Jan-Martin
I've never encountered a situation where something works that would be
labelled misuse. You must have a PhD.
Bad practice to some may be good practice for others. We had two seperately
built 500W transmitters we wished to combine. Why build a new one? Second
the combiner acts as a filter so we could remove the two redundant LPFs.
From experiment I can push the two seperate transimitters abit more without
threat of an over current shutdown...
Don't be so negative. It works and it took only a few hours to rig....
Thinking outside the box...
73 Scott
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Wednesday, March 02, 2005 1:23 AM
Subject: LF: Re: Re: Big Bad Amps -or " misuse of Wilkinson combiner"
But if you wish to combine two signals which has the same source, and they
are obviously in the same phase, the wilkinson thing is only adding to the
complexity, and it is very bad practice to do so.
The signals could much better be added directly in series or paralell
73
Jan-Martin, LA8AK
-----Opprinnelig melding-----
Fra: [email protected]
[mailto:[email protected]]På; vegne av Scott Tilley
Sendt: 2. mars 2005 00:11
Til: [email protected]
Emne: LF: Re: Big Bad Amps <was re: ... --- ...>
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" <[email protected]>
To: <[email protected]>
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: [email protected]
[mailto:[email protected]]On Behalf Of Scott Tilley
Sent: 01 March 2005 10:59
To: [email protected]
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" <[email protected]>
To: <[email protected]>
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" <[email protected]>
> To: <[email protected]>; <[email protected]>
> 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
>
>
>
>
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