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Message-ID: <002c01c74fb4$282e9ec0$6401a8c0@derekm3uttnxf9>
From: "DEREK ATTER" <derek.atter@blueyonder.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <45CF58BD.7080900@telus.net>
Date: Tue, 13 Feb 2007 21:15:58 -0000
MIME-Version: 1.0
Subject: LF: Re: TIL Grabber back online...
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Hi Scott,

I have carried out a number of tests on the MiniWhip cct. and like you, I 
found that at +12V DC supply there were signs of inter-mod products - such 
as weak phantom broadcast stations just below 400kHz which should not be 
there

At +15 and above, they pretty well dissappear.  I also then tweaked the 
values of the 2.2K/10K potential divider feeding the base of the 2N5109 to 
drop the base voltage a bit because with the original values, the 
collector-base voltage was only about +2V which is not really enough I 
think. I was also using about 150ft of 50 ohm RG58U coax to the shack from 
the garden but with hind sight, I think it woiuld be better to have used 
70ohm feeder to reduce the capacitive load on the emitter of the 2N5109 and 
probably insert a 70 ohm series resistor at the emitter to provide a better 
source impedance for the cable and help absorb reflections back down the 
line although wouild incur a 6dB signal loss.
I have had to take my MiniWhip down temporarily due to building work on a 
conservatory at the back of the house, but I intend to return to the subject 
when all the mess is cleared away!! I still think it is very neat design and 
mechanically simpler than the AMRAD design.

73  de  Derek Atter G3GRO

PS - I seem to remember that the Royal Navy used to employ an RX antenna 
multi-coupler using several 807 tetrodes years ago!

----- Original Message ----- 
From: "Scott Tilley" <sthed475@telus.net>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, February 11, 2007 5:56 PM
Subject: LF: TIL Grabber back online...


> After an epic struggle with my miniwhip I discovered that it likes a much 
> higher input voltage then documented in the construction article...
> Running it at around 17V seems to clear up the intermod problem.
>
> So the grabber is back up.
> http://www3.telus.net/sthed/argo/
>
> 73 Scott
>
>
>
>
>
>
>
>
> -- 
> No virus found in this incoming message.
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> Version: 7.5.441 / Virus Database: 268.17.35/680 - Release Date: 
> 10/02/2007 21:15
>
>