Re: LF: Wellbrook RX loops

[pat <g4gvw@aol.com>]

Pete,
I have that book and have found it useful. However, apart from the academic arguments (we are trying to arrive at a definition for the word antenna, I think), I still prefer simply getting on with the thought I mentioned earlier ie. I think of a "small" antenna as being one plate of a capacitor whose other plate is the rest of the universe! The environment contains so very many other physical influences and variables that it is even difficult to concieve of an isotropic element in practical terms.

My three'aporth

73


On 05/07/13 15:26, M0FMT wrote:

Hi Roger

 

In My Humble Opinion after spending a small fortune on one of these "Frame Aerials" (I have not) nobody will give you a bad report. That outfit relies on "Black Magic" since they will not publish their Schematic.

I am glad Dave has given an honest appraisal of its performance. It is about the same as any frame antenna. I have made frame antennas from about 3m to 1m currently in use down to 250mm. They are great for direction finding. They could be said to allow one to steer away from noise but if the noise is between you and the desired station they are of no advantage. 

 

Make up a simple frame inductor and tune it with a capacitor and amplify it there are plenty of schematics  on the net.

Also there is a technical treatise in the 1938 BR 230 Admiralty Handbook of Wireless Telegraphy Vol II Wireless Telegraphy Theory section T page 1. available from any good book shop!! But pirate copies from FMT press.

73 es GL Pete M0FMT IO91UX

From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Sent: Friday, 5 July 2013, 10:28
Subject: Re: LF: Wellbrook RX loops

Dave,

Thanks for that. Yes I can see the potential issue: you transfer the overload issue from the active antenna to the RX. A bandpass filter for each band is not hard though. Guess it is a question of whether the wideband/no tune approach is better/more flexible, than a tuned loop.

My current RX situation is not good on 136/472kHz and I am looking for a good solution on RX at the new QTH - moving in August all of 300m further east!

73s

Roger G3XBM

On 5 July 2013 08:27, DAVE PICK <daveyxm@virginmedia.com> wrote:

Roger

I have used a Wellbrook for many years on 136 and (now) on 472kHz. It performs well but it will put massive signals from broadcast stations into your RX! You may need a band-pass filter between the loop and the receiver. Obviously it is directional.

It will be around 10dB down on a proper aerial, but that's not a problem on LF.

Dave G3YXM

On 5 July 2013 08:00, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

Can anyone advise, from actual use,  how well a Wellbrook loop works on 136 and 472kHz RX ? The excellent OIP2 and OIP3 figures and directivity suggest one could be very useful.

73s
Roger G3XBM

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73 de pat g4gvw
es gd dx
qth nr Felixstowe
East Coast UK