K1 Builder Alert #2: Different toroid cores in some band module kits
Updated - 19 Dec 2000 

Impact: All K1's through S/N 350

Background:
It has been reported to us that a small number of the 40M band module kits for the K1 have the incorrect size of yellow toroids in them. Some contain T50-6 toroids (0.50 inch outer diameter) instead of the correct T37-6 toroids (0.37 inch). This may also have happened in any of the other band kits (40, 30, 20 and 15M). Both toroids are yellow.

All of the band module kits used in the K1 normally use the smaller T37-6 yellow toroid. If you find you have some of the larger, T50-6 toroids, you can use them temporarily while waiting for replacement T37-6 toroids. ( Contact support@elecraft.com or call us at 831-662-0830 to request the T37-6 toroids and additional wire if needed.) The T50-6 cores will work fine electrically with a modified turns count, but they will be a little tight on the Filter PC board and may also be too close to the KAT1 ATU option when it is mounted above the filter board.

You will need to use a different number of turns to get the same design inductance.  Failure to use the correct number of turns will make it difficult to get maximum power out and to peak the receive sensitivity.

Modification instructions:

Either size core may be used for any band. Please observe the following new data
for winding the toroids on the larger T50-6 cores:

40m: 18 turns
30m: 15 turns
20m: 13 turns
15m: 10 turns

Please accept our apologies for this inconvenience. We have inspected our current inventory and we have purged all of the incorrect toroids.