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Topic: OVI40 UI and ATU in a classical mcHF (Read 2562 times)
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F4HTX
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Posts: 66
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OVI40 UI and ATU in a classical mcHF
« on: 14. December 2020, 16:08:53 »
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Hello Friends,
This message to share with you the results of this weekend bench work.
On one side I had a classical homemade mcHF from the v0.6 PCB's running UHSDR software, 2.8" screen and slow cpu ; on the other side OVI40 UI plugged in an mcHF RF I never took the time to nicely fit in a box.
So I decided to upgrade the original mcHF :
- swap the mcHF UI for an OVI40 UI
- install the UT0UM AT100 internal ATU
- swap the 7805 for the Murata OKI-78SR
Everything went fine, the ATU from Alexey UT0UM, which wasn’t initially designed to work with the OVI40, fits nicely as far as you do the following :
- move LED yellow wire from pin 22 to pin 20 on the mcHF RF board
- in order to use the blue LED D3 for the ATU, remove R116 resistor
- connect OVI40 UI pin 20 to the anode of the blue LED D3
- cut and lift the (not grounded) pin of the choosen switch encoder in order not to interfere with OVI40 UI
The attached little video demonstrates the tuning of an 21meters long wire (and an adequate earth counterpoise) with the ATU.
There is still some metal work to fit the original top case, open it for the 3.5" screen and reuse the soft buttons...
This is not revolutionary stuff, but this will end with a very convincing little rig, the OVI40-UI is far more usable than the original mcHF and because of the internal ATU, you travel lighter.
73’s
François
the ATU from UT0UM : https://www.mchf.at/
the Murata regulator : https://www.murata.com/products/productdata/8807037992990/oki-78sr.pdf?1583754815000
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 test_ATU.webm
« Last Edit: 14. December 2020, 16:28:50 by F4HTX » |
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F4HTX
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Posts: 66
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Re:OVI40 UI and ATU in a classical mcHF
« Reply #1 on: 14. December 2020, 16:11:17 »
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The guts inside the beast 
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S58J
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Re:OVI40 UI and ATU in a classical mcHF
« Reply #2 on: 18. December 2020, 09:21:04 »
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Good morning François
Really very nice job. I would love to include the ATU as well but I found it a bit pricey (I wish UT0UM could also offer only PCB with programmed MCU).
What really cought my attention was the 5V voltage regulator replacement. Current 7805 gets really hot, (together with LM2941). Why did you decide to do the replacement? I guess OKI-78SR produces much less heat (because of its better efficiency)? Is this the correct replacement part - 580-OKI78SR5/1.5W36C (Mouser)? Are beside possible less heat any other benefits of replacing 7805?
For me less heat alone would be already a very worthy investment, because all mcHFs get really hot and less heat means less stress to the surronding components.
Looking forward to your reply.
Janez, S58J
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S58J
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Re:OVI40 UI and ATU in a classical mcHF
« Reply #3 on: 22. December 2020, 08:19:11 »
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Good morning
I was hoping to get the answer. So far nothing, but I have a Mouser order on hold, which I would really like to move forward. Therefore, could please someone else give me the answers to the following questions:
- Is there an improvement to replace 7805 with OKI-78SR?
- Is there a reduction of the heat compared to 7805?
- What about a possible unwanted RF noise produced by OKI-78SR?
- Any other known issues with OKI-78SR?
Kind regards and have a lovely Holidays.
Janez, S58J
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F4HTX
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Re:OVI40 UI and ATU in a classical mcHF
« Reply #4 on: 17. January 2021, 10:45:35 »
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Hello Janez,
Sorry, didn't noticed your questions earlier.
I probably bought mine @RS or @Mouser, do not remember, it was on shelf overhere.
Yes it's purely about heat dissipation. Those Murata regulator are very useful when a 78xx is heating a lot, and in this case not noisy at least in my receiver.
The consumption lower about 100mA and the heat drastically reduced too. I didn't notice any negative concern with this component.
Best Regards,
François
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