In a message dated 00-05-01 22:51:52 EDT, N4NT wrote:
<<
Well, I was apparently mistaken about the 580 Delta's IF scheme. I had
thought it the same as the Corsairs -- knew it took different filters from
the older Omni's, but was designed to work the WARC bands without the 18 MHz
spur.
I may be mistaken about this, too, but thought the rebuild kits for the
PTO's of the 580 Delta and the Corsairs were the same. Thought the Tritons,
older Omni's and Argosies were alike.
>>
I just looked at the manual for the Delta and technically it actually is
double conversion. It mixes the input signal with output from a band crystal
to generate an 11.0 - 11.5 Mhz signal which is then beat against the PTO
which goes from 5.2 to 4.7 Mhz to get the 6.3 Mhz final IF.
You are correct in that the rebuild kits for the PTOs are the same since they
all use the same set of parts that come in the kit. The drive rod for the
Delta is left threaded so that the frequency varies in the opposite direction
from the one in the Omni's. This is due to the 'upside down' mixing scheme.
Remember some of the old rigs where you tuned the dial one way on say 80 and
in the other direction on say 20? This was due to the economy of using a
single band crystal for both bands and adding it in one case while
subtracting in the other.
I agree that the other you mentioned are pretty much alike. I did not like
the inaccuray of the digital readout when I had my first Delta, but these
days it doe not seem to matter for some reason.
Walt
--
FAQ on WWW: http://www.contesting.com/tentecfaq.htm
Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|