Re: LF: Can I match 2 frequencies with one loading coil?

[Andy Talbot <andy.g4jnt@gmail.com>]

Try this, but you'll have to adjust iteratively:

Bands referred to as LF and MF

First make your LF loading coil so it resonates the antenna as it stands.    Now make an MF loading coil.  The problem is that t=when both are connected to the antenna teh lower value MF one shunts teh LF.  So add series C to the MF one to make a series tuned circuit, increasing the L to keep the system at resonance.   The net effect now, at LF will be an increased value of X shunting it.  As your additional C reduces and L increases, the residual at LF across the LF coil goes up.    Now adjust teh LF colil to bring it to resonance, then go back and redo the MF L or C.  Iterating between teh two until they both go.

I'ts a complicated setup, with two frequencies and three variables to play with - so an infinite set of values to end up with, but if I were doing it, I'd make up a spreadsheet and play around with values until a workable solution that resonated both antennas was found and looked OK.  Once resonated you can bring them to a match if needed.   But on Rx just resonating them ought to suffice

Or use a circuit analysis prog.     

Andy

www.g4jnt.com

On 28 June 2018 at 20:04, Chris Wilson <dead.fets@gmail.com> wrote:

Hello Mal,

Thanks Mal and Stefan, but Mal, I want to listen to and decode both bands
at the same time on 2 different receivers, sharing the one antenna. I
tried  shorting out the loading coil but LF reception is much poorer.
Not  sure how much of an effect no loading coil has at MF ,but suspect
a loading coil to resonate would be pretty helpful?

Thursday, June 28, 2018, 7:55:55 PM, you wrote:

> I use aircore loading and matching
> Use 2 coils and SW between them for desired band
> G3KEV







--
Best regards,
 Chris                            mailto:dead.fets@gmail.com