From: Chris Wilson <dead.fets@gmail.com>
Date: Fri, 28 Apr 2017 17:12:47 +0100
Message-ID: <29981529.20170428171247@gmail.com>
To: "Dr. Wolf Ostwald" <rsgb_lf_group@blacksheep.org>
In-Reply-To: <5dfe6b21-f2aa-d0d1-2d3e-b38d728fa988@t-online.de>
References: <15b946bf359.marcocadeddu@tin.it> <5dfe6b21-f2aa-d0d1-2d3e-b38d728fa988@t-online.de>
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Subject: Re: R: LF: Dummy load testing without LPF?
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Hello Dr.Wolf,
24 April 2017


Thanks  for  the  reply  Wolf,  I  tested  with  no LPF and the output
transformer  got  pretty  hot. With the rebuilt LPF all was fine. So I
now  have two reliable, identical amps. Combining them is still giving
issues  though,  as  despite  a good drain waveform and identically in
phase  signals, \I get some dead FET's, sometimes mid TX, sometimes at
the  end of a TX. I will start another thread asking how I could check
the  impedance  that  the  impedance  transformer  of  the combiner is
offering  to  the  combiner. I feel that may be the issue, or that the
impedance matching transformer is saturating.

> hi Chris !
> if the dummy load used, presents a reasonable low SWR for the highest 
> harmonics with an amplitude of interest, then yes.
> I used a split filter after the output of the push-push amp. that opened
> up at about 900 kcs and bypassed into a 50 ohm load. the other branch 
> went into a regular 7pole Tchebycheff.
> Wherever harmonics are generated, they have to be taken care of.

> 73 de wolf  df2py


-- 
Best regards,
 Chris                            mailto:dead_fets@gmail.com