Transmitter Tuning..........

[RolandSWL]

Hi All,

 I am trying to understand what is happening when a tube transmitter is tuned from a cold start or when changing bands. I can understand the sequence but I don't have a grasp of just what is going on internally and why.
 Sorry if that is not too clear.
 Can someone steer me to a more technical explanation of the tuning process?

Thanks, Roland...........

[Pete, WA2CWA]

I would suggest initially going to You Tube, http://www.youtube.com/ . In the Search Box, type: Tuning A Tube Transmitter. A bunch of videos from basic to the more technical for all types of rigs will be displayed. This should provide you with a good starting background.

[W2PFY]

Well one of the things that happens if your using a vintage transmitter that has it's own VFO, the transmitter needs to be on for at least thirty minutes for the VFO to stabilize to minimize drift. This will help the people your talking to from chasing you around the band.

[kb3ouk]

The tuning process can vary depending on how the RF stage is designed and even what modulation scheme you are using. A plate modulated final usually just requires peaking the grid, dipping the plate, and setting the loading to where you want it, but a screen modulated final requires the loading to be heavier so that the efficiency at carrier is low enough to allow headroom for peaks (the efficiency of the final increases on peaks). With a link coupled output with a swinging link, you swing the output link out of the tank coil, then dip the plate, which means it is at resonance, then swing the link in towards the coil for loading. I'm not quite sure how a pi-net works for tuning.

[RolandSWL]

Thanks to all who replied.
I was thinking about getting my hands on an old copy on the ARRL handbook. i remember there was plentiful info on all things hollow state. How far back should I look ? mid sixties?

Thanks again, Roland.....

[KB2WIG]

Get an online copy of The Radio Handbook. Lots 'o stuff inside.

http://www.tubebooks.org/technical_books_online.htm


klc

[w1vtp]

Well one of the things that happens if your using a vintage transmitter that has it's own VFO, the transmitter needs to be on for at least thirty minutes for the VFO to stabilize to minimize drift. This will help the people your talking to from chasing you around the band.

Unless you are operating in the "drift-o-matic" mode     then it is a matter of relatively.

You're right, Terry.  Just yanking yer chain.  Where have you been lately?

Al

[KA0HCP]

Roland,
It's not possible to give specific answers to your general question, but here are some thoughts on how to approach a new transmitter.

-Always obtain clear copy of the manufacturer's manual with changes and addenda, with a full schematic.  Economy here is foolish.

-[edit]  Make a working copy of the manual and schematic!  Mark it up with pencils, pens, colored makers; whatever helps you understand and remember how to operate!!!!

-Read the whole manual with attention to warnings, caution and notes.  Study the control functions, and typical settings.  Review the schematic from a functional perspective, i.g. master oscillator, buffer, frequency doubler, modulator, PA, and familiarize yourself with the tube numbers and types for future reference.

-On a notepad, write out the entire sequential procedures for turning on, tuning and transmitting.  Include expected or typical voltages, currents, knob settings etc.   You may add grease pencil markings on dials or meter faces (or cut little triangles of colored tape), put tape above dials to mark setting points, etc.

-Do several dry runs (no power) with your checklist, then repeat with power into a dummy load.  Then get on the air!

-With experience condense your list to the essential check items and reference settings for each band and antenna configuration.  This will save time, and reduce wear on your transmitter in daily operation.

cheers, bill

[kb3ouk]

Having a manual is fine unless you're dealing with a homebrew rig, in that case having some knowledge of how things work and how different designs handle com[ared to others is gonna be more important, since most homebrew stuff doesn't come with a manual.