KitsAndParts.Com Forum

I noticed in one of you previous posts that you ordered some encoders from BG Micro. Did you get them? The add says no hardware so I am wondering if you had any problem mounting the encoder? I assume they are just missing a nut for the shaft. I had order before from BG and got the same optical encoder but I had to remove it from a gimble type camera mount. I'm using it with my DDS-60.
It sounds like you have a high quality junk box. Keep us posted with your progress.

I decided to not use a whole 'Audio Detector' board up for a transmit mixer. I made up a simple circuit with just one of Diz's multi-purpose boards consisting of an SA612 and not much more. I'm getting a lot of good ideas for my SSB chain from the Epiphyte transceiver http://www.norcalqrp.org/files/Epiphyte3Mnl.pdf. Nothing is simplar than this and I like simple.



The TX mixer is missing the VFO input (very important) and the BPF hasn't been modified for SSB yet. The only things that work for sure at this point are the mic amp and the balanced modulator.

By the way, do you have a name. I looked up your call and couldn't find it so maybe you want to be anonymous .

Tom, ak2b

This recording is the SSB TX chain as shown above with the exception that the LPF is not being used. The output of the TX mixer (bottom connecter) has a wire acting like an antenna attached to it. I added the VFO input connecter to the SA602 and use the FCC-1/2 at about +7dbm to feed it. The microphone is an old Panasonic electret from a cellualr hands free kit - which is why it sounds like it's being handled too much. The Epiphyte speech amp has the bias for this. The recording is from the earphone jack of the K2 with antenna attached - which is the reason for all the background noise. I know I could make a better recording but at this point I have more important fish to fry - like boosting the output power of the TX mixer and deciding whether to modify the LPF I already have or make up a new one. Over-all I'm amazed that I got this far

Tom, ak2b

http://tomnyc.no-ip.org/audio/SSBtxTest.mp3

Well, I thought I was close to getting on the air . I have a few more problems, obvious now with the added gain.
Last night while transmitting with the exciter and listening to myself on the K2, I could hear some decent sounding SSB. But, tuning away from where the SSB sounded best, produced a noise that sounded like a choir of cats. I had no idea what the problem was. I also realized that I didn’t quite know what I was doing. After doing some reading http://www.arrl.org/tis/info/bldgeqp.html ‘The principles of building SSB gear (part 2)’ by Doug DeMaw, I found that my carrier oscillator should be at 5.065.500 MHz (1.5 KHz lower) if my crystal filter center frequency was 5.067.000 MHz (for USB). This should put the carrier frequency about 20 dB down on the skirt of the crystal filter for adequate carrier suppression. My crystal filter is so messed up that finding the center frequency through the ripple is going to be difficult. In any case, the BW is way too wide so the whole filter needs to be redone. The caps I’m using are 39pf but I think 49pf is more like it. Properly terminating the filter might also help. Hopefully a better filter will chase the cats away. Or, I might end up using a 9 MHz commercial filter that I have on hand.

Tom, ak2b

Hi Ken,
I have an N2PK VNA (which has a very steep learning curve for me). The filter looked pretty bad. I really didn't take my time with it. The crystals Diz sent were right on the nose, frequency wise. I checked them before I built the filter. I used the AADE filter design program last night and it actually didn't look so hot either using the Min-Loss (Cohn)type Ladder design (using all the same caps that I used). Using a Butterworth design looked a bit better. I'll give it another shot using your suggestion of adjusting parallel trimmers while sweeping.

I probably will try the Inrad filter since I also have the 9 MHz USB and LSB crystals. At least I will find out if everything else is working ok.

There is a group at http://groups.yahoo.com/group/dds_controller/ which has a program for controlling a variety of DDS's including the DDS-60. The group started out with the idea that serial ports are disappearing and they wanted to be able to control a DDS-60 via the USB port. I believe the program is still available although the group has gone on to other, newer DDS chips. The programs should still work with the DDS-60.
Steve Weber, KD1JV http://kd1jv.qrpradio.com/butterfly/bflydds.HTM uses the AVR Butterfly to control a DDS-60.

