SWL PSK-20 for JT65 & WSPR

PSK31 is fun, agreed, however, would there be an additional option for using the PSK-20 transceiver for other weak signal modes? The question is, would it be possible to modify the PSK-20 such that instead of operating in LSB on 14.071MHz, it would also be operating USB on 14.0775MHz (corresponding to a "dial frequency" of 14.076MHz)?

Lets have a look at the PSK-20's design. We are dealing with a 9.000MHz i.f., with a 9.002MHz b.f.o. obviously. The l.o. operates at 5.070MHz. Both oscillators use crystals, a pulled up 9MHz one and a pulled up 5.0688MHz one.

Looking what could be done for the LSB to USB modification, I figure the 9MHz xtal could either pulled down by means of inductors, "penned" down or it can be replaced with another one.
Replacement would be provided by two different options. Since 9MHz is a very popular i.f., side-band crystals are available for not too much money. The second option possibly already sits waiting in the junk-box somewhere. The CB channel 3 transmit (overtone) crystal has got a nominal frequency of 26.985MHz. On the fundamental that would result in a 8.995MHz beat frequency. Still somewhat too low.... but.... in the original design, the 9MHz crystal is pulled up, remember? The CB crystal would therefore fit perfectly! Lets just assume the b.f.o. would be at 8.9985MHz.
Penning the crystal in place down, I would do "in situ". That way, everything will be set when the desired frequency is reached and only the crystal's housing would have to be soldered in place again.

Now lets have a look at the local oscillator. The JT65 centre frequency is 14.0775MHz. With an i.f. of 9.000MHz, this would be reached by a l.o. at 5.0775MHz obviously. Equally you could add up the b.f.o. and l.o. frequencies to end up at the "dial frequency". 5.0775MHz looks a an ambitious 8.7kHz up-wards pull for a 5.0688MHz crystal, and most likely it will be in the existing discrete oscillator.
 However, all is not lost. Seen that 2x5.0775 results in 10.155, there would be a couple of great options for (pulled!) digital gate oscillators and Flip-Flop dividers, namely CB synthesizer crystals.

• 10.160 / 2 = 5.080 for JT65a: 5kHz downwards pull on 10MHz
• 10.140 / 2 = 5.070 for PSK31: 2kHz upwards pull on 10MHz

Such digital stuff is very rich on harmonics. This is something rather annoying. However, there is a crystal ("Y4") built in the rig already. It is serving as an oscillator... ok... but... with removing the jumper "L4", and bridging (removing) the oscillator circuitry, the attenuated and Flip-Flopped digital oscillator signal can be fed into the crystal, which then will serve as a harmonics filter.

Alternatively, the 10.160MHz xtal could be "penned" down to 10.155MHz; equally, a 10.150MHz xtal could be penned down to 10.142MHz to allow for the 20m PSK31 frequency.

In this way, I hope I can create a decent dual frequency narrow-band data transceiver.

Look What I Found!

A local hardware store offered those:

F2BNC

F Type Connector to Bayonet Nay Connector adaptor. Those essentially conclude my usage of overpriced 50Ohms stuff for QRP applications.
Well, the adaptors did not came cheap, they are €2.40/pc, but I feel they are totally worth it.

QRSS Studies - the Results

Seen that there is no more for me to investigate in QRSS, other radio topics will soon become more relevant to me, and also to this blog.


The results I can report on QRSS

• You can operate a decent visual grabber in very densely populated regions. One will see the neighbours' TV sets, which in many cases is not more than just annoying.
• The reception of WSPR is not affected by urban noise, low profile and even indoor antennas give good results.
• There is no need to occupy your expensive main rig or a professional receiver, a cheap and cheerful home fixed frequency RX does the jobs.
• Setting up an online grabber is something that anyone with internet access can do, no excuses here. The demands on the respective computer are minimal. An Intel ATOM can easily operate two grabbers and WSPR (rx in my case), have a third instance of speclab running, be a print and file server and operate winamp for internet radio... all at once.

