[Hammarlund] SP-600-JX14 and my -JX1

[Richard Knoppow]

    This is ringing a very loud bell and may have been an early 
post of mine.
    It does seem to me that one of the military manuals had some 
piece of nonsense in it.
    Aligning the IF is simple, you can use a 455Khz oscillator or 
even just a signal. The crystal establishes the IF frequency. 
Find its peak with the bandwidth minimum, Then used that 
frequency to peak all the IF transformers in the 455 Khz IF with 
the bandwidth set at 3Khz. When that is done make sure the test 
oscillator is still at the exact crystal peak. Then set the 
bandwidth at 1.3 Khz and modulate the test oscillator at about 
1500 Hz. Adjust to the _audio_ output. Adjust the loading coil 
for _maximum_ level. The purpose of the loading coil and 
resistors is to load the crystal to lower its Q and widen the 
bandwidth. There is an input transformer for the crystal which is 
peaked at the IF frequency. The phasing control is set at the 
diamond mark and checked to see that that is really the center of 
its adjustment. You can usually judge this by the noise. At 
1.3Khz it should be minimum at the center. Also check for 
symmetrical nulls. If the phasing is way off and you are sure of 
the alignment it may be one of the phase splitting caps C-110 and 
C-112. The carrier level out is not much affected by bandwidth 
with the signal peaked but there may be slight reduction for the 
narrowest bandwidth. Part of Orem's patent is the claim that the 
gain through the filter does not change with bandwidth. Nor 
should the peak frequency change with the phasing control. It is 
a very good filter.
    In some earlier versions, such as the one in the HQ-120-X, 
HQ-129-X, Super Pro after the filter was adopted for it, there is 
a trimmer for the phasing adjustment. A stiff wire for the 
cheaper receivers and a compression trimmer in the Super-Pro, Its 
not used in the SP-600 perhaps because it uses a sealed crystal 
and they are more uniform.
On 8/22/2020 1:54 PM, Kenneth G. Gordon wrote:
> On 22 Aug 2020 at 12:56, Richard Knoppow wrote:
>
>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL