under construction


Handwritten code made with Cute-HTML

        A collection of radio oriented diagrams,        
add-ons and designs


Always    busy    all    those    years   ...............


walter PE1ABR
In the seventies... RTTY on a VDT (TV-set)!!
There were NO home computers yet!
Demonstration IQ-nullius terminal!!


walter PE1ABR
In the early eighties... one more time RTTY
And some repair and alignment
Homebrew counter PLL (T-aerial!) in action


walter PE1ABR
In the late eighties... again RTTY on a real homemade VDT
JRC NRD-515 range available!!
ME, tuning a custom designed VFO for my NRD-515


©CopyRight,  modifications add-on design, drawings, photographs,
 gal programming, and research by: W.A.J.  Geeraert  ( PE1ABR )    email

Click over   HERE   for some utilitiesnew
to work with old LAYO1 and ORCAD for DOS.
All the work you find over here has been made with it!

Almost all the drawings are made available in PDF format.
You MUST have Adobe Acrobat reader installed, see at the bottom of this page.
If problems: copy PDF files to harddisk first without double click, but with "copy to" option.


This loop aerial uses the same principle as a small 10 sq. cm coaxial EMC pickup-loop coil.
If we make that loop as hughe as possible (150 sq. meters !!! in my case) we could use it as a wideband receiving aerial, working already from very low frequencies.
Much amplification was needed for a usable result. But it works great!

PDF with the latest high dBm amplifier
PDF with construction details of the Loop Aerial


high dBm amplifier PE1ABR

An early
version with 2 P8002 power FET's

The old drawing for the above Amp

high dBm amplifier PE1ABR

The latest
version according the drawing with J310 and 2N3866

A dutch text written by me about this loop and published by the Dutch amateur radio magazine Electron in februari 1999 in text only on the   VERON site  

The same "coax-loop" piece from  ELECTRON februari 1999   about my loop aerial now in original PDF print quality.
The above is available in Dutch only, but the original article has been referred to in English in

UK Radcom April + May 1999

The above link brings you to an English PDF version of the Radcom articles (200 KBytes)
If PDF's won't view properly copy to hard disk first!!


PDF with publication in Electron Febr. 1999 and Radcom April+May 1999, the additional 136 kHz filter
PDF with modified T-match, for more common use

For a good receiver as the NRD-515 sufficient extra preselection with only this device.
Adding an extra switchable C-L network at the output, only one network for each two successive coil ranges, corrects the Hi-Pass effect.


The basic idea behind this project was to make a good active aerial with a very high intercept point, especially for those frequencies where a normal (too short) long wire was not good enough.

Optimised for frequencies from about 10 - 50 kHz to about 10 - 25 MHz. So longwave, beacon, medium wave a.s.o.
It is basically a symmetric (balanced) circuit that is used a-symmetric. By varying the class-A current and at the same time varying the balance too, a point can be found where the two FET curves are mirrors of each other. If tested with heavy overload, this point is the point with minimum cross-modulations, it cancels out!!
I use a two tone test generator with 2 and 3 MHz, and cancel out 5 MHz. Because 5 MHz is NOT in the original signals.
The generator I've created is crystal controlled so the signals are in phase, nice view on scope, up to 10Vpp linear HF on the primary of the transformer!!

PDF with Circuit diagram of the early first public 1996 version (only in Dutch)
Now abandonned due to unavailability of the VHF power-FET semiconductors.

PDF with circuit diagram outdoor active aerial unit and now / en nu: NL versie
PDF with layout component side CAD outdoor unit
PDF with layout solder side CAD outdoor unit
PDF with outdoor unit mount and now / en nu: NL versie
PDF with circuit diagram power supply unit and now / en nu: NL versie
PDF with layout component side CAD indoor unit
PDF with layout solder side CAD indoor unit
PDF with SU board mount and now / en nu: NL versie
PDF with layout mainsfilter
PDF with mount mainsfilter
PDF with front and back panels indoor unit
PDF with mounting overview all components power supply unit

for surprise!


Page with nice new photographs active aerial system

Page with some re-scanned EMC/ferrite related photographs

Click for my adapted version of a MFJ phasing unit, made suitable for beacon reception and medium wave band
Only one unit is equal to none!
With more you can add directivity with a phasing unit!

Now some Radio add-on hardware, aerial info, diagrams and photos


  This is a modified copy of a Radio/TV splitter adapted for the frequency range of a general coverage receiver.

Works with perfect separation from lower than 100 kHz to at least 15 MHz. (This is something else than signal pass-through, that works to 50 MHz.) With extra care and an extra compensation capacitor the separation specifications are valid up to 25 Mhz, but pass-through drops to 35 MHz. Mounted in a small tin-can previously used for purée of tomatoes!
Intended to connect an aerial to two receivers with very low mutual influence. Signal drop about 4 dB, mutual suppression more than 25 dB.
It can also be used to connect two aerials to one receiver, it will reduce QSB. But it can also cause cancellation on a rare single frequency, so be carefull!
DC pass-through (2 active aerials...) is also possible with an extra capacitor in transformer ground.
PDF is simple drawing.
  Here is the UK splitter drawing in PDF.