Conclusion I learned from my experiments, on-air and off-air

• There are many more transmitting stations than receiving ones.
• Despite my efforts to motivate the installation of additional grabbers, there are still only a few.
• Operating a grabber blocks other activities, at least on the bands the grabbers are active on.

What I miss in QRSS is interaction, consequently, I will for the time being cease QRSS activity until further notice.

My focus for the time to come will be on data modes such as PSK500, ALE, etc.
Another thing that crossed my mind occasionally, going QRO with some homebrew kit. Saying QRO, I mean QRO, i.e. legal limit. It is not so much the urge of being heard, it's more the design challenge here.

Froyo & Market on the A7ht

Someone hacked it, the Archos 7 home tablet. What a pleasure to see froyo and google market running on the gadget. At times it seems to struggle during bootup, this could be due to the lack of cell-network hardware.
With expanded options of market, the cheap tablet is really useful to me now. Let ne give you an example, there are apps out there for watching webcams... perfect to keep an eye on one or more grabbers...
Froyo is not slowing down the device, this was the first thing I feared. What  like about froyo in particular, the orientation of the plain desktop changes with rotation of the device. Occasionally is comes really handy.
Now looking for some interesting ham-radio apps...

The Ultimate Icom IC-M700D+

OK, this may sound a little unfair and overdone... today I managed to secure an Icom IC-M700 purchase. That means, I will create the ultimate IC-M700(whatever)+++.
Here is the idea: All of the IC-M700xx brought their individual pros and cons. The aim is to create the ultimate transceiver based on whatever Icom had to offer in the M700 series.
I believe, I have found it!

Basis: 

• IC-M700D: three power regimes, USB only (limited TX-QRGs, see mod)
• IC-M700: USB/LSB, TCXO, one power regime only

Plan:

• the modified IC-M700D will be equiped with the RF-unit of the IC-M700 and hence providing USB and LSB voice operations at three different power levels, which to me sounds like a nice rag chew transceiver.
• the IC-M700 seems to be crippled by the use of the USB-only RF unit of the IC-M700D. However, the base band stability of the TCXO makes the USB-only unit a perfect transceiver for digital modes.

Still there is this perfect all in one box sitting in my shack, the IC-M700TY.
However, since it is very hard to get your hands on one of those, merging the IC-M700D(or F) with  an IC-M700, will get you at least half the way to an IC-700TY.

73!

Super Radio SS-301

Yesterday I got a notification to pick up a parcel at the local supermarket. Yes, supermarket, the post office was closed and "out sourced" to my local grocery. Actually, this even has an advantage to me, opening hours are much more convenient.

So, today it was pickup time for a parcel from Thailand. In the parcel, a "Super Radio SS-301" handheld transceiver. You may not have heard about this brand nor the model... it is a clone of the Albrecht AE2990AFS, aka Magnum 1012, aka Dragon SS301. Imagine, the radio incl. shipping set me back not even €170.- (check ebay for the present conditions).

A guide for frequency coverage modification was provided inside the box. However, other than this single sheet of paper, the radio, a battery case, and wrist strap and a rubber duck aerial, the box did not contain anything in addition. I guess, I will have to hunt down a manual on the internet (probably not the most difficult task ever).

The actual modification itself, from whatever mode to 12m/10m operation, was done in not time at all. Contrary to the guide, two solder bridges had to be removed (Soder Wick) first. Temporary shorten terminals 1 and 2 whilst switching on the radio is a bit tricky, not difficult however. Having selected the correct code, for hams "0" would be ideal, the two solder bridges 2-3 and 4-5, have to be put in place again.

The radio is a bit annoying what beeping is concerned. Julian G4ILO describes how to solve is issue.

Listening to my 10m MEPT (A1A), which happen to run today, I noticed a slight jitter in the PLL. I am not yet sure what this means and what causes it, I hope that this could be solved in the same way the PLL-jitter in the Target HF-3 was removed, by retuning individual sections of the frequency synthesis.

