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Pete and co
You are wandering away from the subject. My
question was not on the merits of detectors etc, simply how to build a razor
blade detector and suitable earphone using scrap parts available in a trench or
Jail, for instance in 1940
I have all the answers if you get stuck and I
did not get it from an internet source. Its fundamental knowledge
that a radio amateur should know and especially if the BIG BANG
should happen
g3kev
----- Original Message -----
Sent: Wednesday, January 07, 2009 9:35
AM
Subject: Re: LF: Razor blade RX .... Try
a Cohere?
Hi Rik and LF
But that's the point, an envelope detector will not detect CW
(ON / OFF Keying) unless A/ you have a local oscillator (DC rx) to
create a beat in the detector, added complication in design or B/ unless
the carrier has got noise on it (sparker) or it is modulated, added
bandwidth for no extra intelligence.
If we go away from a simple detector RX and add amplification to an
envelope detector the recovered DC from a CW signal could be used to
operate a switch to activate a Buzzer, light or side tone oscillator
but I don't think thats in the spirit of the spirit of the
challenge.
However a Coherer detector does everything for CW in one simple
easy to construct mechanical device with no fiddling with cats whiskers
or the risk of cutting a vital artery with a sharp razor blade! And no
need for high impedance cans.
The challenge is to make a QSO using the Razor Blade RX I am
working on it. But a counter Challenge is to use a Coherer for a two way
QSO, I am working on that also. However it's very cold in my garage
right now so don't expect a result from me soon but better setup ops may
have a result sooner.
From:
Rik Strobbe <[email protected]>
Subject: Re: LF:
Razor blade RX .... Try a Cohere?
To:
[email protected]
Date: Wednesday, 7 January, 2009, 8:11
AM
MCW: what a waste of bandwidth, Mal will allert
OFCOM ! 73, Rik ON7YD - OR7T At 00:42 7/01/2009,
you wrote:
No problem! Use
MCW! Has been typical for 500 kHz.
73
DJ1ZB
"M0FMT" <[email protected]> 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 <[email protected]>
wrote:
- 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 -----
- From: [email protected]
- To: [email protected]
- 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" <[email protected]> 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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