Re: LF: Re: Increased ERP on 137.5kHz - WSPR reports please

[Roger Lapthorn <rogerlapthorn@gmail.com>]

This agrees well with my calculation Rik. As I said, the issue is where the power is going: with such a short vertical section (5m long and assumed Heff of 3m) without any real top loading most of the energy is being dissipated in the coil on the bedroom table.

Currently TXing into the earth electrodes and G6ALB is getting me at -18dB S/N at 3km. I've a lot of work to do...

73s
Roger g3XBM

On 11 January 2011 19:03, Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> wrote:

Hello Roger,

 

3m Heff @ 2200m --> Rrad = 1580*(3/2200)^2 = +/- 0.003 Ohm

radiated power = 0.18^2*0.003 = +/- 100uW

Gain of a short vertical = 1.83 --> ERP = +/- 180uW

But "greenery loss" can be up to 6dB (or even more), so instead of 180uW it could less than 50uW as well.

 

I have wspr running, being very very optimistic ;-)

 

73, Rik  ON7YD - OR7T

 

---

Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger Lapthorn [rogerlapthorn@gmail.com]

Verzonden: dinsdag 11 januari 2011 19:43
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: Re: Increased ERP on 137.5kHz - WSPR reports please

0.18A and an assumed Heffective of 3m Andy.

73s
Roger G3XBM

On 11 January 2011 18:39, Andy Talbot <andy.g4jnt@gmail.com> wrote:

What antenna current are you getting?

 - OR -

What is the total resonant input resistance of the vertical + ground system (before any matching network) .and the RF power being delivered into this,

 

Either of  these will allow a reasonable estimate of ERP

 

Andy

www.g4jnt.com

 

 

On 11 January 2011 18:26, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

So much for the theory then....

The signal level at G6ALB in the next village (3km although WSPR shows it as 0km) is some 10dB down on my loop antenna. Not sure if I got my sums wrong or there is some unexplained loss. The RX system at G6ALB is unchanged.

73s
Roger G3XBM

On 11 January 2011 17:32, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

Dear All,

Today I rigged up and matched a simple, small, Marconi vertical on 136kHz instead of the vertical loop. Based on measurements of antenna current and some reasonable assumptions of effective height, I now believe I have around 200uW ERP on the band - heck this is high power for me!

>From now until late this evening I will run the WSPR beacon (136kHz USB dial) in the hope that a few more people will be able to copy the QRPp signal. Please have a go and let me have any reports.

73s and good luck

Roger G3XBM

--
g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088

--
g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088

--
g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088

-- 
g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088