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Hi David.

So today finally got round to applying RF into the input and a 50 watts Dummy Load on the Ant Output.

With 10 watts out of my known transceiver absolutely Zilch nothing and no relays chattering as there should be.? So done some continuity? checked all of the input through the transformer to the L1 infact right through all of the coils and continuity right through.

Also checked continuity through from Ant Output to the diodes and again ok.? So I am totally baffled again.? Could you throw any light onto the problem as I don't know what to do next.? I wound 10 turns on one side of the Balun and 10 turns on the other side.? Started the windings at the bottom with thin PTFE wire.? And One covered PTFE wire through the middle once and terminated at each side.? Cannot see what I could do wrong there.?

Maybe you have a quick test to check all is well BUT clearly is not.

I've also checked the polarity of the diodes and checked they are working.

WHEN I check from input to Output I get a short because of the transformer windings and imagine you obviously get the same.

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I was waiting for all of the relays to start singing to me but not a thing.

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73s David? ?G4RVH

Hi David,
With the ATU in bypass, does the meter show a PWR/SWR reading when you transmit?

If not, then check that injecting a DC voltage on the Stockton bridge diode D2 (Cathode) shows a reading on the display. With around 2.7V on the cathode, the meter should read about 10W.
If this doesn't work, then check the potential divider R4 and R21, there should be 0.9V on the PIC with 2.7V at the D2 (cathode).
73, Dave

Hi David? G8PTN

Yes all ok thanks and I will check this out and report back to you ASAP.

It's been the Dr. Today for appointment and Dentist and Car tomorrow afternoon but try to work around to get the results back to you ASAP.

I did put my MFJ258 on the input today and a 50 load onto the output and in Test Mode didn't want to really do anything but putting the load on the input of the ATU and the MFJ on the output I could see the meter moving around altering the L & C but could not tune to 50 ohms with 1.0? ?SWR so not sure at all what is going on at all.

So please wait for my results.

73s? David? ? G4RVH

Hi David? ?G8PTN

Arrrrrr I did that test today as you suggested in an earlier post.? Pressed Bypass and Transmitted with 10 watts and NOTHING displayed on the OLED Display no power and no SWR

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73s? David? ? G4rvh

Hi David,

Try injecting a DC voltage onto D2 cathode as described previously and see if the meter shows a power reading.

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I expect you have already looked at the following.

- Check the winding directions on the binocular core.
When I looked at your photos, I am sure it looked as expected. If the coils were wound in the same direction, I think the FWD and RVS signals would be swapped.
See references below from other threads.
/g/ATU100/message/72

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- Check the connections to the IN/OUT ports on the ATU-100.
IN? ? ? ? From Transceiver.
OUT ? ?To Antenna
Again if these were swapped, the FWD and RVS signals would be also swapped.

73, Dave

Could you just check this Balun winding first for me David please the other 2 yellow windings finish at the top back of balun

73s? David

Hi David? ?G8PTN

Please point me to D2 Cathode on photo . Then I am sure of doing the correct test

73s? David? G4RVH ps I know that both Cathodes are on the LEFT of the photo

Check that there is no short from the RFOUT connector casing to the signal trace which is very close.
When you did a bypass test, was you able to confirm that there was RF coming out of the RFOUT port?

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All I did for the Bypass test was to squirt 10 watts plus out into the transceiver port and I put a 50 ohms dummy load on the antenna out of the Atu so unless I had an external SWR Bridge and then the load I would not know but will check that with all of the other tests as soon as possible.

It's a really weird fault.? Because with the VNA connected yesterday I was able to achieve tuning around the Smiths Chart on my Laptop

But today using the MFJ258 I wasn't getting any sense at all so back to square one until I do these important tests for you.??

Hi David,

Images below of the signals I traced out when I did my initial testing.

D2 cathode will be the point I have shown as "FWD" at the diode.

I hope that helps.

73, Dave

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Hi David,
That’s good news.
Yes, to see the effect of the RVS voltage, you need to keep the 2.7V on the FWD diode and then inject another lower voltage on the RVS diode. As you increase the RVS voltage you should see the SWR reading increase.

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If you have 2.7V on the FWD diode (equivalent to 10W) and 0.7V on the RVS diode (equivalent to 1W), it should show an SWR of around 1.9.

73, Dave

Arrrrrr that's brilliant David.? So I checked the sockets and get a short on both because of the transformer inline.? So is it looking like I've wound the transformer wrong? ???.

Hope you can analyse the fault I've got.

I wound each toroid as the photos in the manual and they just fit the holes correctly.? If wound wrong they wouldn't fit in the holes properly.

