Thor's Hammer Frozen Again

The Grabber is down, again.

It is running unattended, so will be restored when someone can attend to it.

It still needs some recovery program if a reboot should occur (e.g. due to a power failure).

Thor's Hammer back on track

Thor's Hammer has been down for a while due to a thunderstorm putting it offline.
The grabber is on line again.

If I have sufficient time one or two new bands will be added to TH when I go there next time. 80m is a likely candidate, since I have a 80m RockMite built and ready. However, I may have to add another low powered PC to take the load off the current one. SpectrumLab is not the easiest on processor load.

I may see if Argo or Spectran is better in that respect. Tests needed, or, if anyone has experience, please tell me.

Thor's Hammer up and running

During some work at the place the PC had been switched off.

The "Hammer" is running nicely again since Christmas.

It is running on 10MHz and 500kHz as before. Possibly with an extension in a few months. Some antenna work and some soldering needed.

Next band will probably be 80 (3500kHz). and a simpler receiver for 10MHz. The original receiver will then be set to yet another band. Some wideband antenna work will be necessary for this to work out.

Time to get the soldering iron warmed up again.

On the PA9QV front the next soldering project should be the FA-SDR. All components including the housing have arrived, only a PA (1W) is missing yet. I may build a small wideband PA myself.

Still a lot of kits to build, but slowly getting started again.

Grabber : "Thor's Hammer" at OZ9QV : updates

During a holiday (and being there for other reasons) in Denmark I have made an update to the "Thor's Hammer" QRSS grabber. More will happen later at another visit.

The grabber can, as usual be found at :
Thor's Hammer

The grabber now works on two bands, a more stable receiver (old TRX with defective TX) has been installed for 10 MHz and the viewable frequency range reduced. Still using an older low powered PC

10 MHz Grabber :
RX range : 10139.880 - 10140.120 kHz
SpectrumLab set for display of 3 stripes of consecutive periods
Antenna : indoor dipole

500kHz Grabber :
RX range : 502.700 - 505.500 kHz - some noticeable frequency drift, but acceptable
SpectrumLab set for 3 strips as above
Antenna : indoor multi turn tuned loop

The 500kHz RX seems to have some problems with receiving WSPR, only once or twice the WSPR signals from PA0A and PA0O have been received.
The signal from (I think) G3XIZ was visible, but no decodes.

All in all I am fine with the improvements, but more is needed. I would like to add more bands, e.g 80m, 40 and 20m, possibly 136kHz but things do take time to get running, and new antennas will be necessary.

I may experiment with a wide band active loop antenna (H-probe) or an E-probe (short active whip).

Simple 80m Grabber Receiver Ready

Next time I will visit the OZ9QV grabber "Thor's Hammer" there will be another band active in grabbing : 80m

I have finished encasing a modified RockMite 80 (RX only)

Frequency drift is acceptable :
10 deg C : 3499.955
23 deg C : 3499.915

Yes - negative temp coefficient.

Since the temperature is expected to be within that range (most likely 15 - 25 for the majority of the time, and I expect to put the RX and PC into a cupboard, I would expect the local oscillator to stay within 3499.925 +/- 10 Hz for most of the time, quite acceptable.

The addition of another band to the grabber is worth it alone, I think.
New antenna needed as well.

I know that more activity is on 40m by now, but the winter should be good for 80m experiments.

The grabber is expected to run with an older, low powered PC, together with the 10 MHz grabber.

The new grabber receivers should be installed before the end of the year.

I am playing with an idea for a more stable grabber receiver for 3500/7000/14000 kHz, more on that later.
It will be a bit more complicated to build, so I will be taking my time.

Thor's Hammer again

Yet another alignment,

The receiver is drifting quite a bit, so the 'window' has been widened to 550 Hz, at least some signals are visible.

Further improvements to the grabber will happen later.

Thor's Hammer with frequency drift

The receiver has a considerable frequency drift, even more than I expected.

When I visit next time I may have a better RX at hand. - if there is enough time to ge one going.

