The AM Forum

"Amateur Wireless Station" with headset circa 1920. Note photo of the young operator. 5x7 glass negative, George Grantham Bain Collection.

http://www.shorpy.com/node/1268?size=_original


Now speaking of strapping...

http://www.shorpy.com/files/images/33351u_1.jpg


Check the rest of the site.  Some amazing historic photos (mostly non-radio related)

http://www.shorpy.com/

Wow Don, very cool!
Esp. love that photo of the BIG transmitter.

Thanks for sharing.

-Bruce 1UJR

Headphones ya say?

Just picked up some 1938 QSTs the other day.
The May issue has the story of the ARRL pres, who was kilt dead as he touched the HV B+ wire of a high power experimental TV transmitter under the bench in his shack while wearing headphones!

Quite the story.

           _-_-

You must mean Ross Hull, quite a guy, and a very sad story indeed.
Unlike our modern TV sets, that was a high voltage AND high current, much more dangerous.

I have an old Hartley transmitter of his design, from a 1928 QST article of his.
http://www.w1ujr.net/hartley_oscillator.htm

Ross Hull wasn't the ARRL president though.  His position was something like chief  lab technician.  He never held a US ham licence because he was Australian by nationality, and at that time, non-citizens weren't allowed to hold a ham ticket.

Working along with him at ARRL HQ was Bob Parmentier.  I don't remember what callsign he held back in the 30's, but he assembled a lot of the equipment shown in pre-war QST and Handbook articles.  He built the first prototype of what became the "standard" superhet design: rf amp>mixer/oscillator>455 kc i.f.>diode detector/BFO>audio amplifier.

Later, he moved to Scottsburg, IN and worked in Louisville, KY.  His call then was W9WT.  He was one of the last holdouts on AM back in the 60's when tremendous pressure was being exerted on all hams to convert to SSB, and AM was supposed to be "dead".  He finally succumbed, after all his radio buddies went to slopbucket and he was the last AM holdout in his group.

He developed alzheimer's sometime in the mid 80's and was placed in a nursing home.  His wife let Mike W4AEE, Roger N4IBF (SK) and myself have his radio stuff - a large garage and several rooms of a vacant house filled with a 50-year collection of old gear and parts.  The local ham club people had advised her to have it all hauled to the dump because "nobody is interested in that old stuff any more". It took us two trips with a large U-haul trailer and pickup truck to move it all to Nashville, where we divvied it up.

Don, just as an aside to you,

Slab almost has that  HB W4DKE transmitter I picked up when I came down there done. Another few weeks of work and it will be on the air again. He did his usual FB OM resto job on it, looks like a million bucks.

Hi Bruce,

The 1928 Aero repro is still a work in progress. As I find stock parts, I sub them in. I am still looking for a set of dials for the front. But she works good on CW and I used it twice on the 1929 AWA Bruce Kelly contest with good effect.

Tuning TPTG transmitters up is interesting. What does one do with two tuning controls and one loading control, all of which cause the plate meter to react and the frequency to shift wildly? I was a babe when I first attempted to produce decent sounding RF on 80M.

The TPTG depends on capacitive feedback through the tube along with a phase shift. If the grid circuit and plate circuit are exactly on frequency she stops oscillating! It turned out that the best results occurred when the grid was below resonance. The other way it would work and produce power, but the chirp was horrendous!

Mike WU2D

Mike, if you need new knobs for your TGTP, guess what
they looked like and make your own. One type of mix
is naptha with a good dash of powdered sulphur. It makes
hard rubber vulcanite. Another is shellac. It can be made
red- brown with powdered rust. It`s prone to heat
warping, though. Another is to use lathed solid wood and
paint it with home- dyed, Japanese- style, in other words,
extra hard, varnish. If you`re used to soft pinewood
failures, try redwood or Irish bog wood. That stuff`ll keep
you busy for a while. Don, that station in the wonderful
Shorpy collection is wonderful to look at. The Ham who
made it must have been quite rich, because all the
required parts were bought at exactly the same time.
Please note that the heavy steel slug on the spark
coil indicates that it was a slow heavy vibrator before
the days of the rotary gap design. Also the, aluminium?
cases on the headphones makes them look like they
were made after the rest of the equipment until you
spot that the screwed on lids are an older shape and
kind; our confusion, a victim of looking at a truly hideously
expensive pair of headphones in their times.
I think a check with a 1959 CQ magazine collection
will reveal that this station design fell abruptly behind
the times with the arrival of the rotary gap transmitter
design which came in maybe 1916. Needless to say, some
of us would promptly work 160 as soon as we had 
high shined and batteried it up if we had it. Mike, my
first TGTP Morse hated crystals and worked beautifully
otherwise. Triode oscillator users have all the luck, simple
screen voltage resistance droppers, none. If one wants
to make a TGTP work on 20, 15, or 10, one puts the
antenna in the attic, fed by balanced twin lead so it
doesn`t blow in the wind, drives the grid plus, not
negative to unkey (or modulate) and uses no grid leak
circuit, that`s almost all. A frequency meter and a
frequency spotter are both required, though. 