The radio employs the following modes of operation: FM, AM, USB and LSB. There is no CW. I noticed that between USB and LSB pure noise sounds very differently. Another indication that factory tuning may not be ideal.
The transceiver is provided with microphone and external speaker jacks. Digital modes, provided the jitter is gone, should therefore not be a problem.
The lack of CW, although kinda natural to a HT, kinda sucks. As soon as the bands are open again, I will use a keyed sine generator for transmitting CW using the side-band modes via the microphone jack. Due to the low locking speed of the PLL, QSK is no option... so what! Audio keying a transceiver has got an added bonus: power regulation can be done by audio level control.

Can't wait until CONDX provide us with open high bands, so I can have DX-QSOs whilst walking to work.

Day to Night Transition

Just a spectrum I would like to share. It nicely shows the transition from day time propagation to night time propagation.

Skanti Marinetta TRP 1

I got lucky! Ever since I made my GMDSS-GOC, I wanted one of those:

Skanti Marinetta TRP 1 portable survival radio

In the Scheepvaart en Transport College Rotterdam, where I studied for the GMDSS-GOC, those units are on display. You can only guess how happy I am to finally got one into my collection of marine radios. The best thing on this purchase, the set is complete with all standard accessories.
I would like to thank Willy PA0WMR for keeping this rig in near original state. Willy also stated that the transmitter delivers about 5W on 600m.

What is all the fuss about a yellow box anyways you may ask. And the question is well justified. First of all, the box, with the lid closed, swims ;-) It is yellow! (That would be a reference to Douglas Adam's Hitchhiker's Guide to the Galaxy).

OK, lets be serious, why am I so happy to finally posses one?
Having a look at the manual/schematics we see that the rig

• has a modern (digital) design
• operates on 500kHz, 2182kHz and 8364kHz
• is crystal controlled
• allows for CW and AM
• has a built in dummy load
• employs an antenna current meter
• contains an ATU
• can create its own energy (by means of cranks)
• can be energized by an external source

500kHz, 2182kHz and 8364kHz are (former) distress frequencies and must not be use by ham- radio operators! 

Where is the hamradio use of these units? Well, we all hope for the 600m band. The 500kHz signal is created by a  2.000MHz gate-XO and digital dividers. Depending on what band we will finally get, this crystal can simply be replaced by a fitting one. However, since it is a digital XO, on simply could remove the crystal and feed a DDS generated signal into the digital gates.

According to the schematics, the transmitter's 8364kHz crystal can easily be replaced by a 40m crystal. However, the receiver employs some resonant LC-stuff with varactor tuning, which should not pose a major problem to modify to 40m, e.g. 7030kHz.

The receiver uses a 2682kHz crystal oscillator to the 2182kHz emergency frequency. The transmitter employs a 2182kHz digital gate oscillator. We got two options for ham-bands here, 160m or 80m. Both have pros and cons. 2182kHz originally is an A3 frequency. The wiring inside the TRP 1 is providing AM modulation accordingly.
On the 80m band, AM is used in places, hence, that would be a nice possibility to join the action. However, filters will have to be modified.
On the 160m band one may want to aim for A1 operation. A 1.843MHz crystal would do the trick here... However, the wiring will have to be changed to engage the BFO in the "2182kHz" labeled switch position.

What is the prospect for the future use of the rig?
I believe it would provide endless fun during field day operations. In particular when operated from cranks, independently from any power supplies.
The (yellow) box contains everything needed for QRP-ops, including a telescopic vertical antenna and a "long(er) wire" aerial.

I figure it could be reasonable to replace the TBA570 receiver with a NE612 superhet design for side-band use.
The XOs could be replaced by either a DDS or some synthesizers for enhanced flexibility.
Some PIC controls seem obvious, the automatic SOS-TXing is inadequate, obviously.

