Built two ATU-100 EXT kits. One works flawlessly the other will not tune and swr reads 9.99
Hello everyone,
I recently purchased and built two kits. Both went together without any issues. One of them works great while the other will not tune. I can hear it trying to find a match and then it appears to timeout and displays an swr of 9.99 but reads the wattage just fine. The kits came with the input torroid wound, just needed to solder it to the board and run the wire through the centers. I've gone through and ohm'd the path to the IC for the fwd and rev circuit. Checked the continuity of the traces in and out of the tuner(after removing the input torroid). Verified that all of the relays are getting a close signal and verified the contacts are closing. I've swapped out the diodes with a matched pair of 1n34s, which were the only ones I had on hand. I ordered 1n5711. I even rewound the input coil and removed all the relays to double check the continuity. I've tried a few versions of the PIC16F1938 firmware. I will give the 1n5711 a go later tonight.
I was hoping someone could offer some advice. My testing was initially through an antenna, Chamelon emcomm but switched to a dummy load.
Thank you for any advice in advance
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Re: Hardware / software wish list
Hi Mike,
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On Fri, Mar 15, 2024 at 03:38 PM, N2MS wrote:
I also have a LDG-Z11 Pro. I will have to see what mix is used in that tuner.
I've looked in quite a few tuners, and nearly all use the -2 (Red/Clear) rather than the -6 (Yellow/Clear), but they use much bigger toroids. The LDG IT-100 derates to 100W (from 125W) on 50MHz, and MFJ 939I claims 200W, but isn't rated for 50MHz.? These both use 130-2 (so 1.3") not the 86-2 (0.86") that the cheap ATU-100 kits use.
I've seen -6 used for internal ATUs, mainly for the smaller inductor values.? I suspect there is some issue with fewer turns, I started working through the maths, and it gets very complicated, very quickly, so I moved on to other things!
I also found -6 toroids used for the low pass filters for the higher bands.
Remote tuners (Looked at AH-4/SG-23x/mAT-40/CG-3000) tend to favour air cored inductors, I suspect it's weight rather than anything else.
Roger.
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Re: Hardware / software wish list
Roger,
Interesting. I use a FT-817 or 857 but haven't used them on 6 meters with the ATU-100. I will have to keep that in mind. I also have a LDG-Z11 Pro. I will have to see what mix is used in that tuner.
73 Mike N2MS
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On 03/15/2024 9:46 AM EDT RogerW/GW6HRU <nospam23@...> wrote:
Hi Mike,
On Fri, Mar 15, 2024 at 11:54 AM, N2MS wrote:
What power were you tuning and operating at? I tend to tune at 5W (the default value from Icom when you push the tune button). I was testing with 10W of FM, but the inductors were overheating at 50MHz (which is why I'm looking at the -6 inductors).
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Re: Hardware / software wish list
Hi Paul,
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On Fri, Mar 15, 2024 at 04:51 AM, paul larner wrote:
changing the caps for decent rated silver mica as on 3 of my atu-100 various caps let magic smoke out.
Using a capacitance meter I think at least one of my Caps has gone.? I've got some high voltages ones, so will try them. Looking at commercial tuners, for the bottom 3 bits, they often use 2 in series (=1/2 value), 4 as 2 series/2 parallel (=value), then 2 in parallel (=2x value).? I think this is to get better power of two progression. I'll also look to hand select those that are closest in value to each other.
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Re: Hardware / software wish list
Hi Mike,
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On Fri, Mar 15, 2024 at 11:54 AM, N2MS wrote:
What power were you tuning and operating at?
I tend to tune at 5W (the default value from Icom when you push the tune button).? I was testing with 10W of FM, but the inductors were overheating at 50MHz (which is why I'm looking at the -6 inductors).
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Re: Hardware / software wish list
Good idea on themica capacitor replacement. What power were you tuning and operating at? I tune with max 20 watts and operate at 50 watts. I derate all of my tunersby 50%.
?
Mike N2MS
On 03/15/2024 12:51 AM EDT paul larner <quadzillatech@...> wrote:
?
?
i think changing the caps for decent rated silver mica as on 3 of my atu-100 various caps let magic smoke out.
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is there a way to get a command signal from the atu when tuning to use the radios alc to tx on low power when tuning?,i am thinking for an old yaesu ft-707.
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Re: Hardware / software wish list
how about one half of a bias-T onboard as well,that would be handy.
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Re: Hardware / software wish list
i think changing the caps for decent rated silver mica as on 3 of my atu-100 various caps let magic smoke out.
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is there a oled display bigger than 1.25"? that can be driven by the atu-100 pic,if so what model number do i look for?,thanks in advance.
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Roger,
??? as the serial is done with bit-banging, it's easy to send the inverted signal to an output pin. There's no need to use CLC block or any other microcontroller's peripheral.
