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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