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Author Topic: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build  (Read 76127 times)

Posts: 3908

« Reply #180 on: August 09, 2014, 06:17:57 PM »

For Jim/N2EY.

Remember that in the old design, the area around the power supply was heating up enough so that after a couple of hours in standby mode, the top of the chassis was hot?

That's not longer the case. With the voltage-divider circuit in place, that area of the chassis after two hours of "burn in" is (by touch) the same temperature as the rest of the chassis.

That's great!

Sometimes a small change can have big results.

W1TS would be proud.

73 de Jim, N2EY

Posts: 15

« Reply #181 on: August 16, 2014, 05:44:33 PM »

Martin, and Jim, Allison and others who posted on this thread: I've been getting together parts to build the transmitter that appeared in the 1968 ARRL Handbook, "The Novice Special", the long skinny version. I first built it in 1972 when my wife got her Novice license, and I've been planning to do it again for a few years now. The rig is virtually identical; it is the one that uses a #47 bulb for metering the PA current. Martin, you mentioned that you don't have the handbooks for '68 and beyond that had the design, but it's the same, with even lower budget in mind.

I've got the great info that is provided in this thread on testing and troubleshooting, especially on the issue of getting the B+ and screen voltages down. Great info, Jim, and also Allison, my good friend. Oh, and those wonderful photos, too!

I'll get a proper 1mA meter and build it Martin's way, and get ready for the Classic Exchange with it. Thanks again, and 73!
Ted, KX4OM

Posts: 812

« Reply #182 on: August 17, 2014, 03:27:01 AM »

Martin, and Jim, Allison and others who posted on this thread: I've been getting together parts to build the transmitter that appeared in the 1968 ARRL Handbook, "The Novice Special", the long skinny version.

Ted, that's great! I look forward to QSOs between the "twins"... W7UUU/Dave has also built a version of that transmitter. So we've got Massachusetts, Washington state and Georgia.

Can you confirm it's the 1968 handbook? I do have that one (paperback version), and the "beginner's transmitter" is all solid-state, using a couple of 2N2102's.

I remember seeing a version of "my" transmitter in a later handbook (or another ARRL publication) with an essentially identical circuit but built in a cabinet rather than an open chassis.

A couple of days ago I bought a copy of the 1974 edition of "How to Become a Radio Amateur" -- which apparently was the last one, after being continuously published since the 1930s. In that final edition, the transmitter is still a simple tube MOPA but it uses a Compactron tube so that both the oscillator and the amplifier are in the same tube. That one would be fun to build too, if one could find the tube!

The solid-state receiver in that book looks fun, too. Among other things, you are taught how to etch your own PCBs using very simple methods such as covering the board with masking tape in the right spots and then dunking it in the solution.

(I am also very slowly gathering the parts for a "museum replica" of the novice station from HTBARA, 1956 edition. Looks like I've finally scored the National dial used in the regenerative receiver, which was the big challenge. The other parts are easier to find. That one's very neat: it uses a single power supply for both the transmitter and receiver. Also, it appears to have been built by thousands of hams and apparently turns up at hamfests from time to time.)

August has been tough (but nice) because of heavy family commitments. But within the next few weeks I'll be getting that antenna hoisted and going key-down for my first QSO: that is my top ham radio priority!

73 de Martin, KB1WSY
« Last Edit: August 17, 2014, 03:40:48 AM by KB1WSY » Logged

Posts: 809

« Reply #183 on: August 17, 2014, 05:59:10 AM »

I don't have a 1968 but the 1970 copy has that.  Its a 6C4/5763 combo.

The 1956 has a nice 6L6 novice transmitter.


Posts: 15

« Reply #184 on: August 17, 2014, 12:04:00 PM »

Hi Martin and Allison,
My bad. It is the 1970 ARRL Handbook (blue cover). A friend gave it to me in 1972 when we were in the Navy. The article has all of my margin notes from the construction in the book (there was already had a lot of scribbling and underlining in ink in the theory sections when I got it.) I have the 1968 (green cover) as well, which I've doing some studying with recently, but the cover is now so worn it looks like it was sandpapered, and the binding is paper packing tape. I momentarily got confused about the years just checking on the bookshelf yesterday.

I have most of the major parts after I disassembled my original "Novice Special about 25 years ago, including the 2015 coil, the square padder load capacitor, the power transformer and a few 6C4s and 5763s.

I also have a fair replica of the very distinctive-looking "An Inexpensive 75-Watt Transmitter" with plug in coils on a large chassis. It's in the '67 Handbook and several others. I got it on eBay about 15 years ago, but the last time I tried it a couple of years ago, something in the power supply blew with a loud bang when I turned it on. Probably the rectifier(s), due to the old paper electrolytics. I stuck it back in a box and declared it a "back burner" project for some future date. That rig has the 1625 PA tube mounted horizontally under the chassis. The meter is propped up on top of the front of the chassis, and the plug-in coils are in shield cans, giving it that distinctive loook. I'm going to fix that one up in the next few days, and then see if it will take HC-49U crystals, since they are available inexpensively for a lot of ham CW frequencies. It has a Colpitts oscillator, which might stress the crystals less than the Pierce of the 6C4/5763 transmitters we are discussing.

