Thursday, February 26, 2009


In 1915 the phasing system of SSB generation was filed for patent. Below is an explanation of generating a SSB signal using the phasing method from the RSGB.

For this explanation, reference is made to figure A1. Diagrams (a) show two carriers A and B of the same frequency and phase, one of which is modulated in a balanced modulator by an audio tone to produce contra-rotating sidebands A1 and A2, and the other modulated by a 90 degrees phase shifted version of the same audio tone. This produces sidebands B1 and B2 which have a 90 degree phase relationship with their A counterparts. The carrier vector is shown dotted since the carrier is absent from the output of the balanced modulators. Figure A1(b) shows the vector relationship if the carrier B is shifted in phase by 90 degrees and figure A1(c) shows the addition of these two signals. It is evident that sidebands A2 and B2 are in anti-phase and therefore cancel whereas A1 and B1 are in phase and additive. The result is that single sideboard is produced by this process.

Figure A1 - Phasing System Vectors
(From RSGB Radio Communications Handbook)

B1 and A1 are additive vectors and B2 and A2 are opposite B1 plus A1 = SSB and B2 and A2 cancel. Note A and B are 90 degrees out of phase..... Wait a minute those are wiggling vectors AND they are 90 degrees out of phase... Where have I seen this before???? Could this be I/Q? This kind of signal generation is quadrature in nature. My first SSB rig was the HT-37. It was a phasing rig and I got rave reviews on the audio. You could crank up the gain and the thing would buck shot all over the band, but when you tamed it down the audio was fantastic. I called it WIDE BAND SIDE BAND W2OY hated it.

The F5K is just such a rig, a rig based in the phasing method of sideband generation. In the HT-37 the 90 degree shifts were accomplished in components and were not entirely linear, but in the F5K the shifts are accomplished in software and the phasing is perfect. I used to be able to get maybe 25 or 30 dB of cancellation with the HT-37. In the F5K you just set all vector values of A2 and B2 to zero. Now that's what I call cancellation!!! No sneaking up on it with little phase shifts, just BANG you're Zero!! Old timers (alas I've become one, I used to look in the mirror and see Robert Redford now I see Captain Kangaroo) will remember the phasing days. When the Japanese transceivers came roaring on the scene all that big iron like the HT-37 or the Central Electronics 20A went the way of the dodo. The new rigs all used crystal filtering in sideband generation. Whenever you put an analogue filter in the line you add distortion because the filter has its own characteristic which get added or subtracted to the signal. When you just cancel things mathematically there is no added distortion, just one sideband goes away and the audio quality is preserved. The F5K also uses its brick wall filters with rejection better than 100dB to set the band width, so the F5K is very well behaved on SSB indeed. In fact the F5K according to some of my buddies even has a particularly clean and distinct note on CW. They can tell when its me tuning up just by the purity of my CW note. I was amazed when they told me that. Personally I'm more interested in the CW performance of the radio but the radio is so feature laden for high quality SSB it deserves some comment. The program gives you pristine control over how you sound.

The F5K (and the 3K) allow for balanced input mics like the broadcasters use or single ended mics typical of communications. The Mic I used on my SDR1K was a balanced output condenser mic and the mic I use presently on my F5K is the Ten Tec 708A dynamic mic. Both mics get rave reviews on the air. I'm not much into the quality audio scene as the quality of my voice is reminiscent of geese farts on a muggy day, but there is a group of dulcet aficionados (W5GI et al) that LOVES this radio for its audio, and whats the point of owning a radio if you don't love it? The balanced mic plugs into the back of the radio and the 8 pin TT mic plugs straight into the front. The 8 pin connector pin out is Yaesu. I went with the 708 because I like the goose neck and the PTT arrangement a.k.a. convenience.

