SDR puzzle

20-Oct-14 11-10-15 AM

Just starting with SDR, so forgive my ignorance. Here is a HDSDR puzzle:

I installed HDSDR and hooked the RTL-SDR adapter up to my TS-590 on the tune connector CN303 (1st IF on RX-2, 73.095MHz). Cable is a normal coax cable with on the center a 100pF cap (don’t know what it’s for, but they told me to put that in). Final objective is to use HDSDR to see the spectrum and to tune the radio.

At first i thought things were not working because i didn’t hear anything on the SDR. Then i tuned in between 70 and 75MHz. Turns out that i hear my TS-590 when i tune the SDR on or around 75.550MHz. First question, why is that? Why is it not 73.095MHz?

Ok, so now i hear my radio. Let’s tune to a frequency where i have good reception and where there is always traffic, 28.120MHz, the PSK31 frequency on 10 meters. Nothing. I do hear my PLC, so i suspect that the frequency i am listening to is far below 28.120MHz. Dialing up i hear truckers on 28.230MHz. They tend to be on the CB band, so that confirms my suspicion that i am listening to 1Mhz below what my radio tells me.

I looked for a strong station on the 10m band and noted down frequencies. This is what i found:

  • Real frequency where station is transmitting: 28.465MHz
  • Frequency displayed on the radio: 31.350MHz
  • HDSDR LO is set to 75.550MHz
  • HDSDR Tuned frequency is 75.1275MHz

Now i need to understand what is happening and calculate the various offsets you can set in HDSDR.

To be continued…



Don’t know what i did, but i seems to have it working.

Here are the settings:

20-Oct-14 3-22-02 PM


And then this is what it looks like: