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References: <20091215112352.36901F3863@smtps02.kuleuven.be>
	 <38A51B74B884D74083D7950AD0DD85E828AC77@File-Server-HST.hst.e-technik.tu-darmstadt.de>
Date: Tue, 15 Dec 2009 13:51:51 +0000
Message-ID: <fc7eccec0912150551n3e85a17cxb903da8adb792ef8@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: AW: LF: "Gain" between qrss3 and qrss10?
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700Watts (or more) direct from Eu mains voltage

http://www.g4jnt.com/137tx.pdf
With a bit less safety margin,  1kW is quite feasible

Andy
www.g4jnt.com

This email has been scanned for damaging side-effects by the health
and safety police



2009/12/15 Stefan Sch=E4fer <schaefer@hst.tu-darmstadt.de>:
> Mni tnx Rik for your answer!
>
>
>
> No, you didn=92t spoil the fun at all ;-)
>
>
>
> I have some remarks/ideas.
>
> The coil losses increase linear with the power but not more than linear.=
 So,
> 10x the power wouldn=92t decrease the antenna efficiency (if no arcing=
 occurs,
> of course). If we assume an antenna, e.g. in 8m height with many topload=
s,
> then the efficiency will be poor but the capacitance will be high and th=
us
> the needed L will be small. Therefore we get a low voltage even with ver=
y
> high power and due to the low efficiency we will keep the legal limit.=
 So,
> if one has no possibility to increase the antenna height QRO is one choi=
ce,
> especially when the operator is already in pension and cannot do a qso=
 in
> qrss10000000000000000000000000 any more ;-)
>
>
>
>
>
>
>
> It should be possible to run a TX directly of the mains (giving about 33=
0V
> DC). But for 10kW the PSU current would be 33A, requiring something like=
 a
> 60000uF/450V elco, these large HV elco's cost a fortune (at QRL we recen=
ty
> had to replace a 4700uF/450V capacitor, it costed over 200 Euro).
> And for a Class-D / Class-E amp running of 330V a 900V power FET might=
 be a
> bit on the edge for a foolprove TX (but since you are spending a fortune=
 on
> elco's you can spend some more money on 1.5kV devices ;-) ).
>
>
>
> Yes, you are right. But i mean i USA, where the voltage is 110V, you get
> about 155V and thus the 900V FET would have 6 times more. For a class e=
 mode
> PA, 4x the voltage can be reached when SWR is correct(!) so there would=
 be a
> goog savety factor. About the Capacitors: You could reduce the needed C=
 when
> using a 3 phase system (of the kitchen oven ;-) ). Then you would get ab=
out
> 268VDC and therefore a factor 3,35 to the 900V which will be critical fo=
r
> the FETs when SWR is not absolutely constant 1:1, so better using a
> IXFH24N100 =A0;-)
>
>
>
> Really nice, that conversation! Tnx!
>
>
>
> 73, Stefan / DK7FC
>
>
>
>
>
>
>
>