Or drawing in a Dutch PDF.
  Click to enlarge the picture
T-Splitter HF PE1ABR



This is a splitter based on a different principle with only three cores in total, only one core is used to split in two. Based on a principle also (re-)published by John Bryant and Bill Bowers: Rolling your own splitter.

With three toroid sets you first split in two with the first set, and afterwards you split both outputs another time in two. Result: a four output port unit with only three toroid sets. Keep in mind that this is the practical maximum without the need for additional amplification. A least you reduce the signal with -6 dB. For stretching the pass-through frequency curve it was handy to add a small capacitor in between both sets of toroids. A gradual decay in signal is equalised with the capacitor to above 30 MHz, above 40 MHz it now has a dip. I've choosen 2x 27 pF to obtain an equalised pass-through.

The cores used for each duo-core-set are: ex-Philips 23 mm 4C65 (purple) AL = 82 and an old 23 mm core comparable with Philips 3H1 (red + yellow) AL = 1850.
Or use for the high AL core a 23 or 25 mm 3F3, 3C85 or 3C11, with an average AL around 2000. FT114A-77 is also usable.

Due to the rather low high-AL core a good Q and lower losses during tests. A little more windings are needed for 50 ohms to reach about 100 kHz as the lowest frequency, if you compare it with orange 3E25 cores.
50 ohm side turns: N = 12, split side: N = 2x 8 bifilar. Usable from under 100 kHz to above 30 MHz. This version is build in a fish tin as you can see....... It only smells if you connect a transmitter to it (HI).

A drawing will be added later

  4-port HF splitter PE1ABR

  4-port HF splitter PE1ABR



  This is a standard attenuator network like everyone builds them. Nothing special.

But please keep in mind that the resistor wires should be as short as possible. After a few -10 dB networks leakage becomes a problem. So screen the sections from each other. See pictures, works up to 200 MHz.
If you want to do it much better, you should make it in SMD, and with much more screening. That's special!! It will work perfectly over 500 MHz!! Although it is a hell of a job to make it.....
More than 5 sections ( = -50 dB !! ) is still unwise due to leakage, use more units then if you need it.

  -10 dB PI PE1ABR

Top of the PI-sections.
Click to enlarge the picture

  -10 dB PI PE1ABR

Inside of the PI-sections.
Click to enlarge the picture

  -10 dB PI PE1ABR

And in SMD! Click to go to a special sub-page about this device
  -10 dB PI PE1ABR

A different SMD version
Click to enlarge the picture
  -10 dB PI PE1ABR

The SMD version in a table box
Click to enlarge the picture
  -10 dB PI PE1ABR

The inside of the table box, with extra common mode suppression.


  This is a dual "impedance correction network" to be connected between a RF-generator with low impedance and a common (old) tube radio with higher-Z "wire aerial" input.
One branch is a simple 1 to 10 impedance transfer. The other branch is an artificial wire aerial simulation circuit for a common home wire aerial. It is needed during RF circuit alignment.
Using a blue 3F3 (equivalent to FTxx-77 material) or white 3C11 toroid in place of the orange 3E25 is less lossy. Using double green wire proved to be better too.
The PDF is a simple drawing.

  UK drawing in PDF

Dutch PDF

The curve is NOT taken when connected to a radio set, but when loaded with a 500 - 600 Ohm test resistor.
  buizenradio kunst antenne - tube radio artifical wire aerial circuit - PE1ABR
buizenradio kunst antenne - tube radio artifical wire aerial circuit - PE1ABR
buizenradio kunst antenne - tube radio artifical wire aerial circuit - PE1ABR

This is designed to give better readout of the LCD display of the Wandel & Goltermann SPM-30

  The SPM-30 is made for battery operation, so to reduce power consumption NO display or scale illumination is present.
Unfortunately the LCD display is hard to read in low light conditions. You always need an extra "desktop" lamp nearby.
I designed a very simple lightguide construction with a piece of Plexiglass (Perspex) with a 90 degree reflection angle.
The light comes from four 3 mm white high brightness LED's in series at the other end. They are glued in the plexiglass. Current consumption is about 10 mA from the unstabilised power with a currentsource stabilisation circuit placed in series with the four LED's.

One picture below gives a very low light picture ("creamy" colored), but perfect readable LCD display.

On the second picture you see how the plexiglass is mounted behind the PCB board on threaded M3 stand-offs and a few washers. The PC-board acts hereby as a light diffuser!!
It's not perfect, but performs remarkably well without any display board modification.
The "green chewing gum" contains the currentsource circuit. Its input is connected to the ON/OFF switch to the wire that goes to SK1-F. Ground goes to the mains LED ground nearby.

The PDF is a simple pencil construction drawing.
I used 6 mm material. For 8 mm you probably have to reduce the height of the standoffs.

  Plexiglass drawing in PDF

For hardcopy use.


Electrical circuit
Click to enlarge
SPM-30  - PE1ABR

A set of Mono or D-cell's for my SPM-30

  Recently I bought a lot of large mono / D-cell NiMh rechargeable batteries for my old SPM-30 levelmeter from Wandel und Goltermann. Batteries purchased at the local Lidl supermarket. By itself they comply with what I was expecting, they work.

