http://www.mrs.bt.co.uk/dubus/9104-3.pdf
http://www.mrs.bt.co.uk/dubus/9201-1.pdf
http://www.mrs.bt.co.uk/dubus/9103-2.pdf
http://www.mrs.bt.co.uk/dubus/9202-1.pdf
Articles about tubes. Primarily geared toward audio applications.
http://soundstage.com/tubeor/tube.htm
Specificatiosns and pictures for a variety of old shortwave receivers.
http://www.dxing.com/rx/tindex.htm
An essay presented to the AES on the much-debated topic of the tonality of different amplifier technology.
http://www.milbert.com/tstxt.htm
Based on Philips TDA7000 receiver chip. It is tuned with a BB105 varicap diode in the 13MHz IF band.
http://jcoppens.com/sat/rx/tda_if.en.php
http://www.wenzel.com/documents/tuning.html
http://www.uoguelph.ca/~antoon/circ/tuptun.htm