de draaggolf ~~~~~

600m SDR RX (TX)

2012-01-17T23:26:00.003+01:00

As we know, presently there are a couple of frequencies of the 600m band open to amateur radio operators.
Most of authorities allow transmission somewhere above 500kHz. In The Netherlands the permitted range is 501-505kHz. In the future, depending on the decision of the WRC12, this will possibly change to 472 to 480kHz. The U.S.of A. proposed the following ranges 461-469 and 471-478 kHz.

Lets look at the (inexpensive) option the box73 SDR. The 80m version of this receiver uses a 14.000MHz oscillator. Operation on the 600m band can be achieved by changing the front-end filter and the SDR-LO.
Considering 48kbps sampling, the LO-frequencies would be the following

QRG: 470kHz - LO: 1.843MHz
QRG: 500kHz - LO: 2.000MHz

This will result is RX-ranges of:

460.8 -/+ 24 = 436.8 .. 484.8
500.0 -/+ 24 = 476.0 .. 524.0

Concluding, a decent 600m receiver can be built with LOs using regular canned oscillators.

600m with CB-XTALs follow up

2012-01-17T23:03:00.001+01:00

Hi there... I am back!
Presently, amateurs in The Netherlands are really happy, not only have we got the permission to transmit on 4m, we also may transmit on 600m again. For the time being between 501 and 505kHz.
For this range (well, to the upper QRG of 504kHz) this article could lead to a cheap signal source.

However, in about a month's time, we will know is we need to redesign our exciters, i.e. to the range 472 to 480kHz. So, lets have another look at the cheap crystal solution.
The new range is not that easy really. One solution would be the mixing of two standard xtal frequencies:

4915.2 - 4433.6 = 481.6 somewhat high, could be pulled into the range

A spot on solution would be a 10m QRP crystal (28.060MHz) on its fundamental mixed with a 9.8304MHz standard crystal:

9830.4 - 28060/3 = 9830.4 - 9353.3 = 477.1

Another spot on option: a 40m QRP crystal, mixed with a 6.5536MHz standard xtal.

7030 - 6553.6 = 476.4

Starting from lower frequencies, crystals from box73.de:

14745.6 - 14270 = 475.6
7025 - 6553.6 = 471.4 (pull!)
3550 - 3072 = 478
4000 - 3530 = 470 (pull!) (*)
3555 - 3072 = 483 (pull!)

Subractive mixing has the advantage that some thermal effects may cancel. Assume to us several standard crystals in a super-VXO.
Mind you, the higher the frequencies, the easier to pull, i.e. create a nice tuning range. However, lower frequencies will give better stability.

(*) Note, there is a 4.00MHz ceramic resonator, which will allows for a nice VFO. Use a Pierce oscillator to obtain a QRG above the ceramic resonator's series resonance.

SDR Meets DJ Gear

2011-11-27T22:43:00.001+01:00

Hi there! Some of you may know that I am quite busy with music, dance and the stuff concerned.
Some rare occasions have it, and hamradio mixes with music mixing, aka DJing. And here is one of those occasions:
The DJ Mouse
http://www.dj-mouse.com/
Basically, there is nothing special about this mouse, other than the regular scroll wheel is somewhat wider and parallel with a jog wheel. It is just this jog wheel that makes all the difference.
All SDR software solutions I am aware of, are using the scroll wheel for sweeping the frequency. I always felt that this was somewhat awkward. Now we got a mouse with a rotary encoder, just like a VFO knob.
Still I scratch my head what can be done with the "scratch" button...

Central Heating Aerial

2011-11-24T21:54:00.001+01:00

Dear readers, there was not much going on here lately, sorry about that!
Today, some weird incident triggered another thought in me.... and here it comes:

Returning home, I felt an unfamiliar chill in my house... That's no good, I thought, and checked the central heating system, which indeed was dead. Quick check and the culprit was found. The expansion vessel (expansievat, Ausdehnungsgefäss, vase d'expansion, whatever you wanna call it) leaked. The local hardware store was still open, hence I hurried up to get a replacement of similar size.
Just €22.- will get you one with a 17l capacity.
Speaking of capacity, that came to my mind on my way back home. What about using the defective one as top-capacity for a short vertical? The roundish things got a nice thread which would easily fit Cu pipes and respective fittings.
The vessel itself is made from steal (Fe) most likely. OK, that's somewhat on the heavy end, electrically however, not that inferior to Al, which is used most.
The plan is to build a short tapered vertical from Cu-pipes with an expansion vessel on top.
I figure, one may also consider a short loaded dipole.
Possibly, just 2 of such vessels could make a broadband dipole for VHF.... one could also think of a broadband vertical for VHF, using just one vessel on a ground-plane.