In some batteries there is something rattling inside if you shake them. How is that possible?
I put a plumbing pipe cutter on the one with the loudest rattle. Great was the surprise. Inside the mono cell just three small AA penlights were in parallel! See the rightmost picture. I emailed bigclivedotcom and his answer was:

  It appears that it is nowadays the habit: almost all cheap recharcheable D/Mono cell's are FAKE!!!!

  Inside is - depending on the on-printed capacity - a C-cell, or 1 to 3 AA penlights in parallel, or a dust-buster (mini C-)cell. Beware of fraud! There are also expensive D cell's that are also fake. If you might think the expensive ones or a real brand like Duracell or Varta are "the real thing", you could be very disappointed. A D cell with 2500 mAh or lower is scam!

So NO, sometimes those brands also are NOT real D-cell's!! Look at the low mAh capacity in the examples below. The only way to know before you buy them is: is the mAh value between 8000 and 15000 ? Or put them on a weight scale to determine the weight. Are they filled with air/plastic or chemicals/energy?.

Fake rechargeable Mono or D-cell batteries with air or plastic inside are between 50 - 80 grams a piece, real 10000 mAh versions above 150 grams! On a site like Conrad or Reichelt you can fetch a PDF with info, the weight is mentioned! Real D-cell's are very expensive, 20 - 25 euro's each!

  A site about fake D-cell's that wants to be linked.

The first picture right is from their site.

Another link with test results.
SPM-30  - PE1ABR
Hilarious, this D-type has 2500 mAh inside. Four times more would be realistic. Scam!
SPM-30  - PE1ABR
The Eneloop C-cell is composed of 4 x AAA cells, the D-cell is composed of 3 x AA cells.
Not the worst, this type (Lidl) has even three penlights inside.
Only 4 euro. And even 4500 mAh.

  SPM-30  - PE1ABR
Hilarious, this D-type also has only 2200 mAh inside. Pure Scam!
SPM-30  - PE1ABR
Also hilarious, this type has 3000 mAh inside.
SPM-30  - PE1ABR
Expensive, 20 euro each, but 11000 mAh inside.
Expensive, 24 euro each, but 10000 mAh inside.


  This is a non standard Rx switch.
If an input is NOT selected it is terminated with 50 ohms.
Also the switching is with a double pole switch, if NOT selected the connect between switch part-1 and switch part-2 is grounded. All the internal HF wiring is with 2.5 mm teflon coax.
Of course all is mounted in a 100% HF-tight cast aluminum box.
The PDF is a simple drawing, the highres original of the PNG.

  Drawing in PDF

Click unvisible drawing right to see a larger PNG version.

For hardcopy use the highres PDF.
  antenne switch - PE1ABR
antenne switch - PE1ABR
antenne switch - PE1ABR

In this row an optimised aerial switch version for a VHF radio. Still too much leakage (in the pictures above).

In this version all the switches are individually screened with copper foil. The small pieces of connecting coax form a parasitic set of stubs. But they are only active on much higher UHF frequencies.

  antenne switch - PE1ABR
antenne switch - PE1ABR


  Over here some info how to build RF-sniffer probes and RF current measuring clamps.
This part is not finished yet. Wait for more to come!!

Because the resulting Z of a sniffer wound on ferrite is frequency dependant (I expect a 1 to 10 freq. range as practical), you need more than one sniffer for a large frequency range. To test it I made two small versions, one on half a pignose with airgap and 10 windings, the other on half a 4A11 14 mm toroid with only 5 windings. Both are "terminated" with 10 ohms, and series connected with 39 ohm to connect it to 50 ohm coax. Ferrite cutting is done with a miniature grinding wheel.

Further some current clamps, one version with more signal output, it has 10 windings directly to a 50 ohms terminator, but it has a smaller frequency range. And a second version with 6 single windings in parallel, terminated with 5 ohms and series 47 ohm to coax. Lower output, buth higher frequency range.

And some bigger pickup-sniffers. One version is simply a wound coax loop, terminated with 51 ohms in series on the short-circuit point. This one has a hughe frequency and pickup range, large signal is picked up within 1 - 2 meters range, also from cables in the ground. Wound on 70 mm wastewater pipe with RG174 - after glueing the pipe is removed. It has 16 windings, it is made in such a way (for relative voltage measurements...) that the total square is 1/16 sq. meter ( 25 x 25 cm square equivalent). Because it is a coax loop it is better screened to electrical fields than a "normal" pickup coil.

The following in RED is withdrawn
For more precise cable identification on very low frequencies ( from 10 - 20 kHz and up) a second "big" sniffer is made on half a clamp. The inductance with 30 windings was OK to comply at the design commands. It is about 80 - 90 uH and terminated with 10 ohms, connected to 50 ohms with a 39 ohm series R.

Step along and click the pictures to have an idea how I made them

  rf-sniffer - PE1ABR

Here it starts with, a modified
pignose and a 14 mm toroid.
Half a pignose and with an air-gap,
the toroid is simply cut in halves.

rf-sniffer - PE1ABR

Damped with 10 ohm, and a 39
ohm series R to 50 ohm coax.
Fixed in place on a piece of PCB.

rf-sniffer - PE1ABR

And here it is stabilised with 2-comp.
resin, and an old felttip pen.
The ex-pen forms a luxury handgrip!

  rf-sniffer - PE1ABR

The basic circuit diagram
of the big new sniffer

rf-sniffer - PE1ABR

The high outputvoltage current clamp and high frequency version (right). All the green windings are in parallel.

rf-sniffer - PE1ABR

The new big sniffer

  rf-sniffer - PE1ABR

The big coax-loop sniffer mounted
on a 16 mm PVC pipe.

rf-sniffer - PE1ABR

Example of a wound EMC-clamp halve
with 30 windings. An earlier big sniffer.
This method is rejected!

rf-sniffer - PE1ABR

And here the new big sniffer clamp on a
16 mm PVC pipe, isolated and protected
with self-vulcanizing tape.

