{Collins} Collins 690D-1 Antenna loading coil

Dear collector friends
for my mobile HF installation I am using a 490B-1 tuner (this is a box containing a 180R-6C tuner and control stuff) which was connected to a 690D-1 loading coil assy. on which the whip was mounted. A control cable feeds a vacuum relay inserting or shorting the loading coil. This unit is unfortunately not covered in the 490B-1 manual.
My question: does anyone know for which frequencies and whip lengths the loading coil was used/needed? Would it be advisable to use it for ham band operation? (the box weighs 22lbs. that's why I wonder...)
Many thanks for any and all opinions!
Best regards,
Ulrich Fierz  hb9aik - vk6bqd

Ulrich N Fierz
Telecommunication Engineering Services
CH-8044 Zurich

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