There may just be one down-side, your neighbors will think you're completely mental, putting the expansion vessel of your heating system 5m above your roof ;-)

Happy experimenting.

Most Interesting

2011-11-08T22:31:00.000+01:00

What is going on here? A local station, a dx station and the radar, which seems to dislike the condx...

Broad-Band Aerial Update

2011-11-08T21:02:00.001+01:00

Short update on the 11m half-wave aerial conversion.

The 4:1 UnUn is placed, that was one of the two options. Actually, this was the easy option, since the UnUn came wound up and ready to use from a surplus dealer.

11m half wafe aerial base portion

The arial, about 5.5m long, w/o any further modification could be matched easily with the IC-703 builtin tuner on the band from 80m to 10m, with the exeption of 30m. I figure, some additional Al-tube extension could solve that problem.

SDR for the 600m band

2011-10-29T19:37:00.000+02:00

Some short not on an idea for the 600m band.
The typical SDR, as we all know, uses 4x the center frequency so that the 90 phase-shifts can easily be created by flip-flops.

In 2012, the Netherlands will most likely open the range 501-505kHz for ham radio operators. I figure a simple RX (maybe also TX) solution could be a 2.000MHz canned oscillator. This will get us spot on 500kHz center frequency, just as you may want. Comfortable 1 to 5kHz audio, which any sound card can handle easily, with a sample rate of only 24kHz. A further experiment should show if side-band suppression is required at all. I figure, a decent pre-selector should be enough already.
Should however, following a decision at the WRC-12, the range open to hams change to the range proposed by CEPT (472 to 480kHz), a 2.000MHz SDR-LO would be somewhat too high. In this case, the oscillator could easily be swapped with a 1.8432MHz one. Resulting in a center frequency of 460.8kHz. Audio up to 20kHz would still be somewhat a challenge for cheap sound hardware, never the less, a sample rate of 48kHz would cover it all.

No to the TX-part of it. One could either use a sound card generated signal, as provided by some software solution. One could also thing of generating an I/Q modulation signal at 4x the audio signal, divide and phase shift similarly to the LO chain. Unfortunately, we would now have a rich audio square wave. I figure some severe filtering will be required here, in order to end up with a sine wave.
I would not consider an AF phase-shifting network. I believe the frequency range is to great as provide accurate phase-shifting.
However, as in the RX part, it may be conceivable to filter the side-band at the RF range. A series of tank and trap circuits could possibly be enough. Mind you, the aerial matching itself is very selective too.

New Item in the Marine Radio Collection

2011-09-23T03:02:00.001+02:00

Could not stop myself from buying an "Emergency Radio Type 610". I believe it is made by Clifford & Snell, but I am not sure about that.
The radio services the frequencies 500kHz (RX/TX), 2182kHz (RX/TX) and 8364kHz (TX). As in this sort of package, cranks are provided as a power source.

The transmitter seem to be built around two electron tubes (have not checked the types yet), while the receiver seem to employ OC transistors, Germanium that is.
Whilst test TXing into the built-in dummy load, on 2182kHz (A3E), the antenna current meter nicely peaks when the matching variometer (coil with dive-in ferrite rod) is agitated. The two other frequencies would require the operator to have a third arm!?? My radio was supplied with the emergency instructions, which showed one operator only, even the text referred to a single operator doing the cranks and the communications all at once. Who ever wrote this may have never operated a radio himself. While in A3E, a carrier in generated anyway. One hand operating the crank, the other to tune the variometer, no problems here.
It is a different story with 500kHz and 8364kHz. Those are A2A frequencies. No, there is not typoe, A2A it is, AF modulated code. And yes, that makes sense. The signal is received in both, an AM receiver as well as a receiver employing a BFO. However, when tuning the emergency transmitter, one would need one arm/hand operating the crank for energy, a second arm/hand for operating the manual key and a third arm/hand for operating the tuning knob.
The makers of the radio seemed to have spent some thought on this issue, although, maybe not enough. The radio is equipped with a mechanical auto-keyer. Keying the transmitter for tuning can therefore be done, sort of, without three arms. However, the designers seemed to never had the code operator in mind. The built-in manual key is so close to the position of the cranks, that operating both at the same time seems to be a challenge per se. However, if that was your option to survive at sea, that what you would be going for.

