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 stuck

I have noticed that Thor's Hammer has stopped uploading. Reason unknown, but could be the Inet connection has been lost, or the PC has been rebooted due to a power outage. I will have to wait and see.

Since I cannot just go there and back again in a day It will have to wait till I can go there for it to be updated

New kits arrived

It took a while, but I now have "a few" kits to build.

Some SoftRock II kits, different bands, each can be made directly for 160,80,40,30 or 20m, all components in the kit. Some SMD soldering necessary, but should be possible, even with my eyes.

Some "Funkamateur" single frequency kits, among those a 10.7MHz kit to connect to my VHF-UHF RX (R7000, possibly AR-8600).
Two kits for 9MHz, one will be modified for use on 10MHz

the other 9MHz might be made "wideband", so a multitude of LO signals could be used, possibly a Si570 synthesizer or the DDS60 kit

Two lower band kits, to be decided

The FA wideband SDR TRX, will need a PA and a programmable LO, not yet ordered. Covering 1.7 - 30 MHz with preselection, so seems quite usable.

The "standard" 1W PA could probably easily be replaced by a home made solution, but I will see if I do not get to order the standard one at some stage. The local oscillator, the so-called FA-SY may be the way to go for full band coverage. A housing is also available, I may order that one, too.

Update :
The FA-SY oscillator has been ordered, along with a housing fit for the FA-SDR TRX
More Update :
The FA-SY kit and the housing have arrived

Lots of kits to build, not too much time, so let us see what comes up here.

The intention is to use some of the fixed frequency stuff for simultaneous WSPR and QRSS monitoring.

600m WSPR at "Thor's Hammer"

Since I visited the QTH of OZ9QV last month I have been monitoring the WSPR reception there.

The WSPR receiver is of course the same as the one for QRSS, with WSPR running concurrently on the PC.

With the tiny indoor tuned multi turn loop (diameter 22cm) the following stations have now been received successfully on 600m .

PA0A, PA0O, G3XIZ, PE1GRL and EI0CF being 1225km from there.

For such a simple setup I am quite happy with the results, even though I know that improvements are certainly possible.

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 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/

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.

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.

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.

WSPR on the Mac

This past week end I have, among other stuff, made a few attempts to get WSPR running on a Mac running Snow Leopard.

Tried a few "Tips and Tricks", using MacPorts and other stuff but none of the tricks were useful.

I was finally pointed to a HowTo for making the install, and this is what will be going on next in that part of the story.

SpectrumLab seems to be running under Wine for the Mac, so it looks like that part is usable.

Fldigi exists as a package and runs, if a bit touchy in the user interface.

Update :

WSPR installed mostly according to the guide, but only on a pristine installation. Not ideal. Thanks to G4KLA for assistance. Now I need to see if I *can* get it installed on my already installed system.

One problem, however : While the >WSPR program starts and runs, it exits at unexpected times with an input overflow message, so not very useful for long term deployment. Back to using Windows for WSPR. (Or possibly Linux, will have to be tested)

Some experiments on the (V)XO of the RM80

After Joachim's experiments with the RM80 frequencies and MEPT, using the varicap, giving some problems with chirp I decided to try another approach, and we will see what the results are.

In place of the varicap I mounted a trimmer capacitor, in parallel with the R10 (feeding the varicap through I mount a 2.2nF capacitor, so that Q2 creates a RF-short of the trimmer capacitor, giving rise to the lower frequency RX LO of about 3579.350.

Just trying, and as expected the oscillator does not oscillate on the stray capacitance of the circuit without any capacitor in stead of the varicap.

First test was with a 2-10pF trimmer, giving rise to a frequency above 3580 (even with full capacitance), and stopping oscillation at low cap. values. Not good enough.

A 2-18 trimmer with a parallel fixed capacitor of 10pF is better : the (high) frequency range is now about 3579.75 - 3580.10. I noticed that the oscillation on the higher frequency is weaker on the higher frequency by about 10 dB, still the oscillation holds. A lower value coupling capacitor to the buffer, as Joachim indicates, is probably in order.

This makes me think that it should be possible to replace the trimmer with another varicap with lower capacitance than the one supplied., and with a zener stabilized voltage make the tx frequency tunable. A range of about 250 Hz should be attainable with one or two BB105 diodes - and I should have some of those somewhere.

On with the experiments, I will leave the RM80 with the trimmer cap for a while and see if the TX frequency remains stable when transmitting.

Update :

The lower value coupling capacitor to the buffer increases the oscillator frequency by 50 - 100 Hz - the oscillator now tunes down to .830 .
Parallel capacitor changed to 22pF, trimmer still 2-18pF, tunes (upper frequency) about .760 - just above 3580.000. nice range.

Rock-Mite 80 update

A new crystal in the oscillator brought the lower frequency down to 3579.350. That is quite acceptable for a grabber, the audio range for the 3579.500 - 3580 will end up at 150 - 650Hz. Not ideal, but workable.

Here is what it looks like with a few minutes of low - high - low frequency :



Still, with the 5V shift the TX frequency only went up to 3579.500, the shift is just too low at 150 Hz.

Enter the Q2 switch transistor and the 12V pull-up resistor. Voila, the upper frequency is now 3579.850, a 500 Hz difference, bringing the TX frequency just inside the 3579.800 - 3580.000 band.

It looks like it will be a good idea to have more than 2 crystals on 3579 for this construction, so a selection of the most suitable frequency can be made, alternatively find a better suitable varactor diode with more capacitance variation at 0 - 5 V.

The other point, with the current (original) "firmware", the RM starts up at the higher frequency rx local oscillator and will have to be switched manually to the lower lo frequency.

Later the test of the receiver as such, enough done for today.

I am optimistic that this will work as a MEPT tx and Grabber rx, but the rx test will show.

Rock-Mite 80 Initial Test

The RM-80 is essentially assembled, first test has been done.

As opposed to Joachim I have only 100 Hz shift between the two steps, that is not enough to be useful. This has to be a fault, and I will seek it out later this week.

Rock-Mite Kits Have Arrived

In the mailbox I found a nice little package today :

Two Rock-Mite kits , one for 80m and one for 30m.

This week end I see soldering in my "crystal ball"

Now which one to begin with ? .... well I started unpacking the 80 kit, so 80m it will be, most likely the color burst frequency around 3579.5 kHz.

DI2AM reception on 505 kHz

The 500 kHz grabber is now set to two narrow frequency ranges, the "WSPR segment" and 100Hz around the frequency of DI2AM.

DI2AM reception seems to be there essentially all the time after sunset, albeit with some (expected) QSB, and WSPR signals coming and going.





Nice result with a "cheapo" frame antenna wound on a cardboard box 35x40 cm small.

A new somewhat bigger frame antenna (more than 70x70cm) will be made some time, but that will have to wait.

In the week end the construction of the 500 kHz TX should begin

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.