[Elecraft] JT65A output power variations.

[Ken Roberson]

Rudolf,

We have worked many times on JT65A , I also use a K3.
I operator in the Data mode , ( setup data mode for USB )
and have had no problem for about a year.
I think this is the best way to run data modes.
I set the shift at 1250 hz and the BW at 1200 HZ.
The JT65 software only looks at 1200 hz bandwidth.
This works for me.
GL 73 Ken K5DNL

------------------------------------------------------------------ 


--- On Wed, 11/11/09, hb9ari <hb9ari at bluewin.ch> wrote:

> From: hb9ari <hb9ari at bluewin.ch>
> Subject: Re: [Elecraft] JT65A  output power variations.
> To: "Elecraft-forum" <Elecraft at mailman.qth.net>
> Date: Wednesday, November 11, 2009, 9:59 AM
> Hello Matt,
> 
> Yes, TX EQ is flat. I've tried to compensates
> with TX EQ, but i've all "reseted" to "flat".
> 
> Thank you for this indication.
> 
> 73 QRO de Rudolf
> HB9ARI
> 
> Matt Zilmer wrote:
> > Since you're using USB, you might want to be sure you
> have the TX EQ
> > "flat".  Or use DATA A, where the EQ doesn't
> apply.
> >
> > 73,
> > matt W6NIA
> >
> > On Wed, 11 Nov 2009 11:28:36 +0100, you wrote:
> >
> >   
> >> Hi Julian,
> >>
> >> Thank you for your fast answer!
> >> A 1st point, as with the FT857, i'm using
> >> USB mode for JT65A. For the filter used,
> >> i ordered a 8 poles 2.8k with my K3,
> >> but i'm not sure if the 5 poles 2.7k "original"
> >> and always installed as FIL2 is not
> >> selected during TX???; next week-end, when
> >> active at my "external" shack, i will look how
> >> to remove the 2.7k filter, as i've also problem
> >> with center filter when i adjust the HI LO
> >> filter controls; when the 2.7k filter is
> (automatically)
> >> selected, i've a big discontinuity  with
> filter setting.
> >>
> >> As you say, i will look if the 2.7k is not
> selected
> >> during TX. I read also the "problems" when in
> >> DATA A mode, but as said, i'm working in USB
> >> (as recommended for JT65A for all RF bands)
> >> and VOX work at perfection too.
> >>
> >> My best 73, Rudolf
> >> HB9ARI
> >>
> >> PS As i expect to get 50W output when i set
> >> the control to 50W, i've adjusted the audio input
> >> level for max bars on ALC. For PSK31, i work
> >> with ~ 10 to15W max for 100W selectes with
> >> the control and "local" receiving give me an
> "acceptable"
> >> -24 to -28dB IMD.
> >>
> >>
> >> Julian, G4ILO wrote:
> >>     
> >>> hb9ari wrote:
> >>>   
> >>>       
> >>>> Hello,
> >>>>
> >>>> As i use principally JT65A (snice ~
> 2years),
> >>>> i've remarked transmit output power
> variations
> >>>> depending where the audio is located in
> the waterfall,
> >>>> as i'm not speaking English, it's
> difficult to explain correctly;
> >>>> if i'm ~ in the middle of the waterfall (~
> 1200Hz)
> >>>> i get over 3dB in output power variations;
> for an expected
> >>>> 50W output power, between some tones of
> the JT65A
> >>>> modulation, the output level can vary from
> 20W
> >>>> to 60W; if i'm working away from the
> "middle",
> >>>> variations are lower and acceptable but
> most
> >>>> of time, "central" frequencies are
> used...
> >>>> I've always worked with this "problem" as
> i
> >>>> expect some AGC effect by the receiving
> side...
> >>>> I would appreciate to have an explanation
> >>>> of this effect.
> >>>>
> >>>>
> >>>>     
> >>>>         
> >>> This topic has been brought up before in the
> context of RTTY. The reason is
> >>> that there is no automatic level control in
> DATA A mode (or rather, there
> >>> is, but it is very slow acting to avoid
> causing IMD on PSK31 signals) so
> >>> there is no compensation for ripples in the
> roofing filter passband. It has
> >>> been suggested that the problem is less when
> using the 8-pole SSB roofing
> >>> filter as it has less ripple than the standard
> 5-pole filter.
> >>>
> >>> The output should not vary as much as you
> suggest while working within the
> >>> normal passband for JT65A operation so I'm
> wondering if you have correctly
> >>> adjusted the audio input level in DATA A to
> get 5 bars on the ALC scale.
> >>> This will not prevent the power varying for
> different tones during a
> >>> transmission but it should help maintain a
> constant average level when
> >>> working at different places within the
> passband.
> >>>
> >>> -----
> >>> Julian, G4ILO. K2 #392  K3 #222.
> >>> * G4ILO's Shack - http://www.g4ilo.com
> >>> * KComm - http://www.g4ilo.com/kcomm.html
> >>> * KTune - http://www.g4ilo.com/ktune.html
> >>>
> >>>   
> >>>       
> >>
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