  Here some theoretical considerations for a second improved BIG sniffer clamp with a hughe ferrite core.

The big sniffer in the story above (in RED) with halve a standard ferrite clamp didn't work the way it was meant.....
It was NOT OK!! The usable frequency range was far too low. Above 1 MHz was a problem.
The used ferrite pickup unit is the middle picture above, wound with blue wire.

The crossover point where the signal will drop off is at the frequency where the Zcoil will become a lot larger than the terminating Z = 50 ohm. To be exact: 50 ohm is in series with the windings and at the end of the cable is also a 50 ohm terminator. So crossover is at the point where the Zcoil will be a lot larger than 50 - 100 ohm. This means L should not be higher than about 1.5 uH for use up to 10 MHz.

The type of ferrite should NOT be of the absorbtion MnZn type (the first clamp halve was....) , but low-loss NiZn. There is lot of "airway", so always a low AL. A few windings are still possible before Lmax is reached. I've choosen a cheap "4C6" lookalike dump toroid, presumably from TDK. It is a clone for the well-known FT114-61. Two of them are cut in halves, 4 halves are glued together to form a new big lossless "halve clamp".
After calculation of the AL, it is between 50 - 100, NO MORE than 4 windings are needed. To overcome negative effects of the skin effect, a litze type of wire was choosen, 6 wires in parallel.
The cores are taped in plastic and 4 windings over them in series with a 50 ohms ( 2x 100 //) resistor. The back is screened a bit from electric fields to reduce pickup of shortwave (HF) signals. How it works?? Perfect!. Also 20 - 50 MHz is well picked up and seen on the spectrum analyser.
In the picture above right you see the new big sniffer, you also see some original toroids and a ready wound "half-clamp" version with 4 windings with 6 mounting-wire (Litze) strains on the 4 halves. They form 1 set of 4 windings.

  rf-sniffer - PE1ABR

The making of the new big sniffer clamp:

Two original 28 mm toroids and
two cut in four halves.

rf-sniffer - PE1ABR

The making of the new big sniffer clamp:

The 4 halves wound with N=4 and mounted
in a PCB frame. Already protected
with a layer of tape.

rf-sniffer - PE1ABR

The making of the new big sniffer clamp:

Now also the back is seen, with a
little electric field screening overthere to
avoid pickup of too much shortwave HF.



  This design is an EMC up-converter for use with the above probes (and a lot more Rx huntingloop-devices) and a portable Sony allwave receiver. The converter is comparable with other wideband converter designs, but with a few differences.
The input is ONLY usable if it is 50 ohms and wideband. And NO High-Z input!! And it should be usable from about 10 kHz. The upper input-limit is just below the medium wave band, lets say 500 kHz. Lots of interference is to be expected on medium wave if it is passed through without filtering, so this MW is suppressed. Also because most portable radio's are perfectly usable on MW as a detector! So the Rx-range becomes 10 kHz to 500 kHz. There is no interference or cross modulation from longwave megawatt transmitters (and small Rx-pickup devices or tuned hunting loops.......)
The output frequency is chosen as high as practical for a standard Sony receiver. The 50 ohm load in combination with the tuned output frequency should be such that no additional manual tuning is needed. Some drop is allowed. Chosen is an available 24 MHz mixing crystal, so the output becomes 24010 to 24500 kHz.
If you connect 12V directly to the BNC in- or output, they are "smoked out". If you won't take that risk add extra capacitors. The input needs at least 1 uF, preferably 2.2 uF !! The output will accept 2.2 to 10 nF.
  Here is the original DUTCH version PDF.

Now a translated English version is also available.

EMC converter PE1ABR
to enlarge the picture

Screened mains current-transformer to accurately measure (very) low power devices.

  For devices like adapters and LED lamps. A current-transformer slightly different than usual.

in short:

Made with 4 glued MnZn high AL ferrite toroids. The inductance should be such, that the secundairy terminating impedance (1 Ohm) is equal or less than 1% of the total Z. So secundairy Z for a 1:100 transformer should be 100 Ohm on mains frequency (= 50 Hz). Further more it should not act as a too high absorber up to frequencies to 100 kHz, so not too high in ferrite loss curve.

This transformer consists of four 3E25 ferrite cores of 36 mm stacked together (TN36/23/15, AL per core approximately 7400, these Ferroxcube {ex-Philips} cores were previously orange colored). Together they are provided with exactly 100 turns and terminated with a resistance of 1 or 10 Ω. 1 Ω gives a better frequency characteristic in the low, 10 Ω gives much more output. Used with an amplifier 1 Ω is the correct choice.