Tom, ak2b

Now that's interesting.  A few years ago I snagged about 250 8.3886mhz rocks in HC6u cans off of fleabay. 
I'd sure like to try making a few IF filters out of them.  I've been told crystals in these larger cans make better
filters than the sub mini micro processor rocks, not too sure if that's true but it could be.
IIRC I paid about $15 plus postage for all those rocks.

I see you have trimmers at half the capacitor positions.  Depending on the filter design you might need to adjust the remaining cap positions to get your slope where you want it.  The filter termination impedance can make a difference, as well as the number of poles (but five crystals does seem to be about the average used in SSB ladder filters.)  If you use more poles you might need a series capacitor or two in the middle of the filter.  Seems you are zeroing in on the thing though.....

I just got brave and hooked my newly built DDS-60 up to my ATmega16 development board.  I wrote some software to initialize the SPI interface on the processor and to send bytes out to the DDS-60.  I had to do some hex math to come up with the right constant to multiply the frequency by to get the correct DDS programming word.  It has to be a binary fraction so that you can use integer math.  The code is written in "C" using WINAVR (avr-gcc), the variables end up being long long int's (64 bit integers) and I right shift out the LS 24 bits to get rid of the fractional part of the product.  Avr-libc DOES have a floating point package, but it's a code/cpu HOG.

Anyway my dumb program simply sets up the micro to dump 5 bytes of zeros to the AD9851 twice to make sure it's initialized in serial mode, then it calculates the DDS tuning word for 10mhz and sends that to the AD9851.  I hooked up my frequency counter to the output, powered up the micro/dds and crossed my fingers.  DANG!, either my counter is out of calibration or the rock on the DDS-60 is a bit off 'cause the output is 650HZ low!  Well actually all considered, that's close enough for government work!

Next step is to hook up my shaft encoder and either an LCD display or an LED display.  I have a module half built with 8 LED's and a MAX6954 display driver that I plan to use.  The '6954 will also give me a 16 button keypad interface too.  I may just hook up a 16x2 LCD just to have something now.  I also can control the micro from my pc using the serial interface, and I'm using that now with printf statements to debug to code.

As soon as I have a way to change frequency on the DDS from a user interface, guess I'll hack up a DC RX front end.

AH HA, the A/C just turned on and started to blow.  The frequency dropped another 10HZ.  Well the DDS-60 isn't exactly THAT good a frequency reference I suppose.

PS, I'll drag the DSLR into the work room one of these days so I can post some pictures.

Hi Gary, I hope you're feeling better.
I remembered your post and looked it up to check my crystals against. They are very close.
Thanks,
Tom ak2b

Hi Ken,
With all those crystals the only thing to do is make some filters. There are a lot of good references out there. Another one I like is:
http://www.k8iqy.com/testequipment/pvxo … 02V1R5.pdf
Once your DDS is done you aren't far from making one.
Tom, ak2b

w4gns wrote:

I'm looking at your K8ZOA crystal fixture, Is there anything special about that other than having alot of ground plane ?

Here is a schematic of Jack's test fixture. In the K8IQY url, there is also a test fixture. Take your pick. You seem to have gotten good results with your analyzer without a fixture.
http://www.cliftonlaboratories.com/Docu … ixture.pdf
Sorry about your back. Good luck with that.

Tom, ak2b

Your measurement run on the Inrad filter looks like a carbon copy of the one on their website, except that
they had a center frequency 10hz lower than yours.

If you can drive your 5mhz filter from a high impedance output and put low resistance carbon pots on the
input and output of the filter, and measure with a 1meg ohm voltmeter, you should be able to vary the termination resistance
till you get it right.  Problem is you don't KNOW what the correct termination impedance for your set of crystals should be
to get the right response curve, though I would have thought that within reason you could vary the capacitance till you
got it right for a given impedance.  Maybe not if the crystal series resistance is too far out of wack.  Did you look at the design of the filter in the K2 SSB adapter for ideas?

