A new rig

AA6E just acquired a new small rig, a Yaesu FT-897D. Small on the outside (size), but big on the inside (features) -- like Dr. Who's Tardis. This is the first Yaesu HF (+ VHF/UHF) transceiver I have used since the days of the sainted FT-101.

A limitation of all compact rigs with sophisticated operating modes is the very limited user interface (knobs and buttons) through which you have to configure the equipment. We have a smallish LCD screen, 14 buttons, and 4 knobs -- and something like 100 parameters that can be set.

I am climbing the learning curve now. So far, it appears that the "information design" is fairly rational and easy to deal with, conquering new features one at a time. It will take a while to know the rig thoroughly. I'm only afraid I'll forget faster than I'll learn - especially since this is meant as a secondary rig for me.

People complain about the complexity of the Ten-Tec Orion, which is my main transceiver. They have a point, but navigation through the menus is much easier. With the Orion, the big concerns IMO have to do with setting up the flexible AGC system, IF DSP parameters, etc. (Not to mention finding and loading the firmware version that works best for your own operating style!) "Fortunately" the 897 has much less to offer in terms of advanced issues like these...

Getting on the air? I tried for a while without success. I was transmitting at 18 MHz into my 80 m dipole -- not a good strategy. Switching in the SteppIR, I made quick contacts with HA8, F5 and Texas for good measure. Nice reports.

Note to self: Improve antenna switching system!

Orion Surgery

My Ten-Tec Orion transceiver was 5 years old in February. It's getting to be an old timer -- in computer years, at least. It needed a few chores done.

1. The LCD panel was flickering. Internet scuttlebutt says this may be because of impending failure of filter capacitors that were undersize (in terms of ripple current handling).
2. With the current version 2.xx firmware, the LCD contrast is close to zero after a hardware reset. This can be a serious problem, depending on room temperature. Contrast is normally set via a menu adjustment -- that requires you to navigate through the LCD display. The display could be so faint that you couldn't make the adjustment. There is an internal bias control that should fix this.
3. Finally, I have been seeing the "RIT freeze" problem that others have noted. At times, the RIT control loses the ability to make any adjustments. Many people have reported this problem, but the cause and cure have not been well understood. It seems that you can fix it temporarily by grabbing the RIT/XIT encoder control and twisting hard in odd directions -- as if there were a bad solder joint on the PC board. A recent report suggests the trouble is actually with one of the board-to-board connectors making unreliable contact.

All the above have been discussed on the helpful Ten-Tec reflector, which I recommend to other Orion users. I have been saving up these problems for some time now. Hopefully, I only have to disassemble the Orion once!

Making a long story short, I pulled the rig out of my operating position, unplugging many cables, unscrewed many screws, and finally spread out the works on my bench. The RIT fix requires disassembling the front panel and the LCD/computer board. That's a fairly big operation, particularly since a wrong move with a tool could lead to a very costly repair job.

I located and replaced 3 electrolytic capacitors on the A9 board with higher voltage, low ESR units, per the helpful analysis of N6IE. Soldering was tricky, to prevent inadvertent short circuits and to get enough heat into the ground connections, which were not thermally isolated from the big ground planes on either side of the board. (That could have been avoided by a better PCB layout!) OK. That's problem #1 done.

The email instructions say that to solve #3, you need to look for bent or misaligned connecting pins on the computer / LCD board. I looked very carefully, but saw no misalignment or other problem. Still, it's possible there was some oxidation or dirt. I cleaned the pins and the sockets as best I could. So problem #3 might be resolved.

The LCD bias issue (#2) turns out to be easy. There is a control on the LCD/computer board that sets the default bias for the display. You just adjust it for a good display with the LCD menu set at the default 50% level (and of course with the power on and the rig having a chance to warm up).

