Re: LF: Re: FR5ZX on MF WSPR

[VIGILANT Luis Fernández <luis@vigilant.es>]

Thank you for your comments Rik. Much apreciated

Last night the only station with two spots into Reunion was IW4DWX. Congratulations Riccardo ! :-)

I'm running about a 1A RF current. So the real "incognita" is the radiation resistance

Will try to make some ERP field measurements. Having my monitor at 7Km will be easy to make it

permanent and to get a real idea of how the antenna is performing. There is still some experiments

to try and would be interesting to get a way to accurately measure the results

Using SHARK110 antenna analyzer as signal generator I tested injecting -33dBm to the antenna and

could see the trace in my monitor at 7Km. I wonder if measuring the signal difference in dB at the Rx with two

different Tx levels

Would it be possible to calculate ERP and so Ra this way  ??

73 de Luis

EA5DOM

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De: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] en nombre de Rik Strobbe [rik.strobbe@fys.kuleuven.be]
Enviado: miércoles, 11 de noviembre de 2015 18:58
Para: rsgb_lf_group@blacksheep.org
Asunto: RE: LF: Re: FR5ZX on MF WSPR

Hello Luis,

 

the radiation resistance of your antenne is probably not the calculated 8 Ohm, due to the fact that the 80m "tower" is not perfect and will introduce some loss.

Or another way to look at it is that the building will rise the virtual ground level, so your antenna is not really 80m above "HF ground".

But without doubt it will be some Ohm and it will be peanuts for you to radiate several Watts ERP.

Eg: Assuming the true radiation resistance is half of the calculated value (4 Ohm) you will need only 370mA antennacurrent for 1W ERP (keep in mind that a vertical monopole has a gain of 2.6dBd).

 

73, Rik  ON7YD - OR7T

 

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Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens VIGILANT Luis Fernández [luis@vigilant.es]
Verzonden: woensdag 11 november 2015 11:11
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: RE: LF: Re: FR5ZX on MF WSPR

Hi MF

 

Interesting conditions to Reunion last night

 

A total of 23 spots from FR5ZX. Only four stations reported

 

1 from G8HUH at -30

3 from SV8CS best -24

6 from DK7FC best -24

13 from EA5DOM best -19

 

From Rick Strobbe ON7YD reference site for LF antennas I have seen his calculations for a vertical

antenna with inductive topload. May be is the closer configuration to what I have managed to get here

 

http://www.strobbe.eu/on7yd/136ant/#IndTop

 

There is no mention to the feeding point for such antenna. In my setup H(L) is 80m and I'm feeding

at the coil base. Total H is 80+11= 91m

 

The Ra calculated from Rick formulas is over 8 Ohm (not mOhm)

This radiation resistance seems too much to be true. But results are proving really outstanding

 

I'm just feeding the antenna with 70W, believe it or not and it is not really resonanting on WPSR frequency but on 488KHz

as I adjust the variometer up at the antenna and then run a coax line to shack which changes it all

 

The 80m pipe which forms the H(L) is really more complex in practice. It goes down to building basement

and there splits into different pipes. One connects to presure compressor and water tank. The other runs

underground 40m to the twin tower and then runs up again another 80m into the twin (parallel) tower

The pipe section running underground is not metal, but plastic. The iner water column should work as

current conductor. That water is confined in the pipes and presurized. Should be saturated with metal oxide

similar to a heating circuit, so probably the plastic pipe got metal deposits inside which make it even better

conductor than the water colum itself

 

Any thoughts ?? Am I getting >10% efficiency ??

 

73 de Luis

EA5DOM 

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De: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] En nombre de VIGILANT Luis Fernández
Enviado el: lunes, 09 de noviembre de 2015 16:01
Para: DK7FC; rsgb_lf_group@blacksheep.org
Asunto: Re: LF: Re: FR5ZX on MF WSPR

From WSPR database, FR5ZX transmitted in 503KHz. Is 630m band not allowed in Reunión? 

 

73 de Luis

EA5DOM

 

Enviado en portable

------ Mensaje original ------
Desde: DK7FC
Fecha: 09/11/2015 14:48
Para: rsgb_lf_group@blacksheep.org;
Asunto:Re: LF: Re: FR5ZX on MF WSPR

Hi Genosse Roman,

FR5ZX is using a resonated vertical antenna with capacitive top load near his house. He also transmits with this antenna.

73, Stefan

Am 09.11.2015 01:35, schrieb Roman RW3ADB:

Parteigenosse Stefan!

Any news about FR5ZX RX-setup? )

73!

Roman