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

To: "[email protected]" <[email protected]>
Subject: Re: LF: Re: Increased ERP on 137.5kHz - WSPR reports please
From: Roger Lapthorn <[email protected]>
Date: Tue, 11 Jan 2011 21:44:47 +0000
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5w

73s
Roger 

Sent from my iPod Touch 4g

On 11 Jan 2011, at 21:17, Rik Strobbe <[email protected]> wrote:

Roger,
 
what power do you need to get 0.18A into the antenna ?
 
73, Rik
 

Van: [email protected] [[email protected]] namens Roger Lapthorn [[email protected]]
Verzonden: dinsdag 11 januari 2011 22:05
Aan: [email protected]
Onderwerp: Re: LF: Re: Increased ERP on 137.5kHz - WSPR reports please

Yes Rik, the ferrite rod ATU is just sitting on the bedroom table. I used a similar arrangement quite successfully on 500kHz but this, plus the very short vertical, are not good enough on 136kHz. At QRP levels I think a ferrite rod is OK in an ATU but I need more wire in the air.

73s
Roger G3XBM

Sent from my iPod Touch 4g

On 11 Jan 2011, at 20:39, Rik Strobbe <[email protected]> wrote:

Hello Roger,
 
"coil on the bedroom table" : do you have the loading coil indoors ?
It might be worth trying to place the coil outside to reduce losses.
 
73, Rik  ON7YD 
 

Van: [email protected] [[email protected]] namens Roger Lapthorn [[email protected]]
Verzonden: dinsdag 11 januari 2011 20:13
Aan: [email protected]
Onderwerp: Re: LF: Re: Increased ERP on 137.5kHz - WSPR reports please

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 <[email protected]> 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: [email protected] [[email protected]] namens Roger Lapthorn [[email protected]]
   
 
       
 
 

Verzonden: dinsdag 11 januari 2011 19:43
Aan: [email protected]
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 <[email protected]> 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
 


 
On 11 January 2011 18:26, Roger Lapthorn <[email protected]> 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 <[email protected]> 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
=
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