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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
Whenever I check presmps for whatever purpose, I always assure the input level to the presmp is around -45 dBm.? I use the Rigol SA equipmed with the tracking generator.? The generator is set to -20 dBm (the minimum).? I add another 25 dB attenuator to that for a total of -45 dBm.? Dave - W?LEV On Sat, Jan 4, 2025 at 7:21?PM Steve Ratzlaff via <ratzlaffsteve=[email protected]> wrote:
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Dave - W?LEV |
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
开云体育Yes, Tom is correct-- it's entirely possible a second attenuator is needed on the VNA's receiver S21 port to prevent overloading the VNA. The specs of the VNA should state the max S21 input. The other consideration is not overloading the preamp DUT--input impedance S11 and gain S21 will not be correct if the DUT is overloaded. I like to ensure the DUT test output is not much over 0 dBm--a decent preamp should not be overloading at that level. The ALA1530LN has about +22 dB peak gain--so for 0 dBm output that would be -22 dBm input. Most of the inexpensive nanoVNAs have a fixed transmit S11 output, usually in the +10 dBm to -10 dBm range--the VNA specs should tell what that level is. Knowing that along with the DUT gain, you can get an estimate of the input attenuator required. 73, Steve AA7U On 1/4/2025 5:10 AM, Tom ANderson via
groups.io wrote:
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Re: OptiLOUPE for OptiVISOR
I use a cheap Chinese copy using plastic lenses, that originally cost around ?8 GBP.
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It has a second drop down lens behind the first, to further increase the magnification, plus a single swivel monocular.
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It also had a pair of incandescent bulbs, either side of the headband, which I have swapped out for LED's powered by rechargeable cells, recovered from discarded disposable vapes, I often find littering the street.
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It works well enough for my purposes, as I still have to wear my prescription spectacles underneath, because they have corrective prism lenses.
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I also just acquired from AliExpress, a cheap <?20 GBP video microscope, with a desk mounted angle poise stand. This works really well when used close up, and can be connected to a PC for a larger display, or for taking videos and snapshots of items being viewed. The contrast isn't quite as good when the object being viewed is a few inches away, such as when soldering a PCB, but it's generally OK. The anglepoise stand is a great addition, as I can quickly swing the whole thing out of the way, when I don't need it.
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Here are some are typical listings.
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Updated version of my headband magnifier
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Some other styles
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4.3" digital microscope
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Anglepoise Stand
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All of these types of aids can be of considerable use, especially as we age. I tend to use SMD components most of the time, even when breadboarding circuits using "dead bug" or "Manhattan" style construction, and I don't really find it any more difficult than using much larger through hole components.
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Regards,
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Martin
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On Fri, Jan 3, 2025 at 09:46 PM, Mike M wrote:
The OptiVISOR is one solution: |
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
开云体育?Francesco, I want to say I might be wrong here so, please double check me. In your drawing you show the 20db attn connected to the input of the amp I assume this is to prevent over driving your amp. ?However, you do not have an attn on the output side.
Is this accurate? ? I have read that you will damage your VNA if you apply to much of an input. S21 port, So in my mind, you should have an attn on both the input and output to protect the VNA? ?If this is not necessary please let me know.
Good luck in your efforts? ? Tom Anderson SDR_Radio@...
On Jan 4, 2025, at 6:03?AM, Francesco Caizzi via groups.io <netsmo62@...> wrote:
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
Good morning, sorry if I didn't answer all the appreciated replies but yesterday I sat there to do some tests and I have to say that maybe the apparent poor sensitivity on the low ranges of the LN amplifier can also be attributed to the positioning of the loop? In fact I moved the test loop (1 mt) inside the laboratory connected to the T-Bias with another shorter test cable (even if the longer external cable is fine) and things seem to be going better. It is true that maybe positioning the loop on a branch of a tree (about two meters high) with a metal net less than three meters away plus one of those mobile shelters for cars probably also made of metal structure, with a sheet metal shed on the side also less than three meters away... maybe it's not the best condition for this reception band, while on others with other types of propagation it goes decidedly better. I tried with the sample made both with the two types of jfet (2SK932 and original 2SK715) and with the normal two transistors amplifier with the BFU590 (qx) and the results are more or less similar, so... I don't think there are problems of construction or electronic components. Having said that, I answer individually to those who answered me:
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Dave Martin: What do you mean? The coupling capacitors are those in the diagram, already used similarly in other amplifiers.
