Apr 5, 2009

Location, location, location..........

I'm lucky to try out the new PERSEUS SDR receiver from Microtelecom.
I have seen it in action at Rens, PA3FGA for several weeks now. It IS a great device.
What I like most of it:
  • It does have a great receiver
  • Very informative GUI, much better than any SDR competition
  • Can show both waterfall bandsweep and separate FFT spectrum on the received passband
  • Can record 800KHz band segments at a time (record the 48hrs contest)
  • Has reasonable measurement capabilities for frequency analysis
The waterfall view together with a small bandsweep and proper averaging settings is the way to find weak ones. I have seen proof on very weak beacons on 144MHz (from my Elecraft XV144 transverter output). I have also watched a recorded night of ARRL-DX-CW contest on 160m. You can spot the weak ones next to the big pistols. Yeah key-clicks are now visual too on some of you :)

Measuring device?
This is a consumer device, but with valuable user settings and good specifications.
As such, it can be a reasonable measurement device with which you can do some rudiment frequency analysis. It is capable of showing clear raw data you can trust.

Now what has it shown me so far?
My current location at the east outer border of a small town has shown me already that I suffer from noise and in band disturbances on both 50 and 144 MHz. When turning the antenna, both the ground noise level rises and several in-band local disturbances turn up.
For 50MHz this is very obvious when turning the antenna to the N-W direction (my town).
Time to do some of that frequency analysis.

I did a bandsweep from 50.000 - 50.200 MHz using the following setup:
5el M2 yagi @12mtr AGL
Elecraft XV50; 50Mhz to 28MHz
Perseus SDR receiver set at 200KHz span and averaging set to 80%

6m band direction N-E (QTF 60deg)

The window is centred on 28.100, which effectively is 50.100 MHz. The transverter is aligned and has the crystal oven build in. Do not look at shown levels and such as this depends on many factors.
The disturbances on 060, 090, 120 and 150 are local man made QRM.

6m band direction South (QTF 180 deg)

See the effect of local noise? The band noise level has already gone up by 5 dB and new other disturbances turn up.

6m band direction N-W (QTF 290 deg)

Even more noise and stronger disturbances.
The measurements where made at 03:00 in the middle of the night (01:00 UTC), when all is quiet. Right?
Think for a minute what it might look like during daytime, or even worse, during evenings?????

Preliminary conclusions:
This is a quick&dirty band scope view only. It only shows the 'Big Picture'.
It might explain, to some extent, why making contact to the USA on 6m is so hard from my current location. However, there is much more measuring to do before jumping to conclusions.

Perform extensive testing in more directions, at different times during the day.
Repeat the measurements to average out any large variations.

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