Perseus Blog

Antenna setup comparison

• the ALA1530S 7m above ground and 15m from the house
• the ALA1530LNP 3.5m above ground on a field 70m from the house

28 MHz:

MW

Spectrum Lab Perseus files

• Spectrum Lab V2.92b02 works fine after I copied all *.sbs files from the Perseus directory into the Spectrum directory
• perseususb.dll must be in the Spectrum directory, too. It only works with the dll from 2009 or 2010. The dll from 2013 (supplied with newer versions) fails.
• if you have things set up like this, the FPGA path in the Perseus control panel can be ignored. It can be anything - still working.

registry diagnostics

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB\VID_04B4&PID_325C\ is the path to the USB ports on which the Perseus has ever been connected. For each connection there is a subdirectory.
• the well working front port entry has a subdirectory:Device Parameters/WUDF/ with an key DriverList as REG_MULTI_SZ with a value WINUSB
• the faulty rear port has a subdirectory named Control instead. It contains the key ActiveService with value WinUSB
• copying the values to the other port did not help

FM+ RDS decoder vs RDS Spy

advantages Perseus FM+ software

• much faster PI guessings (but many wrong). Unfortunately there is no statistic about which PIs are being shown repeatedly.
• RDS-SNR helps to adjust bandwidth and identify sections of a recording which are worth looping
• looping of sections is possible
• live performance

advantages SDR# RDS Spy

• slightly better PI decoding under critical DX situations
• it takes a little while, but then the shown PI is more reliant (though not always correct)
• faster PS with defined letter position
• loads of additional information: AF, radiotext and much more (only with stable signals)

Setting up RDS Spy with SDR sharp software (SDR#)

• install the VB audio HiFi(!) cable
• install the MPX output plugin for SDR# and activate MPX with VB audio (MME or DirectSound work both)
• in RDS Spy select VB-Audio as input source
• in the Mixer settings for recording and playback select properties and then the same 192 KHz mode
• for DX purposes check the Super PI decoder option in RDS Spy settings
• play a recording: RDS data should appear

Waterfall compression

just found out that there must be a spectrum compression in the waterfall in the Perseus software. This is important to know when you interpret signal levels. I've listened to KVRI on the Masset recording (3-Jan-2009, 17 UTC) on 1600 KHz. Until 16:59:56 there is Asian music which suddenly stops. After that a station ID is spoken, followed by 2 seconds of silence. Finally, music starts again.

Watching the waterfall, I first wondered why the carrier signal seems stronger during the station ID and the silence part. Simultaneously, the weaker 1602 KHz carrier becomes visible strongly. When the music starts again, it disappears completely. If the waterfall was linear, it should remain. But actually it's always there. It's just masked by the modulated signal. And the waterfall follows to the overall level. I guess Spectrum Lab wouldn't do that.

Exact frequency measurement

This is a spectrum of 1602 KHz in North Germany (calibrated). The labels of the x-scale are misleading. The center is 1602.000 KHz, the vertical lines would be 1602.002, 1602.004 and so on. You can estimate the carrier frequencies by 0.1 Hz here. There are 9 carriers between 1601.990 and 1602.007 KHz. Most of the MW carriers are relatively stable over a few weeks here in Europe. From February 2009 to September 2009 I've observed that many carriers have drifted about 1 Hz. So does it make sense measuring 1/10 Hz? Well it does if you compare recordings from different parts of the world from a limited time span. Then you can identify weak MW signals even beyond 10.000 km of distance.

Calibration

• tune to the time signals on 10 MHz
• click on CalClr.
• turn "Labels" on
• turn "Zoom" on
• select a resolution of 0.48 Hz in the Span/RBW window.
• detertmine the peak and then tune to that frequency by using the scroll mouse on the frequency counter.
• Click on "Cal"

Beware of doppler effects. The smaller peaks on the right side could be reflected signals from airplanes. Sometimes they're as strong as the main signal.

Unfortunately it is impossible to calibrate the scale as exact as it could be possible theoretically. The minimum VFO step is 1 Hz while you could determine the peak by 0.03 Hz. The shift is proportional to the frequency: If 10 MHz has 0.5 Hz, then 20 MHz would have 1 Hz, 1 MHz would have 0.05 Hz. There is no other way than calculating.

Check the reference frequency (usually 10 MHz) every once in a while: when the Perseus is turned on, it will take one hour until the calibration is relatively stable. During the first 10 minutes the peak of my receiver drifts by about 30 Hz (from 9999.945 to 9999.975 with CalClr for example).

Recordings are affected by calibration but not exactly the way they should be. If the receiver is calibrated correctly, the center frequency of the recording will also be. But the border frequencies will be detuned.

Example: peak found on 9999.980 KHz, calibrated, then started recording with center frequency 1000 KHz.
This means the calibration factor is 20 Hz per 10 MHz, thus 1 Hz per 500 KHz.
If you tune to 1500 KHz in the playback (500 KHz off the center), the peak of an exact signal will be found on 1499.999 KHz (1 Hz less).

The good thing: when you deal with recordings with unknown calibration status, you will only need two refence offsets. The rest is proportional.

Example: The playback contains France Inter on 162 KHz with a peak found on 162.0017 and DLF on 549 KHz with peak found on 549.0030 (both really transmit on exact reference frequency). The offset in Hz for any frequency in KHz will be (frq-162)/(549-162)*(3-1.7)+1.7
I've compiled a list of the detuning on the recordings distributed by the former Five Below Blog. It wasn't always easy to find reference frequencies but I think the result is quite good.

PRS - the Perseus record scheduler

• rename the com0com-Ports to an unused number (see Perseus release notes), example: A0 to 14, B0 to 15
• change the registry VCom-Entry from 10 to the 14
• modify PRS_alternate_COM_Port.bat to 15
• start PRS with PRS_alternate_COM_Port.bat

bugs

• if you listen to recordings and use high resolutions (1.6 KHz span and lower), the "center" option and the CF step are disabled.

2000 KHz recordings