Sept 2007 - SDR1000 144Mhz Operations -Internal Transverter
I resisted the FlexRadio SDR1000 plunge for several years. About the time I
became "serious" about the 1000, Flex discontinued it. I made the mistake one
day of mentioning to Terry WØVB that I had missed the boat, "perhaps
not was his response". Terry had an "extra" and soon it was in my shack. Oh My!
I was having trouble ONCE AGAIN with my IC746Pro on 2meters and soon the Sept
ARRL VHF Contest was going to be upon us. So I made an effort to get my SDR1000
with it's internal transverter on 2m for the contest. Now the internal DEM transverter is not intended for 2m operations, it is a unity gain device to be
used with external transverters with a 2m IF.
It appeared I had everything that I needed to make the transformation. Could I
get the 1000 on 2m in time for the contest? As was the case with my SoftRock IF,
I needed gain at 144mhz and 28 mhz. A ARR 2m Gasfet preamp was being used for 2
anyway, so that was not a problem. I then built a 20db MAR6 preamp that could be
used between the SDR and the internal transverter. This combination made the
system usable, but it is a few db short of the IC746Pro with the preamp.
In this configuration the output power of the DEM PA is about 5w which is fine
for driving the pair of 8560As to 400watts. Signal reports are "complimentary" on the audio quality, as it should be. There is "lots of headroom "everywhere".
I now use a Heil HM-5 microphone and the default 1000 "conventional" TX profile.
DEM 144-28 EC 2m internal transverter
This is an earlier version of the SDR1000/DEM internal transverter. According to Steve at DEM, there was an early version of the internal transverter for the SDR1000 that was indeed a FRS, but the board still carried the EC label since it was an existing design with additional "hooks" for the Flex.
MAR6 preamp for 28Mhz RX gain
This preamp provides about 18db gain at 28mhz. It is switched in the 28mhz IF chain during receive and is bypassed in TX.DEM Preamp and 2m PA (Right)
Currently I am using a DEM 2m preamp instead of the ARR preamp I used earlier. This preamplifier is a couple db short of the ARR gain. At times it seems like it is not quite as good as the ARR/746Pro combo and other times just as good. I am using a weak signal source in the yard to try to make comparisons. One would think it would be "easy" ... I am using this as my main 2m weak signal radio except for EME, where I need more drive for the 8877.
The image above is my Jan 2008 "front panel". This is using K6JCA's console. I really like the flexibility for skin colors etc. The PowerSDR software continues development. That is one area of concern I have with the software specifically for the SoftRocks, they seem to be more static in development. I just wish we could have a waterfall display as good as Rocky!!
KØAWU SDR Page