Contents :

A collection of thoughts, and my notes about experiments and ideas, technical or otherwise, connected to Amateur Radio, Satellite working and monitoring and other electronics.

Saturday, December 26, 2009

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.

Thursday, December 24, 2009

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.

Tuesday, December 22, 2009

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.

Sunday, December 20, 2009

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.

Friday, December 18, 2009

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.

Tuesday, December 15, 2009

The Portable QRSS Grabber runs on Linux now

I visited a friend having done a script for uploading grabber images today. We tweaked the script to my server etc and it is now running.

The portable grabber uses a Sony SW-100 receiver capable of setting the frequency with 100 Hz steps. this means that the maximum frequency error should be contained within 50 Hz

In the first tests, the frequency was not properly calibrated, so nothing at all was seen.

The grabber software runs on a EeePC 1000H, and was running the grabber the past few days in Windows XP .

The whole setup with Linux, (the distribution JoliCloud is used here), installing JoliCloud, WINE and SpectumLab took a few hours from a purely XP machine to a running grabber.

Back home I extended the antenna - well, added a lenth of wire outdoors, extending the indoor part with a part away from the PC, and voila, G6AVK's signal appeared.

I hereby declare The Very Experimental Portable Grabber (TVEPG) a success.

Sunday, December 13, 2009

Portable Grabber Setup

Experimenting with a portable setup for a grabber I am trying out the following :

A Sony SW-100 portable receiver (top) with SSB with a piece of extra wire connected to the telescopic antenna, using a EeePC with SpectrumLab running under Windows XP, upload software is ArgoUpload.

At the moment looking at 3599.850 - 3600.050 kHz for QRSS signals.

Wednesday, December 9, 2009

Grabber changed to other capture machine

The experiment with running Spectrum Lab in a Virtual Machine under Mac OS did not look so good. There seems to be some small frequency shifts, even on a fully static carrier.

The Grabber has been moved to a Windows machine I had anyway. I will probably add WSPR later, but it is getting late, so stopping activities for today. The activities with the Chinese "active loop" took up some time today, so this is it.

The grabber already looks better.

Non ? Active loop antennas

I found some Chinese "active loop antennas" on eBay the other day, the price
was reasonable at $25, so I decided that it was worth the risk trying it out.

Since it had the brand name "Degen" (type "31MS" - guess that would mean MW and SW) Joachim and I joked about it being a "degenerative" antenna.

I picked the antenna up at the post office today, and gave it a brief try, and it looks like it lives up to its name and that the joke was not really a joke at all.

The first thing that happened was that a suction cup for mounting the antenna on a window would not stick to any window at all, poor manufacture quality, even for a Chinese product. It did not bode well.

On MW the S/N is lower on the Degen than on the built-in ferrite antenna. on a part of shortwave it looks like it has some minor gain on frequencies in the 5 - 15 MHz range, but its effectiveness was not easily detectable.

I may have to try it during daytime, but I am not optimistic.

If you see it for sale, it does NOT have my recommendation. I may be able to use parts of it for experiments, but I doubt it will do much for me.

In any case I intend to take it apart and see how they managed to do so little.

Conclusion : Cheap antenna with cheap performance.


Tuesday, December 8, 2009

Grabber mostly on 30m

When no experiments on other bands are going on, the experimental grabber will be on 10 MHz for now

I did not check the images, but I suspect nothing came form the 160m experiment yesterday evening.

Monday, December 7, 2009

Experimental grabber moves around a bit

Tonight I will be on 160m, "listening" for G6AVK and who else might be visible.

Grabber URL

It will move around a bit - hence the "experimental".

Sunday, December 6, 2009

Experimental QRSS Grabber online

I had some trouble getting Linux running on a newer machine here, so decided to test out my Mac and Win XP running in a VM under Parallels.

Using the FT-817 with a 30m loop antenna, the Grabber is set to monitor the low band QRSS frequency on 40m, 7000.780 - 7000.920 kHz

The software is Spectrum Lab in conjunction with ArgoUpload

The Grabber can be found here , subject to change, updates and possibly extensions to more bands.

Saturday, December 5, 2009

Linux QRSS grabber on the way

I just received a bash script for Linux from OZ5AR.

This script looks at the directory where Spectrum Lab puts its capture files, looks if a new file has been saved by SL and uploads it to the website.

The script need a bit of adapting to my needs, but should be tested this week end.

Thursday, December 3, 2009

QRSS on 80m

On Monday evening I was watching out for Colin (G6AVK) on 3559.9 kHz

He was transmitting QRSS3 with about 1W out, and propagation was rather poor. but at 2100Z the signal popped up :

... and stayed for about 20 minutes before fading out :

I am using a FT-817 with a 30m circumference loop antenna strung above the rooftop of the apartment building, and fed inside the apartment with 450 ohm air spaced ladder line and a good balanced tuner.