Check of the design criteria:

L = N2 x AL x 10-9 Henry and Z = 2 x pi x f x L

This makes the 50 Hz Z with 100 turns and 4 toroids: 2 x pi x f x L x N2 x (AL x 4) x 10-9 =

2 x 3.14 x 50 x 100 x 100 x (7390 x 4) x 10-9 = 92.87 Ω

This is very near the design criteria of 100 Ω. So 4 toroids will do! And three won't be OK.

This transformer module is fully electrically shielded to prevent long-wave DX and other EMC interference and noise ingress. Inside the ring cores is a small piece of Bamboo-3 CAI-distribution coax as screen, whose thick middle conductor is replaced with standard insulated mains installation wire of 2.5 mm2. On the outside, 3 to 4 mm plastic foam and a sheet of copper foil (or bronze, or from a tin can) over it, which is connected to the Bamboo-3 shield only on one side. Do not make a short circuit winding. On the sides, some "rounds" of copper foil may come for a neat screening. See pictures.

Eventually, an OP27 (or even better an OP37) low noise microphone opamp is used as an amplifier (thus no longer passive) with a gain of one hundred times. With the recommended 1 Ω termination, amplifier output is 1 V per 1 A (pay attention = 2x 1.414 x 1V = 2.828 Vtt for a 1Veff sinewave). Using the maximum OpAmp power supply voltage (+ and -15 V for the OPx7, instead of only + and -5 V for a current feedback amp) and 5 Aeff measuring current which gives almost 15 Vtt as possible output voltage. Although considering the field strength Bmax, 5A is already on the high side. 1 Ampere mains power already gives about 100 milliTesla. One should rather not exceed 350 mT. I have tested it to clipping in the opamp, that is about 8 Ampere mains current, without any ferrite saturation problem.
Here is a draft sketch of the circuit diagram.

For a known toroid AL value, we can use this simple formula (I designed, see link further down):

Bmax = (N x AL x I x 1.414) / Ae

Bmax in milliTesla, I in RMS (eff.) Amps, Ae in square mm.
N is the number of turns of the saturating current. AL the toroid's standard inductance value.
1.414 is the factor from sine RMS/eff to 1/2 top current value.

Here a scan of a draft calculation sheet in PDF, the search for the easy Bmax formula. Two different ways to calculate the Bmax from the AL and I. The intention was (as a kind of proof...) exactly the same end result, I succeeded....

Compared to the active Hantec CC-65 the results with low current (adapters and LED lamps) are much better:
the same image on the oscilloscope, but no longer provided with a solid noise smear, it is so clean!
Nominal mains current: 0 - 3 Amps.
Peak use up to 5 Amps. Opamp clipping at 8 Amps.

Step along and click the pictures to have an idea how I made them

  rf-sniffer - PE1ABR

Why I made it?

Some very low current LED lamps under test.
lamp5 = "glowing wire" type
lamp1 = TL energy saving lamp
How distorted is the mains current?
What about EMC problems?

rf-sniffer - PE1ABR

Why I made it?

The noisy Hantek image and a
noisefree track (top). Noisefree is with
my new current module, made with
4 ferrite toroids and screened.
It is lamp 2 on the right.

rf-sniffer - PE1ABR

Why I made it?

A scope capture image.
This is a TL energy saving lamp.
Lamp 1, most right on the lamp image.
Due to the higher current the Hantek
is not so noisy anymore.

  rf-sniffer - PE1ABR

The making of a screened current transformer:

How to easy wind 100 windings on the
4 toroids that form the ferrite "sleeve".

rf-sniffer - PE1ABR

The making of a screened current transformer:

Here the 100 windings are finished.

rf-sniffer - PE1ABR

The making of a screened current transformer:

And here it is completely screened.
Ready to connect to the scope or buffer Amp.

  rf-sniffer - PE1ABR

The making of a screened current transformer:

Here it is finished and mounted in a box.
The thin metal Amp box will be closed.

Nominal mains current: 0 - 2 to 3 Amps.
Peak use up to 5 Amps.

rf-sniffer - PE1ABR

A strange LED LAMP 4 curve:

This capture image is taken at night.
It looks absolutely normal.
Top is ferrite module, bottom is Hantek CC-65.
Hantek with the slim 10x loop,
see next chapter.

rf-sniffer - PE1ABR

A strange LED LAMP 4 curve:

This capture image is taken in full sunshine.
A very strong 20.6 kHz signal is visible.
The 50 Hz current limiting capacitor is 400
times less in Z on 20 kHz. It sucks solar
power converter EMC from the mains!

  Earlier current measuring tools and add-ons, very usable for the Hantec CC-65 and others.

