Sangean ATS 909 (first impressions)

Bought myself a new receiver for Christmas. Yes, yet another one. Here's some blabla about my first impressions.

For €199.- the package contains, the receiver (oh well...), some earphones and a 110/230V power supply with an adapter for American sockets. OK, and a very short manual.

When first attempting to engage... nothing... ???? Ahhh, by factory default, the keys are locked. That was a surprise, honestly.

There are a couple of features not really standard to such receivers. One is RDS which can be used to automatically program the internal clock. Interestingly enough, the clock can be set to two time zones and daylight saving time can be toggled by a single key. Speaking of "FM", the tuning range is 76 to 108MHz. There are two memory pages for FM, which can be programmed automatically (aka. ATS) by a single key.

The ATS also can be used for medium wave and long wave. The feature scans the respective band and stores the strongest stations to memory channels.

The MW channel spacing can be selected to 9kHz or 10kHz at a well accessible switch on the right side panel. This side panel also carries switches for "auto time set", "tone" (news/normal/music) and AM bandwidth next to a potentiometer for volume and a rotary tuning encoder.
The left side panel houses connection for DC, headphones, line-out, record trigger and external antenna. Also to be found, a potentiometer for RF gain (nice touch!).

Now to the more interesting things, short wave and first impressions as a grabber receiver.
Frequencies can be selected in a couple of ways, hacking it in by using the key pad, up and down tuning keys (5kHz steps) or the rotary encoder on the right side panel. The steps of the encoder can be toggled between 1kHz/40Hz in SSB mode and 5kHz/1Khz in AM mode, a third position disables the encoder. Since fine tuning in USB/LSB is 40Hz, there is no need for a clarifier, which therefore is not present.
When tuning, the receiver mutes whenever the frequency changes by 1kHz, even when using 40Hz steps. Within the kHz, the receiver does not mute. Seems some PLL locking.

One interesting feature is the memory system. Whenever a frequency is typed in which is stored in somewhere, the memory system changes to the memory page which the frequency is stored in. The mode is change to the stored mode.

During the first night, the receiver was very unstable and drifted a lot, the QRSS test was very difficult, doubts raised on the usability of the receiver for QRSS. The major drift was in one direction only and slowed down with time. That made me believe that this drift was due to fresh components which were not aged. The second attempt was going much better, the gadget was left one for the best part of the day. Before the test, I switched it off for a couple of hours, to see the effects of the warming up. Stability is much better now than it was during the first test.

BTW, for QRSS the RF-gain feature proved itself as very useful.

I hope that further use will further age the frequency determining components and thereby increase the frequency stability. If that will happen, the ATS 909 will make a really nice portable grabber setup.

Receiver for 7059900Hz

Several obvious options here.

SDR using 4x the qrg. Here, we a got crystal from Nick, 28.188MHz, resulting in an SDR center frequency of 7.047MHz. Alternatively the canned 28.322MHz-oscillators provide a center frequency of 7.0805MHz.

SDR using half the receive frequency, phase shifting of 90 degrees done by an RC circuit. A crystal is available: 3.535MHz (from Rich). This results in an SDR center frequency of 7.070MHz.

And finally, there is a crystal available, from box73.de, having a frequency of 3.530MHz. This is too close for SDR, but allow for a subharmonic direct conversion receiver, more or less in the same way as I use it for 30m. The only drawback here, there is not 7.060MHz crystal yet, hence, no easy way for a sideband filter. However, there are crystals for 7.055MHz (Rich, box73.de) and 7.058MHz (Rich), which could serve as a notch filter, just like in Gene Marcus 30m WSPR transceiver.

20m FSK/FM MEPT

Did some soldering today, that how far I came. OK, nearly. Check out the diagram. All is done besides the frequency modulation input with its diode (LED or rectifier) and capacitor. The amount of capacitors in the crystal network is due to experimentation, and this is what drops my oscillator from 13.999MHz to 14.006MHz with 14.001MHz in the mid tuning range of the capacitor.

Design idea here: use as much of the 74HCT240 as possible. Hence, one inverter as oscillator, three buffer (I know, this does not really make sense, but wait!) and the block of the other four gates as power amplifier, all four in parallel for use with a step-up transformer. The "PA" is equipped with an enable/disable switch.

