Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Secondary of T1 is not more overcrossed like in Wellgood amp ALA clone?
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Hi, F.
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Thanks for the schematic diagram, Steve.
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Some days ago, I stumbled upon some nice 3D X-Ray images of what the author claims to be an ALA1530 amp, but that version uses only a couple NPN transistors. Do you know when did they redesign the amp with j-fets and how does it compare to the simpler bipolar version ?
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73,
Caaarlo.
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Re: JFET matcher using an OpAmp
Yes. It will be interesting to see how well the j-fet's that matched with the op-amp circuit still match well with the TC-1. Let us know.
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Re: JFET matcher using an OpAmp
On Sun, Jul 21, 2024 at 09:00 PM, Tom - VE3PSZ wrote:
You can also buy a very inexpensive TC-1 Multi-Function Tester...
The only issue I see with the CSI-TC1
https://www.circuitspecialists.com/content/430516/csi-tc1.pdf
Is the Id is tested at 3.56V for 6.3uA per the manual. I'm not sure the TC1 is suitable for serious matching.
It looks to be useful for general device testing. It should be here Thursday of Friday, if Crowdstrike hasn't screwed up UPS.
I'll compare the TC1 with my FET matcher and post the results.
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
This is just a very tiny piece of data for wellbrook-archeologists. Redarding FLG100LN, shipped November 2020:
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"You have latest model with 26dB gain. Kind regards, Andrew."
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73, Jukka
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Re: I've posted JFET Evaluation for active antennas Trask
I'm having problems sending you a copy of the Russian document.
Your article appears as pages 29-34 of a much longer document. If
you google the title of your document the Russian link shows up at
the end of only a few entries. There's also a German site
mentioned. The best I can do is a text version of the Google
entry.
domcxem.ru
infocenter> Характер... DOC :
Характериограф для транзисторов
Chris Trask/N7ZWY, "An Evaluation of Junction Field-Effect
Transistors Suitable for Active
Antenna Applications", 4 December 2008. В.Б. ГАМАНЮК, Н.Г. ..
Regards, Ian Brooks, Dorset, UK.
On 21/07/2024 14:32, Chris Trask -
N7ZWY/WDX3HLB via groups.io wrote:
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I'd like to see that Russian
verswion. Could you forward it?
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Chris
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When the going
gets weird, the weird turn pro
- Hunter S.
Thompson
-----Original Message-----
From: <loopantennas@groups.io>
Sent: Jul 20, 2024 8:44 AM
To: <loopantennas@groups.io>
Subject: Re: [loopantennas] I've posted JFET Evaluation for
active antennas Trask
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I found this in my saved documents on my PC. The weblinks on
the net no longer work, but I did find a? MS Word version in
Russian.
Regards, Ian.
On 20/07/2024 16:34, wn4isx via
groups.io wrote:
I've posted JFET Evaluation for active antennas Trask in
the files section.
A very nice paper on various JFET response.?
While the paper is for E-Field antennas, the data is
valid for any JFET application.
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Hi Steve,
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OK, if that's what Andrew said he used, I'll happily accept that.
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The cores in mine were different to 73 mix, but he may have changed makes or suppliers over time, or perhaps more likely, Fair-Rite may have changed the formulation, as they have done with other mixes.
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In the UK, it used to be quite difficult to get hold of different Ferrite materials, unless you bought directly and in quantity. Fair-Rite only became easily available a few decades ago, when the main distributors started stocking their product range.
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On Sun, Jul 21, 2024 at 07:42 PM, Steve Ratzlaff wrote:
He told me he uses the Fair-Rite 2873000302
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Hi Mike,
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On Sun, Jul 21, 2024 at 08:19 PM, Mike M wrote:
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Comparing your schematic to Steve's I see a few differences:
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- The secondary of T2 is directly connected to ground in Steve's and through capacitors in yours.
That's how it was
- 1.2k to ground at the output.
2.7K ? I don't know why it was there, but I double-checked when I saw it, and it was definitely present.
