Re: LF: RFI from 136kHz transmissions

[Marco IK1ODO <IK1ODO@spin-it.com>]

At 18.24 02/03/2007, you wrote:

> In the discussion
> that I am currently having with Ofcom over the RFI assessment for
> 501-504kHz applications, the question has been raised as to whether
> interference has been noted with nearby neighbours, etc, from the
> transmissions at 136kHz. The licence allows operation on 136kHz without
> any RFI assessment. It would be helpful to have honest feedback on this
> if anyone has examples to offer. In such cases I would like to know
> details of the aerial, distance to the neighbour concerned, power into
> the aerial and approx ERP, and likely cause (if it's other than straight
> V/m) and cure.
>
> It would also be worthwhile knowing those who have done
> significant operating using up to the 1W erp from aerials that are in
> close proximity to the neighbours, e.g. 5 to 10m or so, and not had any
> RFI problems. 
>
> Not sure the best way of doing this, but rather than clog up
> the reflector with replies it might be best for people to e-mail me
> directly. 
>
> I will of course collate the data anonymously; it could make
> life a bit easier if I could convince Ofcom that from a practical
> perspective -10dBW at 500kHz isn't going to cause much problem as far as
> RFI is concerned. Of course that may be pre-judging the facts!
>
> 73 John, G3WKL 
>  RSGB HF Manager
>
> g3wkl@btinternet.com

John,

I'm QRT on 136kHz since a few years, but I had TVI problems on my own
antenna due to switching parasites from the PA. Cured adding some
ferrites and LPF at the output. No direct problems from RF fields.
PWR> 900W, Marconi 13m high 23m long, neighboroughs at 10m or so, my
TV antenna at 4m from the end of the Marconi. About 18kV on the wire (6A
RMS, 3.2kOhm Z), so RF field at ground was in the order of 1500V/m -
fluorescent lamps were useful RF field indicators ;-), and the field near
the vertical wire and the tuning coil was some 20kV/m, of
course.

73 - Marco IK1ODO