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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.

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.

Raphael Wasserman <wassermanr46@...> added the photo album Design of Chebyshev BPF and Results : Two cases: source load equal to load source load is complex unequal to load The following photos have been uploaded to the Design of Chebyshev BPF and Results photo album of the [email protected] group. Chebyshev 3rd order BPF ( synthesized )_0001.jpg Chebyshev 3rd order BPF ( synthesized )_0002.jpg Chebyshev 3rd order BPF ( synthesized )_0003.jpg Chebyshev 3rd order BPF ( synthesized )_0004.jpg By: Raphael Wasserman <wassermanr46@...>

Hello all, I am trying to troubleshoot an issue with a used Wellbrook antenna. When I set it up the day before yesterday, it was working very well! Then today I noticed a problem with an intermittent LED on the antenna interface not lighting up (as if no power was getting to the unit). I found some troubleshooting steps on this forum and checked the following and found to be good: 1. co-ax is ok (using new RG58) 2. Power is at 12 V to the unit 3. Red LED is now lit up. However, now there appears to be absolutely no signals being picked up, it's completely deaf. Is there something else to check? The only other thing I can think of is checking the connections to the loop at the amplifier (they are tightly taped by the previous owner, so I suspect they would be good). Thanks, Todd

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. Everett N4CY

The following photos have been uploaded to the Caaarlo LZ1AQ sweep photo album of the [email protected] group. LZ1AQ-MPS2222A-3-8MHz+transformer-sweep.jpg By: Caaarlo <caaarlo@...>

We misplaced the small Control Board for our LZ1AQ. Does anyone know how to purchase it only without the whole kit or how to contact the manufacturer to buy replacement? Thanks

Some additional power supply notes. I mentioned there is a severe problem in the way most circuit designs for the uA723 have an error. I said I thought 100 ohms was needed in series with the current sense, it is 1,000 ohms. Most fried uA723 are the result of not using that 1,000 ohm resistor. Re noise from batteries. Mr. Werner Ogiers is a severe audiophile. While I don't necessarily agree with severe audiophiles, I mean oxygen free cryogenically treated copper speaker cables strikes me as a bit unsane, there are some very smart and dedicated people in that clan who actually understand measurement. Mr. Ogiers has a series on power supplies and page 4 has noise graphs from chemical batteries. I doubted his data and performed some tests of my own. [forget the "Some people prefer the sound of the TL431 operating in non-unity-gain" on page 3, even very smart people have their delusions.] I used Rod Elliot's Low Noise Test Preamplifier at https://sound-au.com/project158.htm My Dataq data acquisition unit with the Low Noise Test preamplifier with SpectraPluse revealed that "Yyes chemical batteries do produce noise." Some batteries produce a lot of noise. And I mean A LOT of NOISE! https://www.tnt-audio.com/clinica/regulators_noise4_e.html Take it for what it's worth. I use Charles Wenzel's Reducing Voltage Regulator Noise https://techlib.com/electronics/finesse.html for all of my active antenna power supplies. For really critical, low current, needs I add a capacitor multiplier to the output. The noise is so low I can't measure it. Something all too many RF designers ignore is "rectifier commutation noise." https://www.microsemi.com/document-portal/doc_view/14617-rectifier-reverse-switching-performance [rectifier commutation noise is the term my favorite EE professor used.] I won't get down into the weeds over proper rectifier commutation noise snubber design but this can be a serious problem. By serious, I mean so bad as to render a very well designed linear power supply useless for RF work. One final note, there is no point in lowering your home grown EMI lower then the ambient RF noise floor, which, if you have AC power, telephone, cable TV, and neighbors within ~300 feet, will be rather high. Such is life and why my wife and I try to escape to a nature preserve so I can do some serious DXing.

Some interesting LF audio noise measurements on various devices, including some of our favourites. https://www.mvaudiolabs.com/diy/modern-jfet-noise-measurements/ Regards, Martin

This might, or might not, be of interest to group member, and might, or might not, be appropriate to place in the files section. I did a search in my randomly organized archive and found Chris Trask's "An Evaluation of Junction Field-Effect Transistors Suitable for Active Antenna Applications." This paper shows the curves of various JFETs and might be useful. The paper is from 2008, so it is a bit dated and it is for E-Field antennas and not loop antennas. If there is interest, and a group consensus it is appropriate, I'll drop it there tomorrow or Sunday with a better description of the file. Mr. Trask are you still a member and would you approve?

The following photos have been uploaded to the Caaarlo LZ1AQ sweep photo album of the [email protected] group. LZ1AQ-MPS2222A-3-8MHz+transformer.jpg By: Caaarlo <caaarlo@...>

A quick review of this forum provided no insight into this antenna. Please provide any comments regarding this antenna. TIA & 73 Chuck

Raphael Wasserman <wassermanr46@...> added the photo album IEEE Standard, 1931 : Radio Engineers' Handbook

The following photos have been uploaded to the IEEE Standard, 1931 photo album of the [email protected] group. IEEE Standard,1931_0003.jpg By: Raphael Wasserman <wassermanr46@...> Raphael Wasserman <wassermanr46@...> updated the photo album IEEE Standard, 1931 : Radio Engineers' Handbook

Raphael Wasserman <wassermanr46@...> added folder /IEEE Standard, 1931 Description: Radio Engineer's Handbook, Measurements on Radio Receivers with standard dummy antenna and loop antenna

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. 73, Steve AA7U

The following photos have been uploaded to the 9W2LC's LZ1AQ amp photo album of the [email protected] group. gra_sim gain @ L1.jpg By: biastee@...

The following photos have been uploaded to the 9W2LC's LZ1AQ amp photo album of the [email protected] group. cct_model.jpg By: biastee@...

The following photos have been uploaded to the 9W2LC's LZ1AQ amp photo album of the [email protected] group. dummy_Z--f_sim--g8jnj test.jpg By: biastee@...

biastee@... updated the photo album 9W2LC's LZ1AQ amp