IC9700 frequency lock by Glen English VK1XX
Update blog, Main article, picture , contact
*Rev3 is currently in production, payment and shipping shortly.*
10 July 2019
FULL Altium project and PDF of schematic and PDF and software available for download
project LINK is here :
- ALTIUM PROJECT and GERBERS
PDF of PCB and SCHEMATIC LINK is here :
- PDF of SCHEMATIC AND PCB
software LINK is here :
3d JPG LINK is here :
28 June 2019
Working. done. software all done also!. Only TWO wires (power and CTL) are required. (Ground is by soldering the castellated holes to the shield cans) . Install is a cinch.
1) Have an LED on the board which tells you the level is correct . This helps with positioning. It is very non critical. Works +/- 7 mm in XY or Z
2) Have "board active" LED.
3) Have automatic external reference detection all working (frequency counter in the chip checks for external reference present, and if good, the radio is controlled by the lock board. If the external reference is not present the board is inactive and the
radio manual tuning functions normally . There is a optional cable from the 10 MHz splitter on board back to the motherboard if you really want to use internal Icom sync...
4) phase noise performance etc seems a little better close-in than the prototype.
Board floating around, programming cables still connected...Powered externally. It taps off 8V up on the rear left hand side.
Before I reduced the pickup gain, it would lock 100mm away :-)
The video and audio below shows early in the day - work was in progress. My programming cables to the chip are still connected.
Now 9pm, all finished . You will need to turn the volume up to hear the beat note
The first one, there is no tone at the start because the radio is off frequency. When I push the PCB down, and exceed the minimum threshold for pick-up the lock board immediately pulls it in.
short video and audio of lockup when board is pushed down into position
short video and audio showing that front panel manual freq control is tracked by lock PCB :-)
short video and audio showing that front panel manual freq control works when extern reference not plugged in :-)
20 June 2019
The board will fit ! now just have to load it.
17 June 2019
FULL Altium project and PDF of schematic and PDF and software available for download
LINK is here :
- H18-004 schematic + PCB PDF and Altium project AND software
16 June 2019
3D rendition of PCB with tooling strips attached for mfr. The boards will be back from fab ~ 18 June. It is a 2 layer 1mm FR4.
with approx. 160 parts, all 0603 apart from a couple of 0402 bypass caps.
Care has been taken with not introducing noise into the XO control chain. Interestingly, Icom have used a low noise opamp for their control
circuitry, although there are no freq vs noise density numbers. I have used a good chip ADA4500 but we may get away with something
less $. I do not think a $4 shaved off is going to matter much to discerning users.
I have added a 10 MHz split on the PCB so that users can still use the internal sync if they wish.
The board samples the 10 MHz input at startup. If it is not there within a few seconds of startup,
the board will assume INTERNAL reference and the user can use the Icom sync method against a
reference plugged in after the few seconds. The board will set the control of the XO to Hi-Z.
If the reference is there at turn on,
then it will use the 10 MHz reference to lock and control the XO. I am open to ideas for this selection if a variation is suggested.....
The board solders to the top of the shield cans near the oscillator, you will need a good sized soldering iron tip for that joint.
5 June 2019
MK2 is out of SPICE, in SCH and now on the PCB... only two solder joints on the PCB, both easy. No microscopes required !
2 June 2019
Thanks for all the fan mail everybody.
Rex VK7MO has sent me another (new) IC9700 for mod MK2. (I do not own one, I have too many rigs already) .
I have the mod MK2 in schematic+SPICE, and this will only require two easy solder joints to the PCB, plus grounds.
The MK2 setup will permit
manual control of the internal oscillator from the front panel when the external 10 MHz is not connected.
Nothing from ICOM yet. Maybe the FPGA is a buy-in design and there is no one in house to do the work in the FPGA.
Come on ICOM, it is not difficult for a person skilled in the art.
8 May 2019
I have taken a look at the locking method in the IC7610. It's essentially the same thing we are doing-
they have a oddball frequency oscillator for all the clocks (actually it is not oddball, it's a audio sample rate multiple)
and they lock it to a decent internal or external 10 meg reference ...
The approach they need to take is DIFFERENT from the IC7610. Which leads me to think Icom dont actually have experience with doing it this way.
Anyway, we'll see if Icom get this sorted. They might implement a frequency counter in the FPGA (which is easy ), the counter is driven from their 49.152 derived clocks.
At some period, perhaps a 10 times per second , the frequency count is sent to the microprocessor, and the micro runs some filtering and a PID loop, and drives the VCXO as required.
Getting enough error information at 10 times a second on a small error means a rolling window of counts which essentially produces a high sample rate of errors that can be averaged.
The high rates of update are required to be able to follow the drift when the fan starts and stops.
...and Icom if you do a HW rev, you need to isolate the copper pours under the oscillator so it doesnt follow the bottom and top layer copper temperature....
6 May 2019
Rex VK7MO sent me an IC9700 to frequency lock, and I describe it below. It was a textbook case. Easy.
I probed around without schematic for a few hours, figured out how the radio works, measure all the levels , sensitivities etc.
Icom have done an excellent job of this radio. I mean this radio is phenonomal value for money - I think it is cheap at twice the price.
Things to watch : Running wires around the insides is a bit of a no no.
Wires are antennas and this means potentional unwanted signal injection into very sensitive clock and control nodes.
The radio is sensitive to aliasing up to a couple of GHz so almost any stray signals can be a problem.
Because of those sensitivities, this radio needs a bit more care than other radios when retrofitting other circuitry to it.
For those interested, the VCO Kv is 194Hz/V at 49.152 MHz. You'll need that to properly calculate the loop filter components.
This radio does not need the constant fan mod- the loop filter with a BW on 10Hz and TC of around 2mS can easily track the thermal drift due to the fan.
The radio's sensitivity to microphonics is reduced (since the PCB resonances are within the control bandwidth, mostly.)
This was an adapted board, I am using an ADF4157. Chosen for its high resolution divider.
Next version will have a analog switch on it so that when no 10 MHz ext is detected it can switch back to the internal reference control circuitry .
. Also the PCB will be shaped to minimise wiring distances and have a few more ground connections in better places.
It's a difficult job with all the wires going to 0402 parts on the PCB.
There needs to be source resistors in series to isolate those nodes which I have, but it is a micro-surgery operation.
I will eliminate that need on the next version.
I calculated 0.3Hz error at 1296 MHz and I measure 0.4Hz error +/- 0.1Hz. Not bad.
Yes I do this for a living ... I design custom SDRs and frequency stability is part of the course.
In my opinion (not humble) , the internal oscillator stability is not adequate for digital modes. It is barely good enough for SSB.
Icom you did a great job on 99.99% of this radio, why the fail here ? A solution may be able to be implemented in your FPGA and microcontroller.
The 10 MHz goes into the FPGA, there are dual DACs driven from the microcontroller, everything is there for this to be done inside the radio...
Sure the radio meets spec +/- 0.5ppm, but the drift rate v temp makes it unsuitable for narrow band modes in the higher bands.
The next PCB might include an option for a cheap ovenized 10 MHz oscillator on board so that the internal oscillator is ALWAYS locked to a internal decent oscillator and external reference.
Yes it is a prototype !. Lots of Kapton tape.
The board itself is approx 18mm x 40mm double sided 1mm FR4.
I control the 49.152 MHz oscillator directly , and take 24.576 MHz from one of the digital dividers that feeds the '9518.
I take power from the 8V sub regulator, and a tap of the 10 MHz input.
Radio will go back to Rex today, I will think about the mod a bit more.
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