Message-ID: <4D91B58B.5000408@kpnmail.nl>
Date: Tue, 29 Mar 2011 12:33:47 +0200
From: pa3abk <pa3abk@kpnmail.nl>
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Subject: Re: LF: Re: M0BMU 500kHz /P
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Thanks Jim for the explanation.
Was wondering how you could produce such a "massive" signal.
FYI it was about the same as Nitonrdo/GNI Navtex. I believe they run 
1000 or 400W and QRB 450km. (Yr abt 350km)

Many PA stations enjoyed your presence in the last days of their license.
Thanks!
Jan/pa3abk



Op 29-3-2011 1:47, James Moritz schreef:
> Dear Dennis, Roger, LF Group,
>
> Thanks for the additional reports for M0BMU/P. Here are some details 
> of the station - see the attachment for pictures:
>
> The TX antenna was a 15.3m fibreglass mast with 4 x 10m long top 
> loading wires sloping down to just over 9m. The ground system was 4 x 
> 1m ground rods spaced on a 2m circle round the base of the mast. The 
> antenna was tuned with approx 300uH fixed inductance near the base of 
> the mast, and connected to the 18 - 70 uH fine tuning variometer in 
> the shack about 15m away by a transmission line wire about 1.5m above 
> the ground. The antenna ground was also connected to the tuner via a 
> return wire about 300mm off the ground. The tuner contained the 
> variometer, ferrite cored matching transformer, and a common mode 
> choke to isolate the antenna ground return from the shack ground. This 
> arrangement puts the tuning and matching controls in the shack, and I 
> found it was easy to adjust, with no problems due to unwanted 
> resonances or ground loops. The total antenna resistance was only 
> about 11ohms, including 2 or 3 ohms due to the loading coil and 
> variometer, so antenna current was approx. 3A with 100W PA output. I 
> estimate the antenna effective height was 11m, giving Rrad of 0.53ohm, 
> and ERP of 8.6W.
>
> The receive antenna was a single K9AY terminated loop, oriented to 
> reject wideband noise coming from the Brookmans Park BC site to the 
> west, and give good reception of Eu stations from the east. I found a 
> terminating resistor of about 200ohms gave a good null - this is 
> rather lower than the values quoted for the HF bands. The RX antenna 
> was positioned about 50m from the TX antenna, to minimise interaction, 
> and give the RX preamplifier an easier life!
>
> I used my 200W EER transverter rig, although just for CW on this 
> occasion, driven by an IC-718 as the IF. The minimalist shack ("hutch" 
> might be a better name for it :-)) was supplied with 130m of mains 
> cable going to an outbuilding and into a slightly dodgy mains socket, 
> but much less hassle than a generator or batteries. It was also quite 
> handy to be able to follow the cable and find the gate in the dark!
>
> Cheers, Jim Moritz
> 73 de M0BMU 


-- 
pa3abk<->  dordrecht jo21it