- As noted, 41pF instead of 82pF across loop.
The input transformer was actually 3 + 3 turns centre tapped, but the tap wasn't connected to anything.
- As noted, R4 is 500k instead of 1k
That is a mistake, the part was damaged during the reverse engineering process of boiling the assembly to remove the epoxy. I couldn't check with a multimeter as it had snapped in half, and the coloured bands were unclear. I assume it was actually a much lower value, and 1K or 500R is probably more likely.
Static bleed, as the loop is "floating" above ground. The input transformer centre tap was not grounded or connected to anything else.
That's how it was
- I assume R1 is to bleed of static charge. What is R6 for?
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I have no idea why it was there. As the unit was hand made on stripboard, it may have been meant to be connected somewhere else in the circuit. Or maybe it's serving some other purpose during assembly and test ?
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- Are all of the differences from tracing a different unit or are some things your own changes?
I produced the circuit diagram directly from what I saw and measured in a faulty unit I had been given. I carefully picked the resin away from the circuit board after boiling it for an hour to soften the material.
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The transformers were the most difficult part to understand, as the binocular cores were full of resin. I had to cut the windings and count the number of wire ends to determine the number of turns. I measured the resistance and reactance curves of the ferrite material using a VNA, and compared it with test windings on same sized cores using different materials. It was similar to 73 mix, but a closer fit to N30. The wire numbering in my diagram is incorrect, as there are two number 4's.
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It could be that my unit was an earlier version, in comparison to the ones that others have taken apart, due to the "kitchen table" construction, slight differences and errors have probably crept into each build, and the design may also have "evolved" slightly over time.
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I will revise the diagram and repost it to correct the mistakes.
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Regards,
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Martin
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Re: Urban HF Antenna Dilemma: LZ1AQ vs. M0AYF
Hi Caaarlo,
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I reviewed for a curiosity your work. You designed a BPF as a pre-selector between your LZ1AQ amplifier and the loop antenna. You tested the cascaded together networks by running S21 sweep with VNA. Additional element was 16:1 input RF transformer between the VNA and the balanced in design BPF.
You graphical plot represents case when the source resistance is 50 ohms divided by 16 and and is equal to the load resistance (input of LZ1AQ amplifier 3 Ohms, based on
Levkov's data ( case Rs=Rl=3 Ohms ). Further you concluded that actual inductance of loop 3 uH and antenna loss about? Ra=0.5 Ohms as a source impedance will not change drasticaly the frequency characteristics of your design, allowing to have a flat response within your specified bandwidth.
Unfortunately, the realistic result will be different because Zsorce is unequal to Rload.? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I synthesized a similar Chebyshev 3rd order BPF and simulated the designs for two cases:? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?1. Rs=Rl is purely resistive? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?2. Zs is complex impedance and is unequal to Rl ( actual our case ).
Please find among submitted four photo files - the album is titled "Design of Chebyshev BPF and Results".
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Regards,
Raphael
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Re: Wellbrook antenna troubleshooting help
Thank you, I tried that and also did some
current measurements on what the amplifier is drawing, only
about 50 to 90 mA, when it should be from 100 to 150 mA, so I
suspect a problem with the amplifier.
Best regards,
Todd
VE7CKZ
On 2024-07-21 5:53 a.m.,
enriqueeeeee2001 via groups.io wrote:
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First, disconnect the anttena, Is the red light on?? My
antenna interface is like yours, has a resettable fuse too.
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Ckeck your power supply, and check the interface output with
a voltmeter
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Re: Wellbrook antenna troubleshooting help
Thanks Martin,
I measured the current and I get from 50 to 90
mA, so I suspect there is a problem with the amplifier.?
Best regards,
Todd
VE7CKZ
On 2024-07-21 12:19 a.m., Martin -
Southwest UK via groups.io wrote:
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Hi Todd,
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Measure the DC current being drawn by the loop amplifier,
somewhere along the coax feeding the loop.
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This will determine that power is actually reaching the
amplifier, and if the devices are OK.
