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.

Saturday, September 19, 2009

RFI hunting.

I have been doing some RFI hunting today, in order to find some of the noisy switch-mode power supplies in the appartment.

I found a rather noisy one (cheap "universal" laptop supply) with wideband "carriers" every 70 kHz and the noise level dropped considerably when that one was disconnected.

I have been considering replacing as many as possible of the switch-mode PS's with linear regulated ones, because it is far too noisy here, Maybe not worth it, since some neighbours probably have some noisy ones as well.

In any case I am enjoying the little bit more quiet environment here.

It is far from over yet, but a good beginning.

Monday, September 7, 2009

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.

Sunday, September 6, 2009

Mini QRSS system

I am back from a visit to Denmark, and found a nice little setup for watching QRSS.

I was using the Eee 1000H - running SpectrumLab - with a Sony SW-1 receiver (and an audio cable)

Everything can be run from a battery, so no problems with hum.

The SW-1 has AM and SSB reception from 150kHz to 30MHz with 1 kHz steps, so by calibrating with the Russian RWM time signal transmitter I could find the QRSS band on 30m. The SW-1 needs a bit more antenna than the built-in telescopic whip, so a wire antenna was attached to the whip. The SW-1 does have an input jack for an (active) antenna, so that will be tested later. Probably a small tuned loop antenna.

I was not using it a lot, so very few signals were heard. The concept worked well enough, and the frequency drift was not excessive. I set the bandwidth of the "grabber" to 200 Hz, though.

Nice and easy low power portable receiver setup, I may use it at home as well, with external power supply.

Update :

Next step ? : maybe using the Asus Eee4G with linux/WINE, running SpectrumLab - it could hardly get any smaller.

Further, a simple DC-RX - maybe powered by the USB port ?

Wednesday, July 22, 2009

Too close for comfort - poof !

Looks like I blew my sband LNA.

I noticed that I could not hear the "beacon" sat signal on 2242.488, so checked. changed the LNA to another one, and signals came back - probably with a slightly higher Noise Figure (L-band LNA).

so - I opened the LNA and what did I find ? it is not a GaAs Fet amplifier as such, but a GaAs MMIC. Not really a problem, I have a replacement with the same pinout - only snag - it is SMD, so I hope my soldering and vision will up to the challenge.

LNA Spiritus Basta !

Why did this happen ? I transmitted on 2m with an antenna too close to the sband antenna. Oops !

Tuesday, July 21, 2009

half hour antenna for satellite reception

I was growing tired of having poor reception of the transmissions from ISS on 145.800/825 and 143.625 MHz, so decided for a quick ground plane antenna. What to do for a quick antenna ?

Here we go :

1) use a piece of coax, strip about 53 cm of the shield off
2) connect 2 pieces of (insulated) wire about the same length to the shield connection
3) insulate with duct tape for a quick weather protection (will not hold long, but this is a temporary setup)
4) string the thing up between the clothesline and the balcony railing
5) pull the cable through the wall/door/window
6) add connector indoors to the radio and connect to radio
7) done

Results receiving ISS were better than using mu uhf-satcom log periodic array (no real surprise there)

I still need a better antenna/antenna position (poor reception when the ISS signal has to go through the buildin), and since I have some noise, so more to do.

Probably a 2m antenna with preamp (cable length) in the dormer.

Saturday, July 18, 2009

A bit of slow progress for S-band

In order to test the filter I got via ebay, I just connected it outdoors, not really the best thing to do.

Today I went to the local "elektronica-boer" and got some connector adapters making it possible to move the filter indoors. I had to retain the filter before the extra indoor amplifier in order to avoid IMD problems, so a bit of extra adapters were necessary.

One day I will have to make a web page describing the whole thing, but that is for later.

Busy day tomorrow with non-radio stuff, so hope to get a bit more done today.

Friday, July 17, 2009

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.

