cap-co spc300 mk2 - UK Vintage Radio Repair and Restoration Discussion Forum

g0hze snowy · 17th Apr 2024, 9:04 pm

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

Radio Wrangler · 17th Apr 2024, 9:12 pm

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

g0hze snowy · 17th Apr 2024, 9:17 pm

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

Radio Wrangler · 17th Apr 2024, 9:59 pm

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

g0hze snowy · 17th Apr 2024, 11:00 pm

So, i take your advice and leave as is!

17th Apr 2024, 9:04 pm	#1
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	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

17th Apr 2024, 9:12 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,872	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 __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

17th Apr 2024, 9:17 pm	#3
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	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

17th Apr 2024, 9:59 pm	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,872	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 __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

17th Apr 2024, 11:00 pm	#5
g0hze snowy Hexode Join Date: Oct 2013 Location: Peterborough, Cambridgeshire, UK. Posts: 336	Re: cap-co spc300 mk2 So, i take your advice and leave as is!