The AM Forum

Let's post some PW rig pics and schematics.  What have you been using on the PW Net lately?  Any older rigs from the past?

I'll start by posting my own PW rig.  I've used it on the original PW Net in 1996 and now on the new PW Net for the last month.

This is a fully self-contained rig - a single class C 6AQ5 power oscillator final - series modulated by another 6AQ5 with power supply. It usually does about 2 watts carrier with an easy 20 watts pep. Huge audio peaks available. At 5 watts out it will do about 110% positive.  Diodes are selected to set the carrier vs: audio level.  It has a VXO, variable xtal oscillator built in that will pull xtals up or down about 3kc. This way I can cover 3869 -3892 continuosly with a handful of xtals. It runs on 160 - 20M. It will run CW, but with a slight chirp... it's a single stage TX...

The 6KE8 pentode/triode audio preamp could be substituted with a more common minature tube. I just designed it using what I had lying around at the time. As you can see in pic #3, I made a lot of changes and mods underneath over the 15 years. Our rigs look so good when we first wire them but it's downhill after that... :-)

Notice the built in power supply and Variac that will set the rig anywhere from 250 mW to 5 watts carrier out.

It's a very simple design since the only RF tube is a power oscillator. When tapped into the second audio stage, it takes about 1 volt of audio to drive the three audio stages to full output. Otherwise, the first stage will accept a low level mic input.  Since there is no mod iron (series modulated) it sweeps very cleanly from 10hz to 15khz+.  Fun PW rig!

Schematic:

http://www.amwindow.org/tech/htm/series.htm

T

I like it Tom.  Looking at the top of the chassis, I wouldn't have thought it required so much wiring underneath though.  I need to start a mid-south PW net here.  First, I need to finish that Retro-75 I guess. 

You guys are having WAY too much fun!

Here's my version of the "Low Power Phone/CW Rig for 160" taken from the
1969 ARRL Handbook. The tank coil in this picture was for 160 and 80, but has
since been changed to an air-core coil for 80 and 40. It uses two 6T9 compactrons,
and has an output of 7w CW and 6w phone. The mod xfmr is from a junked console
radio found on the curb-the audio section ran p-p 6F6s.

Audio reports I've received from it always compared it to an unmodified Ranger-
punchy communications audio. It has no trouble achieving 100% modulation.
It's a fun little low-profile radio. It's powered with an HP-23A supply.

Tom,

Nice PW rig, but I would have sprung for the increase cost and put four screws in those SO-239's, instead of just two.

Just my thoughts,

Fred

That only matters if your are running more than 50 Watts.

Steve / K9QS -

Very nice looking PW rig!   That's how they SHOULD look in my mind's eye.. ;D

Do you have the circuit available to scan and post here?   How is it modulated?



T

Punchy audio is probably a requirement to get good results with QRP AM stuff, that's how I've been looking at it.  I'm essentially using a telephone (land line) audio performance as a gauge.

I may have posted this before, but here is one of my QRP rigs that has been a great little transmitter. The rig shown below is a 6AG7 - 6L6 transmitter with a companion pr 6L6 Heising modulator. This rig appeared several years ago in my article in Electric Radio Magazine entitled "Long Live the 6L6" . It has been a super performer and I have worked many stations on AM on 75 and 40 meters with it, running only about 15 watts (max) output. Yikes, that might be in the QRO category  ;D. Lots of Fun!!

Ed, great job with your breadboard rig.  What is that round thing in front of the copper tubing coil?  Sorry, I didn't mean to post this previously on your post about your rig!  

73,  Jack, W9GT

These are all VERY cool!

I am inspired.

Rich

Great looking at the home built QRP rigs!  Fantastic construction jobs!  Jack, what issue in ER was your rig in?
Joe, W3GMS

Tnx Joe.  "Long Live the 6L6" was in ER Sept '94 and I think there was an addendum to the schematic in Oct '94.  I made a couple of subsequent modifications, but I didn't publish them.  I will have to dig out the schematics.  The guy who put out the cake pan kits (EYE?) was apparently inspired by my article.  I remember receiving some correspondence from him back then.

73,  Jack, W9GT

Beautiful job, Jack.  Very neat looking rig. Do you have a shot of the wiring underneath?


You've motivated me to make up some typed labels for my PW rig. The old marker writing is 15 years old and looks it...  ;)


Yep, these rigs are sometimes more fun than a big rig. About thirty-five different ones were built back in 1996 in a three month span.  Nowadays, I'll bet we see more solid state versions.   The Tron said he talked with a guy who owned a 75M Retro. The guy had made some custom audio mods and Tron said it was heavily modulated and sounded great. I understand the mods were posted on a Retro website somewhere.  Does anyone know about the site and could post them here?