Enough about the transmitter, lets have a word on the aerial system provided. A system which managed to impress me. As in all of those sets, the aerial is contained in the box itself. Motto: if your vessel is sinking, throw the emergency radio overboard, get in the life raft and hope for the best. Hence, the floating waterproof box of the emergency radio has to contain everything required to perform emergency communication, including the aerial.
The 610 comes with an antenna base, about 1m long, having a rubber foot (for not damaging the life raft's soft bottom). On this foot, a stainless steel telescopic whip is to be mounted, the whip having an impressive length of estimated 4m (maybe more).

To the downside, and the reason why this radio is not widely available.
In order to keep it smaller, I presume, the designers choose to have a low profile for the cranks. Fair enough... however, they put the cranks so low that they can't be used when the radio laying perfectly flat on the ground. A problem that the very similar TRP1 does not have. Is the TRP1 really as similar? Maybe not... think of it, the TRP1 uses TTL circuits, whilst the 610 employs electron valves and Germanium transistors...

Do I regret having bought on of the 610s? No! Would I buy another one? No!
What is the best thing about the type 610? The aerial provided. I believe, there is no other (convenient) way to get your hands on stuff alike... Think of it!

73!

Cheap Android Tablet Going Strong

2011-09-16T23:02:00.001+02:00

Some time ago, I reported about a very cheap Android Tablet (from kijkshop), which I used regularly for this and that.
The table came with some port accessory, which holds two regular USB ports and an Ethernet connection. Writing this, I am presently using the tablet via Ethernet (thus no WLAN) with a wireless keyboard attached via USB for convenient typing. The port accessory actually seem not to have functioned when I got the device first. However, in the course of time, I really could not believe that a design fault was the cause. Well, the was a design fault, not in the electronics though. The plastics chassis appeared to be too large and had to be sanded down in order to allow all pins to make contact. Seen that the tablet costed € 100.-, I should have bought a second one, since said shop stopped selling those devices.
Still, I have not mentioned any details about the product...
it is an iLC 7" tablet PC using an ARM 800MHz processor with 256MB RAM
the OS being Android 2.2 (Android Market installed) on 4GB flash storage, allowing for a microSD card
the device is further equipped with WiFi, stereo speakers, a headphone connector and a built-in microphone
finally, there is the port accessory, providing 10baseT and 2x USB
All in all, the gadget look comparably cheap, matching up with the proce somehow. At times the device's response is somewhat sluggish. Would I buy the gadget once again? YES!

4:1, 6:1 or 9:1?

2011-09-12T23:16:00.000+02:00

Thinking back and forth a bit, again on aerials, I came to the conclusion that using 75Ohms feedline some 4:1 would be appropriate.
But why?!

The developers at Diamond thought that for the BB6W, or the BB7V for good measures, a 6:1 transformation would be the way to go. This aerial design assumes a 50Ohms feedline. The aerial's feedpoint is therefore considered having an impedance of 300Ohms. Remember, in this design, there is 600Ohms of termination resistor to ensure a maximum SWR of 2:1.

Assuming that the average auto-ATU will match a transmitter's 50Ohms antenna connector to a 75Ohms feedline easily, a 4:1 transformation will do in order to match a feedpoint impedance of 300Ohms when using 75Ohms feedline.
This actually brings together good news from two worlds:

75Ohms coax cable has got less losses than 50Ohms coax (it is cheaper too)
a 4:1 transformer is easier to make than a 6:1 transformer (QRP: old TV-xformers)

So, now what about the 9:1 UnUn that so many use with endfed aerials? Personally, I used a 9:1 transformer with 50Ohms feedline. The 450Ohms feedpoint impedance works with endfed wires, about as good as 450Ohms window line (using a suitable ATU).

As a side remark, the feedpoint impedance at the voltage maximum is considered to be 5kOhms. Neither window line nor a 9:1 transformer gets us there. This can only be matched using ladder line (or open wire line) with a symmetric coupler.

