[Elecraft] JT65A output power variations.

[hb9ari]

Hello Lance,

I use the same settings for ALC(also 5 bars in JT65), USB and use
the rear LINE IN. As you are using the original 2.7kHz filter this
seems not be the problem.; BUT i don't use compression and this
can explain that you don't have "my" output power variation;
i can imagine that 20dB compression should be able to
"compensates" a ~ 3dB HF output variation. In receive, i have
no problem. Some time ago, i do a HF output response
measurement (with a LP-100) and i remember that the
curve was far from flat...As it was before i use JT65, with
voice, my correspondents don't hear something "wrong".
It's only since i use extensively JT65 and monitor my output
power according QRP'ers request, HF band, etc that
i've remarked this > 3dB output variation. For ~ 1000 HF JT65
QSO, i worked from 0.5W to (exceptionally) 300W.
My "usual" power is between 25W and 50W.
I think that compression will correct (if necessary..) "my" problem
but the source seems to be from  the filter  used  in TX.
Next week-end i should be clear about that.

For the moment, i'm not QRV on 6m Terrestrial, MS or EME.
Just SSB when apertures are there.

Thank you for your explanations  and  i will try compression; habitually,
i don't like too much to use it, but...

73 QRO, Rudolf
HB9ARI

 


Lance Collister, W7GJ wrote:
> Hello Rudolf,
>
> I use JT65A all the time with my K3 for 6m EME, and I have always used 
> USB mode for it.  I have no trouble with the USB setting...I have 
> never even tried the DATA options.  I have the standard 2.7 kHz 
> filter, and set the audio just like I do for USB voice.  I make sure 
> to have the ALC fill the 5 bars on the meter, and I use 20 dB of 
> compression to make sure that all the tones come up to the proper 
> power levels.  I use the LINE IN on the rear panel for my incoming 
> JT65A tones from the computer.
>
> I find the K3 a great rig for JT65A because I can make a flat 
> bandwidth 300 Hz to 2200 Hz, and decode callers over that entire 
> frequency range.  I usually run JT65A with the NB on the first setting 
> (IF NAR 1), DSP OFF and the AGC off.  It is an amazing mode because it 
> has 10 dB sensitivity over CW.  Most of the time on 6m EME, signals 
> are too weak to hear, but they are nicely displayed on the SpecJT 
> screen and decoded on the JT65A screen.
>
> Now that we are at the bottom of the sunspot cycle, the ionospheric 
> propagation is very poor.  However, because the geomagnetic field is 
> usually very quiet these days, this is the VERY BEST time for 6m EME!  
> That is why there has been so much growth in 6m EME over the last 
> year, and there have been such successful DX operations by small 6m 
> stations using JT65A mode with just a single yagi aimed at the horizon.
>
> GL and VY 73, Lance
>
> 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.
>>
>> Many TNX for an answer.
>>
>> 73 QRO de Rudolf, HB9ARI
>>
>> PS With the same sound card and software,
>> using my "old" FT857 (non D) TX/RX, the
>> output power variation is well under 1dB
>> until the audio band edges.
>>
>>
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>