Magic super-VXO Frequency?

Years ago, I ebayed a Heathkit HW-8 direct conversion CW-transceiver. It was not in the best shape, but it did not cost the world either. Now, for good measures, finally I want to put some life in it again. So, lets look at the schematics first...
Ahh, mhhhh, aha..... four bands, four crystals and a 250kHz wide VFO.
Lets have a look at the combination for 80m:
The converter-crystal is mentioned to be 12.395MHz. That would determine the VFO oscillating at 8.895MHz at its maximum frequency.

Hmm, 8.645MHz to 8.895MHz, that rings a bell! Yes, you guessed it, there is a widely available standard crystal at 8.86724MHz, resulting a very interesting operating frequency at about 3.528MHz... Interesting, a super-VXO at 8.867MHz, will get us 28kHz off from the lower edges of the four bands.

Now lets see how well a 8.867 super-VXO will do with other standard crystals...

• 8.867 - 9.000 = (-) 0.133
• 8.867 - 7.000 = 1.867
• 8.867 - 12.406 = (-) 3.539
• 8.867 - 1.843 = 7.024
• 8.867 + 5.185 = 14.052
• 8.867 + 9.216 = 18.083

 You're missing 30m? OK, here's your 30m, it's a tricky one however, in particular for filtering!

• 8.867 + (5.000/4) = 8.867 + 1.25 = 10.117

 Or with a not so common 38.0MHz oscillator:

• 8.867 - (38.000/2) = 8.867 - 19.000 = (-) 10.133

I leave it to the reader to find more, in particular for the bands 15m and higher...

QRSS Averaging vs Plasma TV

Well, what about those, would you think that any reasonable signal identification can be derived from this? "Ja hoor!"


Raw Data

Feel free to download the images and try for yourself!

Averaged Spectrum

And we can identify Paolo once again ;-)

Dark Frame Technique vs Plasma TV

A plasma TV creates some more or less static lines, like hot pixels in a long exposure CCD camera. The dark frame technique subtracts the "ideal" hot pixel map, or TV lines, in our case. A dark frame is created the same way as the averaged spectum. In the case of a CCD camera, one simply puts the lid on the objective lens. For TV, life is more complicated. To create a dark frame, I selected spectra were the TV lines were essentially the only signals present. Maybe, in a second step, one may want to try to capture spectra of the particular noise source with an insensitive antenna close by...
That would be my dark frame for tonight (5 selected spectra averaged):

With dark fram "opacity" set to 30%, that's what the little averaging program comes up with:

DF opacity set to 100%, pixel values of less than 160 are set to 0.

Dark Frame Technique vs OTHR

Yep, this technique is suitable for getting rid of radar stuff too. To me, it seems more to help aesthetics than anything else... but... you never know.
Last night, nice radar spectra were recorded. A couple of those resulted in the following radar "dark frame":

Earlier today, that was recorded... (averaged)

Averaged using the dark frame:

Conclusion

Those are my first steps using my experience in imaging gather in long-exposure webcam deep sky photography. I am in a very early stage using said techniques in QRSS imaging. My impression is,
imaging techniques used in astrophotography can help QRSS. Those techniques can even help fighting local QRM. A lot more learning is required... I remember my learning curve in astro-stuff... my first astro-images totally sucked!

Daytime Averaging

Unfortunately, the night did not really reveal any good condx. However, during daytime, very poor condx allowed to see some Southern European signals.

During the time span in question, the regular grabber took the following spectra

In the time between 10:30 and 13:00 UTC, 15 10min spectra were taken. Successive 5 of those spectra were average into 3 intermediate results, which were averaged again. Remember the demo-version of the stacking software allows for max. 10 images to be treated.


Averaging Result

Metallic Effect (irfanview)

Paolo's FSK signal nicely spreads over the full 10min span. Due to fading, the signal never made it into JO22 for any continuous 10min, as the 15 "frames" show.

The SNR could be further improved by selecting the best spectra, i.e. with at least some signal. I went for the "blind" method (using all frames) an automatic grabber would perform.

If interested in the raw spectra (frames), drop a comment, I will make a zip-file available for download.

