Cores for baluns

 I have this printed out as I refer to it often enough so I reproduced it here (I cannot recall the original source tbh but all the values are in several reference books anyway) I got loads of torroids from GQRP club sales and W8DIZ.

The  different material works at different frequencies. These are often used in common mode chokes and wide band baluns.

Material	Common mode choke frequency range (single turn)	Common mode choke frequency range (multiple turns)	Impedance transformer	1:1 Balun (Choke)
#31	3,5 - 100 MHz	1,5 - 50 MHz	-	1,5 - 30 MHz
#43	25 - 600 MHz	2 - 60 MHz	2 - 50 MHz	2 - 30 MHz
#52	150 - 1000 MHz	4 - 150 MHz	1 - 60 MHz	1 - 60 MHz
#61	200 - 2000 MHz	5 - 200 MHz	15 - 200 MHz	10 - 100 MHz
#77	200 kHz - 10 MHz	100 kHz - 10 MHz	0,5 - 8 MHz	1 - 8 MHz

31 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	1500
Flux Density @ Field strength	B H	3900 5	Gauss Oersted
Residual Flux Density	Br	3200	Gauss
Coersive force	Hc	0.28	Oersted
Loss Factor @ Frequency	Tan δ/ µi	20 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.6	%/°C
Curie Temperature	Tc	>130	°C
Resistivity	ρ	3000	ohm-cm

31 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	1500
Flux Density @ Field strength	B H	3900 5	Gauss Oersted
Residual Flux Density	Br	3200	Gauss
Coersive force	Hc	0.28	Oersted
Loss Factor @ Frequency	Tan δ/ µi	20 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.6	%/°C
Curie Temperature	Tc	>130	°C
Resistivity	ρ	3000	ohm-cm

43 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	800
Flux Density @ Field strength	B H	2900 10	Gauss Oersted
Residual Flux Density	Br	1300	Gauss
Coersive force	Hc	0.45	Oersted
Loss Factor @ Frequency	Tan δ/ µi	250 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.25	%/°C
Curie Temperature	Tc	>130	°C
Resistivity	ρ	1×10^5	ohm-cm

52 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	250
Flux Density @ Field strength	B H	4200 10	Gauss Oersted
Residual Flux Density	Br	3300	Gauss
Coersive force	Hc	0.6	Oersted
Loss Factor @ Frequency	Tan δ/ µi	45 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		0.75	%/°C
Curie Temperature	Tc	>250	°C
Resistivity	ρ	1 x 10^9	ohm-cm

61 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	125
Flux Density @ Field strength	B H	2500 15	Gauss Oersted
Residual Flux Density	Br	1000	Gauss
Coersive force	Hc	1.1	Oersted
Loss Factor @ Frequency	Tan δ/ µi	30 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		0.1	%/°C
Curie Temperature	Tc	>300	°C
Resistivity	ρ	1 x 10^8	ohm-cm

77 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	2000
Flux Density @ Field strength	B H	5100 5	Gauss Oersted
Residual Flux Density	Br	1800	Gauss
Coersive force	Hc	0.25	Oersted
Loss Factor @ Frequency	Tan δ/ µi	15 0.1	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.2	%/°C
Curie Temperature	Tc	>200	°C
Resistivity	ρ	100	ohm-cm

QBSA Again...

Postie delivered an old part built project, but a very good one. Feels like an eternity passed looking for a replacement for one I sold in error.

I was about to loose hope as spoke to Steve KD1JV and he didn't have anything from the original (very old) project left.

I must backup that AVR processor read the HEX off it (not an attempt to clone etc) before it gets used.

RASPAD3 and SDR++ on RaspberryPi

Going to be trying a few other SDR.

Raspberian OS and compiled on the RaPi4 (before putting into RASPAD3).

RX only. SDRPlay (version 1)

RX and TX. Lime Mini SDR and Adalm Pluto SDR (found it)

I use an external USB 3.0 powered hub with these.

I expect will also try the DragonOS for the RaPi as well.

I have an SDR and an HF upconverter (basically an RTL dongle) so you can sample down to about 50Hz is needed, will try that was well.

This had already been tested by David Taylor https://twitter.com/gm8arv and the developer https://twitter.com/cemaxecuter of Dragon OS using other SDR.

update: 20th October 2021

I added the software for the Lime Mini SDR and the Pluto SDR, going to be taking a copy of the SD card before do anything else.

Last night checked both the speaker and audio out connections with a simple music WAV file playing in a loop. Didn't want RF issues.

Note: SDR++ used was the source build 1.0.4 obtained from https://github.com/AlexandreRouma/SDRPlusPlus/releases and compiled on the RaPi (see this blog post for details) https://m1kta-qrp.blogspot.com/2021/10/installing-gqrx-and-sdr-on-raspberrypi.html

What it could do when was version V1.0.0 this is what AlexandreRouma at the time:

SDR++ v1.0.0 Released!

Hi everyone :)

After over a year of work, I'm proud to released version 1.0.0 of SDR++!

For those who don't know, SDR++ is a crossplatform (Windows, Linux, MacOS, BSD) and open-source (https://github.com/AlexandreRouma/SDRPlusPlus/releases) general purpose receiver software meant to be simple and easy to use. It has advances features like multi-vfo and uses a fully custom DSP making it very efficient.

Here are the following additions compared to the last version:

• Support for the SpyServer protocol

• Support for all SDRplay devices

• Support for all BladeRF devices

• Support for all LimeSDR devices

• Optional IQ correction

• Optional Decimation

• Broadcast FM Stereo

• Frequency manager to create lists of frequency and optionally display them directly on the FFT/Waterfall

• Network sink to stream the audio output via TCP or UDP

• Options to set the FFT framerate, FFT size and FFT window.

• Theming with Dark and Light themes supplied by default

• RigCTL server module to control SDR++ from, for example, gpredict.

• A bunch of keyboard shortcuts (see wiki on the github page)

• SNR meter

• More info when hovering a VFO

• Colored VFOs to easily identify which is which at a glance

• Meteor M2 demodulator compatible with LRPTOfflineDecoder and Satdump

• Ability to resize VFOs by directly dragging the sides on the FFT and waterfall

• Module manager to easily add or remove any module on the fly without having to restart or edit the config manually

• File dialogs to select directories in the recorder or files in the file source (instead of having to type in the path)

• Ability to disable modules that support it (Radio and Meteor M2 demodulator) with one click (to save CPU power or just if they're not needed)

• Lots of performance improvements

• Ludicrous amounts of bugfix :)

I'd like to thank the many contributors, patrons and companies (SDRplay, Airspy, Nuand, LimeMicro) who helped make this project possible!

If you have any issue with the software, please open a github issue or contact me directly on the SDR++ discord (see readme on github)

I hope this software comes in useful to at least some of you ;)