Transmit and Receive Frequency Calibration

[Carey George]

I have had my RS-HFIQ for several years but never really had time to get it on the air. I operate mostly CW and so also purchased and built the IQ Keyer. I recently got everything set up and am running HDSDR. I have an IFR service monitor and wanted to double check the transmit and receive frequencies. When i am in CW mode and key the IQ keyer with a straight key I am measuring about 750 Hz low on 14.050 MHz. On receive I applied a 2 uV signal on 14.050 MHz and I can hear the tone. I can see the signal on the spectrum scope but not sure how to exactly determine if the Receive frequency is calibrated or not.

I am using the StarTech sound card.

I am not sure if this is a function of HDSDR or other. Any help would be appreciated.

Thanks and best 73,

George, N9DXP

[Mike K7MDL]

There are text commands available in the USB protocol controlling the RS-HFIQ.  You can use a serial terminal or use the companion app you can download for the RS-HFIQ that presents a menu of commands.  (i.e. a test program).

I built a Teensy based SDR that talks to the RS-HFIQ on the Teensy USB Host port and use the same commands, works fine.

- Mike K7MDL

[Carey George]

Hello Mike,

Thanks for you input. I will take a look.

George, N9DXP

[jcve...@gmail.com]

The IQ keyer creates a signal that is 750Hz lower then HDSDR's set frequency that's because it can't actually create a signal directly on the set frequency and you need to by offset from a CW  to actually hear anything. So if you send CQ and someone responds directly on your TX freq, you will hear a 750 hz CW tone in the RX. If you hear a signal and tune it so it's exactly 750 hz in the RX passband, you'll transmit exactly on their TX frequency.

The RS-HFIQ has a FOX924 TCXO it it's probably more accurate than most signal generators.

73,

Jim WA2EUJ

[Carey George]

Hello Jim,

Thank you for your input. I don't doubt the accuracy of the RS-HFIQ but I am a bit confused and am sure I am not doing something correctly. When I key down an analog CW transmitter on say 14.050 MHz it sends a carrier at that frequency. When I receive a signal on that frequency my receiver uses a BFO above or below that frequency to give me say 700 Hz tone. So I am confused about the RS-HFIQ and  IQ Keyer operation and assumed it would do the same thing. This is my very first attempt to use any kind of sound card SDR and also my first use of HDSDR. Is there something with the HDSDR? I am not sure about the LO and the Tune windows and maybe related to that about the RS-HFIQ HDSDR instructions "Tune Offset, in the window that opens, enter 0 (zero)" and "Tune fixed to ‘LO <-> Tune Offset’" Does this have anything to do with what I am seeing?

I double checked and hooked up my Mountain Topper to the service monitor. When I key down on 14.050 I measure 14.050 MHz. I generate a signal on 14.050 and can hear the tone in the receiver. When I do the same with the RS-HFIQ and IQ keyer I can hear the tone in the receive and when I transmit it reads about 14.049250

Thanks,

George