So, here is comes, why use three buffers. Well, the first buffer is required since oscillator gate is operated in "linear mode". This first buffer inverts the signal, or in other words, phase-shifts it by 180 degrees. The second buffer inverts the signal again, providing a signal which is phase-shift by another 180 degrees, delivering an in phase signal to the oscillator. Who knows what this can be used for...

OK, now the third buffer seems really useless, but, it is not ;-) This buffer terminated the second one properly, so that always a nice signal can be drawn from either buffer 1 or buffer 2.

Astronomy meets QRSS

Inspired by last nights experiment, I suggest the following:

Let's transmit in predefined time slots, as the IBP-beacons.

This could be used for the following procedure:

• start a grab a some 10secs before the slot, and end it some 10sec after the slot
• put the spectrum in a file named after the slot + sequence number
• register and stack all files of a single slot (as it is done in modern astrophotography)

The question is, how to automatize this. I'll look into this...

Benefits, extreme noise reduction due to integration over a longer period, as done in astronomy. (check my astronomy stuff at www.qsl.net/dl1gsj - webcam imaging with small telescopes).

Search added to blog

This should help me to find my way through my own blog ;-)

E-probe experiment (30m)

The Suburban Subharmonic Grabber uses a wider than 100Hz range.
Hence, occasionally a WSPR station makes it into the visual
(displayed) spectrum. When I did my E-probe test, under comparably
poor condx on 30m, RW6XC came up, low enough to nicely be seen
on the grabber spectrum. The interesting part, a visual spectrum
of a single station can be compared to the signal to noise ratio
determined by the WSPR software.

Have a look:
Date: 2009-12-09
Station monitored: RW6XC
Power (indicated): 5W
Distance: LN23AS -> JO22DA = 3059km

UTC...SNR
19:58 -20
19:46 -24
19:38 -20
19:34 -19
19:30 -15
19:26 -14
19:22 -12
19:16 -7
19:12 -8
19:08 -7
19:04 -11
19:02 -12
19:00 -19


The other part of the test was, to see if and how many
station are received by this minimal setup. Remember,
this is an E-probe feeding a homemade direct conversion
receiver...

Stations received during 24h using the E-probe:

Date.......UTC...Call...SNR.Loc...pwr.km.
2009-12-09.17:12.W1XP...-25.FN42fo.5.5546
2009-12-09.19:58.RW6XC..-20.LN23as.5.3059
2009-12-09.10:28.RA3ZSE.-19.KO80ws.5.2313
2009-12-09.13:40.OK2SAM..-9.JN99du.1.1008
2009-12-09.13:46.OE3EV..-12.JN88...5..981
2009-12-09.13:42.IQ4DJ..-12.JN54mq.1..955
2009-12-09.09:50.GM4KGK..+1.IO68ve.5..955
2009-12-09.11:32.OK2BUH..+3.JN89oo.5..945

So, second experiment, yes, you can receive stuff with absolute minimal gear...

indoor DCTL & WSPR on 30m

This is what my tiny subharmonic d.c.-rx heard when wired to the indoors DCTL.

Timestamp	Call	MHz	SNR	Drift	Grid	Pwr	Reporter	RGrid	km	az
2009-12-08 03:36	W3HH	10.140158	-24	0	EL89vb	1	PA1GSJ	JO22da	7276	42
2009-12-08 13:40	W1XP	10.140242	-17	0	FN42fo	5	PA1GSJ	JO22da	5546	51
2009-12-08 14:24	RW6XC	10.140147	-19	-1	LN23as	5	PA1GSJ	JO22da	3059	302
2009-12-08 09:46	I0/N2CQR	10.140152	-24	1	JN61fv	0.02	PA1GSJ	JO22da	1283	334
2009-12-08 08:54	F6EZP	10.140189	-20	0	IN93	2	PA1GSJ	JO22da	1029	21
2009-12-08 07:36	OK2SAM	10.140199	-23	0	JN99du	1	PA1GSJ	JO22da	1008	289
2009-12-08 07:30	OE3EV	10.140193	-6	0	JN88	5	PA1GSJ	JO22da	981	298
2009-12-08 07:42	IQ4DJ	10.140228	-5	1	JN54mq	1	PA1GSJ	JO22da	955	331
2009-12-08 09:44	GM4KGK	10.140281	-6	0	IO68ve	5	PA1GSJ	JO22da	955	131
2009-12-08 10:10	OE3WGW	10.140178	+9	-1	JN88cj	5	PA1GSJ	JO22da	937	300
2009-12-08 09:40	IK1ODO	10.140264	-19	0	JN35sa	20	PA1GSJ	JO22da	814	344
2009-12-08 10:34	DL5MHD	10.140212	-9	0	JN58xc	5	PA1GSJ	JO22da	699	311
2009-12-08 10:34	DG7RJ	10.140240	-23	0	JN58th	5	PA1GSJ	JO22da	665	311
2009-12-08 10:46	HB9TMW	10.140144	-25	1	JN36gq	5	PA1GSJ	JO22da	615	345