Accomplishing all this, I reassembled the Orion and put back all those screws, and put the rig back in the operating position. Everything appeared to work, except no transmit power. Oops! There are a lot of reasons why this could happen. Fortunately, I did not smell smoke, and that eliminated some of the more expensive possibilities. Still, I'm not sure how much bench testing and repair I would be able to do, if this turned out to be a non-trivial problem. Thinking of where that shipping box might be, and how much Ten-Tec charges...

So, what did I really do in that repair process? I changed out the capacitors, true, but the fact that everything works in receive mode indicates that the power board was probably working. The other thing I did was to unplug many internal cables, disassemble the LCD boards, and reassemble. There could be a loose connection or a misplaced cable.

The problem was "fixed" by opening up the box all the way again, and carefully reinstalling all the cables and screws. We have transmit power for now. I hope it stays that way!

The triple repair job is done. The LCD is behaving much better than before, and at least for now, the RIT/XIT controls work smoothly.

One thing I hadn't counted on was the trouble of reconnecting my ratsnest of cables to the Orion. I have a linear, a transverter, computer audio and controls, and other gadgets that need to be connected. All these just got hooked up over several years, and of course I had nothing documented on paper. Figuring out how to reconnect took a while, but it should be better next time. Now the cables have labels on them. Documentation is still pending...

Orion, recalibrated

Previously, I blogged about the Orion's Frequency Calibration. I was able to tweak the Orion's TCXO to within a couple of Hz at 15 or 20 MHz, after warmup. The ambient room temperature was 80 F.

So now, after about 3 months, I recheck and find the oscillator has drifted about 14 Hz low (dial readings 14 Hz high) at 15 MHz. The room ambient is 73 F. This is still within +/- 1 ppm, and the oscillator is spec'd at +/- 3 ppm over 0 - 50 C.

The upshot: just because you can adjust the oscillator to +/- 0.1 ppm with care doesn't mean it will hold up for too long, as the oscillator ages and ambient conditions change.

Note: I'm getting ready for the ARRL Frequency Measurement Test tomorrow. The Orion's slow drift doesn't really matter. I will have to measure the the apparent WWV frequency anyway and apply the correction to the measurement. It doesn't matter how closely I can set the TCXO, I still have to do the correction.

Orion Frequency Calibration

The Ten-Tec Orion Transceiver is specified for frequency accuracy of + or - 3 ppm over the temperature range 0 - 50 C. That amounts to +/- 30 Hz at 10 MHz, or nearly +/- 90 Hz in the 10 meter band. In an SSB QSO, an error of 50 Hz is pretty noticeable. In a PSK31 QSO, a whole QSO fits into a 30 Hz band, so such an error could be quite serious. Fortunately, we rarely need to set our VFOs with such accuracy. We need precision, but we can just tune for best reception. It does matter near a band edge, but it would be unusual to have to work within 50 Hz of an edge.

The most likely case where good accuracy can help in the HF bands is when we operate in roundtable mode on SSB. Frequently, a group sets up on a specific frequency, like 3813.000 kHz. If we don't have good accuracy, and if we don't all tune up carefully on one station, we may have to use the RIT every time a different person is speaking. The better our absolute setting accuracy, the less trouble we will have in net operations.

So, how well can we do with a little effort on the Orion? I developed a technique for measuring my frequency error against WWV. (See note below.) My zero beat setting before adjustment was typically about 9.999987 MHz after warmup, 13 Hz low, corresponding to the master oscillator running high by about 1.3 ppm, well within Ten-Tec's spec.

The master oscillator in the Orion is a temperature-compensated crystal oscillator (TCXO) running at 44.55 MHz. It is a Siward series TXO32, apparently, with a mechanical fine adjustment. The following is my record of how I adjusted my oscillator.


First, remove the bottom cover of the Orion. There are 4 screws on the sides and many little Torx head screws around the rear lip. The top cover can stay in place. After the cover comes off, you are treated to the spacious glory of the Orion underchassis. The TCXO (circled) is on the A10 synthesizer board at the top.

