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.

Monday, May 31, 2010

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.

Sunday, May 30, 2010

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.

Sunday, May 23, 2010

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.

Warblers update

I have made myself busy today, mounting the vast majority of resistors and capacitors on my two Warbler kit PCBs.

Tomorrow I should be able to get at least one of them in good receiving order, I will try to make that the 40m WSPR one.

We will see how things go.

Wednesday, May 19, 2010

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.

Monday, May 17, 2010

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.

Saturday, May 8, 2010

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


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.