Sorry Hajo
Looks like the Gibraltar trip ended with a Fleming diode (an enevelope detector) not a Coherer. But they do have useful range, with a whopping antenna though.
From: M0FMT <[email protected]>
Subject: Re: LF: Razor blade RX .... Try a Cohere?
To: [email protected]
Date: Tuesday, 6 January, 2009, 11:59 PM
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Hi Hajo and LF
But you still have the issue of Hi Impedance headphones. A Coherer allows you to switch a light or buzzer on and off. They are amazing in free state they have a very high DC resistance (virtually open circuit) and once they cohere it is virtually a dead short. But may be not as sensitive as a rusty nail detector!
There is a report of UK to Gibraltar using a 2.5kW Sparker on 350m and the RX being a Coherer. Not bad for Mechanical Radio!
From: [email protected] <[email protected]>
Subject: Re: LF: Razor blade RX .... Try a Cohere?
To: [email protected]
Date: Tuesday, 6 January, 2009, 11:42 PM
No problem! Use MCW! Has been typical for 500 kHz.
73 DJ1ZB
"M0FMT" < [email protected]> schrieb:
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Hi Mal and LF
I am disapointed in you Mal to be considering an envelope detector. A true CW man, I would have thought, should only entertain the use of a Cohere detector!
Having played with them, I was surprised how well they work over a range 136kc/s to 433mc/s (the extent of my power RF O/P) probably work over a much lager range of frequencies but not tested by me.
73 pefmt
From: mal hamilton <[email protected]>
Subject: Re: LF: Razor blade RX
To: [email protected]
Date: Tuesday, 6 January, 2009, 9:21 PM
Your own cct and ideas and the headphone construction. Not info from the web.
g3kev
----- Original Message -----
Sent: Tuesday, January 06, 2009 7:58 PM
Subject: Re: LF: Razor blade RX
310113517964 E bay too
Since I mentioned a Razor blade and fence wire RX a while back I have had several requests for a circuit. To give others the opportunity to submit a cct I will await replies. This method was used successfully at Coldiz and other POW camps to receive BBC broadcasts.
Let us know how you would approach the subject. This is applicable to MF/LF since the broadcasts at the time were receicved on these bands.
Build one and have a QSO using this RX
g3kev
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