I've not had success with the modern crystals in tube oscillators. One of the HC-49US short versions that I got from a seller mounted in an FT-243 case blew immediately when I tried it in an HT-40 that I had at the time. Some old publications (and recommendations on this forum last year) suggest I try a 6AG7 oscillator in a configuration that has low crystal current for the HC-49 crystals. I have an endless supply of color bust crystals for 80 meters and 14.318 Mhz to experiment with. Unlike you, Martin I have a only a small set of original FT-243s. Three are from my Novice days in 1960, and unfortunately, the band segments are different now. 3725 kilohertz is inow the 80m phone band, as is my primary 40m Novice one, 7175. That was a tough frequency at night back then, as it was a Radio Moscow frequency! I have one on 7113 that I achieved by grinding and leading long ago, and another that has that as an original frequency. I think I'll attempt to grind the former up to 7122 or thereabouts.

Ted, KX4OM

Posts: 812

« Reply #185 on: August 17, 2014, 02:04:25 PM »

Unlike you, Martin I have a only a small set of original FT-243s.

Ted, for what it's worth, Bryan Carling/AF4K, has a selection of "original" FT-243s although he also said a few days ago that he often has only one of each value and "once they are gone, they are gone." They are pricey ($16 each for the prime 40m frequencies) which is quite a lot more than I paid for my collection, but OTOH they are getting relatively rare and that's how AF4K makes a living. (I have bought various components from AF4K, including custom-ground FT-243 crystals for receiver converter circuits, and have been satisfied with his services.)

You can get more info at

Mind you, it might be more fun to grind them down yourself!

73 de Martin, KB1WSY

Posts: 85


« Reply #186 on: August 21, 2014, 12:55:16 PM »

Once again, Martin, outstanding work.  I marvel at your craftsmanship.  Good show.

73, de Nate
Bremen, KS

SKCC 6225

Posts: 35

« Reply #187 on: September 04, 2014, 09:19:56 PM »

I have really enjoyed this thread!  I've been inactive since 1994 for lots of reasons, but the bug has bitten again and I can't wait to get some wire up into the trees.  When I went QRT, I was running a 6C5-6L6 rig with a handful of 40 meter crystals and a Drake 2B, and had logged 29 states.  The xmtr was built from a Sams book, and when it didn't work, I sent the schematic to Doug DeMaw who redesigned it.  I made the mods he suggested and it worked well. Martin, FB on your rig, and since we are neighbors, I hope to work you on 40 after I get back on the air.  I love these glowbug rigs.  I've learned a lot from all the posts on this website and I am grateful to the whole eham community.  73, Greg WA2EHV  (Wellesley, MA)

Posts: 812

« Reply #188 on: September 13, 2014, 03:12:40 AM »

Yesterday I finally had the crucial "antenna meeting" with my landlord and his wife. The good news is that they have no objection in principle to my putting up a decent ham antenna. However, the Devil Is In The Details.

My Plan A is an inverted-v that would be hoisted in the only viable candidate tree, which unfortunately is right in front of their 2nd-floor deck (UK = balcony) which is a fun space with a barbequeue and deck chairs. The Vee would have its apex far above their deck and about 20 feet away, horizontally, and would be built with black insulated PolyStealth wire which I explained to them would be virtually invisible. I have told them that if they don't like it, I will take it down immediately, and find another solution.

My kind landlords did not veto this idea, but they also made suggestions of their own. One of them would be to string a long-wire, configured as an inverted-L, a few feet above the ridge of the roof of our shared (three-story) house between a couple of TV-type masts. The roof ridge is about 45 feet long -- the total wire length including the drop to my shack would be about 75 feet. I'd have to use an antenna tuner, but it's something to think about if the (more optimal ?) inverted-v doesn't get approved.

It emerged from the meeting that, quite reasonably, the major objection they have to a ham antenna is a visual one. They didn't have major objections to any of the other details, including, for instance, digging a trench and tunneling under a flagstone path in the yard (UK = garden) in order to feed the coax back to my shack.

I am of course very lucky that the owner of my rented apartment is a former ham and willing to consider accommodating my hobby. The meeting ended inconclusively ... but with a mutual agreement that a decision will be made by September 22nd.

Meanwhile I have sort-of vowed not to get a haircut until I am on the air. Last haircut was in March, I think, so I am slowly approaching late-1960s levels except it's even more unruly.

Hair? What is hair? I only grow it around the sides these days.....

A few days ago I caved in and got a haircut. It was reaching early-1970s length, but at my age it just made me look like a rather seedy tramp (US = bum) rather than a groovy 1975 youth. The way the antenna negotiations are being dragged out, I had this vision of waist-length hair by the time I get on the air....

Martin, FB on your rig, and since we are neighbors, I hope to work you on 40 after I get back on the air.

I look forward to it!

73 de Martin, KB1WSY
« Last Edit: September 13, 2014, 03:24:16 AM by KB1WSY » Logged

Posts: 13448

« Reply #189 on: September 13, 2014, 03:01:43 PM »

Quote from: KB1WSY

... the total wire length including the drop to my shack would be about 75 feet. I'd have to use an antenna tuner...

If you can stretch it to 90+ ft then that is 3/4 wavelengths and should be a reasonable
match 50 - 100 ohms). Otherwise a simple L network tuner with a coil and a variable
capacitor will do the job.  I'm suet we can make it look of the right vintage...

You will, however, need a suitable ground system to feed it against.

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