The 10x current "amplifier" without electronics

Here are some hints to make up an 1 to 10 current aid with plug and counter plug for measuring low current devices. It is intended to connect in series and increase low currents by a factor of ten for an ampere/current clamp module. Of course, no currents are externally amplified; It's just a bunch of ten windings that go together through the amp clamp. The clamp beak must be large enough, or use a slightly thinner (transformer enameled) wire, this is needed for the Hantek CC-65.
A single winding is also available, so we can choose between ×1 and ×10 during the measurement. In the pictures you can instantly see what I mean.

  rf-sniffer - PE1ABR

The making of a thin 10x loop:

Some nails makeup the temporary
coil form on a wood pole.
This loop is made with thinner
enameled transformer wire

rf-sniffer - PE1ABR

The making of a thin 10x loop:

Testing of an almost finished 10x loop.
Not protected yet with a layer of tape.

rf-sniffer - PE1ABR

The making of a thin 10x loop:

Here the loop is finished. This
version fits nicely in the Hantek CC-65.
The 1x loop is protected with a teflon tube.

  rf-sniffer - PE1ABR

The making of a 100x !!! loop:

As a test (for very low adapter currents)
a 100x loop was also made.
Due to its higher inductance (750 uH) it
picked up even more EMC.

rf-sniffer - PE1ABR

The making of a 10x loop:

This is the first 10x loop
It fits only in clamps with a wider beak
It is made with wire from standard
mains cord.

rf-sniffer - PE1ABR

The making of a 10x loop:

All sitting together
The first 10x loop and the first current
clamps. For very low LED lamp currents and
the new Hantek CC-65 it needed an update.

  rf-sniffer - PE1ABR

A shitty 10x loop from China

The KJ79A from AliExpress is cheap,
and has a nice enclosure,
but shitty Australian connectors.
Nothing else was available.
Only with some trouble you can find
suitable adapter connectors.
rf-sniffer - PE1ABR

An improved shitty 10x loop from China

And here the connector problem is solved,
I rebuild the connectors! Very stable.
LOOK WELL: there is something very special.
The coil has only 9 windings, but on one
side mains return (blue) forms the 10th, on the
other side start and finish overlap, so also 10.
rf-sniffer - PE1ABR

An improved shitty 10x loop from China

And here a little bit more zoomed in.
It works very well and it looks nice!

BUT: the Hantek CC-65 does NOT fit!

We still need the enameled wire loop.

Pulse - Echo generator box

  For measuring the ideal termination of a cable or (winding) wire strain (for Guanella baluns...), you connect a pulse generator and scope to one end and a low-ohmic termination potentiometer to the other end. Rotate the R until minimal bumbs ==> R-Potmeter = ideal termination-R. This works pretty accurate between 20 - 250 Ohms!

If you also want to do a length or velosity measurement (also of an entire reel ...), you need a single very small pulse combined with an extreme long pause, otherwise you are unable to detect which echo is from which pulse.

My generator box makes these small pulses in 4 different pulse/pause settings. The 4 pulse width's at the same time can give an indication of the common mode suppression frequency range.

The generator consists of a single 30 MHz crystal oscillator module (old PC scrap), a very fast 74HCT4040 for lots of divide by 2 stages, and a GAL-array logic chip wherein all the pulse/pause combinations are programmed. Eight divider chains and combiners would consume an entire eurocard with standard logic, here only 1 GAL16V8 chip. The shortest pulse is made from only one 30 MHz sinewave. So comparable with half a 15 MHz pulse, due to some chip-delay it looks like half a 12.5 MHz pulse. The total pulse/pause can be compared with the T from an 85 kHz wave.

There are two buffered outputs, one low-ohmic optimised for test cable connect, the other positive or negative going selectable to sync the scope. The most time consuming part in the design was a buffer that has low impedances, but also as fast as possible. Too high current = SLOWER, more delay!

The box that is used is a German Strapubox 2002. Conrad number = 522139

DO NOT connect the Y scope input with a T-adapter, but connect a 1/10 probe to the cable-strain connection point.

  Here the CAD PCB files in PDF

Here the schematic in PDF

Here the GAL design files in PDF

Here the GAL program file

Here more explanation in a PDF

Hier meer uitleg in een NL PDF

lantestpulse - PE1ABR
Click to get the front in PDF

lantestpulse - PE1ABR
Inside the lanpulse box.

lantestpulse - PE1ABR
Example adapter's
modified PL-259 ==> BNC
to connect all sorts of cable strains
lantestpulse - PE1ABR
More detailed view inside

lantestpulse - PE1ABR
As a PL-259 ==> N adapter
usable on a MFJ analyser device


Ethernet UTP measuring tools

  Here some very simple tools that make it easy to solve all common UTP wiring errors. To be used with only an Ohm / conductance meter with buzzer or Fluke(alike). Very simple but extremely handy if you are called to solve a problem. Make more than one of them.

1) A piece of PCB clad with the 8 wires connected to solder lugs, you connect your ohm meter with hooks to it.

2) A piece of 15 cm UTP with a connector. The 4 pairs are shorted to each other to do a connection (buzzer) test at the other end. Make more than one of it.

3) A piece of 15 cm UTP with a connector. The 4 pairs each have their own dummy terminator. Each pair has a different value to distinguish the pairs from each other. Use 100 ohm for orange, 150 for green, 220 for blue and 330 ohm for the brown pair. Make more than one of it, you can solve almost any error with it!

Add some UTP/RJ45 inline couplers to your toolkit. WATCH out for misunderstanding! Double check your supplier! You only need coupler versions that connects the pins crossed, pin-1 at one side (crossover) to pen-1 at the other. They are (mostly) confusingly called STRAIGHT! Straight through connected (pin-1 to pin-8) is common called CROSSED! They are only usable for ISDN / Telephone.

