LF: RE: 500 Loops (was PA2NL)

["Dave G3WCB" <ganymede444@btopenworld.com>]

Hi, Laurie, LF.

 

I use a tuned loop for Rx on 136 kHz, and it is also affected by the TX "Tee" antenna. I use a relay to open circuit the earth return at the bottom of the TX antenna ATU  when the loop is in use. The problem isn't due to the presence of the TX antenna wire itself, but the problems occur when the wire is resonated by the TX ATU. The TX ATU earth has a 1 meg bleed resistor left in circuit to leak away any static build up. 

 

73, Dave G3WCB IO91RM

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of lawrence mayhead
Sent: 29 April 2007 10:20
To: rsgb
Subject: LF: 500 PA2NL QRS

PA2 beacon very strong here also, on the south coast.

Interesting antenna effect:-
I run a pair of large grounded loops situated close to the main TX antenna (inv L )
These have worked very well on 136 and are quite directional, providing useful
improvement in SNR. On 500kHz however they are not directional, at least not
in the right directions.
I have spent several hours trying to find out what has gone wrong with them !
By chance this morning I left the TX ant. grounded and was surprised to find that
the loops are now directional. So it looks like there is much more coupling between the
TX and RX ants on 500 than 136.
Could this simply be capacitive ? perhaps I need smaller loops?
Anyway if you are running a RX loop close to your TX antenna, beware.
73 Laurie.