You might need to add a series capacitance at the input and output of the filter, or a series resistance at the input and
or output of the filter.  I've seen these in some ladder filter designs, mostly those with 5 or more rocks though.

Anyway, that INRAD filter looks good, and for $24 not too bad.  I'm hoping I can build something decent out of all those 8.3333 mhz HC6/U surplus crystals I have.  As far as my project is concerned, I got the LED display board wired up with the MAX6954 display driver chip.  Next step is to ohm it out to make sure I wired up correctly, then to add a connector to my Mega16 development board to interconnect the two and try writing a driver for it.  Also need to wire up the rotary encoder and then we can actually try to control the DDS.  I also need to find a serial interfaced D/A chip so I can generate a sweep output with the DDS, that will give me an el-cheapo way to look at the response curves for filters.  Not actually right though since the voltage display on the scope will still be linear, not log ... would need a linear to log conversion circuit between the output and the scope.  Could use the 10 bit A/D on the Mega16 and do the conversion and graph in software, but that would require writing a graphical application on the PC.  Guess I'd have to look at the TCK/TKL, GTK or QT documentation (running Linux here) for that. 

Also need to measure cutouts for the front panel of my project for the LED readout and the 16 switch keypad.  Thinking of using a Dremel to cut out the openings.  The target project box measures about 11"W x 6"H x 14"D (larger than the K3) which should give me plenty of room for the transceiver with a 100W power amp (though I'll start with something in the 10-30w neighborhood based on junkbox transistors I already have).

Last edited by wa2me (2009-09-20 12:58:49)

I modeled yet another filter using AADE filter designer. I pretty much followed the tutorial in the AADE help file - the one by Jack Smith. (Tutorials > Crystal Filter Tutorials > Cohn Filter Example) I even transformed the input and output impedances the same way it described in the tutorial. I used the 5.067 MHz crystal parameters described in anothe post on this page. I ended up transforming a 734.482 ohm impedance to 50 ohms. I built the L network into one of Diz's crystal filter boards. The caps are 39pf. The result is posted below.






I think this will be good enough.
Tom, ak2b

wa2me wrote:

Just found a few of your videos on YouTube.  Seems one of my ideas for an el-cheapo QRP final you already know of, and I just now heard of JBOT.  Nothing new under the sun!  I see you also have a DDS-60 based DSP in addition to the FCC-2.  Which one do you think is cleaner?  That DDS-60 package job reminds me of an old Lionel train power pack!

Hi Ken,
"The WB2EBY design is implemented in the PA-100 from HF Projects.
I can supply bare boards or kitted parts." (quoted from Virgil, K5OOR, the designer and owner of HF Projects)

I also have this kit, it is very handy to have around when 1 watt isn't cutting it.

The Motorola app notes also look interesting, particularly if you already have the transistors.

I don't know which one of the DDS's is the cleanest. I probably should. It has never been an issue in terms of practical use with any of the radios  I've built. I know there are people that won't use either one because of the spurs. I haven't noticed them - I'm sure they are there, though. Maybe ignorance is bliss . I can tell you that the DDS-60 is by far the hottest! The FCC-1/2 is incredibly well programmed to do almost anything you can dream up. Either one makes for a very cheap piece of test gear with great accuracy. I use my FCC-1/2 with a step attenuator as much as my HP8640B generator.

Tom,ak2b

Well I'm still working on the Mega16 controller.  I hope to write some code for the MAX6954 LED driver interface this weekend.  I got side tracked by another idea.  I am going to add an IR receiver interface using a spare interrupt input on the processor.  Since I already wrote this code for a project at work, getting it going on my DDS controller will be easy.  So I will be able to use an IR remote control to operate the DDS and the eventual transceiver as well.  I have a NIles R8 remote control (older version of this one http://www.nilesaudio.com/product.php?p … ID=FG01446) that I can use.  The IR receiver interface is very simple, just a 38khz receiver module (http://www.bgmicro.com/index.asp?PageAc … odID=11069), connected to a spare interrupt on the microprocessor.  The software uses a hardware timer to measure incoming pulses to decode the IR signals.