[600MRG] 600MRG Digest, Vol 81, Issue 4

[Dave Riley]

Hey! Paul,

Don't give up the ship... Do you have a shelf for unfinished projects??
Park it and do something more immediate... I'm averaging 4 projects at a 
time so if one fails, big deal...

There are lots of surplus MICA caps from .1 - .0005

Let me see if I can dig up the diagram for VE1HF PA... It is VERY stable 
and sine wavey...

It is so over built that it just doesn't quit on it's own but only when 
I cause it...:-)
Two HF parasitic R/C nets from the drains to ground keep it as an 
amplifier instead of an oscillator....

I use a pair of IFRP450s and they really are hard to destroy... LOTs of 
headroom... 2 bux each...

If I turn up the drive it shows 190 watts out but I don't know for how 
long so am happy with 35-50 watts continuous and they only take a few 
milliwatts to drive...

For 1W erp I use the output of the transverter direct to loop and then 
add the IRFs for 50W out to cause 5W erp...

Also am using a different approach to see real power... I tap the 50ohm 
line out coax with a resistive voltage divider, then to a diode, 
variable resistor and one last bypass cap.. I calibrate the DC trace on 
the Scope to indicate 10V RMS per CM... Set the zero value down the 
bottom on the trace and add drive till the DC line comes up to the 50V 
rms value ( 5cm ), then easy to square that number divided by 50 to 
indirectly arrive at power that is close to within a DB anyway...
Besides 50V RMS in 50 ohms = 50 Watts, a real handy reference...

I'll get back...   DaveR aa1a

>     1. WIMA capacitors (N1BUG)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 4 Jan 2018 11:51:42 -0500
> From: N1BUG <paul at n1bug.com>
> To: 600 / 630 Meter Group <600mrg at w7ekb.com>
> Subject: [600MRG] WIMA capacitors
> Message-ID: <23061cd5-b433-413f-cfc0-357e946f1d95 at n1bug.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I had one night of glory before my amplifier decided to act up
> again. I spent an afternoon building the thing and now have close to
> 200 hours into trying to make it work. I'm calling it a lost cause
> at this point. Into the dead project heap with it! The bear of it
> is, I can't confirm positively the amplifier is the problem and not
> some other gremlin in my station. Short of trying a different
> amplifier I have no way to determine that.
>
> Anyway, at some point I will want to try again with a more well
> proven design. I was looking at the (modified) GW3UEP 100W class E
> amplifier. I have all the parts except capacitors, but the specified
> WIMA FKP2 capacitors appear to be unavailable. I can't afford silver
> micas in those values!
>
> So I went looking for alternatives. The WIMA FKP1 series is readily
> available in the proper values and voltage ratings, but I am not
> sure they can be successfully substituted in this application. Also
> they are not available in any tighter tolerance than 5%.
>
> Kemet offers an extensive line of pulse rated polypropelene caps,
> but they are so much cheaper I assume they are not appropriate here?
>
> Any suggestions?
>
> 73,
> Paul N1BUG
>
>
>
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> End of 600MRG Digest, Vol 81, Issue 4
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