Thor's Hammer Realigned

I was visiting the house of OZ9QV and got the 10 MHz grabber realigned.

I broadened the viewing frequency window, since the receiver has some temperature drift. In any case, QRSS signals are now visible again on the grabber.

Thor's Hammer, by OZ9QV :

QTH JO65cp
Frequency 10.140 MHz
Cheap transistor synthesized receiver
Older low spec PC

URL :
http://www.xs4all.nl/~jgander/qrss-p/

More RM30 info

The RM30 was tested a bit this week end before the shack update, and the results look encouraging and disappointing.

The sensitivity of the RM30 looks really good, noise increases more than 30dB when a piece ow wire (in the shack) is connected, indicating sufficient gain for a grabber.

The frequency response shows the unmodified RM30 to have a slightly too low peak frequency, about 1kHz, so next test will be a (variable) capacitor in series with the input crystal, the main problem is mounting it on the PCB.

The frequency stability, however is not nearly as good as I would want. I may have to get some of the clip-on heaters that DB6NT has for sale, but initially the RM30 will be boxed and thermally insulated.

Update :

47pF in series with the input filter crystal brings the peak (rather broad) up to 10140.5 , this is quite acceptable since the bandwidth of the filter is about 1 kHz in the RM-30 setup.

WSPR BFO offset test

Tried the BFO offset function on the WSPR2 program.

Using the FRoG receiver I set the USB frequency to 10137.490, same in the WSPR settings, and set the BFO offset to 1710Hz in place of 1500.

Spots are coming in nicely on 10MHz with just a piece of random wire indoors.

Later : tests with the RM30 grabber rx input filter, and see if sensitivity is sufficient - then some compact antenna.

RockMite 30/80 Update

I have run a simple test of temperature drift of the two RockMites :

Using a fan blowing on the PCBs lying on the desk the RM80 drifts less than 10Hz when the fan comes on or off for about 5 minutes, that is quite acceptable, given that the RMs will be boxed, and likely I will use some insulating Styrofoam.

The RM30 is a bit more tricky. I tried to lower the frequency with a choke in series with the tuning trimmer capacitor I mounted, and the drift with fan was about 50Hz at on/off.

It turns out that grounding one side of the crystal resulted in a frequency of 10138.490. Not ideal for WSPR, but should be useable with WSPR2 and "BFO offset". Not tested yet, but will be in the near future. Temperature drift at the fan on/off is now 20Hz, and with a bit of insulation that should result in an acceptable temperature stability.

It looks like the drift is more due to the capacitors in the oscillator than the crystal in itself.

Oh, and I am a bit disappointed that the RMs have several zener diodes, but the oscillator itself runs from the raw supply voltage. Where did that idea come from ? I find it surprising that there is not more stability problems with the LO in the RMs

Next step with the RockMites : input crystal filter tuning - if necessary.

RockMite 30 Experiments

In addition to mounting all but the inductors and transformers for 80m the Warbler and a few more components for the 40m WSPR Warbler I have built a RockMite 30, for use as a Grabber RX only for 30m.

The evening welt with getting the Local oscillator (10.140MHz Xtal) down to 10.138.700. This is done by bypassing the frequency switching, using a simple serial connection of a 10uH inductor and a variable capacitance ( 12 - 30pF ).

The input Xtal filter will be added later, after stability test of the local oscillator, and will probably be a simple SIngle Xtal tunable filter.

Tomorrow will be busy with some non radio activities, so progress will be much slower than it has been this week end.

Sporadic E Season and 10m

At the start of the sporadic E season I have retuned my main grabber to 28.321/28.322MHz , still retaining the secondary image for 500kHz.

The 28MHz grabber is using a FT-817 and the 500kHz grabber is still using the ATS909.

As per the previous post I am in the slow process of building more (simple) grabber receivers and some WSPR equipment for 500kHz and several HF bands, at least 3.5, 7 and 10 MHz.

