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Photo Notifications
#photo-notice
Group Notification
The following photos have been uploaded to the IEEE Standard, 1931 photo album of the loopantennas@groups.io group. By: Raphael Wasserman <wassermanr46@...> Raphael Wasserman <wassermanr46@...> updated the photo album IEEE Standard, 1931 : Radio Engineers' Handbook |
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Added photo album IEEE Standard, 1931
#photo-notice
Group Notification
Raphael Wasserman <wassermanr46@...> added the photo album IEEE Standard, 1931 : Radio Engineers' Handbook |
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Added Folder /IEEE Standard, 1931
#file-notice
Group Notification
Raphael Wasserman <wassermanr46@...> added folder /IEEE Standard, 1931 Description: |
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Hi Steve,
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There has been a bit of variation in the build of the Wellbrooks.
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The one I took apart had two 82pF capacitors, each one connected across half of the transformer primary. I suspect they were originally intended to provide better rejection of strong FM broadcast signals, but it was a "happy accident" that they also improved the performance on the upper HF bands.
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The core material was closer to N30 (u' 4,300) (Epcos ) rather than 73 mix (u' 2,500) , which would tie in with the FG100LN additional transformer, that used something like the higher permeability x38 material (u' 10,000). My thinking is that the Epcos N30 cores would also have possibly been easier to obtain in the UK, when the Wellbrook was initially designed, as RS were pretty much the only big electronic parts supplier at the time, and was used by nearly everyone.
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Using back to back diodes across the loop terminals is fine, however that is not true for other types of antenna, with higher feed point impedances.
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I have tried CPH3910 fets and they work, but a lot depends upon your requirements for frequency coverage.
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Regards,
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Martin |
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
I wish those diagrams works, if my Wellbrook ALA100M someday stop working I will be totally lost, the urban noise in my location is very high. ? It would be nice that somebody in this group could sell them mounted or al least in kit , if allowed. |
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
I don't know much about semiconductor physics. So, my layman's guess is that the 2SK715 must be larger / wider than common JFETs because Yfs scales with gate width. A 90s era JFET intended for AM tuner, BF862A has yfs = 45 mA typ.
Not JFET, but useful for comparison. The more recent ePHEMTs have even higher yfs. The ATF-55143 0.5 x 400 um (Lgate x Wgate) is 220 mS typ., while the ATF-54143 at 0.5 x 800 um is 410 mS typ.
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73,
Chin-Leong Lim, 9W2LC
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p/s where can I find your measurement data on the mini-whip? thanks. |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
On Wed, Jul 17, 2024 at 11:53 PM, <biastee@...> wrote:
Additionally, the Wellbrook teardown showed two pairs of anti-parallel 1N4148 at the input which would have made Owen Duffy sneered in disgust :-). Read Duffy's scathing dismissal of "diodes connected to antennas": ? Thats a valid point for most antennas. But the expected voltages across a small loop in lo-Z shortcut mode are much lower than at fullsize or hi-Z e-field antennas. But in principle i absolutely agree with your advice to avoid antiparallel diodes. Better use biased diodes or bidirectional ultra low capacitance TVS Diodes.
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regards
Fred |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
> ?downloaded IEC 315-1 standard. Item 20 - "Antenna Simulation Networks?
> Artficial Aerials )" basically covers three type of antennas: open-wire? > antenna 100 KHz - 30 MHz, rod and telescopic antennas? ?
The above comment made me realized the Indian version is far less descriptive than my photocopy of the (cutthroat) original. IMHO, the missing information renders the Indian version useless. So, please view the following:
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> I found in IEEE Standard, 1961 the details about the?
> recommended dummy antenna impedance that mimics? > open-wire antenna: Za=1500 Ohms @ 500 KHz, 200? > Ohms @ 2 MHz and 400 Ohms @ 10 MHz. ?
Can you kindly point me to the document? Thanks.?
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> I thought Steve Ratzlaff did some "unpotting" amongst others
> Maybe we need to find out what they found. > I remember seeing results from at least two "unpottings" > I would think an optimized impedance matching over a relativity?
> large frequency range was super critical. ?
Martin's website (now defunct?) pointed to .?According to the teardown, there is no LPF in the Wellbrook amp, save for a pair of 82 pF caps at the input. Hence, there's NO impedance matching at the input that tracks the loop impedance changing with frequency. AFAIK, only LZ1AQ with its LPF has an input impedance that track the loop's - albeit a "happy accident" in Martin's word.?
Additionally, the Wellbrook teardown showed two pairs of anti-parallel 1N4148 at the input which would have made Owen Duffy sneered in disgust :-). Read Duffy's scathing dismissal of "diodes connected to antennas": ?
Duffy's concerns over PN diodes (e.g. 1N4148) causing intermodulation can be addressed by substituting with long lifetime PIN diodes. So, as (ex) application engineer for PIN diode limiters for over 2 decades, I must lend my wholehearted disapproval, too! :-)?
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> Ikin knew all that decades ago !!!!!!!!!!
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I do NOT relish in building and evaluating so many designs - LZ1AQ, PA0FRI, M1GEO, & MLA-30, etc. So, if someone can furnish me with quantitative data showing that Ikin's Wellbrook is the undisputed performance leader, then I will throw the other designs out of the window and fully embrace the Wellbrook! :-)
Digression: Almost all active whips have high input Z. Interestingly, there is contrarian design which sports low input Z using feedback in order to achieve high IP3 (53 dBm). Hmmm... low Z like LZ1AQ minus the LPF :-) https://analog-electronics.tudelft.nl/downloads/NordholtActiveAntenna.pdf |
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
The 2SK715 jfet used in the original has a typical yfs of 50 mS--which is much higher than any other jfet--somehow Andrew Ikin discovered them. When the circuit was first traced out I built a copy and verified it worked the same as an original Wellbrook ALA1530LN. I experimented with other jfets, none came close to working like the 2SK715. I also experimented with different paralleled jfets--I tried one, two, three in parallel (4 in parallel each side on the original). The input impedance steadily decreases as jfets are added--Andrew Ikin apparently decided 4 in parallel gave him the desired input impedance with the input transformer turns ratio he used, for the small one-meter diameter loop. 2SK715s were still available when I first traced the circuit out, though they were already listed as "obsolete", and I was fortunate to get some for my tests.
