"Firebottle3" wrote in message
...
I found this on another forum. All I can say is WOW!!!!!

Thanks to the guys that put all of this information
together.

__________________________________________________ __________________________________________


Perry Sandeen has finalized a remarkable work on the
Hammarlund SP-600
and its many variants. This has been a long process with
input from
many different people who all had something to share on
this fine
receiver.

It is available for download (free) on the Hammarlund
Historian
website. It is in .pdf format and in two parts, each being
approximately 7 megs.

Look he http://www.hammarlund.info/

Downloaded these last night. While a lot of this
information is available already its scattered all over the
place so its quite valuable to have it gathered together.
Some of the modifications are interesting but I don't think
I will modify my RX. Remember, the SP-600 has an IF output
plus outboard terminals for the AVC and detector so its
possible to build all sorts of outboard auxilliary
equipment.
I am also very skeptacle about modifying RF stages for
low-noise tubes. The noise level of the receiver is already
pretty low and for communication frequencies, at least up to
30mhz the antenna input noise is likely to be many times the
front end noise plus the 6BA6 has excellent dynamic range.
BTW, I disagree with Andy Moorer and some others who think
the AVC system is poorly designed. Actually, its pretty good
with increased "delay" to the RF stage to keep the noise
level down. For those using the SP-600 mostly for broadcast
listening its helpful to lengthen the AVC time constant
considerably, this is easily done by hanging a capacitor
across the AVC terminals on the back. Try about a 0.1 uf for
starters. This will eliminate the low frequency
intermodulation due to the AVC following low frequency
modulation in the signal plus it will keep the signal
strength meter from following the modulation.




--
Richard Knoppow
Los Angeles
WB6KBL