[hpsdr] SB104A Power Amp

[Daniel Quigley]

Hi Jeff,
 
I am working on interfacing a salvaged SB-104A PA and Penny too.  I am not a broadband RF amp expert by any means, but here is what I know so far:
 
The SB-104A  PA input impedence should be about 50 ohms. Because the SB-104A driver stage is connected directly to the antenna when in low-power mode.  So Penny should interface directly without a transformer. 
 
The SB-104A driver stage is spec'd at 1w minimum CW and SSB.  I've seen 1.5w out on my working SB-104A so levels seems compatible too.
 
The PA is probably biased AB1 - though I don't know that with certainty. The bias circuit uses a circular power 16 ohm resistor mounted under the SB-104A chassis and a hefty diode mounted to the PA heatsink. 
 
The LPF board is manually switched (from the bandswitch) and covers 80-10m. I don't know how the filter will behave on the 160m or WARC bands.   Initially I plan to use the Heath LPF board, but I plan on using Alex once that board is available. 
 
ALC is derived off of a sensor on the LPF board - and is used pretty much throughout the SB-104A TX chain; that combined with no SWR protection on the PA probably means ALC and PA protection is going to be one interface challenge.
 
The SB-104A T/R relay biases the and routes RF from the driver stage through the PA - interfacing that seems easy enough.
 
I don't know how the PA will perform above 30mhz.
 
With any luck I will have some time during the next few days to work on this more and will let you know what I find out.
 
73,
Dan
> Date: Sat, 3 Jan 2009 22:53:11 -0500> From: jkelly at bellatlantic.net> To: hpsdr at lists.hpsdr.org> Subject: [hpsdr] SB104A Power Amp> > ***** High Performance Software Defined Radio Discussion List *****> > I am intriqued by the idea of using an amp module from an older rig> in storage in the shack for a HPSDR power amp.> > I have a working SB-104a laying around and taking a quick look at the boards> it looks like it might work out.> > Here is a top view photo:> http://mysite.verizon.net/jkelly/ham/SB104-3.jpg> > This is a little out of my league but would appreciate any comments on> whether this could work with Penny and any ideas to get started.> > thanks,> > Jeff> KT2K> > _______________________________________________> HPSDR Discussion List> To post msg: hpsdr at hpsdr.org> Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org> HPSDR web page: http://hpsdr.org> Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
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