[Collins] Split Mode

[David Thompson]

Split mode goes back much further than the SSB days.  I have 263 countries
confirmed on 2 way AM.  Dx stations on 20, 15, and 10
would sit below the band (even non rare DX) and listen up.  On a normal
Saturday afternoon  F8PI would call DX stateside below 21259 and listen up.
Often there wuld be 40 or 50 callers from 21255 to 21300.  On CW the band is
the same so a small 3 to 5 khz split is normal.

The splits used when SSB became popular were simliar.  I remember Reg FS7RT
(and other calls) would sit on 21200 and listen 21400 up.  Back then the USA
only had 14200 to 300 as a 20 meter phone band.  Some Dx (most of the SSB
Dx) would transmit above 14300 and listen around 14290 for stateside.  The
biggest pile up I can recall was EA2CA's trip to Ifni (a Spanish Province in
Morocco).  Juan worked across SSB and AM tuning from 14240 to 14300.  He
used a KWM1 with the Dx adaptor and he had two or three crystals so he could
move around QRM above 14300.  I looked and he was on 14321 when I worked him
with my 500 watts of AM (I called for 6 hours).

I recall the problem with the Collins S-Line on splits. Collins Engineers
developed the DX adaptor the KWM1 and later KWM2.  I remember Doc of ZM7
fame saying he would never take any rig except the Collins M2 with adaptor.
World famous Dx traveller used a M2 on both CW and SSB.

The Drake and Heath equipment came later and standardized on the 500 khz
tuning ranges.  Before then 200 was the standard with Collins, Eldico, and
the KW series from the UK.  One additional limiting factor was the receiver
preselector tuning.  So even if you had a split from say one end of the
tuning range (say 14100 to 14280 as W0MLY used on his African trip in 1962).
The signals on either end of the split were normal but reduced quite a bit
as the preselector needed to be peaked at the other end (the receiving end).
Dick reported S9 signals became S4 to Collins Engineers hoping for a fix.

73 Dave K4JRB  Be there done that.