Posted by
John Ragle on
Jun 25, 2011; 10:14am
URL: http://elecraft.85.s1.nabble.com/Boots-for-the-XG3-tp6514422.html
A few days back I inquired of the list if anyone knew of a small
post-amp that would prefilter the XG3 square wave and give it about 30
dB boost. There were no answers. The problem seems to be that most QRP
or QRPp amps already require a few tenths of a watt input, and the 1 mW
from the XG3 is just too tiny...
I have been specifically thinking about using the XG3 (in its spare
time) as a 6 meter beacon. Just hooking it up to a "resonant" antenna is
not (IMHO) legal, since antennas (think center-fed half wave doublets)
do not discriminate against ODD harmonics. FCC requires better...see
§97.307 Emission standards, section (e).
I have been thinking this over, and it looks like the best answer is to
build around a 20 dB gain block running in to a power module, such as
the MAR-6 gain block into a M57735 power module. The output from the XG3
would need to be low-passed before the gain block, since the usual gain
blocks are quite wide band (e.g. DC-3 GHz, etc.).
HOWEVER, a glance at the manual for the XV series transverters already
shows a transmit path designed and ready, in the schematic for the XV50.
Aside from ~dozen SMD caps in the filtering (not needed!) connecting the
mixer to the SGA7489 gain block, the needed component list is rather
short, about 26 parts, most of which are mundane. I asked Wayne if
Elecraft would bag up these parts and sell them to me as a partial kit,
and his response was more or less positive, but he requested that I poll
the list to see if there is any other interest:
-----> A partial kit, no enclosure or circuit board, to assemble a 6
meter post-amp for the XG3 that would produce 1-5 watts. <-----
Note: the SGA7489 gain block is obsolete but the device remains in the
supply chain.
Note: the RA30H0608M power module is designed to put out 30 watts in the
68-88 MHz range. To drive it to this power level from the XG3 might
require cascading two gain blocks. A substitute part is the M57735
mentioned above, designed for 25 watts at 50-54 MHz.
I think that a post amp built "ugly style" around these ideas would fit
into an Altoids tin. The only hitch is proper heat-sinking of the power
module. The layout used for the XV50 takes care of the biasing.
*****
So, I am asking the list: "Is there any interest out there amongst XG3
owners in having Elecraft bag up a partial kit as outlined above?"
*****
This note is also going directly to Eric at Elecraft, who holds the
reins for manufacturing...
John Ragle -- W1ZI
P.S. The schematics for the XV50 is included in my manuals for my XV144,
which BTW works wonderfully...
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