So folks, here you have it, you can receive weak signal living in a concrete building in a dens suburban environment.

In another experiment, I will use the E-probe, outside at my balcony, stay tuned for the data.

new low frequency ideas part 2 (RX)

There is another added bonus on CB crystals for low frequency operation. At least for the 136kHz band.

A CB-channel 22 TX crystal (27225kHz) would result in a frequency of 138.9kHz, just 1.1kHz off the upper band edge and 3.2kHz off the lower band edge.

Given the fact that the two last frequency divisions (see the earlier blog entry) resulting in 4 (two flipflops) it appears somewhat obvious to use just this crystal in a direct conversion SDR receiver.

new low frequency ideas (TX)

Working with dividers seem to have advantages to me, amongst: greater stability and easy digital design. The only question is, are there enough crystals in a close range?

Well, what about old CB crystals? And how would those get us onto the 136kHz band?

First things first!

Here is what I came up with and how I started the process:

There is an industrial crystal 27000kHz crystal, divide this by 196, get us to 137.76kHz, just 60Hz off the QRSS COA (center of activity).

How to divide by 196, well, that actually easier than I though:

1. 196/2=98
2. 98/2=49
3. 49=7*7

The recipe is hence, two counters to 7 in series (so that they multiply) and two FlipFlops. There we go, a 50% duty cycle with a cheap crystal in the middle of the QRSS range. Drift should not be an issue here, assume, the oscillator drifts by 1kHz, that would result in a 5Hz drift on long wave.

I think, there is even a canned oscillator of that frequency, making the design in particular simple.

And now to the added bonus: CB-XTALs!

I reach in my junk-box to see what crystals I got from old CB radios. Some calculation revealed the following:

1. 26600/196 = 135,71
2. 26610/196 = 135,77
3. 26620/196 = 135,82
4. 26630/196 = 135,87
5. 26650/196 = 135,97
6. 26660/196 = 136,02
7. 26670/196 = 136,07
8. 26680/196 = 136,12
9. 26780/196 = 136,63
10. 27000/196 = 137,76
11. 27005/196 = 137,78

This covers essentially the whole 136kHz band with junk crystals from CB radios. Even better, look at the channel count, to me that looks like I will be using the casing and the channel selector too ;-)

I missed a couple of frequencies, since I got no crystals for those in my junk box.

The internet discloses that there are RX crystals for the CB channels 8 to 40 ranging from 26600kHz to 26950kHz with 10kHz increments, a few channels skip however. 10kHz steps will result in 51Hz steps in the 136kHz band.

Additionally, there are TX crystals for CB radios. CB channels 1 to 4 (26965kHz to 27005kHz) would be interesting here.

One may consider to experiment with VXOs, since old CB radios have those anyway, ranging +/-5kHz, which would the cover essentially the whole band, with just a few gaps due to the lack of crystals.

The same principle could be serving for the 500kHz band. Here, one would require a division by 54, which would be two counters 9 x 3 = 27 and one flipflop => 54. CB TX crystals from upper channels could be used. Since I don't hold a licence to that band, I will not look any deeper into this. Nevertheless, I hope, that someone finds this useful.

80m results (06.12.2009)

Colin and I did some tests on 80m lately. The following spectrum shows the final minutes, before Colin QSYed. Receiver setup on my side: NASA Target HF3 + E-probe. The computer used for analysing is a Packard Bell "dot" netbook with an Intel Atom N270 processor.

The darker regions on the spectrum are due to a local (The Hague) sideband station pulling the AGC to the max. But still, there is some F1A (FSK-CW) coming through... The cheap'n easy setup still allows for detecting weak signals...