Here's my one-valve CW transmitter, produces up to 10W on 80m and 8W on
40m:
http://www.hanssummers.com/radio/cwtx/index.htm. In this circuit I have
found that modern HC49 type crystals work perfectly well. Before building
it, I was warned that HC49 crystals are too small for valve circuits and
would fracture. Fortunately I decided to give it a go anyway, and have not
yet had a crystal fracture. Some have suggested that this may be due to
the
DC blocking capacitor in series with the crystal (see my circuit diagram).

Quartzlab charge £7.50 per crystal (minimum order £10). A cheaper way is
to
buy a bunch of standard value crystals and lower them by painting the
crystal surface with felt tip pen, see my page about it:
http://www.hanssummers.com/radio/penning/index.htm. In this way it would
be
possible to build up a bank of crystals covering a segment of the band.
3.579 (TV colour burst) crystals are available almost anywhere extremely
cheaply, and I found it easy to lower it by 30KHz. 3.560 crystals are also
available, it's the 80m QRP calling frequency. See the links page on the
QRP
website http://www.gqrp.com for some suppliers. Similarly 7.030 (Europe) /
7.040 (US) is the 40m QRP calling frequency, and they can be easily
lowered
to anywhere down to 7.000.

My TX has 4 relay switched crystals: 3.558, 3.560, 7.010 and 7.030. All
are
(or were originally) HC49. After 2 years and over 400 QSO's, no
fracturing.

73
Hans G0UPL
http://www.HansSummers.com

Hello Hans,

Thankyou very much for the information regarding the xtals, I have been to
your site many times to admire the equipment you build and is it that which
has inspired me to build a piece or pieces of valve equipment.

Thankyou again,

Simon G7CPN.