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 #515
Joined: Sun Feb 11 2007, 02:06PM
Location: Slovenia/Ljubljana
Posts: 94
Hello
Quite some time ago I built a VTTC and I tried to audio modulate it by puttinga a transistor betwen grid1 and R2 C3 but then it didn't even oscillate . I haven't yet tried modulating the power supply I also haven't tried connecting a staccato controller. The schematic that I used is CTC labs valve no.2 and instead of the GU-50 tube I used a PL519. It works just fine with the PL519 tube. So if you could please help me because I'm kinda new at these things.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
It won't work with grid 1 because grid 1 expects an AC signal superimposed on a negative DC bias. The transistor will kill the AC that's trying to get through, and stop the circuit from oscillating.
You have to modulate the DC supply to grid 2 as shown in the second schematic, or make a different circuit that modulates the negative voltage on g1 without killing the RF signal.
Registered Member #29
Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500
Grid modulation should work. However, plate modulation is often more common (I seem to remember it behaves more linearly..
Another technique that I've seen with low voltage transistors is cathode modulation. Low voltage (<100V) transistors can modulate Vgs by modulating the cathode potential with respect to the control grid. If you want, I can try to dig out the reference...
Registered Member #29
Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500
Andrew, I could not find the reference. However, the a popular way to modulate AM transmitters in days of old was plate modulation... This requires basically a big fat audio amplifier with a big heavy audio power transformer. Grid modulation is somewhat less linear, but clever use of feedback can reduce non-linearity. Cathode modulation, like grid modulation, can use low voltage devices without the need for transformers. The benefit of cathode modulation lies in its ability to be easily used with grounded grid triode PAs or oscillators. I am not sure about tetrodes or pentodes, tho'. Triode tubes can often be modeled with modified JFET models in Spice... For more complex grid arrangements, I can't say... Sorry!
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.
Audio modulating a VTTC
. I haven't yet tried modulating the power supply I also haven't tried connecting a staccato controller. The schematic that I used is CTC labs valve no.2 and instead of the GU-50 tube I used a PL519. It works just fine with the PL519 tube. So if you could please help me because I'm kinda new at these things.
. But it didn't work.