QRSS Image Averaging

First test on 10min QRSS spectra averaging using http://tawbaware.com/imgstack.htm
Thanks to NH7SR, it seem somewhat obvious how to record timed spectra. With good stability and timing assume, image registration seems not to be required. Hence, simple stacking or averaging would be a promising start. Here's some first stuff, not refined yet... a somewhat early pre-alpha stage.


Raw Data

The following 6 images are raw spectra, as recorded and used for the averaging.

Raw

Raw

Raw

Raw

Raw

Raw

Averaging Result

Average

Conclusion

The settings are pretty much same used for the online grabber. For an averaging grabber, more noise, i.e. contrast & brightness, could be tolerated. Data acquisition with more aggressive settings is presently ongoing.
I believe, the first hour, compressed into 10 minutes show a promising start and some potential when the learning curve is surpassed.


Update

Some more spectra are in, as promised, more aggressively set. This is what those look like.

Raw

Raw

Raw

Raw

Average

MF/LF Dual Band SDR

Just an idea, what about a 2.000MHz local oscillator. For regular SDR purposes, this will and up at 500kHz centre frequency. Ok... not that surprising.
What about taking this 500kHz signal and use it as LO for another SDR setup. Well, that would provide as with a centre frequency of 125kHz.

Assuming a regular 48kH sampling, two interesting frequencies are in reach:

• MF: 476-524kHz
• LF: 101-149kHz

H-Probe (the Aerial Formerly Known As Shielded Loop)

Short update, not only the name changed, some more happend.
Parts are collected, the TL592 based amplifier should be done in minutes.
The shielded loop is past now, I will reorganise the inside of the tuning-box. The toroid is removed, coupling will be done at the high impedance region of the loop, i.e. at the tuning capacitor.

Oh, should you wonder about the new name, this contraption is near to entirely screened, any E-field should therefore essentially be excluded from detection. A magnetic field, or H-field, will induce a current in the loop. This current will peak at the resonance frequency, creating a high impedance RF signal across the tuning capacitor. The aerial therefore probes the H-field, hence the new name.

Multiband QRP TRX

Just an idea, which pop up when I replied to G4CWX and had a chat with PA9QV. The question was, what to use as a low power travel CW setup.
And this is the idea: a couple of RockMites in a box.
All transceivers could share the connector, i.e. antenna socket, control button, key. Band select, in my plan, would be a rotary switch powering up an individual transceiver PCB.
As said, just an idea....
And... I still got the RockMite kits for 20, 30 and 40m waiting for solder... the 80m version could be brought from QRSS to QRP... the 4-band-QRP-TRX would be completed.

Shielded Loop (some photographs)

No new development yet. Here are some photographs to help the imagination. The loops will be provided with some amplifiers soon-ish.

There seems to be a rule of thumb for the dimensions:
Loop Diameters [cm] = Wavelength [m]
(e.g. 30cm loop diameter for a 10MHz loop)  :-))

For more information on materials and dimensions, please use the label "shielded" down below.

The loops for 30m and 40m.

The gap in the shield, opposite the capacitor.

The capacitor and coupling "box".

Digital Flashback

Lately I was digging a bit in my goodies boxes... and some treasures surfaced in the for of digi-mode controllers.

Next to two TNC2s, a Kantronics KAM (w/ Pactor I), an SCS PTCplus, an AEA PK-900 and an SCS PTC-IIe found their way out of the dark.

Hmmm, this has been my active Packet-Radio and Pactor period. Now:

• What happened to the controllers?
• Are still in a working order?
• Would they be able to communicate with modern computers?
• Is there still software available, for these controller, which runs on modern computers?
• Is there still activity?
• What could the stuff be used for?

Questions questions....

I tested all controllers but the PK-900, which simply is too clunky for the tiny test space I freed.
The tests concerned the compatibility of modern computer hardware with those old controller, hence no radios connected, no RF generated.
So, here's some of the results and thoughts.

All tested controllers still worked.

