Transmitter BL-11

We knew of transmitter BL-11 long before we began our project.  Kid brother of the famous transmitter BL-10, the diminuitive BL-11 provided backup capability for KPH on MF.  Archival photos showed BL-11 installed on the upper gallery above the Alexanderson alternators in Building 1.  A later photo showed BL-11 installed in Building 42, the tuning house for BL-10.  When we first arrived at the Bolinas site to begin our project, one of the first tasks was the removal of decades of detritus that had accumulated in the various buildings, including the generator building near Building 2.  MRHS member Richard Dillman writes:

As we started cleaning out the generator building various historic items started to emerge.  After moving some junk the corner of a table was revealed, a table I recognized.  It was the table on which transmitter once rested.  Nearby were the motor-generator sets that once powered the transmitter.  But BL-11 was not to be found.

Later we discovered where BL-11 was located but circumstances prevented its recovery.  But circumstances change and finally, ten years after the discovery of the table, BL-11 returned home.  The MRHS Transmitter Department has already begun a preliminary examination of BL-11 with a view toward returning it to life.


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BL-11 as installed in Building 42.  Once we had the transmitter in hand a lot of the layout in Building 42 started to come into focus for the first time, including the method for switching between BL-10 and BL-11.

Richard Dillman writes: Finally, after yers of waiting, I was able to enter the dark basement room where BL-11 was thought to be.  After some searching and not a litttle tripping over various objects my flashlight revealed the little transmitter, partly hidden behind other artifacts.  It was a real thrill to finally see it in the flesh.  I felt a little like Indiana Jones.  This flash photo shows BL-11 as found in the dark room.

On the top deck sockets for three 813s (ony two still present) may be seen.  On the lower deck are the remains of the 500kc and 426kc frequency sources.  There is also a BNC connector of an external frequency source.

BL-11 appears to be a highly modified Radiomarine shipboard MF transmitter.  Of course any documentation that might have existed was no longer with the transmitter.  But the front panel controls were labeled with classic Dymo labels.

Grease pencil markings show the antenna current for 500kc and 426kc.  What might be considered defacements are in fact important historic fabric that connect directly with the radiomen that were in charge of keeping the little transmitter on the air.

Immediately after its arrival back at the Bolinas transmitter site, Steve Hawes and Richard Dillman pose with BL-11 in front of the PW-15 KSM 12Mc transmitter.

BL-11 was moved to safe storage in the Bolinas parts room.  Quite fittingly, the final tubes used in BL-10 may be seen to the left (BL-10 used just one of these tubes).  Later, the original table and motor-generator sets were moved in around BL-11.