If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1412
Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278
I want to build several retro(old style) radios just for fun.So I build this vacuum tube radio.But it dosen't work.I can't hear any sound or noise.
The circuit diagram is on the attached file.I found this circuit on an old book published exactly 50 years ago.
The chinese word near the 1M resistor says crystal earphone.I have tried piezoelectric speaker and crystal earphone.but I can't hear any sound.I prefer to use piezoelectric speaker if it works because crystal earphones are hard to find.
By the way, anyone knows what is detector coil and how to make one?I saw this on another vacuum tube radio circuit..
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Hi,
First, you have a tuned circuit with an antenna, an inductor, and a variable capacitor. This circuit selects a radio signal and delivers it to the anodes of the double diode detector via the 100pF capacitor, which demodulates the signal and turns it into audio frequency that you can hear.
This is a circuit that will not work well without a good antenna. I suggest at least 10 metres of wire. The diagram does not give values for the inductor and the variable capacitor. If you want to listen on Medium Frequency - AM - if the variable capacitor is 500pF, then the inductance should be about 120uH. What values have you chosen?
The demodulated signal now at audio frequency moves through the 100K resistor to the top end of the variable resistor volume control. At this point there is a capacitor of 100pF to pass high frequencies to the Earth so the triode valve will not start oscillating.
The signal now arrives at the triode grid.
What voltage can you measure on the triode anode - pin 7?
Can you see the valve heater glowing? What is the voltage across pin 3 and 4?
Taking care not to get electric shock !!! touch a screwdriver or the end of a piece of insulated wire on the triode grid - pin 1. Is there a humming sound in the earpeice?
Can you hear a scratching sound in the ear piece when you rapidly turn the volume control variable resistor up and down?
When you have tuned in a very strong station, then the audio voltage across the 1M resistor in parallel with the crystal earpiece should be 20 or 30V. The triode valve in this circuit will have a gain of about 60, so you will understand why you need a good antenna. Unless you have about 0.5V of RF signal voltage across the tuned circuit before the diode demodulator, you will not have much audio volume.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Vacuum tube radio problems