T

Aw gee, tnx Tom!  I will have to see if I can find the old pictures, or just take some new ones.  It looks pretty good underneath, as well.  (Even if I do say so myself)  ;D  FB on the Retro 75!  Mine works great stock, but I suppose it could use more audio punch.  The discussion about those mods has been on this board.  I think it was authored by WD5JKO.  I've had my Retro for about a year and had lots of fun with it.  I have even managed to make several Retro-to-Retro QSOs.  Maybe not as fun as "strapping" with da big boys, but neat anyway.  I like a challenge.

73,  Jack, W9GT

Jack,
I pulled the articles out of ER.  If you could post an updated schematic that would be great.  A friend of is thinking about building a beginners type 2 tube transmitter and the one you did looks like it would fit the bill very nicely for him.  Every time I pull those old ER issues off the shelf its like a great re-acquaintance! A great OT receiver article by Bob Dennison, W2HBE (sk).  Bob authored some great articles in both ER and the AWA OTB now referred to as the Journal.  In addition, Paul WA3VJB authored a great article about the AM station at the Gaithersburg Hamfest.  When I was working for a living all I had time to do was to "skim" my magazines.  Its great to have the time to go back and read the article in their entirety!
Joe, W3GMS 

Here's my screen-modulated ARC-5, about 10W carrier (a simple speech amp/6AQ5 based on early '60's ARRL Handbook examples; plate trans is a 480V control transformer "backwards" for about 600V B+ and the large filament trans is for enough 28 VDC to run the transmitter filaments as well as the matching receiver with original dynamotor)... How do you like my snazzy PTT switch?  ;D

I used it to make one contact to Belleville, IL (about 200 miles) and promptly sold the receiver (they are "cute" but waaaay too broad for today's 75m). That was several years ago... need to get back on AM someday  8)

OK, here are a few more shots of my little 6L6 rig.  The first picture is the modulator chassis. The second the transmitter itself with power supply. The 5U4 was replaced with a plug-in solid state replacement.

73,  Jack, W9GT

More pics of the 6L6 rig.


73, Jack, W9GT

Nice!

Here is my AC-DC version of the 1936 Frank Jones pushpull oscillator xmtr.  Maybe I should build a modulator on a 2nd chassis.  I could Heising mod it with another 50L6. This rig puts out about 3 watts on 40 M CW.  Didn't modulated oscillators used to be illegal below 30 MHz?  Maybe drive this with a VFO?

(Yes! I use an isolation transformer with this rig.)

73, Jack, W9GT

Love seeing all the photos of all of this home brew gear!

My skill level and time commitment is not quite there, so keep it coming and us those of us less fortunate to live our radio lives vicariously through your creations.

This is the closest I have come...so far...

Nice stuff Bruce!  I like those little novice transmitters with the wood slat chassis.  I remember seeing those in the old Handbooks.  There was a guy selling kits to build them at the Fort Wayne Hamfest.

Well, I'll see your wooden slat transmitters and raise you my reproduction of the Frank Jones 1936 breadboard push-pull 6A6 oscillator rig...it does an honest 5 or 6 watts output on 40 CW.  Check out the cloth wiring and cloth line cord with the old-style plug.  I really need to build a matching regen receiver of the same vintage. 

73,  Jack, W9GT

and one more shot, now I've probably bored everyone because I think I might have posted this before.  Anyway....would like to see some more home brew creations from some others here.

73,  Jack, W9GT

I don't post here much, but here is my TNT. It will modulate if I bang on the table. Does that count? ;D But seriously I think a PA stage and a heising modulator for this would be cool.

Nice looking stuff all. There's nothing like some good ol' homebrewing to bring out the spirit of radio.

That's a nice little TNT, Chris. I've got the bits in a box somewhere to build one, but I think it's still in storage up north. Another one of those round tuits that needs getting to.

Jack -very cool, and NOT boring, keep them coming...reminds me of a good story.

About 10 years ago, back when I lived in Buffalo, and was KG2IC, I started building that very Frank C. Jones TX.
A very gracious lady ham, Roberta Baramore, anyone remember her, sent me the wood for it, for I had no wood working tools at that time.
I got the project about 2/3s done, had started it in the middle of my move from NY to Maine, so the TX went into storage for 10 years, like much of my other radio gear..until September of last year. When the items finally got moved up here this year, it was like Christmas, unpacking boxes which had been wrapped up for the better part of a decade. In the midst of my unpacking, I found I found the little TX and let out a whoop of joy.
So its back in the project line up, the longest running project I've ever had. Never did find out what happened to Roberta, seems she had dropped off the glow bugs list and that was it...hope all is well with her. Larry and I were talking about her last fall, think she used the name "Bobbi" rather than Roberta. In any case, would be neat to contact her and let her know the outcome.

