To: rsgb_lf_group@blacksheep.org
References: <1608d073056.marcocadeddu@tin.it>
From: N1BUG <paul@n1bug.com>
Message-ID: <d877cf2d-4e75-b372-9bd2-302791f416b0@n1bug.com>
Date: Mon, 25 Dec 2017 07:14:45 -0500
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Subject: Re: R: Re: LF: TXing 2200m WSPR
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Hi Marco,

I don't detect any heat in the LPF but at this low power level it 
could be difficult to detect it.

I already have plans to build the big T type LPF. I have the 
T-225A-2 cores and metal to make a compartmented box. Capacitors are 
on the way, could arrive around 29 December. I still need to order 
the wire and some kind of material for mounting the big inductors.

I'm making that LPF because eventually I will also build the big 
amplifier. I'm not sure when that will happen, probably a bit late 
for this LF season.

The most curious thing is what seems to be some measurement error or 
impedance transformation but the cause remains elusive. I hope to 
find the reason so I can be more confident about measurements when I 
go go high power.

73,
Paul N1BUG


On 12/25/2017 04:35 AM, marcocadeddu@tin.it wrote:
> 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