Hello everybody,
it's ever interesting to read that somebody else has some troubles as
experienced from myself ;-)
Me too am grateful to Andy for the support I received
while struggling with odd experiences..
Let me join the discussion and share a possible solution: I see that
LPF is a PI version, similar to what I used in the past. It was nice in
RL, armonic suppression and losses when tested with low power
instruments, than I was increasing the wire diameter of coils because
it was a... warming thing! The current was indeed very high in the FETs
(2+2 FETs in push pull) and the RIP area was growing...
After I tried the T LPF (see attachment) no more problems, no more
warming boxes..
You could re-arrange your LPF components for a quick trial and save
some caps ;-)
In my version I had to make some change because the cores were not
available and used T200-A2 cores calculating the turns to get 59 and
109 uH coils.
Maybe it's worth to try ;-)
CU on 137kHz
Marco, IK1HSS
----Messaggio originale----
Da: [email protected]
Data: 25-dic-2017 0.16
A: <[email protected]>
Cc: <[email protected]>
Ogg: Re: LF: TXing 2200m WSPR
Yes
Try anything and try to work out what is happening. But first of all,
he
needs to know what power being deliverfed into a 50 ohmsload is
seemingly
higher than it 'can' be. The Vdd^2/2/Rl cannot be violated.
If it appears to be so, then Rl or Vdd or the measurement has to be
wrong.
I once had to go though a similar
try-everything-and-believe-nothing-until-tested process to work out why
my
700Watt 137kHz Tx appeared to be more than 100% efficient!
It turned out my Bird 30dB 1kW attenuator only had 29.4dB attenuation
at
DC. And for a 1GHz jobbie, 137kHz is DC.
On 24 December 2017 at 23:03, Chris Wilson <[email protected]> wrote:
>
>
> Hello Andy,
>
> Is there any point in Paul putting his dummy load on the end of his
> 75 odd meters of feeder co-ax outside? And then on the secondary of
> his matching transformer when tapped one to one? In case the co-ax
is
> iffy or the impedance matching transfomer's doing something odd?
>
>
> Sunday, December 24, 2017, 10:42:16 PM, you wrote:
>
> > Well ... Using exactly the values in the filter circuit diagram,
> > 50R transforms through the filter to 48.5 - j2.86 (Ret Loss = 30dB,
> > VSWR = 1.07) [Using GM3SEK's original Netcalc prog.]
>
>
> > So that's pretty conclusive the ideal filter values will not be
> > upsetting things at the fundamental frequency.
> > According to Google, the T106-2 has a stated Al value of 13.5nH
> > /turn^2 so 72 turns does indeed give 70uH. So IF your core is
> correct, the filter should be OK.
>
>
> > It's a bit difficult from now on, at a distance, to try to work out
what
> is happening.
> > Anyone else, any suggestions ?
>
>
> > BTW ...
>
>
> > Peak to peak of a { symetrical }square wave needs to be multiplied
> > by 4/pi to get the peak-to-peak of the fundamental component. So
> > the amploitude you see will be lower by about 1.3 times for teh
same
> fundamental power component.
>
>
> > Andy G4JNT
>
>
>
>
>
> --
> Best regards,
> Chris mailto:[email protected]
>
>
>
LPF.pdf
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