Message-ID: <O3SWxIAqXp8$EwWn@telemetry.demon.co.uk>
Date: Wed, 31 Dec 2003 09:24:58 +0000
To: rsgb_lf_group@blacksheep.org
From: "Tom Boucher" <tom@telemetry.demon.co.uk>
References: <200312301817.hBUIHvQ11107@mailgate5.cinetic.de>
In-reply-to: <200312301817.hBUIHvQ11107@mailgate5.cinetic.de>
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Subject: Re: LF: TR-Switch for new TX
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Hans

I put two back-to-back silicon diodes across the relay output to my
receiver as overload protection.

73, Tom G3OLB

In message <200312301817.hBUIHvQ11107@mailgate5.cinetic.de>, Hans-
Albrecht Haffa <dk8nd@web.de> writes
>    p {margin: 0px}
>
>    Dear Lowfers,
>    just I am designing a TR-switch for my new TX. Estimated Power 
>    about 60dbm/60 Ohm.
>    The current situation with my TX 70W/60 Ohm:
>
>    The RX-Path is swiched via two reed-Relays (homemade coaxial ones, 
>    for qsk operation) to the receiver input, the TX-Path is switched 
>    via a reed-relay to the PA both from the common input of 
>    low-pass-filter, whitch is allways in the aerial path. My RX is an 
>    EKD 300 (Funkwerk Köpenick, late DDR). In transmit operation this 
>    will cause an sidetone with an pretty high volume, but not too much 
>    annoying noisy.
>
>    My experiments with an 1 Watt driver circuit:
>
>    The signal Path: Oscillator - Driver 1 Watt - Attenuator switchable 
>    0d B...50 dB - TR-relays - RX-Input 
>
>    TR-relays is a series of one Vac-Relay and three Reed-Relays (2 
>    spst, 1 spdt). 
>
>    All build up with coax connectors. It seems to be that I am still 
>    far away from a S9 signal durig transmitting, even with this 1 
>    Watt-Driver. 
>    How You have solved this task? What is done in commercial equipment 
>    with similar power?
>    Is it necesary to have anyway a mute circuit for the receiver? An 
>    input voltage of 1 Volt will not be dangerous for the RX-input and 
>    cause some distortionin the audio-signal, but for a sidetone this 
>    is not a problem. 
>    Waiting for reply 
>
>    55,
>
>    Hans-Albrecht Haffa
>
>    DK 8 ND
>
>     
>
>    ______________________________________________________________________________
>    Erdbeben im Iran: Zehntausende Kinder brauchen Hilfe. UNICEF hilft 
>    den
>    Kindern - helfen Sie mit! https://www.unicef.de/spe/spe_03.php 
>

-- 
Tom Boucher
'Hedgerows'
Sheldon
Honiton
Devon EX14 4QS