Thursday, July 16, 2009

MMDS converters have arrived

About two weeks ago I decided that my setup for S-band reception needed to be upgraded seriously.

So I looked into possibilities for improvements. I found the filters necessary for the AR8200 receiver to work, and looked around to see if I could find some converters that were (relatively) easily modifiable.

I think I found it . MMDS converters cover the bands around 2150 MHz and around 2600 MHz, and it should be possible to modify the filters

TranSystem Inc makes some MMDS converters, I found some on ebay, TranSystem Model EIDC 3033 Down Converter, apparently with the following spec :

RF bands :
2150 - 2162 MHz and
2500 - 2682 MHz,
Intermediate frequencies :
116 - 128 MHz and
222 - 408 MHz

This is possible with a LO frequency of 2278 MHz. Since I want to use the converter for the 2200 - 2300 MHz band, some modifications are necessary :

RF filters - one pair at the input and one pair between the RF amplifier and the mixer - must be modified to cover 2200 - 2300 MHz

The Local Oscillator (LO) needs to be moved away from the wanted passband, preferably for a low side LO.

I took a look at the inner workings of the converter, and the RF frequency filters are stripline filters made of copper with air insulation (not microstrip etched on the PCB), so they are expected to be fairly high Q filters. For satellite S-band I think the best strategy will be to shorten the 2150 MHz strips (careful - we do not want to get too high in frequency), then disconnect the higher frequency filter (hmmm - that may not even be necessary).

The other modification concerns moving the LO down. The LO is a PLL with a frequency divider (256x) 2278MHz down to 8.898438 MHz. (Xtal in the reference oscillator).

It would be nice to have the oscillator running on a "rounded" frequency like 2000 or 2100 MHz, but that would require new Xtals to be made. Since I would like to be able to lock the LO frequency to a stable source that complicates things.

The other option will be to use a 8 MHz crystal oscillator, then lock that to a 10MHz TCXO or other standard. This will provide the converter with a LO frequency of 2048MHz. not exactly very "rounded", but still with a full MHZ, so the readout of the converted frequency should not be all too confusing (that remains to be seen). After all, a computer can do wonders in calculating the correct frequencies and control the receiver(s).

Time is a bit tight this week end, but I hope to be looking into it after all.

Wednesday, July 15, 2009

LRO without GSM

This morning I woke up early and saw the moon was out. Tested the reception of the LRO, and it was not loud but clearly there, even audible in the speaker, more details later.

Saturday, July 11, 2009

GSM interference not quite gone .... well - it was, really

It looks like I spoke too soon.

The interference from the GSM has re-appeared, tough not as strong as it was. After setting up some 260MHz antenna and preamp again, it came back. I may have to use a different preamplifier (tuned) for that system.

More work to do ....

*****Update : It was *not* the dreaded return of the GSM interference ....

Apparently , by adding the second amplifier (and a second receiver) in the system, I inadvertently made a loop creating humm in the system.

with less "MIC boost" at the pc sound card input the problem disappeared (only the base 50Hz and the 3rd overtone 150 Hz are visible on the spectrogram now), and I am now back to a quiet S-Band reception.

Phew !

S-Band filters have arrived

I picked up the S-band filters on the post office today, and it turns out that there are indeed two different filters

1) Centre frequency 2125 MHz, Bandwidth 295 MHz (I assume 3 dB B/W)
2) Centre frequency 2375 MHz, Bandwidth 295 MHz

I tried both filters and it looks like the lower freqeuncy filter does not - to a sufficient amount - attenuate the unwanted signals, so I will use the second one .

The GSM sidebands have completely disappeared, much to my relief. (Not a trace of them in the spectrogram). I need a bit more amplification, but that is easily arranged using a second satellite TV in/line amplifier.

It looks like my theory of insufficient image rejection in the receiver is correct.

Now for some S-Band satellite signal hunting - and of course the LRO on S-Band.