This is the temperature compensated crystal oscillator (TCXO)

Here we do the actual adjustment. Note the pickup loop for the Icom R-8500 receiver to monitor 44.55 MHz. Fortunately, the TCXO does not require a non-metallic adjustment tool. An ordinary jeweler's screwdriver works fine. The adjustment feels a little coarse if you are trying for exact zerobeat with WWV -- i.e., sub-1 Hz beat. Keep in mind that 1 Hz at 15 MHz is .07 ppm, much finer than the specified oscillator accuracy. Because the oscillator temperature will be substantially less than normal with the case open, you do not want to zerobeat WWV. (See text below.)

The Icom R-8500 communications receiver was useful to monitor changes to the TCXO. It has its own internal TCXO reference. Such a receiver is not required for the Orion adjustment, but it is a help if available.

At the end, we put it all back together and give ourselves a professional-looking (?) calibration sticker.

Procedure
Before attempting the adjustment, it is useful to study the warmup characteristic of the Orion TCXO by zero-beating WWV over several hours, as the operating temperature stabilizes. Room ambient temperature was about 78-80 F. Naturally, you need to do this with the transceiver in its operating position with the covers on. Here is a typical warmup run monitoring WWV on 15 MHz.

Time (min)	Frequency	Error (ppm)
0	14.999 980	1.3
11	15.000 000	0.0
38	14.999 995	0.3
73	14.999 989	0.7
85	14.999 986	0.9
101	14.999 984	1.0
137	14.999 983	1.1
177	14.999 980	1.3

It would have been interesting to measure temperature along with time, but I did not have a temperature probe. (The A10 board runs pretty hot to the touch, and it is in a poorly ventilated area under the chassis. I would estimate the operating temperature is around 50 C.)

After running the warm-up curve, we note that the TCXO ends up 1.3 ppm high. The dial reading is 1.3 ppm or 20 Hz low. Therefore, we want to trim the TCXO so the dial reading increases by 20 Hz. That should bring the TCXO very close after warmup.

Another issue is which WWV frequency to use: 2.5, 5, 10, 15, or 20 MHz. Other things being equal, the highest frequency gives the best setting precision. One Hz at 20 MHz is .05 ppm. Propagation is a concern, however. We need a strong and steady signal. If the signal has much QSB (fading), it is likely to have a lot of frequency dispersion. You won't be able to find a steady zerobeat. You may want to avoid periods of significant solar or geomagnetic activity for the same reason. (Check http://www.n3kl.org/sun/noaa.html for current data.) For the most part, for my path the 15 MHz transmission worked best. I compared my results at 15 MHz with 10 MHz as a check. They were in good agreement.

Conclusions
The Orion's TCXO can be adjusted to within a few times 0.1 ppm, and it will stay put if the transceiver's operating temperature is stable. Crystal aging is a factor, however, so the calibration may have to be repeated periodically.

---------------

How to Zero Beat the Orion with WWV.
I have tried two methods of finding a precise zerobeat between the Orion's effective local oscillator frequency and a reference frequency transmission.

1. Zerobeat using CW Spot tone. (easiest for me) Set up for normal CW reception with say 300 Hz bandwidth. Hold down the Spot button and tune until you hear the beat note when the signal frequency equals the spot tone. Again, you should find the zerobeat within +/- 1 Hz.
2. Zerobeat on noise. If the IF passband offset (PBT) is set for say -100 Hz and the bandwidth is 200-300 Hz, set the AGC to "fast" and the mode to USB or LSB. The Rx audio deemphasis should be zero or positive. The tuning step needs to be 1 Hz. Find the beat note and adjust slowly for lower and lower audio tones. After the tone becomes sub audible (about 60 Hz depending on your speaker), carefully tune to zero. When you are within one or two Hz of zero beat, you should hear the receiver noise fluctuate up and down with the beat. (This is the effect of AGC.) It should be possible to locate the zerobeat to +/- 1 Hz. This method requires a fairly strong reference level.

