[HBQRP] Fwd: [QRP-L] 5W HF PA kit with raised cosine key shaping

[Sam A Seikaly]

I ha.ve a projector but I will not bje able to make it.  I had eye surgery yesterday. And you kow the rest




Sent from Samsung tablet


-------- Original message --------
From: Ray McNally <raymcn at gmail.com> 
Date: 01/12/2017  6:23 AM  (GMT-06:00) 
To: hbqrp <hbqrp at mailman.qth.net>, Steve Carter <kd0pxx at gmail.com> 
Subject: [HBQRP] Fwd: [QRP-L] 5W HF PA kit with raised cosine key shaping 

Found this in the email this morning.  Looks like more kits to build this
winter...

Also, this saturday, I will plan on a presentation on simple printed
circuit layout.  If someone has access to a projector with vga input, or a
larger lcd monitor, it will be easier for the group to see.

See y'all this saturday.

73,
Ray - N5SEZ
---------- Forwarded message ----------
From: "Hans Summers" <hans.summers at gmail.com>
Date: Jan 12, 2017 1:39 AM
Subject: [QRP-L] 5W HF PA kit with raised cosine key shaping
To: <qrp-l at mailman.qth.net>
Cc:

Hi all

This may be of interest. I have produced a 5W HF PA kit,
http://qrp-labs.com/pa costing $20. This uses an IRF510 to provide about
16dB of gain. I measure 7 or 8W power output on 40, 30 and 20m. Decreasing
power above and below that. Down to 4W on 10m, and 4W on 600m band (LF),
when using 13.8V supply.

The unique feature is the discrete component power modulator with foldback
current limiting, that is set by an 8-bit Digital to Analogue Converter
(DAC), which is controlled by an 8-bit shift register 74HC595. A
microcontroller, using only three I/O signals, can load a sequence of 8-bit
numbers into the shift register, and if these numbers replicate a raised
cosine profile then you end up with a very nice raised cosine RF envelope
shape, click-free 5W CW!

If you don't want to mess with microcontroller programming, there is also
an optional key-shaping chip called "RC1" (really a programmed ATtiny84
microcontroller) which can be plugged into the 5W HF PA kit instead of the
74HC595 shift register. This RC1 chip creates the raised cosine keying
profile. All you need to supply is an RF source, and a keying signal. The
key signal is active-low, so a simple straight morse-key to ground could be
used to key it. The rise/fall time of the raised-cosine shape at key-down
and key-up can be adjusted from 2 to 113 milliseconds. 5-10ms would
typically be used.

A nice 5W CW transmitter could be made from our VFO/SigGen kit
http://qrp-labs.com/vfo - which uses an Si5351A Synthesiser, rotary encoder
tuned. That would be the RF source and feed the 5W HF PA kit. We also have
LPF kits for all bands 2200m to 6m, http://qrp-labs.com/lpfkit so one of
these could be used at the output. Or make it 6-band with the
relay-switched LPF kit http://qrp-labs.com/ultimatelpf and some more LPF
kits. Lots of possibilities there. App Note AN005
http://qrp-labs.com/appnotes describes how to use the 5W HF PA and RC1 key
shaping processor, and shows as an example the use of the VFO kit to make a
5W CW TX.

Lots of possibilities!

73 Hans G0UPL
http://qrp-labs.com
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