Hello N1BUG,
When I have blown a FET on Jay's amp design and replaced it / them I
have sometimes seen less than optimal gate and drain waveforms from
the replaced FET's. A simple meter "diode test" on the parallelled
diodes / 10 Ohm resistors showed the diodes to be OK, but changing
them restored things to a good pattern. i now change them as a matter
of course if a FET blows. My matching transformer is a multi tapped
primary / secondary pairing on three individually Kapton taped 77
material 240 size cores stacked together. I see no heating t full
power WSPR15 or Opera but they are in a sealed plasic box of more than
generous size. I *HAVE* had issues with the ground terminals on the N
type connector screws arcing although they appeared tight. I now
solder direct to the socket flanges before mounting with the socket's
flanges on the inside of the box. Hope you get it sorted soon, a box
of spare FET's is a necessity, "things `appen" ;)
The only thing that gets warm is the LPF, it's in three divorced
compartments like Jay's and i think yours? I use a small PC processor
fan on the middle box with an exit hole meshed over opposite the fan.
Air flow is adequate to keep all three toroids near ambient with this.
I do see a mismatch s things warm up and the vario needs a tweak after
a cold start. The loading coil becomes tepid after a while.
I was very pleased to be heard by W3SZ three times last night! I have
discovered a limitation in only being able to have one call sign with
the U3S which makes divorcing WSP2 and WSPR15 TX's on the reporter map
impossible unless there's another option?
Tuesday, November 20, 2018, 10:54:15 AM, you wrote:
> Hi Stefan, LF
> I see some very interesting reporters on that list. :-)
> I would like to transmit as well, but the PA is not repaired. I must
> look into it to see if anything in addition to the FETs is dead,
> then order FETs and whatever other parts...
> When the PA is repaired I need to do some more testing before I try
> WSPR-15. During every WSPR-2 TX period, the scopematch shows the
> resistance of the antenna decreasing during the transmission. I am
> worried this is caused by something heating. Maybe the ferrite in
> the antenna matching transformer, maybe the the big coil? Or maybe
> it is in the scopematch detector itself but that would be a little
> difficult to believe. I would like to find the cause of this before
> transmitting the long WSPOR-15 periods.
> I just woke up and sent the rest of my overnight spots to WSPRnet:
> DK7FC and DF6NM.
> 73,
> Paul
--
Best regards,
Chris mailto:[email protected]
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