--------
Note added (1/8/2006): An alternative procedure is given by K6SE at http://www.n5na.net/download/Orion_Freq_Calibration.pdf .

Why I'd like a digital IF output on my Orion

What could you do with a digital IF output from the Orion transceiver connected to your PC? I have a few ideas. Maybe you can add more.

• Custom IF DSP filters in your PC - like an optimized RTTY filter. (The Sharc DSPs are efficient for DSP, but modern PCs should be plenty fast enough to process a 20 kHz band.)
• Support interesting modulation modes (ISB, synchronous AM, DRM, PSK31, and all the other strange modes). Avoid the compromises of audio soundcard interfaces.
• Detect multiple data streams simultaneously
• Record your IF for later playback and analysis
• Real time spectral display.

If you had a digital IF input for Tx, you could generate interesting modulations in your PC, multiple audio/data streams (ISB or multiple SSB, digital audio) - FCC permitting.

The programmers among us would be able to enhance Orion's "software defined radio". Eventually there will be killer signal software for general use on everyone's PC.

A Little More Python for the Orion

I've posted a nifty little tester for the Ten-Tec Orion at my main website. It lets you send & receive arbitrary ASCII strings to the serial port. It's in Python, and Python is supported on many OS platforms. I have recently verified that the software will run under Windows, using Python for Windows, win32all, and pyserial for Windows. (The only module missing in Windows/Python is a "curses" package for my original octl program.)

Work continues on the Hamlib driver for the Orion. Latest: TT designed the antenna switching matrix "inside out". You select the transmitter/receiver(s) that want to be attached to a particular antenna, instead of the other way round. Oh well, we can fix it in software. We recently declared the driver to be "beta quality". Anyone care to prove me wrong?

Ten-Tec Orion S-meter & Hamlib

We have been making some progress with the Ten-Tec Orion backend software in the "Hamlib" package, an open-source project to provide a device-independent programming interface for amateur radio equipment in the Linux/POSIX world.

Here's a tid-bit you won't find everywhere: the Orion S-meter calibration curve.

#define TT565_STR_CAL { 15,  {
{  10, -45 }, /* S 1.5 min meter indication */
{  13, -42 },
{  18, -36 },
{  22, -30 },         
{  27, -24 },
{  30, -18 },
{  34, -12 },
{  38,  -6 },
{  43,   0 }, /* S9 */
{  48,  10 },
{  55,  20 },
{  62,  30 },
{  70,  40 },
{  78,  48 }, /* severe dsp quantization error */
{ 101,  65 }, /* at high end of scale */
} }

The first column is the Orion's response to the "?S" command in computer units. The second column is indicated decibels (dB) as read on the actual S-meter.

(Literary event: I just defined "S meter" in the Wikipedia! See my article.)

The Orion has a couple of peculiarities when measuring power. The minimum reading (on my unit) is about S 1.5 on all bands when looking at a dummy load. What does that mean? If S9 = 50 µV, then S1.5 is 6 dB x 7.5 S-units or 46 dB down in power = 2.5 x 10^-5. The voltage ratio is the square root of power, or about 5 x 10^-3. So the equivalent RF voltage level is 50 x 5 x 10^-3 = 0.25 µV. The Orion's sensitivity spec (main receiver) is "< 0.18 µV" says that the receiver's internal noise will be about this level, which is consistent with the meter reading. In other words, Ten-tec seems to have this right.

(On the other hand, the tried and true RST system says that S1 means "Faint signals barely perceptible". That's an argument for using 5 dB per S-unit, as some have defined it, at least with our current generation of receivers.)

The other feature of note on the S-meter is the behavior at very high signal levels. As you can see from the calibration table above, the raw S-meter units are spread out roughly 8 units per 10 dB. However, the meter reading is highly quantized. You only see values of S9+48 and S9+65, nothing in between. This indicates that the software computation of received power has a quantization problem. Of course, it's hard to complain too much, because such power levels are almost never seen in real life. (If they are, better switch in some attenuation!)