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Tom VE3PSZ: Ferrite material is always 73. BN 73-302 ferrite core.
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Steve Ratzlaff: Yes, I have had a NanoVNA from some time and in fact I really needed to understand how to do some bench tests of the amplifiers with that instrument. I made a diagram that I put together with the photos of the two boards, to understand if I understood well how to make the connections you suggested, if you can take a look at it... /g/loopantennas/photo/299839/3872714?p=Created%2C%2C%2C20%2C2%2C0%2C0
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Martin Southwest UK: Windings are correct, I have always taken into account the construction diagrams that appeared on the Wellgood Loop page which are always valid. However, for the test I tried to invert or rather "rectify" the connection of the secondary of the first transformer and obviously the amplifier DOES NOT WORK AT ALL...
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Everett N4CY: In the meantime, thanks for the private replies, that's why I asked you if you sell an unpopulated board of your version to see what differences there may be... mine is already double-sided, since SMD elements need to be mounted. I also did some tests with the insulation of the copper wires from the ferrite body using 3D printed insulators and although I can confirm that the 73 material conducts (we are about 25-30 Kohm) at least audibly I don't see/hear differences, which surely there will be instrumentally...
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On the side of the discussion, yesterday I also tried to build the "Everett N4CY" version of the LZ1AQ amplifier using 4 BFU590GX transistors (the ones in the bigger case) and I have to say that the first tests are really impressive, at least inside my lab it receives better than the LNs and even better than the original LZ1AQ that I also placed outside hanging from a tree and powered via CAT7 network cable!! I was really amazed...ok thanks to everyone, Francesco Caizzi IU4TSV
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OptiLOUPE for OptiVISOR
Not affiliated with them but have used them ever since I was trying to solder and wondered why I couldn't focus close enough.
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As you age you inevitably run into the issue. The OptiVISOR is one solution:
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I am posting this because I just got the OptiLOUPE accessory and it works really well. I could read the markings on a SOD-123 diode:
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As I understand it the OptiVISOR has glass lenses and the OptiVISOR LX has plastic lenses. The plastic lenses may not be as good, so bear that in mind if you are looking.
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I have the DA-4 lenses for the OptiVISOR and they work well for soldering surface mount components. I have the DA-5 lenses on the way. Thought I would see how they compare to the DA-4.
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=================================================================== Mike M |
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
开云体育Hi Francesco, Have you used a nanovna to sweep the gain and input impedance? You'll need a 1:1 input transformer (unbalanced to balanced). You'll also need an attenuator on? the nanovna TX output to reduce the level, I'd suggest something like 20 dB so the loop amp isn't being overloaded. If you sweep it please post the results. 73, Steve AA7U On 1/2/2025 11:55 AM, Francesco Caizzi
via groups.io wrote:
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
I have built several from the esign in:
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So far two of he 1530 configuration and one of the 100 configuration have been built and tested. The PCB is designed to fit into a Hammond 1555E2GY enclosure. It is two sided with ground fills on both sides.
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Since it is winter here I have not tested them outside but have done preliminary 3/4MHz IMD tests.
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=================================================================== Mike M |
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
I can't see anything called "Wellbrook_Loops.Kicad_sch" in the files section, can you provide a link ?
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Regards,
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Martin
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On Thu, Jan 2, 2025 at 06:55 PM, Francesco Caizzi wrote:
the schematic found in the files section named "Wellbrook_Loops.Kicad_sch." |
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
Yes, I understand that, but if it is close to oscillation, due to incorrect transformer phase, the gain can appear to be much higher at mid-frequencies.
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I have seen this myself with some builds.
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Regards,
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Martin
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On Thu, Jan 2, 2025 at 07:46 PM, Everett N4CY wrote:
His ALA1530LN clone is working on 7 MHz without any problem, but in not working on 2MHz and below. |
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
Martin,
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His ALA1530LN clone is working on 7 MHz without any problem, but in not working on 2MHz and below.
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Everett
In a message dated 1/2/2025 1:28:50 PM Central Standard Time, martin_ehrenfried@... writes: ?
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
Have you got the transformer feedback windings in the correct phase / direction ?
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It's a 50:50 chance of being the right way around if you build it yourself, don't ask me how I know :-)
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Have you used the correct ferrite cores and the required turns ratio's ?
