mrhaney wrote:

I have about 60 military crystals ..they are marked Channel 277 thru CH
347 .Anyone know if they are overtone ,and, know of a good way to
check them.. My grid dipper will not oscillate with them like it does
with basic fundamental crystals ,like 7193 KHZ. etc..THEY ARE FOR
SALE TOO..W4PQW



Hi !

You are raising nostagig memories.
In 60 tales those FT241 xtals were used for home brew 455 kc xtal
lattice filters for SSB transmitters and home brew receivers.

Bought some 100 pcs of them from "Jan Xtals" surplus shop in USA.
Oscillator circuit for those FT241 xtals was not so trivial as for ham
band xtals (as you experience with your dipper)
Used BC-221 to select individual xtals for lattice filters.
You can check them by measuring series resonance.
You can also make a simple J-fet oscillator

Oh those surplus times
A school boy had to consult a couple of hotel porters to change
Finmarks to USD to buy surplus xtals from USA to make lattice filter to
contruct SSB transmitter.

73 de Risto OH2BT