Monday, July 6, 2009

S-Band Filters

I found someone selling some filters on eBay. The description said centre frequency 2125MHz and bandwidth 295MHz

However, when looking at the photo it looks like there are two different filters :
2125/295MHz and

If that is correct I will have two very useful filtersone covering approx 1975 - 2275MHz (useable for most of the satellite S-band downlinks (2200 - 2300MHZ), and one covering 2225 - 2525MHz also useable for a good part of the Satellite S-Band downlink band , as well as the Amateur radio *and ISM) band from 2320 - 2450MHz.

Both filters are indeed usable for reception of the LRO on 2271.200MHz

If the two filters in the photo are indeed what I will receive.

When I receive the filters, I will be able to test whether my theory of poor image rejection in the receiver is correct, or if the problem is caused by IMD outside my RX system.

In any case this is going to be interesting.

Thursday, July 2, 2009

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 :

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

Preliminary image 2 :

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.

Saturday, June 13, 2009

Acer Aspire One as QRSS grabber ?

Today I installed the Ubuntu version made for netbooks - the "Easy-Peasy" distro - on my Acer Aspire One.

The install rendered the Wireless LAN inoperable, but after a standard update (via the wired LAN) it was working fine.

After installing a few of my well known applications I tried to get SpectrumLab up and running under WINE.

After an attempt to install on the "Z" drive failing, I finally got it installed to the "drive_c"

It took a bit of playing around with the mixer to get the input from the radio running. Apparently the sensitivity of the AA1 mic input is somewhat lower than on an older machine I have working here.

After some hours of work with the AA1 I intend to leave it for now and continue my reading. Later for trying to get WSPR/WSJT running - that should be "fun" (yeah - right!).

With SpecLab I should be able to make some simple grabber software for image upload, possibly with a script. I will need more knowledge of Linux than I have now, but this is part of getting things working.

Tuesday, June 9, 2009

80m SDR, p3

Finished the PCB (except the canned oscillator), needs testing , but later. the box needs one more hole for external LO connector - not originally provided for.

Finished second novel of the marathon reading, now 3 mopre novels, some novelettes and novellas until July 3rd. Let's see what can be done.

Wednesday, June 3, 2009

80m SDR, p2

More solder smoke released, only missing the ICs and the oscillator - I am going to leave out the oscillator and make a local oscillator input, making a switchable Local oscillator possible.

Now for some more reading.

Tuesday, June 2, 2009

Building SDR for 80m

Today I received the kit from the magazine "Funkamateur" with all necessary parts to build a "single frequency SDR", similar to the SoftRock, along with a few other components for my constructions.

Like for Joachim, one resistor had a 1000 times larger value than the one needed. No problem, since I had one of the correct value.

Some solder smoke generated, not quite finished yet, but it is time for some reading.

Monday, June 1, 2009

Spotted on 10m

Twice today I spotted IZ1ERR on 28 MHz, and now I see he spotted me, too :

Spot Database

Specify query parameters

Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az
2009-06-01 17:14 PA9QV 28.126170 -22 -4 JO22db 0.2 IZ1ERR JN35 758 164

Nice to see someone else is there. Now let us get some activity on 28 MHz WSPR before the Sporadic E season is over

Wspr on 10m

I am currently running the WSPR station on 10m, Dial setting : 28.124600MHz, also looking for QRSS signals on 28.125900 to 28.126000MHz.

Using a FT-817 running 10% tx-ing when I am home, otherwise just rx-ing.

I have only had a single spot today from IZ1ERR in JN35, so I guess activity is quite low atm.

I am looking forward to the peak(s) of the sporadic E season.

FT-817 PA

The FT-817 PA seems to be prone to overheating.

I have been running the 817 on 13.8V till now, and since it runs fine down to about 9V, I am thinking of finding a 10V regulator to take some heat out of the equation.

Will be looking for a 7810 IC, or possibly using the LM317 for that purpose.

More soldersmoke coming out some time here.

