[Collins] More on 30L-1

[root]

On Wed, 2005-03-30 at 10:14 -0600, Jim Isbell, W5JAI wrote:
> I noticed that in the manual it states that the rf cable from the
> exciter to the 30L-1 was exactly 20.5 feet in length.  Is this a
> maximum, minimum, or an exact length.  Must it be exactly 20.5 feet
> long?  This seems an odd requirement.

This was the published requirement for both the 30L-1. With an untuned
input it was felt that "magic" length of coax improved IMD of the PA
when used with a 32S or KWM-1 or KWM-2. There is some evidence in recent
times that the improvement isn't substantial. Its most probable that if
the coax is just long enough to reach from driver to PA that the added
IMD products are still 10 dB or more below the latest solid state radios
since the Collins exciters used PA tubes that were inherently low
distortion and then used RF feedback to reduce the intermod products
further. What is accepted today is far poorer than these radios ever
produced.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer