Message-ID: <000701c12354$795197e0$4e0a87d9@robing>
From: "Robin T. Greenwood" <robin@g3lba.freeserve.co.uk>
To: rsgb_lf_group@blacksheep.org
References: <5.0.2.1.2.20010812180342.00a40ca0@mail.pncl.co.uk>
Subject: Re: LF: decca
Date: Sun, 12 Aug 2001 18:30:16 +0100
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After testing, I finished up with a 3mm stainless rod 750 mm long on my Amp
of this type  for satisfactory performance.
Robin
----- Original Message -----
From: "Walter Blanchard" <blanch@pncl.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, August 12, 2001 6:28 PM
Subject: Re: LF: decca


> At 08:49 12/08/01 Sunday, GII3kev wrote:
>
> >Does anyone have the in/out connection for the decca amp.assy 80355/cf
> >and what is the frequency range. (small rf preamp)
>
> This was used at Decca transmitter sites for reception of the other TX in
> chain.
> Antenna in is the floating Faston connector
> Ground is TB1/2 and TB1/4
> Power in (was designed for 26v but works OK at 12v) depends whether you
> want to feed it up the inner of the coax output or not.
> If yes, connect coax outer to ground and inner to TB1/3. Check Link B
made.
> If no, disconnect Link B, feed power to TB1/1, take output from TB1/3.
> TB1/5 can be used as separate ground for static discharge off antenna if
> Link A disconnected.
> Gain and frequency response can be altered by adjusting R9 but should not
> go below 500 ohms otherwise will oscillate.
> If R9 is missing then voltage gain is nil but power gain is maximum i.e.
> maximum impedance transformation. Bandwidth is then something like 10-500
> kHz.  If  R9 made 1k or so voltage gain will be 30 dB and bandwidth
50-150
> kHz.
>
> >I think some are using these amps and wonder if anyone has discovered
> >the optimum antenna whip length for best match and avoiding overload.
>
> They were designed for use with a "barrel" antenna (about same size and
> shape as a small beer barrel) but work OK with ants up to 1m.
>
> >I have another cct board and not sure what it is, but looks like some
> >interface to the aerial/coil control.
> >The terminals are marked on one side as AE -CL+ K2 K1 G2 G1 and opposite
> >terminals ST F 1 2 3 4 5 6 7 A B C D P and L N (expect this is mains in
> >at live and neutral) The board is about 170 x 120 mm. I have 2 of these
> >cct boards and each one has a small grey box. On one cct board the box
> >is marked 27.24v and 28.8v and the other cct board box is marked 72v and
> >68v.
>
> Don't know what this is. Main power around Tx ccts was 65-70v but 28v was
> used to drive auxiliaries.
>
> The interface cct board that fed the preamp has eight screw terminals
> marked  AUX, RX, AE, POWER (26v)., two pot cores and a transformer.
>
> Where did you get them? Looks like some Decca surplus is getting on the
market.
>
> Walter G3JKV.
>
>
>
>