Robert Johansen
@srfbob1.bsky.social
Retired geek (general electronics engineering knowledge), specializing in RF electronics, design and make things, ham radio enthusiast, reader and cat lover.
I was running some speaker impedance measuring tests earlier today in my bedroom. Lucky was my helper, pawing alligator test clips.
November 14, 2025 at 2:55 AM
I was running some speaker impedance measuring tests earlier today in my bedroom. Lucky was my helper, pawing alligator test clips.
I miss my mom, dad, sister every day
November 12, 2025 at 5:54 PM
I miss my mom, dad, sister every day
Remembering my dad on Veterans day. He fought in the Pacific during WWII was a private in U.S Army infantry, hand to hand combat. He suffered with PTSD, was bipolar, could not forgive himself for killing. Rest in peace Dad.
November 11, 2025 at 4:39 PM
Remembering my dad on Veterans day. He fought in the Pacific during WWII was a private in U.S Army infantry, hand to hand combat. He suffered with PTSD, was bipolar, could not forgive himself for killing. Rest in peace Dad.
Lucky says trick or treat
October 31, 2025 at 10:44 PM
Lucky says trick or treat
Bad selenium rectifier
October 27, 2025 at 2:23 PM
Bad selenium rectifier
Hallicrafters S-72 portable AM-SW chassis that I am slowly restoring.
Replaced line cord and selenium rectifier, Selenium rectifiers get weak with age, this one had a large voltage drop. Radio came to life after replacing with a silicon diode, mounted on a terminal strip bottom right of picture.
Replaced line cord and selenium rectifier, Selenium rectifiers get weak with age, this one had a large voltage drop. Radio came to life after replacing with a silicon diode, mounted on a terminal strip bottom right of picture.
October 27, 2025 at 2:21 PM
Hallicrafters S-72 portable AM-SW chassis that I am slowly restoring.
Replaced line cord and selenium rectifier, Selenium rectifiers get weak with age, this one had a large voltage drop. Radio came to life after replacing with a silicon diode, mounted on a terminal strip bottom right of picture.
Replaced line cord and selenium rectifier, Selenium rectifiers get weak with age, this one had a large voltage drop. Radio came to life after replacing with a silicon diode, mounted on a terminal strip bottom right of picture.
At NJARC repair clinic earlier today
October 25, 2025 at 8:58 PM
At NJARC repair clinic earlier today
Any guesses what this is ?
I picked it up at the VCF East swap meet yesterday
Bench test, after a little coaxing it works.
I picked it up at the VCF East swap meet yesterday
Bench test, after a little coaxing it works.
October 19, 2025 at 8:34 PM
Any guesses what this is ?
I picked it up at the VCF East swap meet yesterday
Bench test, after a little coaxing it works.
I picked it up at the VCF East swap meet yesterday
Bench test, after a little coaxing it works.
Calibrating (de-embedding) my new Digital wattmeter using a HP437B power meter with attenuator and thermistor mount.
October 13, 2025 at 1:56 PM
Calibrating (de-embedding) my new Digital wattmeter using a HP437B power meter with attenuator and thermistor mount.
Crosley pup 1920's regen radio with repro A cell and B battery in my collection
October 8, 2025 at 12:59 PM
Crosley pup 1920's regen radio with repro A cell and B battery in my collection
Nice, animals are wonderful. I have one house cat and feed some feral's. I lost my cat Pawlette she was 18 in February. I took in a stray cat. Named it Lucky.
October 7, 2025 at 11:56 PM
Nice, animals are wonderful. I have one house cat and feed some feral's. I lost my cat Pawlette she was 18 in February. I took in a stray cat. Named it Lucky.
1296 MHz amplifier control box, EME
WWII radio destruct switch
AMSAT cubesat simulator
WWII radio destruct switch
AMSAT cubesat simulator
October 6, 2025 at 2:54 PM
1296 MHz amplifier control box, EME
WWII radio destruct switch
AMSAT cubesat simulator
WWII radio destruct switch
AMSAT cubesat simulator
Ping pong anyone ?
October 5, 2025 at 1:52 PM
Ping pong anyone ?
Well isn't that special
October 1, 2025 at 9:03 PM
Well isn't that special
I recently assembled this 1802 kit for fun. Reminiscent of a COSMAC ELF I built in the 1970's
September 30, 2025 at 11:13 PM
I recently assembled this 1802 kit for fun. Reminiscent of a COSMAC ELF I built in the 1970's
Hp410A VTVM 1948
Their first RF voltmeter. also has DCV and Ohm functions
One of my eBay purchases that I restored this year. Was clean, easy restore, original parts, only problem was the AC zero pot was seized, had to free.
I also have one Hp410B and a couple of Hp410C's
My favorite analog meter.
Their first RF voltmeter. also has DCV and Ohm functions
One of my eBay purchases that I restored this year. Was clean, easy restore, original parts, only problem was the AC zero pot was seized, had to free.
I also have one Hp410B and a couple of Hp410C's
My favorite analog meter.
September 21, 2025 at 8:03 PM
Hp410A VTVM 1948
Their first RF voltmeter. also has DCV and Ohm functions
One of my eBay purchases that I restored this year. Was clean, easy restore, original parts, only problem was the AC zero pot was seized, had to free.
I also have one Hp410B and a couple of Hp410C's
My favorite analog meter.
Their first RF voltmeter. also has DCV and Ohm functions
One of my eBay purchases that I restored this year. Was clean, easy restore, original parts, only problem was the AC zero pot was seized, had to free.
I also have one Hp410B and a couple of Hp410C's
My favorite analog meter.