Re: LF: Razor blade RX .... Try a Cohere?

[M0FMT <m0fmt@yahoo.co.uk>]

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!

 

73 petefmt 

--- On Tue, 6/1/09, hajo.brandt.dj1zb@t-online.de <hajo.brandt.dj1zb@t-online.de> wrote:

From: hajo.brandt.dj1zb@t-online.de <hajo.brandt.dj1zb@t-online.de>
Subject: Re: LF: Razor blade RX .... Try a Cohere?
To: rsgb_lf_group@blacksheep.org
Date: Tuesday, 6 January, 2009, 11:42 PM

 No problem! Use MCW! Has been typical for 500 kHz.

73 DJ1ZB


 "M0FMT" <m0fmt@yahoo.co.uk> schrieb:

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.

 

http://home.earthlink.net/~lenyr/coherer.htm

 

73 pefmt

 

--- On Tue, 6/1/09, mal hamilton <g3kevmal@talktalk.net> wrote:

From: mal hamilton <g3kevmal@talktalk.net>
Subject: Re: LF: Razor blade RX
To: rsgb_lf_group@blacksheep.org
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 -----

From: riese-k3djc@juno.com

To: rsgb_lf_group@blacksheep.org

Sent: Tuesday, January 06, 2009 7:58 PM

Subject: Re: LF: Razor blade RX

310113517964   E bay too

 

On Tue, 6 Jan 2009 18:00:45 -0000 "mal hamilton" <g3kevmal@talktalk.net> writes:

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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