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Part of the fun or some would say "The Madness of Amateur radio", is the Homebrewing of circuits that create something useful we can use for portable or emergency communications. . When I
get the urge to brew, I don't go shopping for Hops and Barley, noooo... I start gathering circuit ideas from the ARRL HANDBOOK FOR RADIO COMMUNICATIONS, Qrp Classics
"The Best QRP Projects from QST and the ARRL Handbook" and Experimental Methods in RF Design
by Wes Hayward (W7ZOI), Rick Campbell, KK7B, and Bob Larkin (W7PUA). If you are not careful, you could learn something and pick up some habits.. This page is one of my latest Ham adventures titled the 30 mtr CW Xcvr. I'm thinking of a CW Xcvr that covers the 30 meter band using nothing but junk box parts, Manhattan circles and squares, and some combo circuits from masters and then whella -- a work of art.. Remember beauty is in the eye of the beholder... UPDATED 12/6/08 -- Just about done -- link to it here |
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Yea See, What we have heeeerre is a Failure to Communicate... Okay, reading the good stuff mentioned above, it's time for action. I'm busting a move by
grabbing some radio knowledge and pulling on some past experience into something that will work and communicates on 30 Mtrs. I'm thinking a simple pierce oscillator.. 2n3906 or 2n2222A and
maybe VXO crystal control with maybe 5-10 kHz swing, and final amp that brings the levels up to about ~160mw.. a 2n2222A should do it. Then when I want to increase my chances of contacting
someone, maybe a "Power Amp" using a 2n3866 or 2n5109 with a heat sink... giving me close to 1 watt out! Yea, that's the ticket... |
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Starting with the oscillator and one of those nifty qrp crystals from NorCal Club, I put it down on copper. She sings into into my monitoring receiver. Adding a
Variable cap around the crystal gives me some frequency movement. Now, I add the 2n2222a amp to generate a whopping 160mw out. Hey, this looks similar to the tin tuna circuit.... I
know the basic values for the tank circuit, so I use variable caps to fine tune and adjust the output match on the scope.. Looks clean... let's proceed. I found a 2N5109 in my junk box... and
thought this baby would do the job... And hey it's rated in the HF range and above at 11dB gain for about 2.5 watts max... bingo... Couple to the 160mw unit to the base with a .1 uf cap and
a low value resistor from the base to ground to get rid of any parasitic oscillations, and your in business. Don't forget a Nice output tank circuit to match to 50 ohm load and keep
everything clean. Oh did I mention a heat sink... Don't forget a dab of heat transfer paste and your favorite TO-39 top hat! Scope shows nice sine wave at 1
watt! Mission accomplished... |
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Hey, I still have room on my board, I might as well make a receiver to go with it... There are a few 30mtr receivers out there, but not a huge selection... First, signals
on 30 are usually <=100 watts so something sensitive but yet selective. hmmmm... That Improved Neophyte I built for 40mtrs worked well... I'll barrow some of its
finer points and merge it with my junk box scheme... Here you will see in the lower left corner the SA602 circuit with oscillator running at 10 Mhz. So far so good.. I'm using the 2n2222A for an
audio preamp. Not the optimal choice, but I have quantity of these little suckers.. |
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That's it for now, my XYL has other things for me to do... go figure...yes honey...88's Until later... QRT... de KD0ZW AR SK CL |
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