[HomeBrew] "Rockin' Fifties MOPA"

[km1h]

An octal tube socket will hold up to 2 FT243 xtals, add a switch for instant 
QSY.

Carl
KM1H
National Radio 1963-69




----- Original Message ----- 
From: "Philip Atchley" <beaconeer at sbcglobal.net>
To: <homebrew at mailman.qth.net>
Sent: Saturday, July 23, 2005 6:38 PM
Subject: [HomeBrew] "Rockin' Fifties MOPA"


> ** Please do NOT cross-post messages when posting to HOMEBREW **
>
> Hi all,
>
> Last night I started the construction of my little homebrewed "Glowbug" 
> transmitter.  After looking around the web for suitable ideas to adapt to 
> my own unit. In the "true" ham spirit (translated reads tight budget ;-) 
> the goals of this project are to use entirely recycled parts, with no 
> expenditure of funds, unless absolutely necessary.
>
> Anyway, I settled on the 10 Watt one tube design (6T9) from the 1973 ARRL 
> handbook, but substituting a 12AU7 and 6AQ5 for the tube, along with a 6X4 
> rectifier.  I first prototyped the power supply using silicon diodes for 
> the rectifiers.  The power transformer, chassis, tube sockets (even the 
> 6AQ5 and 6X4) are the same ones that was in the Eico signal tracer which 
> "donated it's organs for this project.  I expected a little higher B+ 
> voltage with silicon rectifiers, the no-load (same as Key-up) Voltage rose 
> to somewhat over 400 Volts, and it took a significant resistive load to 
> bring it down.  WAY too much for a 6AQ5 final stage.
>
> So, I decided to use the 6X4 rectifier, unloaded Voltage dropped to a more 
> reasonable level.
>
> THIS SET A NEW GOAL FOR THE PROJECT!  A transmitter based entirely on 
> circuitry and components that a ham in the late '50s could be reasonably 
> expected to build from parts secured from Junked radios (except for things 
> like an Xtal socket, meter, relay etc).  Since the late '50s also saw the 
> "birth" of Rock and Roll, and the transmitter is "rockbound" I coined the 
> name "Rockin' Fifties MOPA".
>
> But don't think that this is any "bare bones" transmitter that requires 
> external antenna relays or anything.  The design I came up with includes 
> antenna changeover via an internal 120VAC relay (So I don't need to use 
> silicon rectifiers to provide DC for a relay), "Standby", "Spot", Tune and 
> "Operate" switch (ala the Johnson Ranger) etc.
>
> Anyway, construction is well underway and I hope to test the oscillator 
> section this evening.  With only a couple "exceptions", everything in the 
> rig will be vintage, right down to the recycled fastening hardware to 
> avoid that shiny stainless look.  The tube sockets are better quality than 
> came in the Eico (military ceramic for the final).  Here are the ONLY 
> concessions to modern construction.
>
> 1.  A little bit of JB Weld was used to secure the Ceramic Xtal socket as 
> I wanted to use an existing "oblong" hole and that was the only way to 
> mount it (Don't think they had JB in the '50s).
>
> 2.  For the sake of reliability (and because I had them), a few modern 
> "yellow" Poly capacitors are used rather than paper capacitors.  But I'm 
> using ceramic disks wherever possible.
>
> 3.  Items yet to procure.  A 100mA meter and a 7040KC "rock" (I'll test it 
> higher up in the band around 7200 where I have an Xtal).  A friend brought 
> me a meter, but it's WAY too large and is rather "strange" to say the 
> least.
>
> FINALLY.  When the project is finished and I have a chance to get a friend 
> to take pictures I'll put this project up in the homebrew section of my 
> website, along with the other "projects" already there.
>
> 73 de Phil,  KO6BB
> SWL QSL GALLERY: http://photobucket.com/albums/y123/KO6BB/
> THE BEACONEER'S LAIR:    http://www.geocities.com/ko6bb/
> Merced, Central California, 37.3N  120.48W  CM97sh
>
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