Kizomba, the Name of the Game

2011-09-09T23:28:00.000+02:00

Hi folks,
this is completely off topic.You may have wondered why I am sooooo slooooow writing technical articles, well, there are some reasons. One of them reasons being, I am much more into dancing once again... and kizomba is the name of that game. Some may already know that I am severely into mambo dancing, this remains. For those of you readers that are into dancing, check out kizomba, aka. African tango. The dance is from Angola, the music is a mix of French creole "zouk" and Angolan "semba".
Dear fellow ham radio operators, there is more to life than a microphone or a Morse key. Get out, get social enjoy life, also on the dance floor!
BTW, WCS (West Coast Swing) is cool too! Go for it, grab a girl and off you go!

Surplus RF-Transformers for Random Wire Antennas

2011-08-27T21:06:00.001+02:00

In some of my last posts I was sharing thoughts about broadband aerials using transformers to match the high impedance of the non-resonant "random" wire. Well, the leghth of those wires is not that random at the end. Some typical lengths that come to my mind 6m, 7m, 7.5m, 11.5m, etc. you may know some more...

Now, let's have a look at some options provided by surplus (the junk box respectively).

CFL bulb transformer vs. surplus iron powder toroid

On the left side we have a transformer that was in a (defective) CFL bulb, aka as energy-saving light. The thing on the right side is one of the is a surplus transformer based on a T68-2, which came in bags of 5pc for just 0.80 €-cents.

So, what do we have, the CFL transformer countd 3:3:12 windings. Using the black and the white in series, that would be 6:12. This would be, in other words, be a fine 9:1 UnUn.

The T68-2 is provided with 12 bifilar windings. This would therefore make you average 4:1 UnUn. Obviously, those can also be 1:1 isolation transformer.

Both junk-box items are proven in ham-radio designs. I figure, I will experiment with both out of the box options. Additionally, I may possibly try a 6:1 UnUn, as in the BB6W/BB7V design. Staying at QRPP levels would even offer the change of trying the termination resistor used in the BB6W/BB7Vs.
Oh, I forgot, to get closer to the BB7V, I will add some additional Al-pipe to top of the 5.5m long 27MHz vertical.

Half-wave 27MHz Antenna as Broadband Vertical

2011-08-25T23:58:00.005+02:00

Years and years ago, a friend of mine gave me a (brand new) half-wave CB antenna. Well, I have never used it, for the reason of not being QRV on 11m. For 10m I had my double bazooka, so there was no need for it. Now that it has been sitting in a corner for a while, I thought, maybe it could be useful for something else. Some else as in broadband vertical...

Now, let's have a look how those things are built:


aerial schematics

This drawing is not made by me, however, it nicely sketches what the following photographs of my very own version of that antenna show.

all still in one part


taken apart

What we have is the cavity and the transformer that was sitting in it. The air core transformer has got a winding ratio of 7.5:2. I figure, using a ferrite or iron powder toroid would improve performance on lower frequencies.
The cavity measures 35mm in diameter, having a depth of 24mm. This clearly offers enough space to house a smaller toroid transformer.

At this place, I would like to remind you of the BB7V (Diamond) having an UnUn transformer with (resistive) termination shunt. This vertical would be 6.7m tall. The regular 11m half-wave vertical could possibly be stretched to a tallness somewhat beyond 5.5m. Close enough to me.

Now let's think... for QRP work a T80-2 would make an ok UnUn. With some luck, transformers with a T130-2 core could possibly be squeezed in the cavity, if made carefully.
Reconsidering the BB7V's terminator, would I put one in there? Only if I would be using this aerial for QRPp only. The base of the CB-aerial is made from plastics material, which is not able to conduct any heat. Hence, heat created inside the cavity would never be dissipated. For QRSs/QRPp, the resistive terminator is a very appealing option, in particular since for such power levels, a T50-2 transformer would offer sufficient empty space for the terminator.
A T130-2 would possibly be good for a regular 100W rig. However, in a worst case, 50W of heat have to be dissipated, hence, some cooling of the termination would be required, therefore, this is a no-go. Some adjustments and selective use of bands would still be an option for such an arrangement.
Personally, I am very tempted to try a version of a T68-2 transformer (not sure about termination yet), in combination with my IC-703. This is somewhat of a compromise...
Should I ever again get into QRPp/QRSs/WSPR/WSJT/ROS actively, my preference would be the small transformer&terminator option.

Additionally, I figure, it could be of use to add an additional Al-pipe of about one meter to the top of the vertical. This will result in a total length of about 6.4m and a further distance to a quarter-wave on 20m, without getting too close to a quarter-wave on 30m.

There you have it, a new life for a cheap half-wave 11m vertical.