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73, Steve AA7U On 7/17/2024 5:44 PM, Steve Ratzlaff via groups.io wrote:
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Wellbrook traced-out loop amp schematics uploaded to Photos
开云体育I made a folder in Photos just now and uploaded the schematics
for ALA1530LN, ALA100LN, FLG100LN that I've traced out in the
past. There should be complete info there for anyone to be able to
make their own. The original leaded 2SK715 jfets are now
unobtainable, but there are two SMD equivalents that work just as
well, with the 2SK932 preferred since its typical yfs is the same
as the 2SK715. One should be able to make one of these for around
$50--maybe less. On eBay I see a Chinese seller claims to be
selling an ALA1530LN or an ALA100LN for a very high price of
around $250, for the loop amp alone! I have no idea if it's a
direct clone of the Wellbrook. /g/loopantennas/album?id=296460.??? The name of the folder is "Wellbrook official traced-out schematics ALA1530LN, ALA100LN, FLG100LN". 73, Steve AA7U On 7/17/2024 2:15 PM, Paul V Birke via
groups.io wrote:
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Re: 2e0ero Magnetic Loop Antenna
i was just grumbling that i could not add a picture .. all good
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soooo ... anybody who wants to take a look .. look my qrz page dg9bfc sigi Am 14.07.2024 um 15:53 schrieb Simon: Hi Sigi |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
There are various people who have un-potted, various antennas.
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The details of the designs were are discussing are known, and typically feature input Low Pass Filter Networks.
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Regards,
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Martin
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On Wed, Jul 17, 2024 at 09:15 PM, Paul V Birke wrote:
I thought Steve Ratzlaff did some "unpotting" amongst others |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Dear Martin I thought Steve Ratzlaff did some "unpotting" amongst others Maybe we need to find out what they found. I remember seeing results from at least two "unpottings" best wishes Paul
On Wednesday, July 17, 2024 at 03:03:33 p.m. EDT, Martin - Southwest UK via groups.io <martin_ehrenfried@...> wrote:
Hi Paul,
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Well, I guess we are all "standing on the shoulders of giants" in one way or another.
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The key thing is to build on that, and continue to move things forward.
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Regards,
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Martin
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On Wed, Jul 17, 2024 at 05:31 PM, Paul V Birke wrote:
I can only wonder what we have lost in your great British genius passing away. |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Martin and Chin-Leong,
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I found in IEEE Standard, 1961 the details about the recommended dummy antenna impedance that mimics open-wire antenna:
Za=1500 Ohms @ 500 KHz, 200 Ohms @ 2 MHz and 400 Ohms @ 10 MHz.
That tells me IEC 315-1 Standard, especially with requirement that " the network impedance shall match the signal source to a sufficient degree of accuracy" is for birds...
So, the design of dummy small loop antenna will include less uncertainties.
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Raphael |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Hi Paul,
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Well, I guess we are all "standing on the shoulders of giants" in one way or another.
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The key thing is to build on that, and continue to move things forward.
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Regards,
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Martin
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On Wed, Jul 17, 2024 at 05:31 PM, Paul V Birke wrote:
I can only wonder what we have lost in your great British genius passing away. |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Dear Martin Andy likely was the most knowledgeable receiver loop GURU on the planet!! (A good friend of mine bought one of his antennas LF here in Canada and could not say enough about it,) All that potting went to hold his engineering secrets from all "potential stealers" That was his livelihood on the line !! So he must have had a literally strong grip on what "elements were important for his outstanding loop antenna performance. I would think an optimized impedance matching over a relativity large frequency range was super critical. I can only wonder what we have lost in your great British genius passing away. p
On Wednesday, July 17, 2024 at 01:16:58 p.m. EDT, Martin - Southwest UK via groups.io <martin_ehrenfried@...> wrote:
Hi Paul,
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I'm not exactly sure what you are referring to, but maybe he did.
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Unfortunately, he is no longer around to be able to provide any information, so although it may seem that we are retracing his steps, there isn't really much else we can do.
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Do you have any details, that may further assist us in our quest for knowledge ?
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Regards,
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Martin
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On Wed, Jul 17, 2024 at 04:57 PM, Paul V Birke wrote:
Ikin knew all that decades ago !!!!!!!!!! ?
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?
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
Hi Paul,
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I'm not exactly sure what you are referring to, but maybe he did.
?
Unfortunately, he is no longer around to be able to provide any information, so although it may seem that we are retracing his steps, there isn't really much else we can do.
?
Do you have any details, that may further assist us in our quest for knowledge ?
?
Regards,
?
Martin
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On Wed, Jul 17, 2024 at 04:57 PM, Paul V Birke wrote:
Ikin knew all that decades ago !!!!!!!!!! ?
?
? |
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Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos
get a grip !! u could not even spell my name correctly Paul Victor BIRKE ( BASc Toronto MEng McMaster )
On Wednesday, July 17, 2024 at 01:05:54 p.m. EDT, Raphael Wasserman <wassermanr46@...> wrote:
Paul V Burke,
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Do you have Frankenstein's brains ?
Are they lumped or distributed enough ?
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