For testing, I used three relatively new computers in the setup, running different operating systems: an Acer REVO w/ Windows Vista, an Acer Aspire One running jolicloud 1.0 and an MSI Wind under Windows XP. None of these computers have RS232-ports, which in modern times seems the first hurdle.
In a recent order, I purchased a cheap no-name USB-to-serial adapter (Prolific PL2303 chipset), which plugged into the SCS PTCs directly. For the other controllers, a "9to25"-adapter was required.
BTW, Vista provided me with the most struggle, a lot of blue screens, core dumps and what not...
jolicloud was the only real plug&play what the PL2303 is concerned, and smoothly installed the device as /dev/ttyUSB0.

Struggles aside, let's have a look at the results.


Packet-Radio

Software: PAXON under Windows Vista
TNC2 (TF2.6, modified to 10MHz Z80, 38400bps): doing just fine!
Symek TNC2S (TF2.7): something caused the TNC to stall in TX (remember, no radio connected!), with my hand placed on the controller, this did not occur. Seems there is some grounding problem between the PC, the USB-device, the TNC and the TNC's (linear) PSU.





AMTOR & Pactor

Windows software: Airmail3 for hams, Alpha 3.2, Simple32

Airmail3 seems to be the reference, it could talk to all modems, on either Windows flavors, although, it has been a struggle to have it talking to the KAM under Vista, no problem with XP though. Airmail3, as the name suggests, is an HF email program, which makes use of the WINLINK2000 Global Radio Email System. Airmail3 is therefore mainly programmed for handshaking with the servers of said system and therefore is essentially limited to Pactor.

Alpha 3.2 did only talk to the SCS PTCs, however, it did it well.

Simple32 simply did not work on Vista, whatever I tried (run it under admin, etc.). I got the main screen just once after hitting ignore on all error-messages, and, it did not at all look simple, hence I decided to not (yet) give it a try on XP.

Linux software: Kptc, minicom

Kptc flawlessly installed on my jolicloud 1.0 netbook. The program works perfectly with the SCS PTCs.

minicom seems the only easy way to communicate to the KAM. A software called Kamplus was written some years ago. I will try to compile it on my machine, I will post any success story; I will however spare you stories about failed software porting efforts.


Conclusions

Packet-Radio seems a dying mode, at least here in my region. When I moved here, I was eager to keep contact with my friends via the PR-network, I soon learned, that this region is not connected to anything. I wonder I that changed. Maybe APRS would be an option.

AMTOR was a very advanced technique, to the time when I got on the air for the first time. Those chirps were everywhere.... I have not heard many on the ham-bands lately. However, there seems to be one BBS station in Germany, DA5TOR, still on-air. I should give it a try, once my NVIS antenna is set up.

Pactor = eMail nowadays... DXers are busy using narrowband modes like PSK31. Pactor, when I did it last, could provide an even better robustness, but, for what price? Modern PTCs are more expensive than decent HF transceivers! No wonder that the mode more and more drifted towards professional application, e.g. marine communications such as SailMail.


Next Steps

Yes, I will take next steps. Among my transceivers, I will find the ones that make the least noise and provide the fastest switching.
A good start in this respect could be the Ten Tec Scout, if the frequency stability proves to be sufficient. I used this transceiver with PSK31 and Pactor I before, back in the days. The Scout is, besides the strange noise created by the PTO, totally silent, no relays involved... could be perfect.
Then there would be the Kenwood TS-140, which I used for WSPR for some weeks a year ago. The TS-140 has got relays, and is therefore somewhat unpleasant when used with ARQ.
Technically, the best fit would be the ICOM IC-M710. Not only was it built for the purpose, remember TOR (Teleprinting Over Radio) is a marine application, Airmail3 can actually control the radio via the NMEA bus. The IC-M710 also provides a frequency stability superior to most ham-radios. The radio however employs a lot of mechanical switching.
Last but not least, the following approach could be considered (this will be a new blog entry, when taken seriously): Use a DDS, controlled by a PIC, PICAXE or Atmel, as a LO for something that either already transceives silently, e.g. an old Scout, SmallWonderLabs PSK-series, N3ZI's 612-PCBs (see earlier blog entry) or this.

Grabber up

The grabber is back online for some hours now. No adverse effects yet. Let's hope it stays that way.
There is one minor change, the grabber is now using my G5RV-jr and not the DCTL.