Sunday, May 31, 2009

Back to some radio stuff

I have been away for about a week and I am back from the holidays. My spare FT-817is now here and will be set up for WSPR/QRSS and other experiments, while soldering.

I know there is some stuff waiting for me, eg. a "single frequency oscillator" SDR kit like the softrock design, that I will solder as soon as it is here.

I do have quite a bit to read in the next month, so the radio activity will be somewhat limited. I will have to solder a bit between th words ;)

Tuesday, May 19, 2009

FT-817 PA failure

Looks like the PA of my FT-817 gave up the ghost. Maximum 50 - 100mW out of the transceiver, whatever I do.

It looked for a day or two like my WSPR signals on 10MHz were soewhat down, and quite right, minimalist output there.

I have decided to leave it as is for now, a bit of output is still there, but a repair has to be done at a later stage.

Also, I decided to move the FT-817 *as it is now, on 10 meters, so listening and *really* WSPRing on 28.126120 MHz if anyone pops up there I will be leaving the reporter on and with an estimated output power of 50mW, running concurrently with SpectrumLab for QRSS on 28.125900 - 28.126000 MHz, running with a full wave 10m loop inside my balcony, tuneable from 10 - 20m with reasonable efficiency.

Sunday, May 17, 2009

First test 10 MHz RX

looks like the AF amplifier is fine now, using abt 3 mA at 12V, Xtal oscillator uses abt 5 mA at 5V. Quite a bit lower power than the FT-817.

Having only one power supply in the shack for experimantation, I need to find a 78(L)05 in my pile of components, so I can test the XO and mixer. I wonder if the output of the XO is sufficient to drive the relatively low impedance (abt 2kohm) of the mixer. but guess it will.

No more soldersmoke for today. maybe a bit of reading for now.

WSPRing away

As an intermediate solution I have set up my FT-817 for running WSPR on 10.140MHz - with 200mW out. The receiver does QRSS reception, too, but of course blacks out while WSPR is transmitted.

I made myself an interface similar to the VK2ZAY one, and it works nicely. The AF level out of the computer is a bit low for operation of the "VOX" circuit, and should be modified a bit, but otherwise it works fine.

Now, it is a bit of overkill to use the FT-817 for just 200Hz of the spectrum, after all it covers all bands from 160m to 70cm. So the 10MHz direct conversion receiver of the previous post is just the beginning, a "proof of the concept", used for WSPR transmission and reception and QRSS reception

The intention is to build, at a later stage, a full, but simple, "single frequency ssb direct conversion transceiver" and a dedicated 30m antenna tuned to 10.140 - probably a "magnetic loop".

For now I have a fairly large reading project, so the ful TRX will have to wait a bit.

10MHz qrss rx

I left the 10m TX for a while and got started building a simple 30m direct conversion QRSS reveiver.

Discussions with Joachim resulted in two receivers one already built by Joachim and the one I am building now, with a local oscillator at half the RX frequency and using a RA3AAE type mixer

For this RX I am generally following this concept found at PA2OHH, the difference is that I - like Joachim - use a canned oscillator at 5.0688 MHz

The Oscillator/mixer and the AF circuit is ready for an initial test (tomorrow), and the RF input circuit is yet missing.

Tuesday, May 12, 2009

QRSS transmitter under construction

In talks with Joachim, PA1GSJ we decided to build the simplest possible (construction wise) transmitter for 28MHz.

Using a "canned" - in my case IC-like housing - oscillator on 28.322 MHz and a 74HC(T)240 as the "power amplifier" it is possible to get an output of around 50 mW, sufficient for a QRSS MEPT.

Joachim already has his model working, and I am in the process of building mine. The oscillator is there (duh)and the "PA" is just about wired, now I need to make the keyer , will be using a PICAXE processor, and the output matching circuit/low pass filter.

Monday, May 11, 2009

PA9QV on Ham radio

This will deal with my Amateur (HAM) Radio activities, newly started with a bit of QRSS and WSPR activities, more later.