4) If you want to investigate impedance imperfections with the above LAN Pulse Echo generator, you also need a 15 cm piece of UTP with a connector with the correct termination dummy R's connected. A value of 4x 110 ohm will do (or 2x 220 for each in parallel). For length measurements use left open or the "short" dummy at the other end. You also need a very short twisted pair cord with BNC (female chassis with male-male plug) at one end and crocodile clips to the other to connect the generator to the UTP pairs - You really need only to test the orange-white and the green-white pairs. Connect the very short cable with the clips to the lugs on the PCB-clad board, also connect your scope to those lugs. If you have mental problems with the a-symmetric to symmetric measuring connections add 10 windings UTP on a high AL ferrite core in the cable to the PCB-clad board. This suppresses the imbalance in the measurement setup.


Some cable measuring results:

old UTP Solid CAT5 test 18 meters: measured Z = 110 ohm, velocity = 0.676

UTP Stranded CAT5E test 48 meters: measured Z = 102 ohm, velocity = 0.696

EMC converter PE1ABR
to enlarge the picture

A NON-standard ESR meter

A combination design. Both 50 and 150 kHz pure sinewave measuring signal, accidentally 230 V misuse protected, extreme low-Z signal, output independant of load changes and frequency.
All switch-over with a 4066 IC, 50/150 kHz switch = "cold".
Add-on buffer possibility to use large 500 - 10000 uA (=10 mA) meters.
Without buffer: 50 uA to 300 uA.
Not a stripped minimalist design!!

Schematic in PDF





Meter scale in PDF                



  This design is an add-on audio amplifier for use inside a Racal RA-17. Gives much higher audio volume. A few watts real audio output. Works without extra power supply transformer, uses doubled heater voltage.
PDF set is drawing, CAD layout and assembly files.

Here is the complete RACAL amplifier PDF set


  Connects all your computer / decoding and interface hardware without a ground loop to your receiving system.                    
Each individual output has its own modem transformer, bufferamp and volume control.

Here is the complete PDF set (5 sheets)


  Special RTTY op-amp decoder adapted for NAVTEX DX purposes only. Extraordinairy good decoding performance. Signals in noise - between S0 and S1 - almost error free decoding is possible. Can be used as an external FSK decoder in HAMCOM and CODE3.
This op-amp decoder uses an EMC free negative voltage converter, so ideal for mobile (car or boat) use!!
  Remark: These are my original drawings: comments are still in Dutch

Here is the first PDF drawing, the modified telex decoder
Here is the second PDF drawing, the voltage converter
Here are the PDF PCB-CAD files

Some DX results (From Canada to Egypt), Rx in The Netherlands!!

navtex decoder interface PE1ABR

to enlarge the Navtex decoder


  This is a black box with 2x 25pins Canon-D sockets. It fits in a standard RS232 cable.
It is used with the RS232 on my Tektronix 2232 oscilloscope to avoid ground loops and to prevent a blown up device if a ground loop occurs during measurements in mains connected switch supply units (yes I know I must use a separation transformer).
The device can do much more: data rate 150 kHz, handshake rate 75 kHz, withstands 230V AC between in and out!!

The opto coupler and PSU boards layout files in PDF

Very early/old sketch which shows the basic idea in PDF


to enlarge the RS232 interface



  A NON-standard CAI buffer amplifier with a build-in amplification correction that is the reverse of the frequency dependant attenuation in a common home.                   
So some frequency dependant amplification correction has already been build-in, gain is about 12 dB at 450 MHz and about 18 dB at 800 MHz, no further alignment needed. So after this buffer and many meters of cable before or after it the highest and lowest UHF frequencies are equal in level!!!

IP3 problems can arise caused bij too high leakage of your own internet Tx signal under 70 MHz. At the cable modem side a 300 to 1000x difference exists between Rx and Tx. (Rx between -10 to +10 dBmV, Tx between 40 - 55 dBmV). The CAI provider filter/splitter box supresses only 20 - 30 dB to the TV port. A 7-pole Butterworth 85 MHz high-pass was not sufficient, it gave only -30 dB on 65 MHz. With ELSIE (ARRL Handbook student version) I designed a 7-pole -50 dB Cauer high-pass which works perfectly! It is in a small tin box with F-connectors.

Here is the latest high dBm amplifier schematic in PDF
The internal high-pass is meanwhile replaced with the external Cauer version.

Here is the original -50dB 85MHz Cauer high-pass design from ELSIE in PDF.

Here is the edited Cauer version with real-life component values in PDF.

  cai cauer PE1ABR

The design curves from ELSIE.

Click to enlarge the picture

  cai cauer PE1ABR

The real life simulation with
standard component values.
Click to enlarge the picture

  cai cauer PE1ABR

The real life performance.
10 MHz and -10 dB per division. Range 0 - 100MHz and 0 to -70dB
Click to enlarge the picture
  cai cauer  PE1ABR

A look inside the tin box
With pushing and pulling the coils are aligned.

Click to enlarge the picture


  This is a robust "extendable" 12V power cannon.
Meant to feed a standard transmitter that needs about 15 Amps. It is of the old dissipative analog type. The more power you want, the more power Transistors you add with current divider resistors. Start with at least 4x 2N3772. It is based on a SGS L200 application with good overcurrent/foldback limitation. But it is extended and more thorough tested on the edge of currentlimit and attempts to let it oscillate. Every attempt caused counter actions during the design stage!! Also an extra diode brigde for high power is added ON THE OUTPUT to make it almost idiot proof by too heavy experiments. Try to understand the special way of wiring, keep to it to make it stable and also try to keep it EMC proof. The plus and minus "bar" are low impedance points on heavy output terminals, possibly enlarged with some heavy copper lugs. EMC capacitors from those points with very short wiring to ground = metal frame.