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The current will ?most likely be in the region of 100 to
150mA if it is working correctly.
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It is possible the previous owner has accidentally
transmitted into to loop interface and caused damage. This has
happened to the majority of faulty ones I have been asked to
look at.
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Regards,
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Martin
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Re: JFET matcher using an OpAmp
You can also buy a very inexpensive TC-1 Multi-Function Tester on Amazon and other sellers for less than $25. It will allow you to test and match J-Fet's as well as mos-fet's, bipolar transistors, diodes, LED's, resistors etc. Tom
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Re: JFET matcher using an OpAmp
How important is gate capacitance?
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https://www.ti.com/product/JFE2140?bm-verify
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From
https://www.ti.com/lit/ds/symlink/jfe2140.pdf
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Low input capacitance: 13 pF at VDS = 5 V
? High gate-to-drain and gate-to-source breakdown
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The 2SK715 has 10pF gate capacitance.
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The jfe2140 has a slew of diodes for protection.
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I clearly don't know enough to have any idea if the jfe2140 is suitable for a loop antenna electronics.
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The jfe2140 costs $4.39 (on July 21, 2024) from Digikey.
It'd be interesting (and no I'm not asking) to learn what?
Everett uses in his clones.
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FWIW, I hate winding confusing transformers, as a dyslexic, it is way too much like tying obscure knots.
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Re: JFET matcher using an OpAmp
The TI JFA2140 is a matched pair of JFETs on a single die. No need to test and select.
Rick N6RK
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On 7/21/2024 10:11 AM, wn4isx wrote: On the off chance there is interest in matching JFETs for a clone of the Wellbrook loop antenna, I've posted a PDF of a simple and effective unit.
Layout isn't critical, I constructed mine on vero-breadboard with 0.1" centers and used point to point wiring and mounted it ~1/8" above an unetched PCB for a ground plane.
Note 1: I did not design the unit, I built one late last night and tested a bunch of 2N3819.
A lifetime ago, 1975, I was given several hundred prime TI 2N3819s. Sadly the 2N3918 isn't the most useful JFET but it was nice to test 50 and find 3 that matched extremely closely.
YMWV
Note 2: The 2n3819s aren't for sale.
The file name is
JFET-matcher-rullywow.com-Build-Doc-v1.01.pdf
It can be found in the files section.
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Re: Wellbrook ALA1530 Clone for sale
I should have said that the amp is a Wellbrook ALA1530LN.
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Everett
In a message dated 7/21/2024 3:11:43 PM Central Daylight Time, everettsharp@... writes:
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If anyone is interested I have a Wellbrook ALA1530 clone for sale. It is built with SMD JFETs. You can contact me off list if interested. everettsharp (at ) aol com.
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Everett N4CY
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Steve,
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Thanks! Yes, that is an "R", not a "k" on the trimmer on closer inspection!
--
===================================================================
Mike M
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Martin,
?
Comparing your schematic to Steve's I see a few differences:
- The secondary of T2 is directly connected to ground in Steve's and through capacitors in yours.
- 1.2k to ground at the output.
- As noted, 41pF instead of 82pF across loop.
- As noted R4 is 500k instead of 1k.
- R1 at input.
- Extra ferrite beads.
I assume R1 is to bleed of static charge. What is R6 for?
?
Are all of the differences from tracing a different unit or are some things your own changes?
--
===================================================================
Mike M
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Wellbrook ALA1530 Clone for sale
If anyone is interested I have a Wellbrook ALA1530 clone for sale. It is built with SMD JFETs. You can contact me off list if interested. everettsharp (at ) aol com.
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Everett N4CY
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Re: Urban HF Antenna Dilemma: LZ1AQ vs. M0AYF
I might play a bit with the inductors and try to improve the pass band at around 3MHz, but I guess the overall behavior of the filter is quite acceptable. This is with a resistive source. THe loop is inductive and according to the simulation. the "flatness" does not change much between a 3uH loop and 50 ohm resistive source.
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Caaarlo
Ian Brooks
Everett N4CY