Idea Box : Simple Two Band Grabber Receiver

This could be extended to 3 or 4 bands with some effort, but here is the basic idea :

I have some Crystals on 3500 , 7000 and 14000 kHz. This could make for an easy setup of a dual band grabber using a single local oscillator :

Here is the trick :

- make a single oscillator on 3500 kHz
- use two buffers (possibly use the gates as buffers)
- take one signal and use a direct conversion receiver circuit on 3500kHz, using the crystal filter of Joachim's QRSS receiver

- take the other signal and use the 3500 kHz LO signal for a receiver almost exactly as PA1GSJs receiver,

- making it a *simultaneous* dual band grabber receiver for :
- 3500.800 - 3500.900 kHz
- 7000.800 - 7000.900 kHz

Of course, the same idea could be used to make a 7000 / 14000 kHz dual band grabber receiver using 7000 and 14000 kHz Crystals.

There is even the option of making a doubler for the 3500 kHz signal, using this for extending the dual band grabber to a 3-band grabber for 3500/7000/14000 kHz.

Actually Joachim and I have been talking about the 3-band idea, but I have come to think that the 2-band idea is better in terms of simplicity of construction

Idea Box : Long Wave SDR

I found those 4.224 Crystal oscillators (ex equipment) on eBay .

Divide 4224 by 32 (first 8 and then make the quadrature signals), and the LO frequency ends up on 132 kHz. Not bad for a 136 kHz SDR.

Idea box : 10.7 MHz spectrum scope (1)

I found a nice crystal frequency on eBay : 10.6875 MHz

Yes, 10700 - 12.5 kHz.

Combined with a 15 kHz wide 10.7 MHz FM filter and a direct conversion receiver this should make a 10.7 MHz spectrum scope with 15 kHz bandwidth, so :

10.7MHz signal from R7000 or similar receiver -->
possibly a preamplifier, in any case some termination for the filter -->
10.7MHz FM filter for 25kHz channel spacing (BW = 15 kHz) and 2nd termination -->
DC-mixer with oscillator frequency of 10687.5 kHz (possibly pulled up to 10690 kHz) -->
AF amplifier -->
output to PC running spectrumLab

Looks like yet another 'little' project.

should be good for looking at satellite transponders with (not too wideband) digital signals, and some Doppler tracking at the lower satellite frequencies.

TVEPG in JO65CP now on 40m

The TVEPG has been set to monitor 40m. QRG 7059.850 - 7060.050 kHz



Colin, G6AVK is coming in nicely with his 500mW into a dipole.

The TVEPG will be running mostly on 40m during daylight hours, for the next few days.

TVEPG success : G6AVK strong tonight on 80m

Tonight is really good on 80m.

G6AVK is showing nicely on the TVEPG :



Lovely signal, peaking over 30dB S/N, I think it is the best I have had here with my little portable setup.

News about the grabber script

The script was running smoothly until some time yesterday when it just seemed to stop (freeze).

I suspected the number of files in the backup directory and moved them away, and the script runs again. It looks like the script will have to be able to move the files, eg. to directories per date, or alternatively avoid saving the files when running unattended for extended periods.

I am conferring with Allan (the script author), but I could at least change the moving of the file in the script to a deletion.

Otherwise the script has been running very nicely, I am quite happy with it.

600m test for the TVEPG

I tried this afternoon, the first identifiable Amateur radio signal comes from DI2AM, a museum ship in Rostock. The signal has a nice S/N of about 20dB, and given the distance of somewhere between 150 and 200km it is not very surprising to receive it.



Not bad for a very portable setup : EeePC, Sony SW-100 RX and a wire of about 20m length.

Update :

Just tested with the built-in ferrite antenna of the RX : The signal is now just visible and barely readable. The wire antenna does its work. Back to the wire antenna.


The Very Experimental Portable Grabber has been om 600m.


Tests with frame antennas and external ferrite antennas could become interesting.