455kHz SDR - a second thought

2011-08-06T22:53:00.000+02:00

My previous blog was all about the idea of adding a softrock, or any other simple SDR-DC-RX, to a cheap (synthesized) AM radio. Well, honestly said, when thinking of it, this may be a totally unnecessary overkill.
Why? Well, very simple. The main purpose of all the quadrature stuff is to make the two sidebands that a DC-RX receives different. But, what if there is not other sideband? The following may not apply to the absolute cheapest of AM-receivers.
Concerning the ATS-404, I have ambiguous information. While some technical data mention the AM i.f. being 450kHz, the schematics diagram mentions a LT455H, which is a 455kHz ceramic filter having +/-3kHz 6dB bandwidth (+/-9kHz for attenuated bandwidth). If we tap before that filter, we definitely need quadrature, should we however tap the i.f. behind that filter, a non-quadrature SDR would be OK too.
Most of the better world-band receivers use a first i.f. somewhere high with a relatively wide crystal filter. Most of the narrow filtering is done at 455kHz. In this case, we probably wont need quadrature at all. All we have to do is to ensure that our SDR center frequency (or SDR-l.o.) falls close to but outside the range of the intermediate frequency range. In such a scenario, there would not be a second sideband to care about and also a simple mono-audio interface would already do the job.
The Target HF3 would be an example for such a receiver. The first i.f. is at 45MHz having a bandwidth of +/-3.75kHz. The second i.f. band would consequently be 455-3.75=451.25 to 455+3.75=458.75 kHz. In yesterday's example, using a 1.8432Mhz local oscillator, we ended up at an SDR center frequency of 460.8kHz, which is close but outside the HF3's second i.f. band. A regular direct conversion receiver with a local oscillator at 460.8kHz would therefore receive only a lower side-band, since there is no signal in its upper side-band.
My idea would be to try that out using a canned oscillator and two flip-flops for frequency division. With some isolation amplification a singled ended diode mixer and a cheap USB audio adapter should round up that experiment.

ATS-404 idea

2011-08-06T12:30:00.001+02:00

Using the second intermediate frequency, often at 455kHz, is widely known. A suitable I/Q-SDR would be based on a 1.8432MHz (canned) oscillator, resulting in a 460.8kHz center frequency. Assuming a 24k sample rate, would be adequate to cover the range from 450 to 460kHz perfectly.

Many I/Q-SDR kist are available, due to the size and the low price, the softrock lite could be suitable best.

So, why the ATS-404. I was looking for a relatively cheap wide coverage receiver having direct frequency entry. The 5kHz tuning steps on shortwave suit the 10kHz wide SDR just fine.
The ATS-404 uses the TA8132AN AM/FM-receiver IC. This IC has go the advantage of providing an IF-out at pin 9 (see data-sheet). Slight downside: the TA8132 employs a 450kHz intermediate frequency...
A service manual for the ATS-404 can be found here:
http://www.thiecom.de/ftp/sangean/ats404/

The remaining question... where to put the I/Q-SDR? Using a softrock lite, one may consider using the battery compartment. Speaking of battery, the radio runs of 4 AA cells. It can also be operated from 6V external power. I wonder if 5V from a USB-port would be sufficient, finally, the idea is to use a computer for the SDR anyway.
Which brings me to the last idea... a cheap (stereo!) USB-sound-interface could also be accomodated in the battery compartment, so that only connection would be a USB cable to the computer.

PFR-3 with W5JH paddles

2011-08-01T21:10:00.000+02:00

BB6W / BB7V clones for QRSS

2011-07-17T22:29:00.007+02:00

If you browse the wide of the internet on the hunt of information about Diamond's BB6W or BB7V, you will most likely come across some images and blogs. One of the most helpful blogs, in my view, is Martin's ECLECTIC AETHER. The link points to the actual article....
As to images, for me, the image found here: http://www.cqcqde.com/shop/88_108.html is most informative.

Referring to Martin's blog, it seems that the "matching" device actually is a 6:1 UnUn ferrit toroid transformer with a 600Ohm (120W) termination resistor. The aerial being rated 250W, this means that up to 50% or 3dB of power is burnt in said resistor. The bandwidth of the aerials is mentioned to be 2Mhz to 30MHz.
Martin mentions the inferior performance of the 6:1 UnUn the why it was wound in the original BB6W. To my believe there is actually some thought in this. Japan, that where the aerial comes from, is a very noisy, QRM that is, country. Hence, Diamond seems to have decided to compromise power coupling versus common mode noise by reducing the capacitive coupling between the windings.