Here is a schematics "sketch" set

Here are some sheets with CAD circuit layout and setup (text in Dutch...)

Here is the circuit of a special "current sucker" to test it all.


Mains Master-Slave ON/OFF unit:

  Here you find a homebrew mains master-slave unit, copied from a Dutch Elektor magazine from 1996.
Switch ON/OFF together with the master-device all the other equipment, like adapters and other complimentary equipment.
Usable for a computer or radio-set as master and lots of adapters for small equipment on the slave.

Complete set with plug and connectors

Here is the complete story and circuit, copied from an old Dutch Elektuur (Elektor).
Here is my circuit version with some changes and improvements, meanwhile a thermo fuse is added in the supply of the relay, you can see it on the picture right.
Here is my latest CAD layout, the "ON" LED has its place on the board now.

There is a peculiar point to mention. There is resonance effect with the toroid inductance and the capacitors in parallel to it. And: the main "ON" current lowers the inductance. The point with maximum effect = some resonance (is also a higher gate control voltage), should be at the high ON current and NOT at the "zero" current. Otherwise it won't switch off!! You have to add MORE capacitance to shift F-res to a lower inductance if it hardly switch-on and hangs for switch off.
If you "plug" a test-C (1 - 3.3 uF) to lower the "zero" gate voltage KEEP IN MIND this is a HOT circuit!
I've used the biggest toroid with at the same time the highest AL value ( 7000 - 10.000). You have to make some sort of fishermans knot tying lever tool to wind this type of toroid. You make it out of PCB clad, 1 cm wide and 25 to 40 cm long, use it as a wire holder during winding. See picture on the right.

Circuit board pulled out of the box

The winding tool
A fishermans friend

Homebrew counter for an Analog Rx

  An add-on counter system for an analog broadcast Rx.

An example of a non-standard universal counter system (Digital readout) with cheap standard components for an old but perfect working analog receiver. In my case build-in in a Sony Rx. Fast six digit readout on FM, 3 to 5 digit on long-, medium- and shortwave, all with 1 kHz resolution, 64 msec refresh. So fast readout that follows the tuning!! Pre-load for IF substraction, two different IF's possible, with two substraction schemes ( FM / AM ). Something else than 455 kHz ( 468 f.i.) no problem. Ripple blanking on 3 MSB bits. Circuit tricks to buffer and amplify existing local oscillators and feed them with RG174 to the counter. NO SCANNING display readout, that's asking for trouble ( beeps and whistles). Sandwich construction with three tiny boards ( wire wrap experiment cards - NO CAD layout) Total enclosed in PCB-clad, size 1,5 times a 10/ 1.44 floppybox . EVERY LED display bit has its own feed-through capacitor (placed even after the current limiting-R). Brightness setting with diode voltage drops. NO expensive divide by-10 pre-scale, whole counter system works with 1/64th principle. NO expensive all-in-one chip with scanning ( beeps and whistles) readout (and with only 4 digits)

The set with all the sketch drawings in one PDF

It was needed to add a small mains transformer and a PSU board
A CAD file for a (bit big) display mount board

to enlarge the Rx front

to enlarge the Rx front


Homebrew counter for a Sweeper

  Another add-on counter system for an analog 0 - 200 MHz Sweeper System.

Here is another special purpose counter.... For this version the whole control system is made in SMD to make it as small as possible, as small as a tiny matchbox, for build-in in a small metal mixer box in a 0 - 200 MHz sweeper system. Overthere in the box available were input frequency as well as a marker oscillator, who now also functions as a clock oscillator. Design problem: the whole range from zero to 200, standard components don't reach 200 MHz, prescalers don't go under 50 MHz to zero. So two input circuits in parallel are needed with the same divide ratio. Somewhere (halfway) the varicap control voltage range a switchover is made from the 0 - 40/60 MHz to the 40/60 - 200 MHz input circuits that work in parallel. You don't even notice the switch-over during tuning!!
Again, all because 0 to about 50 MHz is impossible for a standard ECL prescaler. More than 50 MHz from zero is possible by the use of very fast 74HC74 SMD dividers ( NO HCT !!) with a transistor buffer in front, I got the fast HC74 from scrap from defective motherboards. Timing principle is comparable with the above "Sony" counter, also with 64 msec refresh. Layout boards available in SMD for control and standard layout for divider and display latch. Again with ripple blanking!

The set with all the sketch drawings in one PDF

The set with the CAD layout files in one PDF

Click to go to a subpage to see how
I made my own VHF attenuator pad

to see a part of the front
(Not finished yet)

to enlarge a standard driver board

to enlarge the tiny control system. ECL part is on the back


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A short visit to the "inventors" workshop,
all the talk is in Dutch and there are no subtitles.
Play in slow motion to see all the details!!

Video Title: "May I come in for a short visit?" - part 10 - The Inventor
Video copyright:   PZC   - Daan Wallis

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by Walter - PE1ABR - 2017-07-24