Mic selection and audio output in the F5K is via the mixer screen

As you can see you can choose audio inputs, audio outputs, and set various levels on these devices so you get a smooth transition in the program when you make the switch. This means I can set up the balanced mic and the TT mic such that I don't have to reset the mic gain on the front console

This is a shot of the 3 band version of the graphic equalizer

And here is the ten band version

I'm simple and mostly a CW guy so I use the 3 band version. Interestingly enough the RX equalizer sometimes comes in very handy. On 40M in the midst of the Foreign Broadcast I have some times been able to make stations otherwise uncopyable into Q5 copy by adjusting this feature. The TX and RX equalizers can be tuned off and on from the front console in the SSB modes

This brings up another point. When you switch modes the console changes. Here is SSB:

And here is CW:

Notice the control changes in the bottom right screen near the center. In CW mode CW relevant controls are visible and in SSB, SSB relevant controls are available. The change is automatic. The filter bandwidth controls also change their range from very wide SSB filters down to very narrow CW filters. The filters themselves are continuously variable by right clicking the filter control for example I have one of my filters set to 100Hz under CW. I set this by right clicking the particular filter button I wanted to set to 100. The set up screen looks like this

My center freq on CW is offset by 350hz and this filter is 50 hz above and 50 hz below 350 hz. Each mode can have its own compliment of custom filters. This scheme is one of the contributions I added to this software, so customer input does get added to the mix. (Of course Eric is the one who coded the idea).

Compander and DX Compander. I must confess I don't know how these work at the present. I have a line into the maven (N4HY) who wrote the code, so when I know more you will know more. Suffice it to say these really bring up the average talk power but they do so with virtually no distortion and no increase in band width or splatter at all. I run my compander at 3. If you crank it up it starts to sound crappy, but it you run low mid range, at least with the mics I am using, it basically adds a wonderful presence or depth to the audio quality similar to how stereo amps that have a "presence" control bring out greater texture and detail in the music, at least that's how it sounds to me. DX compander is compander on steroids and I never use it. I have only one SSB DX contact in my log, and thousands on CW so you can easily see where my interests lay.

The Vox controls controls are readily apparent. You can set sensitivity but the delay is set up in one of the setup screens and to change that you have to dig down a couple of menus. The Vox is very good not too sensitive and its not clicking all the time.

You can set up multiple transmit profiles so you can have a custom: contest profile, ESSB profile, regular profile, make the coffee profile and DX screamer profile all set up in the drop down menu all selectable at a moments notice. You can do whatever blows your skirt up, and save it for later skirt blowing with this radio.

You can show the TX filter on the display under the RX filter so you can see if your TX bandwidth will offend someone up or down the band. How civilized.

In addition you can set up a gate mode, which is a noise gate where it takes a certain level of audio before the radio will send audio down the pipe. Very handy for when you have that 3cx10,000 cranked up for the Gator stakes. You remember the gator stakes don't you? WB8BFS would hold forth on 3895 and invite everyone to dump it in. The loudest station he could hear was the winner. If you ever heard of the amp supply LK-800 tny (3 - 3cx800's with a big honkin peter dalh transformer in a separate power supply box), that amp was built originally for WB8TNY by Amp Supply so Chad, who lived down the road from BEEFUS could win Gator Stakes. W4MPE, the PUKE of Paducah always kicked his butt. They didn't call him the puke for nothin'. Them big bottles glowing white hot always kicked them little squirrel nuts. Good old 75M, its tame today compared to the past. We had a lot of fun. (now I'm really sounding like a geezer)

Transmit bandwidth is set up in the setup screen. The transmit filter looks like this

This filter is set at a low end cut of 200hz and a high end cut of 3100hz for a bandwidth of 2900hz. The filter will only allow 3khz in SSB. You can see the brick wall nature of the filter. Ultimate rejection is down about 130 dBm. If some kilocycle cop comes carping about how "wide" your signal is, you can just email them a pic of your transmitted signal along with a polite "fix your friggin receiver!!!!" Slaughtering OO complaints is like shootin fish in a barrel.

In the upper right hand corner you can see the drop down of the things that can be monitored by the meter on TX:

Each of these parameters can be monitored and adjusted for optimum and each has some input on how the final transmitted signal sounds.

I have presented a lot of pictures for a reason, not to just hear myself blow, (though I do dearly love to hear myself blow). If you ignore my witty banter and just spend some time looking at the picture, including the things I have not mentioned you will come to understand a lot about this radio and how it is designed. The pictures give a lot of insight. You can combine that with the F5K manual and gain even more insight. This post is getting a little long and has a lot of info to digest, so I am going to do an Audio 2 to show case the various functions of the display Way cool stuff stay tuned....