Roger,
what power do you need to get 0.18A into the antenna ?
73, Rik
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
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
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
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
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G3XBM GQRP 1678 ISWL G11088
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G3XBM GQRP 1678 ISWL G11088
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g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
G3XBM GQRP 1678 ISWL G11088
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g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
G3XBM GQRP 1678 ISWL G11088
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