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Regards,
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Martin |
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Re: LN 1530 Wellbrook amplifier replica deaf on LW - MW
I think you may have a oscillation problem that is causing your problem on the lower frequencies. You need to make the board more compact and you need double sided copper shielding on the board.
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I have designed several PCBs for the ALA1530LN and they all work fine, with no oscillation issues.
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Everett N4CY
In a message dated 1/2/2025 12:55:57 PM Central Standard Time, netsmo62@... writes: ?
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LN 1530 Wellbrook amplifier replica deaf on LW - MW
Good morning, I'm wondering if anyone like me has made a full working Wellbrook 1530 LN amplifier based on the schematic found in the files section named "Wellbrook_Loops.Kicad_sch." with smd 2SK932 jfets (but others schematics are very similar) I'm asking because I made a couple of them over time, one even with the original 2SK715 jfets but in the end they have the same problem, that is, they seem completely deaf up on LW and MW to the shortwave range, where they work much better...a classic amplifier with only two transistors (BFU590QX) works regularly. I tested the jfets (taken from the European electronics e-commerce portal TME) and they are all ok, the absorption is normal at about 115 mA at 12V. The toroid windings are the ones described on the schematic: input P3/S12 (plus the two single turns) secondary with crossed wires - output P9/S5. Test loop hang from a tree in my garden at about 2 mt. from ground.? I'm adding the link with a short video and I've put two photos of the boards so you can see the construction. Thanks in advance, F.
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Re: 2N5109 amp directly biased with ZD
Thank you all for your advice and experiments.
It looks good, so I was wondering why I hadn't seen it. As for the noise, I am not too worried. in last year I tried a noise generator with zener diode. However, did not get the Noise level that I expected, Anyway, I will try this style with 2SC3357 during the New Year holidays. I don't have a low voltage zener diode so will try it with LEDs. of course it may replace to the common resistor divider. I wish you all peace and health in 2025. 73, Hisami 7L4IOU |
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Re: 2N5109 amp directly biased with ZD
I do not see a compelling reason to use 2N5109 for new designs, it is an obsolete part. Central and Microchip terminated the production. The last direct equivalent, the NTE278 is discontinued since last year. New 2N5109 are chinese substitutes, some of them are of decent quality, some are not.
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For temperature compensation it may make sense to use a Diode to bias a transistor. Avoid Zener/avalanche diodes, they generate noise. LEDs may make sense, if you can double use it as power indicator.
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regards
Fred |
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Re: 2N5109 amp directly biased with ZD
开云体育In all these common base preamp circuits it doesn't matter what
type of base bias is used--I've seen a LED used in place of a
standard 2 cent resistor, so using a 25 cent zener diode is just
another way. The emitter resistor is varied to set the desired
overall current. I built the circuit just now; I used Steward fat toroids for the two transformers, but that doesn't matter much either. My bag of 3.3V zeners gave one that had an actual 3.0V; the final emitter current was 28 mA with the 13V supply shown--the circuit showed 31 mA so mine was close. I used a genuine Central Semi 2N5109. I used the 0.1 uF caps as shown. I used the DG8SAQ VNWA to measure gain and input/output impedances. My circuit had peak gain of +9.2 dB at 1 MHz; +9.0 dB at 10 MHz; +8.2 dB at 30 MHz. Input impedance was 23 ohms at 1 MHz, 27 ohms at 10 MHz, 45 ohms at 30 MHz. Output impedance was 111 ohms at 1 MHz, 116 ohma at 10 MHz, 150 ohms at 30 MHz. IMD with? 3 and 4 MHz test tones set for 0 dBm at preamp output: 1 and 7 MHz +60 dBm OIP2; 2 and 5 MHz +43 dBm OIP3. P1dB measured at 1 MHz with 50 ohm load: 0.12 watts = +20.8 dBm. HP noise figure meter, 10 MHz 3.75 dB noise figure. I would say don't waste your time with this circuit. You could use a standard Norton circuit with much better NF, better in/out impedances for the same current as this circuit uses. Use standard resistor base bias. The article's goal was a decent HF-higher bands preamp for the old Atlas? 210 transceiver--the Norton would have been a better preamp circuit than this one. 73, Steve AA7U On 12/30/2024 4:55 PM, hisami dejima
via groups.io wrote:
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Everett N4CY