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PostPosted: Wed Mar 13, 2013 4:00 pm 
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Location: holleygrove,wv
http://s1280.beta.photobucket.com/user/ ... 20Twinplex
Just completed my 3A5 Twinplex receiver last night. Regeneration is smooth through both the 10 turn pot controlling the voltage and the varicap on the tickler coil. No noise from the pot when adjusting. The volume control works great and does not affect regeneration. There is plenty of volume. On weak signals you only have to go half volume or a little more. The headphone jack is isolated from frame ground. I'm using Western Electric 600 ohm phones like the telephone operators used to use. The main cap is reduced through an National Velvet Vernier. Although just a 5 to 1 reduction tuning isn't real critical as I'm using a band spread method and only tuning about 500 Kilohertz end to end. The antenna tuning varicap is 3 to 30 pf and isolated from frame ground. I'm using a 300 foot loop about 25 feet in the air and the little varicap does a fine job of not loading the tank. I'm using Millen miniature 4 prong plug in coils. I only have the 80 meter coil wound right now so I guess you could say I'm not really done...I based a lot of this radio on the 1934 Short Wave Manual Twinplex , page 49, that uses a ''53" Tube. I think this might be the oldest Twinplex design. Somebody correct me if I'm wrong. Listening to it this morning before going to work this Twinplex design really Amaze's me. It tunes smoothly, regeneration is smooth and has plenty of volume, enough to hurt your ears o strong signals. So very few Parts. Mr. J.A. Worchester , Jr. came up with a winner. Low parts count great performance! Pictures and schematic both at link. :D

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PostPosted: Wed Mar 13, 2013 4:37 pm 
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Location: Beaver Dams, NY
Congrats on the very nice job building that receiver! I'm sure it works as nice as it looks.

Dave

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PostPosted: Wed Mar 13, 2013 4:43 pm 
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Nice-looking radio, Tim! I recognized the cabinet you re-purposed right away. 8) http://www.prismnet.com/~nielw/nat_list/vfo62.htm

73,

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PostPosted: Wed Mar 13, 2013 5:05 pm 
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Location: holleygrove,wv
Thanks Dave and Kr1s! Yea It's a National VFO 62. I got it at a Flea Market in VERY bad shape. The top of the case was busted all to pieces and the guts dirty and corroded. I had to clean the inside and out with a Brillo Pad. I glued and patched the top front but rest of the pieces was gone. So I cut it as square as I could and made a removable panel to cover the hole. Which worked out since I needed to access the plug in coils anyway. I had lots of fun making it but lost a little sleep staying up to late working on it. Lol

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PostPosted: Wed Mar 13, 2013 5:37 pm 
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Tim,

Wow! Nice set!

Thanks for sharing that!

Please keep us posted. . .

Mike

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PostPosted: Wed Mar 13, 2013 5:49 pm 
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Location: holleygrove,wv
Thanks Mike. I got the idea of printing my dial from your site. Great site and products I've bought some parts from you in the past. Great Service!

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PostPosted: Wed Mar 13, 2013 9:11 pm 
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Location: Maryland
"I'm using a 300 foot loop about 25 feet in the air ...."

Is that diameter, circumference or length of wire in the loop?


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PostPosted: Wed Mar 13, 2013 9:12 pm 
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Location: Western Washington State
Tim,

I like everything about that set. . .Low B+, few parts, tight control of regen, tuning, and volume. . .Simplicity, and good looks. . .All that is, what a neat regen is to me.

Thanks for the Kudos! Remember, my website is, what it is, due to Dave Schmarder. . .He's a real genius, there.

Please keep us posted, and I'd like to build that set, myself :-)

Also, like that cabinet, as Jim pointed out.

Thanks for posting that. . .

Mike

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PostPosted: Wed Mar 13, 2013 9:29 pm 
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Location: Australia
Beautiful job.

Q. The 3A5 is often accused of being microphonic.
Have you found this to be the case?

Thanks.

.....................................


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PostPosted: Thu Mar 14, 2013 2:19 am 
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Location: Corona, CA
ZP,

Congrats. That is one nice set! Classic design, great layout, nice parts, etc...If that doesn't inspire someone to build a regen, I don't know what will. Love the map, too. I've wanted to do that myself, if I ever manage to get beyond the breadboard stage.

I've been getting the itch to build another regen. Making the final decision on what tube(s) to use. Seeing your project is inspiring me to get in gear.

George


Last edited by gramlow on Thu Mar 14, 2013 1:04 pm, edited 1 time in total.

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PostPosted: Thu Mar 14, 2013 10:12 am 
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Great looking project, OM ! Looks like a winner.


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PostPosted: Thu Mar 14, 2013 1:15 pm 
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Location: holleygrove,wv
Thanks for all the kind comments. And thanks to Dave for having this great Forum and his Makearadio Site. He has so many plans I can't decide which one I want to make. I've got it narrowed down to a couple though. The hikers 49, The #52 miller clone, And the medium wave loop using the 6418 pentode.
Richard,..The ant. is 300 foot of wire strung from tree to tree through insulators in somewhat of a circle. Both leads come to the radio. Along with a ground wire that gives multiple combinations to play with. It works great on my Crystal Sets too. Golf,..The 3A5 can be microphonic. To try to eliminate this I used large #12 solid (stiff) wire to wire a lot of this set. Everything is mounted solid and tight. nothing to vibrate. A spring loaded tube shield helps.
I also put felt feet on the bottom of the case. Now..while tuning through the radio sometimes it will get microphnic, but all you have to do to eliminate this is re-adjust the the two regen controls and the microphonics go away. The benefit of being able to vary the voltage and tune the reactance comes In handy for multiple things. Eliminating the microphonics tuning in cw and ssb very precisely. Also as a Rf gain on strong signals. Tuning through the 80 meter band yesterday evening about 5:00 a counted over 50 ssb stations multiple cw signals and am'ers on two different places on the dial. The north country(Canada) was booming in! I heard some French language ssb. I figured that coming in from the French speaking Canadians.

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PostPosted: Thu Mar 14, 2013 4:43 pm 
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Tim,

See PM. . .Hope these work for you. . .

Mike

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PostPosted: Thu Mar 14, 2013 11:10 pm 
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Really nicely crafted! Thanks for sharing.


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PostPosted: Fri Mar 15, 2013 1:09 am 
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Location: holleygrove,wv
Added new schematic pic to photobucket kindly redrawn by Mike Peebles. Thanks Mike!!

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