Re: LF: Re: 'JNT Dual purpose beacons

[Andy Talbot <andy.g4jnt@googlemail.com>]

hi Jim / group

 

Ok.   I've put it on air with some preliminary values.   The WSPR signal is on 503.850kHz  and its running 6db down on the 15 minute beacon at 50% duty cycle.  Teh hiuh duty cycle is for my local monitoring purposes - save haviign to wait too long.

 

When its had a run at this setting, I can reduce the duty cycle a bit (the S/W hasn't been tested at lower DCy yet) and could increase power a bit.  Don't really want to run at full power, mainly in the interest of longevity of the PA and my leccy bill!

 

The WSPR slots are currently at  0,2,6,10,14,22,26,28,32,36,40,44,46,52,56   minutes past the hour, with the orther signal at 4,19,34,49 minutes past.

 

Any changes are just a case of reprogramming the PIC EE Data

Andy
www.g4jnt.com

this email has been scanned for political correctness by the nanny state

2009/9/19 James Moritz <james.moritz@btopenworld.com>

Dear Andy,

I would suggest a frequency between 503.825 and 503.900, to avoid the QRM around 504kHz some people experience, and give a bit of tolerance for receiver frequency errors, which are sometimes suprisingly large. For some reason, the frequencies below 503.9 seem to be less widely used. But since there are only about half a dozen stations transmitting in this mode, there is plenty of space.

A 25% or 33% duty cycle seems to be frequent enough to catch most "openings" - probably less would be OK. As for power, I would suggest running as much as possible - monitoring signal level of a strong beacon  is easier than a weak one, and a relatively high power will give the greatest chance of being received by the maximum number of stations under the maximum range of conditions. You could argue that the presence of a "strong" beacon would sometimes prevent reception of very weak signals nearby in frequency, but since this only can happen 25% or 33% of the time, and the signal is not so strong at a few 100 mW ERP,  it is probably not a serious objection in practice.

Cheers, Jim Moritz
73 de M0BMU