??? Proper differential receiving is more complicated. One could use the comparator as you said, but doing that isn't simple.
??? Easier way would be to add a SN75176 as I mentioned in the previous reply. But then it would be good to also add line protection etc.
??? It's way easier to simple use a cheap TTL<->RS485 board.
??? 73
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Hello Harald,
??? glad its working.
??? There are some TTL<->485 interface boards with automatic data direction control.
??? But you're right, if one wants to use a simple EIA-485 receiver/driver like a SN75176, a pin of the microcontroller will have to be dedicated to DE+RE. It's easy to do though.
??? I plan to change the firmware to support Modbus. Then it will only send data when asked to. Direct control (read/set) of the relays would also be implemented.
??? I tried to find how hams use Modbus to automate stuff on their shack but haven't found any relevant information. If someone can help me with that, it would help me understand better this use case.
??? 73
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Re: Erratic behavior when mounted close to a random wire antenna
Thanks? lot David!
I'll do that: use o longer cable between the antenna and the tunner.?
I did not mention, but a counter pole, and also a big ground plane (that is a part of the building? ) is conected to the ground side of the 9:1 unun.
I'm not sure , but I suspect, that the 1:1 choke should not be used between te tunner and the unun.
Greetings from Rio.
Paulo PY1JDX? Em qua., 13 de mar. de 2024 21:01, David Fainitski < rolin791@...> escreveu:
Nothing wrong with the tuner I think, just not enough ground pole.?
Try to Google "artificial RF ground system".
Or, add that length of coaxial with the better results, can control it with VNA.
Couple meters off fider in additional can change everything dramatically.
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Re: need my atu-100 firmware checking
DC ground from center connector is via the SWR bridge transformer. RF path to ground is high impedance above 80 m up to high end. Em qui., 14 de mar. de 2024 03:19, Bill Maxwell via <wrmaxwell= [email protected]> escreveu:
Well Paul, we can't exclude other possible issues being present
but if you look at the circuit schematic it clearly shows the
bodies of the input and output? sockets being connected to the
ground of the pcb. Without that your circuit is incomplete and
can't be expected to work.?
In addition, assuming that by some miracle, the antenna was
coupled and it was say a half-wave dipole, you would only be able
to use one quarter wave wire. Connect the grounds and see how it
performs.
Bill, VK1MX & VK7MX
Bill, VK7MX
On 14/03/2024 1:07 pm, paul larner
wrote:
Hi bill,no it was a kit so was an oversight by me,i just wondered
if that would cause the no responce to rf or if its a firmware
fault etc.
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Re: Erratic behavior when mounted close to a random wire antenna
Paul, that wti mn 
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Looks like it is Python versions 2 and 3 differences.
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"pysmithplot-fork" does not work for me, I don't know why.
I find "mpl_smithchart" and change `from smithplot import SmithAxes` to `from mpl_smithchart import SmithAxes` than all will be fine.
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Hi Harald,
If you just want differential signalling, I've used the CLC block to invert the TX pin so you get the TX and TX\ directly out of the PIC (probably needs a PIC with PPS, so something like the 16F18456 which also has a 12-bit DAC).
For the RX I wire the RX inputs to the comparator, and map the USART input to the comparator output pin (using PPS).
I've done a number of DMX projects this way.
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I was looking at some of my previous RS485 projects and there I had to use DE & RE pins on the transceiver module when transmitting. So this might require another pin when the ATU wants to transmit data.To avoid collisions, usually one "node" is the master (e.g. also for modbus) talking to a specific unit, and that one then does reply. With the current scheme it would be possible that the ATU sends status while the controller sends a command at the same time. One possible approach would be to only let the ATU reply with the current status on request (e.g. 'S' command).
Maybe it would also be nice to have some functionality to directly set the tuning values. A smart controller could then recall previous tuning solutions depending on frequency fetched e.g. via rigctl.
73 de OE6HKE
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Re: need my atu-100 firmware checking
Well Paul, we can't exclude other possible issues being present
but if you look at the circuit schematic it clearly shows the
bodies of the input and output? sockets being connected to the
ground of the pcb. Without that your circuit is incomplete and
can't be expected to work.?
In addition, assuming that by some miracle, the antenna was
coupled and it was say a half-wave dipole, you would only be able
to use one quarter wave wire. Connect the grounds and see how it
performs.
Bill, VK1MX & VK7MX
Bill, VK7MX
On 14/03/2024 1:07 pm, paul larner
wrote:
toggle quoted message
Show quoted text
Hi bill,no it was a kit so was an oversight by me,i just wondered
if that would cause the no responce to rf or if its a firmware
fault etc.
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RogerW/GW6HRU