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 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/

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.

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.

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.

New toy : HF3

I could not resist any more, so got me a new LF/MF/HF receiver, the Target HF3 covering 30kHz - 30MHz

It will take a while to get used to the frequency settings, though I can see why it is made like that.

Otherwise the receiver is simple enough to operate, I used the same method of QRSS calibration as I did for the SW-1, so now it is test receiving the 30m QRSS band.

Just had the 50Hz sidebands in here, stopped a few minutes ago, presumable an OTH radar system.

Another alternative for S-Band

I just found yet another alternative for "watching" satellites on S-band.

I have an Icom R3 receiver, covering up to 2.5 GHz, albeit only for FM and ATV. However, I found a rather simple modification for an IF output at the site of G6LVB where he describes the mod.

I think I will do that one and see how it works, even before I start modifying the converter. Only problem seems to be frequency stability.

The IF in question is 26.05 MHZ, but I have one of the Elektor programmable SDR's covering up to 30 MHz, so that looks like a useable, if not ideal solution.

This could, of course also be used with a HF receiver for receiving SSB or CW on the 13 cm amateur band

So many ideas, so little time.

Lunar Reconnaissance Orbiter

The last week or two I have made an attempt to receive signals from the Lunar Reconnaissance Orbiter (LRO).

The LRO is currently in a polar orbit about 50km above the surface of the Moon, and has a transmitter on 2271.200MHz. It is possible to receive on Earth, as several people have done, already in it early days.

I decided to see if I could do this using "off the shelf" equipment with the antenna on a balcony.

I started my efforts using a handheld scanner , the AOR 8200 Mk3 which covers this frequency in SSB mode. Since I know that the sensitivity is insufficient on that frequency I started out using a LNA2227 (LNA), having a Noise Figure of less than 1.5 dB and finally a logarithmic-Periodic antenna (LPDA). no luck, but got a grid of "carriers" spaced about 215 Hz .... hmmm ... sounds like GSM.

After a few days I found myself digging out a WiFi grid dish with linear polarisation. still no results, and still GSM carriers.

Testing if this was Intermodulation Distortion (IMD) in my receiving system was done with a 10 dB attenuator ... the interference duly reduced by 10 dB, eliminating the suspicion of IMD in my system. I suspect two possibilities : Either IMD created somewhere outside my RX system or poor Image Rejection of the receiver. Most likely is the Image Rejection problem, since the GSM sidebands are strongest in the direction of a nearby base station.

Testing the connection between LNA and receiver revealed that the LNA had insufficient gain to overcome the high noise figure of the receiver, so what to do now ?

A quick test was set up using a satellite TV in-line amplifier, powered by a satellite receiver (off-the-shelf, remember). Still no success, but the noise performance was clearly better, as witnessed by other satellite signals in the 2.2 GHz band. Well, the moon was hidden by a tree at the moment of testing, making it difficult to point the antenna in the right direction. Still no signal from the LRO. I was beginning to doubt the usability of my system, but not yet giving up.

Finally, yesterday evening, the Moon was clearly visible, the antenna was pointed to the Moon, and bingo .... there was the signal ! A slanting line on the spectrogram showing a downwards change in Doppler shift.

Preliminary image 1 : http://www.xs4all.nl/~jgander/LRO1.jpg

I followed the signal till the LRO disappeared berhind the Moon, with the Doppler change getting much lower.

Preliminary image 2 : http://www.xs4all.nl/~jgander/LRO-gone.jpg

So - after a week of experimentation, finally success.

The receiving system need much more work, the first test will be making a filter that should (ideally) get rid of the GSM interference.