Analogue Display Digital VFO

Following the original by JF3HZB (PW October 2022 p56) I have bodged mine sort of based on the original

https://github.com/tjlab-jf3hzb/Digital_VFO_with_analog_dial

https://tj-lab.org/2019/02/17/vfo5/

I will use for bench signal source and an older direct conversion radio setup I have.

The ESP32 I used seems to be a bit different.

The upload speed 115200, 240MHz, 40Mh flash, 4MB flash

Anyway programmed it.

I used a 2" rotary controller as per the PW article. Ruler and JLCPCB squeaky duck for size comparison.

TE-2101 antenna analyzer

 This is tiny.

Amazing bit of homebrew.

The manual is in Japanese but the block diagram explains how it works

 

nifty bit of engineering with the case (3D printed and bent acrylic sheet). The PCB doubles up as support of the OLED and the uPC and battery charger are on separate PCB underneath. The components are gnat shite size though! This is some nice homebrew.


Looks like they are building some more...

Just fitting battery.
Mine is 180mAH so lot smaller than original.

Small battery fitted

working

at just 80grams, this will be a good one for /p operations for sure. It doesn't work without the battery inside but it will work (and keep recharging from USB if it is) so I suspect one of those USB power packs might be useful.

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