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Hi Jeff,<BR>
<BR>
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:<BR>
<BR>
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. <BR>
<BR>
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.<BR>
<BR>
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. <BR>
<BR>
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. <BR>
<BR>
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.<BR>
<BR>
The SB-104A T/R relay biases the and routes RF from the driver stage through the PA - interfacing that seems easy enough.<BR>
<BR>
I don't know how the PA will perform above 30mhz.<BR>
<BR>
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.<BR>
<BR>
73,<BR>
Dan<BR>
<BR><BR>> Date: Sat, 3 Jan 2009 22:53:11 -0500<BR>> From: jkelly@bellatlantic.net<BR>> To: hpsdr@lists.hpsdr.org<BR>> Subject: [hpsdr] SB104A Power Amp<BR>> <BR>> ***** High Performance Software Defined Radio Discussion List *****<BR>> <BR>> I am intriqued by the idea of using an amp module from an older rig<BR>> in storage in the shack for a HPSDR power amp.<BR>> <BR>> I have a working SB-104a laying around and taking a quick look at the boards<BR>> it looks like it might work out.<BR>> <BR>> Here is a top view photo:<BR>> http://mysite.verizon.net/jkelly/ham/SB104-3.jpg<BR>> <BR>> This is a little out of my league but would appreciate any comments on<BR>> whether this could work with Penny and any ideas to get started.<BR>> <BR>> thanks,<BR>> <BR>> Jeff<BR>> KT2K<BR>> <BR>> _______________________________________________<BR>> HPSDR Discussion List<BR>> To post msg: hpsdr@hpsdr.org<BR>> Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org<BR>> HPSDR web page: http://hpsdr.org<BR>> Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/<BR><BR></body>
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