2LC |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Hi Raphael,
Actually, the low pass was the first topology I considered, if only for the reason it agrees with , which will then add legitimacy to my work. Unfortunately, the low pass dummy results in a modelled impedance (see the bottom right graph in ) that is totally incongruent with Ehrenfried's loop measurement.
Moreover, the low pass dummy exhibits decreasing sensitivity with frequency, which is the opposite of observed small loop behaviour. Link to modelled gain of low pass dummy with LZ1AQ preamp below:
/g/loopantennas/photo/297909/3835201?p=Name%2C%2C%2C20%2C1%2C0%2C0
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It is not hard to understand why a low pass network will have the opposite gain / sensitivity response from the real loop.
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Since you did not respond, I will assume that your concern has been addressed by the above statement.
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Hi Martin,
I just realized that I haven't answered this question. I agree with the statement. I have added a paragraph before fig. 5 to explain the balun placement trade-off. :-) Moving on, there will be a side-by-side performance comparison in version 2, either by me or someone else!
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Thanks again to all reviewers who have unstintingly given their time.
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73, Chin-leong Lim, 9W2LC
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Re: BFU590 strange behavior
Thanks for the reply, everything seems to be working fine now. As you have suggested I put two 33 Ohm resistors in series with the collectors of the two BFUs and now amplifier is regularly working. Now I have that absorption has normalized (now around 100-110 mA stable) and I am able to keep the voltage at the ends of 2.2 uF capacitor C3 with a little adjustment of 100 ohm trimmer, practically stable at 0V (so I also respond to Steve Ratzlaff who wrote to me privately) as well as from the description taken from the Wellgood loop pages here: https://www.george-smart.co.uk/projects/wellgood-loop/wellgood-loop-history/ Ok thank you very much. |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Good point Keith, English was not one of my better subjects at school, actually most of them fell into that category...
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On Sun, Sep 29, 2024 at 04:12 PM, keith Lockstone wrote:
The 'or' is inclusive not exclusive. |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
The 'or' is inclusive not exclusive. Keith.
On Sunday 29 September 2024 at 17:03:52 BST, Martin - Southwest UK via groups.io <martin_ehrenfried@...> wrote:
Art or science ?
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I'd say it's both.
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You can design something using scientific principles, but there are many ways of implementing it, which is where the "art" kicks in.
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Like good art, you instinctively know when you see a good design,
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Apart from form, function, cost etc. which all have a part to play, there is something else that makes it "elegant".
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It's knowing what to add in, and what to leave out...
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OK, that's enough nonsense for today, let's get back to the "nitty gritty"...
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Thanks for humouring me.
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Regards,
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Martin
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Art or science ?
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I'd say it's both.
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You can design something using scientific principles, but there are many ways of implementing it, which is where the "art" kicks in.
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Like good art, you instinctively know when you see a good design,
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Apart from form, function, cost etc. which all have a part to play, there is something else that makes it "elegant".
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It's knowing what to add in, and what to leave out...
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OK, that's enough nonsense for today, let's get back to the "nitty gritty"...
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Thanks for humouring me.
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Regards,
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Martin |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
OK....? I can't resist replying to the philosophical question: Creativity is art. Engineering is applying that art while still being faithful to the hard science of solving the problem. Dave - W?LEV On Sun, Sep 29, 2024 at 3:28?PM Raphael Wasserman via <wassermanr46=[email protected]> wrote:
-- Dave - W?LEV |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Hi Simon,
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You brought up an interesting point that engineering is not an art ( at least in electronics ).
I would say it is currently an art when you deal with designs of lumped elements on your board or switching photonic light pathways in fiber optics engineering.
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Raphael
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Martin,
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You raised a good question how to motivate people in engineering profession who hits the door of your department.
My question to them always was the same - what you can bring new to us ??
Every person who selected engineering profession and rising through his ranks knows very well where is the border between art and science.
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Have a pleasant day,
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Raphael
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Hi Martin
To answer your question.. its an art. I, me Simon know no where near as much theory as most on here do¡ yet I can look at an antenna ( say a Marconi T for 160m) and know within a turn or two on loading coil how many required, plus what L/ C to add to matching network..I can just ¡° see it.¡± Or an amplifier and make it work..however my Mum ( no longer here.) and Sister and I are artists..( paint, ceramic, (metal in my case..)) Cant explain it..just can. So i say its an art.. Simon g0zen Ps main job is on maritime vessels as engineer..( art dont pay.) |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Yeh well, excuse my digression.
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I used to manage a department full of different project teams, so this sort of thing interests me. How to motivate people, and at the same time, get stuff out of the door.
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One of my favourite questions to ask interview candidates, and get a discussion going was - Engineering, is it an Art or a Science ?
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I come from the North of England, and an old saying there is "'Owt's better than nowt."
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Number 30 on the list.
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Back to the mundane stuff...
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Regards,
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Martin
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On Sun, Sep 29, 2024 at 01:42 PM, Raphael Wasserman wrote:
Are we here to discuss philosophical trends or solve some technical-engineering issues ? |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Chin-leong LIm,
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A presence of writer's tunnel vision ? C'mon, don't be silly with that! You made my morning for a good laughing that positively effects the health. There I am on same page with Martin...
In order to design or propose a dummy antenna device, especially for small active antennae, I consider the antenna and its apmplifier should be as one integrated unit, where any elements between them shall not be altered ( that impedes comparison process between various SMA designs ). For example, if there exist balun, equilizer or filter they will stay unaltered ( not requiring additional elements ).?
If you experience issue of connection an unbalanced output of your VNA to balanced dummy antenna device input, worry about that connection correction exactly between these mentioned ports.
Your suggested dummy equivalent circuitry for SMA is wrong - the series element leg shall be inductance and shunt leg capacitor. In your design it is reversed.
There are some other shortcuts but I will allow you to find them on own.
In some extent it reminds me a story when I bought inexpensive chineese made SDR finding later that front end of preselectors perform funny. I discovered issues with their design - blindly copying western design and deciding to make a quick buck selling world wide. So, I redid that SDR. Later the owner of chineese outfit ask me to mail him all made corrections. I refused that because I do not like an idea of? stealing technical patents for profiting later. Anyone can reverse engineer some electronic devices but it should stay with that person.
Since you have been designed wrongly the dummy aerial, subsequentially all? your published graphs of frequency responses for a number of mentioned SMA shall be rerun as well.
Take a minute to suppress somehow your writer's tunnel vision. Your presentation of dummy antenna is a simplistic high pass filter with one section where the cutoff frequency is about the frequency of first parallel resonance of SMA. So, your frequency graphs should show attenuation between 0 and F0 ( resonance frequency ).
In actuality, the dummy antenna shall represent a low pass filter with same cutoff resonance frequency ( when it is used? as Thevenin's circuit presentation ).? All this discussion is for a bandwidth from LF up to resonant frequency unless you want to design a broadband dummy antenna beyond the resonance frequency.
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Good Day,
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Raphael
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Bill Riches
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