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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 17th Apr 2024, 9:04 pm   #1
g0hze snowy
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Default cap-co spc300 mk2

Good Evening peps, just acquired the above ATU now the 2 x switches on the front are missing as is the ballun, can anybody offer advice on the makeup of that ballun, ferrite or iron ring, size, amount of turns and wire diameter etc.
I have managed to down-load the circuit diagram for the 1st version but unable to anything pertaining to the MK2.As always any and all advice greatly appreciated
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Old 17th Apr 2024, 9:12 pm   #2
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Default Re: cap-co spc300 mk2

Easy.

Based on experience of building a monster SPC transmatch, you'll quickly find that baluns though they can be made to work over a range of frequencies cannot do a wide range of frequencies AND a wide range of impedances.

The balun Capco sold was a toroid of about 70mm dia in Micrometals number 2 iron dust (T300-2 or something like that) with about 20 turns of bifilar.

So the best advice is 'don't bother'. Use that ATU with unbalanced antennae and do a proper balanced ATU for balanced antennae. I'm using a Z-match.

David
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Old 17th Apr 2024, 9:17 pm   #3
g0hze snowy
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Default Re: cap-co spc300 mk2

Thanks David, just wanted to fill the holes in the front panel, i suppose i can still do that but not wired to anything!.
I have a Step-IR beam and 80m vertical, mainly want the cap-co for the inverted l that i have up.
so i will not bother to fit relay's, ballun etc then.
Good advice taken on board.
Snowy
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Old 17th Apr 2024, 9:59 pm   #4
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Default Re: cap-co spc300 mk2

I went far OTT with mine.


Relay switching for 5 antennae
In/Out/dummy load relay switching
Logarithmic power meters, forwards and reverse PEP or fast. Can show return loss, dB.
Phase meter for return loss.

So the crazy thing is a VNA, showing antenna impedance (at ATU) in polar format. Or presented by ATU to Tx.

All in all, utterly useless for my balanced antenna. A right prat-fall. The further you go in the wrong direction, the dafter you look....

David
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Old 17th Apr 2024, 11:00 pm   #5
g0hze snowy
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Default Re: cap-co spc300 mk2

So, i take your advice and leave as is!
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