It all comes down to how much modification is actually wanted. Maybe the greatest fun can be obtained when staying as close as possible to the original functionality, i.e. AM on 80m, CW on 40m and 600m.

Other than that, it is an extremely nice addition to my marine radio collection.

Magnetic Loop Antenna Idea

Had an idea... again, I have not tried this yet.
A magnetic loop antenna, as we all know, are relatively narrowband. For mono-band QRSS, WSPR or WSJT activity this is not a problem at all. But what if one would like to receive (well, let's start looking at RX only at this point) on an additional frequency at the same band or maybe even in another band, such a simple magnetic loop antenna would not be so ideal.

Now that the problem is defined, let's have a look at possible solutions. The basic idea is to build two loops sharing one coupling loop by using heavy gauge speaker twin lead.

RF-principle: Two parameters determine the resonance of a magnetic loop antenna, the diameter of the loop and the capacitor.

For a second frequency in one band one may consider to shorten one cable of the twin lead by just the right amount. This will certainly result in a second resonance close to the first resonance. Since the two leads are somewhat close, there will certainly be some capacitive coupling, what influence this will have, if at all, will be subject to experimentation. The second consequence of the proximity of the leads would be that the lengths cannot be drastically different, hence, using the same capacitor, the frequency offset would be small.

For dual-band use, the two loops should be resonated by individual capacitors. Here, the capacity between the loops will certainly have a dramatic impact on the resonance frequencies.

There is yet another possibility, probably the most messy one... Connecting the second loop to the resonating capacitor of the first loop symmetrically using identical high(er) value capacitors. This will (slightly) increase the resonance frequency of the second loop. I figure, this third possibility is somewhat impractical.

Whatever option is chosen, the (single) coupling loop will couple both loops equally well, since the size of the coupling loop is defined relative to the size of the main loop(s), i.e. 1/6 to 1/4 depending on the loop's environment.

17m XTAL Controlled QRSS / WSPR / QRP / SDR

Sorry for having been silent for a while. Some new thought, although not entirely mine, I believe sharing it this way would be more than appropriate.
The idea about the frequency generation is borrowed from DJ1ZB. Ha-Jo uses CB crystals on their fundamental and doubles the result.

Doubling sounds very much like two things I previously disclosed on this blot, namely, the subharmonic direct conversion receiver (e.g. this) and the subharmonic I/Q-SDR (see earlier posts on the SDR and possible frequencies).
Both designs rely on a local oscillator on half the operating frequency.

Concentrating what could be interesting for QRP, QRSS and WSPR, lets have a closer look to the available crystals.

• 27.105MHz (12T) => 9.035MHz x 2 = 18.070MHz
• 27.135MHz (15T) => 9.045MHz x 2 = 18.090MHz
• 27.155MHz (16T) => 9.051667MHz x 2 = 18.103333MHz
• 27.165MHz (17T) => 9.055MHz x 2 = 18.110MHz

The frequency generated with a 15T-XTAL appears to be ideal for I/Q-SDR since the whole CW & Data & beacons range will be covered by 48kHz sampling rate. Have a look: difference 18.090-0.024=18.066 and sum 18.090+0.024=18.114.
Additionally, 18.090MHz is the quite close to the QRP frequency, a subharmonic direct conversion receiver would be an obvious choice, so would be a transmitter with a doubler...

Very obviously, the other frequencies are directed more to QRSS and WSPR. I am not going into the QRSS feature here, it is kinda trivial (see above).

Remaining topic: WSPR. The frequency produced by the 16T-XTAL is very very close to the WSPR "dial frequency" 18.1046MHz. With a Pierce oscillator the tiny amount of 633Hz upwards pull should not be a big deal; remember, on half the frequency, one only needs to pull half the distance.
RX: subharmonic direct conversion.
TX: subharmonic mixing of the local oscillator with an audio signal should create a DSB signal... that's the theory... I have not yet tried it yet, however, I fail to see any reason why this should not work.