LF: 500 / OLB test-sig...

["Tom Boucher" <tom@telemetry.demon.co.uk>]

Thank you Rog and Brian 'YKB.

 

Rog, tell me where you find the programme you use, 'RFSim'?

Brian, thanks for the pointer to the G4FGQ site which looks very useful. I think G4FGQ is SK now but nice to know his web site is still available.

 

Also thanks to Dave G3WCB for another report.

 

Tom, G3OLB

----- Original Message -----

From: GW3UEP

To: rsgb_lf_group@blacksheep.org

Sent: Friday, August 03, 2007 4:15 PM

Subject: LF: Re: Re: 500 / OLB test-sig...

Tom,

I use the L-match on all ants, from half-waves to verticals, with a simple differential version for open-wire doublets.

Currently, I have ~3000pF across the 50R coax at the remote feed on MF [the resonating vario/L forms part of the L-match].

Your 6600pF is a good indication of a low input-resistance and resistive transformation from 50R downwards towards the ant.

Coincidentally, Mike has just tried the L-match with my sensitive resistive-reflectometer cct - he nulled at 5600pF.

Your R_in looks like ~24R [Mike's ~28R]; mine is an appalling ~40R.

Rog.

 

P.S.

I use the L-match to arrive at  i/p resistance by measuring the C/L values of the nulled cct.

Then, use RFSim to simulate the ant load & find X & R_in.  The results can be verified by substitution on the bench.

A really good/low R_in [<10R] will require ~15000pF or more on MF.