My interpretation of this aerial comes close to a short end-fed random wire, which is broadened by a sort of termination known from aerials like the T2FD, with a twist however.
Here is what I believe is interesting about the concept. Usually end-fed random wires are used in combination with 9:1 UnUn transformers, which result in a feed point impedances of 450Ohms. The BB6W matching unit however transforms to 300Ohms only, where the termination is twice that. Obviously, one does not want 300Ohms of termination, that would just form a dummy load...

So, what we got here is a short broadband aerial, horizontal or vertical in which half the power is absorbed.
In QRO, the tricky bit is the non-inductive resistor. It is doable, and certainly to a lower price than Diamond sells the aerials.
In QRSS, which essentially is QRPP, we are not troubled by the problem mentioned above. In fact, we could use a regular 1/4W carbon resistor and still we would be fine.

Two things came to my mind

use a 9:1 UnUn with a 900Ohms resistor
use an air-core (auto-) transformer

Further, I would use a longer radiator to improve performance on 80m and allow for 160m. A low horizontal broadband aerial for 80m and 40m could be an interesting solution for NVIS operations on modes other than QRSS.
It would also not be too difficult to build a termination resistor being good for 10W or so....

Last thing, what way of winding the UnUn would be most appropriate? You decide... Diamond's way would provide you with less RX-QRM, Martin's method would pass more TX-power to the wire.

XPware was made freeware!

2011-06-11T14:23:00.001+02:00

XPware is freeware now! It runs under WinXP (have not tested any other win-flavor).
http://www.glaswerks.com/xpware/

It can talk to the following controllers (test myself):

Kantronics KAM(+)
AEA PK900
SCS PCT+
SCS PTCIIe

The handling of the software depends on the respective controller.

I did those tests on the grabber pc, which in parallel was running one instance of winamp, two instances of spectrum and argoupload. Since modern PCs are not equipped with serial ports anymore, USB2Serial cables were used. All in all I believe being fine to going on with NBDP acitivities.

NBDP what's that? You may ask... This is the modern name for the mode family FEC, SelFEC and TOR. The acronym stand for Narrow Band Direct Printing.

PS: if you are on facebook, feel free to join the recently created group "Teleprinting Over Radio"

Teleprinting Over Radio Revival?

2011-06-07T23:25:00.004+02:00

Guys, I was wondering if it would be possible to revive a mode that seems to be lost, TOR (AmTOR or if you want - or NBDP as it is called today). To it's time, AmTOR was kinda expensive/hard to get qrv on easily. Transceivers needed a certain RX-TX switch over timing, modems were not cheap, software hard to get hold of. I remember, to the time I had some AmTOR software running on my trusted Apple II.... but that is a long time ago.
In that time, multi-mode controllers came on the market, worth more than a short-wave transceiver... so, I could not afford any of those. Even worse, the transceiver I could afford was a second hand Drake TR4, which would never have had a single chance to meet the timing demands of AmTOR. Hence, I was stuck to my trusty combination of the TR4 and a Siemens T100 doing Radio TeleTYping (aka RTTY).
Oh... and those ARQ signals where present everywhere!
Today, TOR (AmTOR for good measures) is relatively dead. Although, hardware is cheaply available today, and there is also some software downloadable, emulating the hardware solutions. Today's transceivers don't need to be modified anymore, to achieve the timing required for ARQ. AmTOR is a robust mode, good for some straight keyboard communication.... I wonder if we could revive this mode for amateur radio.
Mind you, this mode TOR (Teleprinting Over Radio) is still in use in GMDSS. Actually, it still is the preferred mode in today's maritime communication. Actually, for my GMDSS GOC, I lately had to learn how to connect to a Telex land-line.
Folks, would it not be cool to give this AmTOR a second life? In particular since second hand hardware is available as cheaply as presently....

PS: if you are on facebook, feel free to join the recently created group "Teleprinting Over Radio"

SWL PSK-20 for JT65 & WSPR

2011-05-27T18:19:00.008+02:00

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!

2011-05-24T19:32:00.001+02:00

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

2011-05-23T09:16:00.001+02:00

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

2011-05-19T20:46:00.001+02:00

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+

2011-05-16T01:42:00.002+02:00

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

2011-04-28T21:22:00.002+02:00

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.