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

[<g3kevmal@talktalk.net>]

If you cannot hear or see the signals on the band of interest you cannot communicate, therefore it is important also to have  an efficient RECEIVE system

An efficient Antenna system is very important for both TX and RX  especially with low level amateur radio signals .

I would adopt a different approach if I wanted to listen on two separate receivers simultaneously to two different amateur bands.

I would use two separate Antennas each one resonated on the band of interest, in fact  I do this for MF/160  and MF/630

g3kev

 

From: Andy Talbot

Sent: Friday, June 29, 2018 6:53 AM

To: LineOne

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

 

Mal ...

 

Did you not read the requirement properly?

 

It was for RECEIVE only.  So loss is of no consequence

AND

he wants to listen on two receivers simultaneously, so switching is not an option.

 

 

 

 

Andy

www.g4jnt.com

 

 

On 28 June 2018 at 22:16, Mal Hamilton <g3kevmal@talktalk.net> wrote:

Andy

Your method too lossy and complicated, interaction etc

Use one coil for each band and switch  between them for the desired

Band

G3KEV

 

On 28 Jun 2018, at 20:32, Andy Talbot <andy.g4jnt@gmail.com> wrote:

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