Chris - Frequency modulation is still modulation, great looking rig!
Nice job on those copper coils, there is a real art to do those well.
My friend John Rollins W1FPZ shared that with me a short time before he became a silent key, he was the master of that.

-Bruce

Thanks for the nice comments.

These rigs are really handsome; they all would make good desktop-
sized pix:) Jack, I've heard your 6L6 rig-it sounds great on the '129X.

Especially like the VXO on Tom K1JJ's rig- I've found the lack of it on mine confining,
especially on CW.

The 6T9 is a lower-power triode and power pentode in one package. One tube serves as the
driver/modulator, while the other one serves as a xtal oscillator/RF PA.
The driver triode in the modulator tube is driven by a 12AT7 mic preamp.
It's plate modulated, using a take-out p-p 6F6 audio xfmr, with one set of windings left unused.

Sorry, I don't have a scanned schematic. If I find one, I'll post it here.
It's on pages 193-196 of the 1969 Handbook.

Steve

Here is a shot of the 6SK7 Suppressor Grid modulated Oscillator with 1.5 Watts out next to the soon to be finished 807 Linear.

Mike WU2D

Well the 807 linear works! I just need to lash it to a decent power supply. I will post the schematic. I set the 50 uA Radio shack meter to be 200 mA on the Plate and 5 mA on the grid using a DPDT SW and a couple of shunts.

Mike WU2D

Bruce,

I'm going to be winding some copper tubing coils in the fairly near future. I've never done that before, so any tips on the art that you'd care to share would be much appreciated.

ldb
K5WLF

Nice set up, Mike.

The 807 linear idea is too cool.  A quick 10 watts QRO when needed for those "special" moments... ;D

Maybe you can add a linear-in/ linear-out relay to demonstrate it's raw power on the next PW Net.

T

Happy to do so, I've got to say that the Zen Master of that art was my friend John Rollins W1FPZ, now a SK.

However, all is not lost, right before his passing W1GIG sat down with John at his home and he shared his radio tricks and treats with us. I think the coil winding story is on Part 2 about the 3:30 minute/second mark, along with the story of how a Navy helicopter became ensnared in John's massive dipole antenna!

http://www.w1ujr.net/w1fpz.htm

http://www.youtube.com/watch?v=9qG6i8uvPhY&feature=player_embedded

Bruce,

What a wonderful video about a remarkable man. His bio reads almost like an adventure novel. I watched all three parts of the video and enjoyed every minute. You and Tim are to be complimented for making the video to preserve a part of our amateur radio history. It's something that should be done more often with other pioneers of our hobby before we lose them.

Excellent coil winding techniques. I believe that now I'll be able to make a coil without creating a pile of copper scrap. And at today's copper prices, that's really handy.

Thanks for posting that, Bruce. And, as a fellow videographer, let me say "Great camera and editing work".

73,
ldb
K5WLF

[/quote]

 Kind of like lug nuts on a 1/2 ton pickup carrying only 1/4 ton. :) The good ol boys regularly run 3 or 4 out of the customary 5.

Hi again Idb,

Glad you enjoyed it, we were most fortunate to record it as John had been in failing health for some time.
Little did we know that next month he'd be a SK.
As you say, he lived quite a life, sailor, aircraft pilot, ham, geologist, marvelous home brewer and restorer, and a real gentleman.
Perhaps even more significantly he was know for his generosity to others, he was always building and giving away rigs to get and keep folks on the air, even Bill Orr W6SAI send him a rig to restore, and later keep.

I was privileged to be be the recipient of John's largess when he gifted me the rig he built for Marshall W2ER -->> http://www.w1ujr.net/w1fpz_photo_essay.htm

Later, I came to own the former Bill Orr Gross transmitter -->> http://www.w1ujr.net/restore_gross_cb-25.htm

Both won blue ribbons at the AWA Conference, a tribute to John's work more than my restoration efforts.

Thanks for the kind words about my friend, really now through the video, all of our friend,glad that you too could share some of his life.

-Bruce


 

For my next act.....I'm planning a little PW rig using 954 and 955 acorn tubes.  Anyone else tried this?  I have a number of these little tubes that need to be used for something worthwhile, not just take up shelf space.

73,  Jack, W9GT

I remember Bobbi and recall she kind of dropped out of sight on the Boatanchors mailing list as well.  Is that list still active?