[hpsdr] MW DXpedition Ozy/Janus/Atlas Comments

[dx at guyatkins.com]

I'm currently in the middle of a week-long medium wave DXpedition on the
northern tip of Masset Island, in the Queen Charlotte Islands chain off the
coast of Northern British Columbia, Canada. My four DXer friends and I have
six SDR radios of various models amongst us, but I am the only one with a
SDR-1000 & HPSDR boards.

Some may recall my recent posting of photos and descriptions of my homebrew
enclosure for the radio, HPSDR boards, and custom LP filters for the MW &
LW bands. On the DXpedition, I have been able to do very careful listening
and comparisons for results on weak signals with the balanced IQ connection
between Janus and the SDR-1000, using Ahti Aintila's nice modification
(bypasses the INAxxxx amplifier to send balanced IQ direct to the Janus
board).

It turns out that this balanced input approach does not have the needed
gain to resolve very weak signals, at least on the MW "splits" on 9 kHz
spacings. While other receivers in the group heard discernable languages as
signals faded in, I was only able to hear the fact that there was audio
with the SDR-1000 combo (until the signal increased further in strength).
This became evident over time...it was a subtle difference compared to the
rest of the receivers in use here. No manner of adjustments in PowerSDR
seemed to make up the difference when chasing these threshold level
signals. 

I eventually hooked up the *unbalanced* connection between Janus and
SDR-1000, and the weakest of signals were again audible (languages could be
identified as early during fade-in as the other radios could resolve). 

Using the "stock" unbalanced connection means I am not getting the very
lowest noise floor possible, nor the very best dynamic range, but at least
in this RF-quiet DXpedition location this connection is needed to hear the
weak signals as they fade in.

Fortunately for all of us on the DXpedition, many if not most MW signals
from both Asia and Europe are being heard at good levels. Best DX catches
from here in the Pacific NW British Columbia have been: 1548 kHz Sri Lanka
(Deutsche Welle relay); 1215 kHz Virgin Radio (UK) at amazing strength;
other MW catches from Europe including many "synchros" from Spain; 801 kHz
KTGW Agana, Guam; numerous low-power (< 1kw) Japanese MW relays; and 1251
kHz Tripoli, Libya are a few that come to mind. 

Overall, the SDR-1000/HPSDR combo has been a dynamite combination for MW
DX, especially after reverting to the "stock" unbalanced IQ connection. 

Ahti or anyone else-- if you have suggestions on improving the signal
levels with the *balanced* connection, I would love to hear your ideas.

Best DX,

Guy Atkins
Puyallup, WA
DXing from Masset Island, BC, in view of the Alaska panhandle


--------------------------------------------------------------------
mail2web - Check your email from the web at
http://link.mail2web.com/mail2web