I am interested to participate in the 160m WSPR summer project, so looked for a suitable set of Xtal frequencies. It looks like 9MHz, BFO 8999.5 (I have a Xtal filter, or could probably use some 9 (27) MHz Xtals) and 7159kHz, pulled a down about 4kHz, this should work.

I may need to add sound cards to the grabber PC in order to monitor more than two frequencies.

RM80 update

I have been operating the soldering iron and modified the RockMite 80 for 3500kHz.

The kit will be used as receiver only, so I bypassed the crystal tuning, ending up on a LO frequency around 3499.920, nicely suited for a grabber on 3500.800kHz

The receiver is probably not too sensitive, so I intend to test it, first with my 30m tuned loop, then most likely with an active antenna of some variety.

The first test has been monitoring the drift of the LO, it looks fairly stable, so a later test will be the rx sensitivity.

Next on the workbench will be the 80m Warbler, usable for PSK31 (of course) and a grabber on the colour burst frequency. I will be building it exactly as intended in the original design, then later build another for use on 40m WSPR.

QRSS Grabber in OZ

This week I have been in Denmark on Holidays.

During this I have set up a grabber receiver at the QTH of OZ9QV

The receiver is a simple one running on the 30m band, 10.140.0 - 10.140.1

QTH : JO65CP

Antenna : Indoor dipole (I don't want to risk too much in thunderstorms).

The system is running SpectrumLab and ArgoUpload, as well as WSPR in receiving mode

I hope to keep this running 24/7, but no guarantees, Internet may go down, power may be out, etc.

I hope some people will have fun using this grabber, and will try to get a bit more up and running there at a later stage.

Update : the OZ grabber seems to lack sensitivity, but is still operational.

Rock-mite kits

A discussion with Joachim today made me go buy some more kit stuff.

The Rock-mite kits look very suitable for a simple QRSS modification , as seen on Joachim's blog.

I ordered the 80 and 30m versions, one of each.

The best thing is that it is useful as both a grabber receiver and a QRSS MEPT - and the price of $32 a piece to have it sent here should not discourage anyone from doing QRSS.

The Rock-mite is a simple crystal controlled CW transceiver and can be used as such. It is a single frequency device with a crystal as the input filter and another one as (VXO) local oscillator/TX oscillator.

TVEPG up and running from The Netherlands

I got the TVEPG set up with the HF-3 and the 500 kHz antenna, you can find it at here

The grabber is running on an Acer Aspire One 110, the old model with 8 GB SSD, under Linux, running SpectrumLab under Wine and an upload shell script originally written by Allan OZ5AR.

The frequency range is set to 503.5 - 505.5 at the moment, but I do have another setting for the 500 kHz WSPR band.

Update :
New setting for the 500 kHz Grabber : split screen with WSPR segment and a wider segment shown together.

Idea Box : Direct Conversion RX for Color Burst Frequency Grabber

Using 3.579 crystals as crystal oscillator and filter for a PSK31 receiver/transceiver is well known. Getting a decent sideband rejection with a simple circuit is not easy with this design.

Here is a thought : One of the reasons for the lower sideband rejection is the proximity of the 'BFO' frequency to the signal frequency. Possibly oscillator phase noise is contributing to the problems. Here is a trick for a simple QRSS receiver for 3579 :

N4ESS has crystals on 3575.6kHz this is quite a bit further from the signal frequency than is easily done with 3579 crystals. OK, the beat (AF/'IF')then is at about 4kHz, but using SpectrumLab that is not really a problem, since it can 'convert' and filter signals. Of course, the input filter as in Joachim's 30 QRSS Grabber RX is necessary to get some unwanted sideband suppression.

This should make for a simple design for a DC RX Grabber for the color burst frequency on 80m.

Edit : I looked in the 'stock' and I have a 3575.6 crystal (and of course 3579.5 as well, so building this rx for color burst rx is possible. Other projects come first, such as finishing the setup of the 80m SDR from Box73.

Note :

The same concept should be usable with a 160 RX at 1843kHz with a 1856kHz Xtal, also available at N4ESS, albeit with a somewhat higher 'IF' of 13 kHz.

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.