QRP Club

QRP Station => Builder's Corner => Topic started by: ve3lyx on October 09, 2016, 00:18:46 UTC

Title: Longfellow Transmitter
Post by: ve3lyx on October 09, 2016, 00:18:46 UTC
A few years ago I stumbled on to a batch of NOS 25L6 tubes. I always had a hangering to build an old style Longfellow Transmitter but instead of the usual two tubes (osc and PA) build it with a crystal osc and a quad four PA. Over the last to weeks I have been working on it and today it came to life. 25L6s are not real powerful being intended for light duty audio but 4 gives enough to do the job. Mostly I built it for fun.
The OSC runs constantly and has a pair of crystal so you can choose between them should QRM be a problem. There is also a standby position for when you are listening. The quad four screens are keyed and are lightly biased neg during key up to prevent unexpected excitement. Can do 40M or 20m at the flip of a switch which halves the coil by shorting out the upper windings to centre. Initial testing seems good but I need some crystals in the Cw portion of the bands before I get too serious. (ordered and on their way). It has a transformerless PSU hidden under the chassis. Filaments are in series so 120 to 127 volts which is what I have measured here does the job. When I get the good crystals and am assured it is good to use on 20m hopefully I can connect with some of you. Pic is when it was about 80% done.
Title: Re: Longfellow Transmitter
Post by: GM0LVI on October 09, 2016, 20:15:48 UTC
Congrats Don!!
What a super project. You must have had a great kick of pleasure when it came to life.
Looking forward to a QSO before too long.

BTW - Your joinery skills look pretty good! :-)

Title: Re: Longfellow Transmitter
Post by: ve3lyx on October 10, 2016, 13:58:39 UTC
Bless you my son. May you live an extra day! I struggle with the pretty side of homebrew.