It's got to be a simple fault surely

73s? David? G4RVH?

Hi David,
The bridge windings look correct.
Perhaps tomorrow check that you are getting power output from the RFOUT port.
73, Dave

Hi David,
Looking through your previous pictures, I think I have spotted the problem.
It looks like you have fitted the wrong termination resistors on the Stockton bridge.
These are 0.1? (0.05? with two in parallel). I suspect you thought they were 100?.

Sorry, I should have spotted that before.
Hopefully, once you fix that everything will work as expected.
73, Dave

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Good Morning David? G8PTN

VERY WELL spotted ?.? WOW

I've just measured them.? There are what I thought as 100 ohms resistor.

I have 2 x 100 in parallel to give me 50 ohms.??

But having checked them they actually read on my multimeter 1.6 ohms on both pair so they must have got really hot ? probably could have fried an egg on them.? Would you agree.? Because yesterday when I never got a squeak out of the ATU I put about 30 watts into the unit.

BUT this definitely looks promising. It certainly wouldn't Tune with that Fault situation.? Thanks so much David.? Let you know shortly.? Just ordered them.? So few days before they arrive.? Not abit of wonder I couldn't get and power reading in Bypass Mode.? Just measured some brand new R100 resistors that I bought specially for this project and again measuring 0.5 ohms.

Cannot believe it.? Of course years ago this didn't happen buying through hole components.? I bought those as 100 ohm SMD.? Your clever to have spotted this to save me a massive amount of hassle.

So well done David.? I take my hat off to you Sir.?

It just goes to show that a picture paints a 1000 words in a text form

73s? David? ?G4RVH? ?

Hi David,

Yes, the resistors would have probably got hot, as well as the bridge, but the radio would have seen a high SWR, so it should have folded back.

I hope it has not caused any damage to the radio.

73, Dave

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For general information, more details below just for your reference.

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- Stockton bridge

With the 50? dummy load on the ATU “RFOUT” port and the 0.1?//0.1? on the Stockton bridge the radio would be seeing a load of approximately 8.3?, which is a VSWR of 6:1.
With the radio set to 30W, this equates to a reflected power of 15.3W (i.e. this would need to be dissipated by the radio).

In reality I expect the radio would have folded back because of the high VSWR.
Worst case the resistors would have been dissipating a total of around 12.3W (3W per resistor) and only around 2.5W in the dummy load.

With 50? on the Stockton bridge and 30W from the radio, the 50? resistor would be dissipating 0.3W.

If you use 100?//100?, each resistor will need to dissipate 0.15W with a 30W input.

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I hope that all makes sense and I expect once you have made the changes, the ATU-100 will work correctly.

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- ATU100 Auto Mode

Once everything is working, just a couple of points if you haven’t already discovered.

When you power the ATU ON (not test mode), if there is a dot at the top right, then the ATU is in auto-tune mode.
If not, you can toggle the auto-tune state with a press of the “Auto” button.

This state is saved to EEPROM, so next time it should power up to the state you set.

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When RF is detected greater than the 5W (EEPROM configured value) is should start tuning.

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When the ATU is not in auto-tune mode, if you long press the “TUNE” button, the ATU should enter the tune state and waits for RF to be detected.

Again it needs to see a power level greater than 5W before it will tune.
If you short press the “TUNE” button the ATU should exit the tune state.

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Hi David? ? G8PTN

Yes all understood.? Yes my transceiver is absolutely fine thanks.

So no problems there at all.

I am still in shock at those resistors only being 0.5 ohms.? So what I normally do with my WSPR system is tune my auto ATU with 10 watts and make sure the ATU has found a good match and then use my attenuator bank of switches from my H/B wspr transmitter which gives +8db out and reduce my power to anywhere between 1 milli-watt to 300 milli-watts.? At the moment transmitting on 14 mhz with 100mw and of course being heard all over the planet.? So hope to use my new ATU-100 in the same way with another H/B wspr system but on another frequency and a different aerial.

So once the ATU-100 has found a match on say 10 watts and then turn the wick down to 100mw hopefully it won't keep trying to tune because obviously there won't be enough power there to do anything if you understand what I am saying.

I might have to cut away a little more of the double sided PCB box so that I can get my soldering iron in to take off those resistors but not a problem.? Good job I build the ATU like I did for servicing quickly.

Thanks for all of your very useful data David.

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73s? David? ? G4RVH?

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Hi David,
Yes, the ATU-100 should work the way you think. It will remember the last tuned settings in the EEPROM. These are loaded on power up.
However, if you short press the “TUNE” button it will reset the settings to the default values L = 0uH, C = 0pF, SW = Output.
73, Dave

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