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Re: LF: Matching transformer for LF and MF question, ferrite material? <

To: Chris Wilson <[email protected]>
Subject: Re: LF: Matching transformer for LF and MF question, ferrite material? <TYPO>
From: Chris Wilson <[email protected]>
Date: Sun, 14 Apr 2019 13:03:54 +0100
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Hello Chris,

 I meant to type "having a play listening on *MF*",  not LF, sorry.

> Hello  LF'ers

> I  am having a play listening on LF. I have found the variometer alone
> in   my  loading  coil  will  resonate  my  strapped  vertical  feeder
> horizontal  quad  loop antenna, I do not need the main loading coil. I
> have  a  question  re  the impedance matching transformer though. It's
> based  on  a W1VD design, an excerpt from Jay's web site describing it
> is pasted here:

> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> The gray box at the lower right houses the transformer which matches
> the antenna resistance to 50 ohms. The transformer has a tapped
> primary and secondary. The two rotary switches select 12 different tap
> combinations that provide a matching range from 12.5 - 35 ohms up to
> the 50 ohm transmission line impedance.

> The transformer is wound on a stack of three FT-240-77 cores. Each
> core is individually wrapped with Scotch 27 glass electrical tape. All
> three are then wrapped into a single three core assembly. #14 solid
> THHN is used for the primary (14 turn) and secondary (10 turn)
> windings. It's important to wind the primary and secondary so that the
> turns are interleaved and not wound so that they are on opposite sides
> of the core. The primary is tapped at 12 and 13 turns and the
> secondary at 7, 8 and 9 turns. Wiring between the switch terminals and
> the transformer and connectors is made with flexible #14 stranded
> THHN. Eye terminals are used throughout the transformer box, loading
> coil and variometer to allow for quick disassembly and repair,
> replacement or modifications to the system. All eye terminals are
> soldered rather than crimped and brass machine screws and nuts are
> used at all connection points.

> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

> Will I be OK still using the FT-240-77 cores at MF, both for RX and if
> I manage to get my full licence or a friend with one operates here for
> TX?  Or  do  I  need to build another with different cores? What type?
> Thanks.


Best regards,
 Chris                            mailto:[email protected]

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