Message-ID: <005401c51eb4$00f61140$0201a8c0@private.network>
From: "Scott Tilley" <sthed475@telus.net>
To: rsgb_lf_group@blacksheep.org
References: <PAEFLMFGBDKKCONLMLBIKEKJCCAA.ganymede444@btopenworld.com>
Date: Tue, 1 Mar 2005 15:11:30 -0800
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Subject: LF: Re: Big Bad Amps <was re: ... --- ...>
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Dave

> If you're into Big Bad Amps...

Don't put those kind of thoughts in my head ;-)

I think with Steve's antenna setup and 1KW we are very close to 1W ERP.  The
Wilkinson seems to work great... Ran it full out last night for a couple of
hours into the dummy load...  I couldn't measure the loss from the combiner
as it is very low and the system remains >80% eff.

73 Scott


----- Original Message -----
From: "Dave G3WCB" <ganymede444@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, March 01, 2005 3:13 AM
Subject: LF: Big Bad Amps <was re: ... --- ...>


> Hi, Scott.
>
, you should check out G4FTC's site
> http://www.qsl.net/g4ftc/amplifiers/136khz/home.htm He describes a 3kW LF
> amp. that uses 8 x IRFP450's in a bridge arrangement. Biggest PA I've seen
> so far!
>
> BTW, if you have two identical TX's already, and you find the Wilkinson
> thing doesn't work out, you could re-configure your amps. into a bridge
> arrangement instead, bit like the Decca TX's.
>
> Keep that fire-blanket handy!
>
> Cheers,
>
> Dave G3WCB.
>
> -----Original Message-----
> From: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of Scott Tilley
> Sent: 01 March 2005 10:59
> To: rsgb_lf_group@blacksheep.org
> Subject: LF: Re: Re: ... --- ...
>
>
> Hey Alan
>
> We got the bugs out...  Once I found the problem with the lack of sinc in
> the 4013 divider stages things have been working as expected.  I thought
> about the inductor coupling; however, based on my observations the
combiner
> is not doing anything negative to the signal train.  We still have >80%
eff.
>
> I would like to try this with toroids next and compact it down.  I'm also
> dreaming up a bigger badder amp using this concept.  It seems real stable
> and doesn't require running the system 'balls to the wall' to get some
> serious power from 4 FET and a reasonable PSU voltage.
>
> 73 Scott
>
> ----- Original Message -----
> From: "Alan Melia" <Alan.Melia@btinternet.com>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Tuesday, March 01, 2005 2:49 AM
> Subject: LF: Re: ... --- ...
>
>
> > Hi Steve I have just had a thought your construction looks fine....BUT
> maybe
> > the two coils are too close together and there is some coupling. I
wonder
> if
> > it is possible to temporarily turn one at right angles to kill any
> coupling
> > and see if that helps??
> > The biggies in my Web page were made with big toroids I believe probably
> > iron dust rather than ferrite, as the inductance reqquired is not that
> high
> >
> > Cheers de Alan G3NYK
> >
> > ----- Original Message -----
> > From: "Scott Tilley" <sthed475@telus.net>
> > To: <lowfer@lwca.org>; <rsgb_lf_group@blacksheep.org>
> > Sent: 01 March 2005 06:51
> > Subject: LF: ... --- ...
> >
> >
> > The smoke test of this Wilkinson Combiner was successfull in that no
smoke
> > came out and nothing died.  However, we get enough heat to cook an egg
on
> > the 100ohm balance resistor.
> >
> > We have a scope match on the output to the dummy load and it shows about
> > 225W from one transmitter, add another and we get 450W, success NOPE!
The
> > transmitters are outputting ~450W each! Therefore, half the power is
being
> > absorbed in the 100ohm balance resistor.  Examining the phase
relationship
> > of the input to the combiner waveforms indicates they are in phase
within
> > ~10degrees and almost equal in amplitude.  So what gives!  Anyone have
> some
> > idea what may be going wrong?  Of course we have checked and doubled
> checked
> > the circuit for errors and nothing...  All seems as it should according
to
> > formulas and drawings we have viewed and designed it from.
> >
> > Does anyone have an idea how we could troubleshoot our way through this?
> >
> > Any advice would be appreciated.
> >
> > 73 Scott and Steve(It's all his fault ;-)
> >
> >
> > Check the status of radio beacon 'TIL'  in CN89lg at:
> > www.scottboxx.com/radio
> >
> >
> >
> >
>
>
>
>
>
>