You need to find some period components to make it authentic.  Besides the dials on the front panel, nearly all the internal components are non-period.  One of the variable caps is obviously taken from a 1940-60 vintage broadcast receiver, and the other looks like it's from a WW2 command set.  The tube socket also is not from the 1929 era.  The same goes for the mica caps and wirewound resistors.  Also, the grid coil looks like a 60's vintage B&W Miniductor or equivalent.

But you can keep an eye out for period components and change them out one at a time as you find them, and eventually end up with a rig that is indistinguishable  from one actually built in the era.

That's more or less what I did with my HF-300 rig.  It was originally a mid 30's 250 watt AM broadcast transmitter, but someone had completely gutted it and all I got was the empty cabinet and a box with maybe 30% of the original components.  I didn't even try to reproduce the original BC transmitter, but to build a plate modulated 1 kw ham transmitter of my own design, as close to the period of the original BC transmitter as possible.

When I fist got it going in about 1970, it was full of non-period and cheap "ham radio quality" components, particularly the audio transformers.  But over the years, nearly everything inside has been replaced with top-of-the-line (in its day) period broadcast quality components.  I still occasionally run into a part that I think would go better with the transmitter and swap it out with an existing one.

There would have been very few, if any, hams in 1936 who could have afforded to build the transmitter I have to-day, even though just about every part inside was available at that time.  I roughly estimate that in to-day's dollarettes, the parts to build that transmitter would have cost about $30,000 in 1936.

But of course it didn't cost me anything near that, since 90% of it is made of stuff that somebody else didn't want.

Well done Mike, I particularly favor the wooden rack construction!
Actually, anything  with wood looks great with old radios.

Where did you come across those "Aero" meters, did you have an Aero parts set?
They look great on the black painted front panel.

You mentioned the AWA '29 contest, what is the final tube?

You need the General Radio Absorption Wavemeter which I picked up at the Union Maine hamfest today!
I'll post a photo soon.

Thanks for sharing your project, hope to work you on the air with the Rollins rig.
I've got that fired up and making RF, just need to build some method of period appropiate T/R switching.


73 Bruce W1UJR

Hi Don,

You are correct on all counts. It is the circuit that is vintage - not the parts! The Areo Meters are reproductions that I did by scanning the original meter face and photoshopping it!

Here are a couple of pictures of the real deal: These pictures were sent to me by Mike Monnier W8BAC

"It is a MOPA. The design was adapted from an article in QST, July/August, 1932 and The Radio Amateurs Handbook, 10th addition, January 1933. It uses 4/#46 tubes.
 
It was built by Ronald "Bib" Flickinger W9HBN of Lanark Illinois and used on 1750 Kc between 1932 and 1934.
 
If you want to shrink the pictures and post them that's fine. I tried but I need Photoshop and don't have it loaded on this machine. Thanks"
 
Mike Monnier
W8BAC


Mike WU2D

Bruce,

The Aero should be using a 210 final modulated by a 210 Hiesing. I have not done the modulator which lives down below.

I actually am using a single 45 tube in the final with a home made 2.5VCT transformer which is actually wound on a period core.

I took third place in the 1929 this year with this TPTG rig and a MOPA. I used a MOPA on 40M with a type 27 Colpitts oscillator into a neutralized Type 45 Final. This rig was built fast and dirty on an old rack panel. Again- no period parts.

Mike WU2D

Hi Mike,

Thanks for sharing the photos.

A most interesting and clever output coupling arrangement on the '8BAC rig.
I like the sliding inductor bracket, that gives me an idea for a homebrew rig which I am working on. It was built by Stu W2AO for the AWA Contest some time back.

He did a wonderful job, but the output coupling coil was suspended inside a larger coil with a putty material. I was trying to think of a non-metallic and yet period way to allow that coil to slide, so as to alter the coupling. I had considered nylon fasteners, but nylon was not generally around in 1929. So that bracket arrangement just might do the trick!

I've really grown to appreciate the time and effort it takes to make a well constructed homebrew. When I was a new ham I used to dismiss such, but now old homebrews, and their history, hold much more interest for me than any commercial gear. A friend and I were speculating a few months back, if we would not find deeper enjoyment in the radio if we had but one homebrew station, operated on just a few bands. The classic 1920/30s novice set up. I find that I often have to remind myself, that sometimes, less is more.

(http://www.maine.gov/newsletter/dec2003/L7%20Beverage%20Ham%20station%201915%20maybe%20UMO.jpg)

Here's to vintage radio!

73 Bruce 1UJR

I know I learned more about radio when I built my rig than doing anything else.

(http://amfone.net/Amforum/gallery/71_29_04_07_12_25_36.jpg)

it took 2 years gathering parts, 3 original pre ww2 transmitters (most js construction or not desirable to restore as was) but it only took 4 or 5 weeks to build the thing. hardest part was a speech amp/ P-P 2A3 driver deck.

Nothing like homebrew.

So did I, back in 1963.  After building and re-building a QRO plate modulated rig over a period of about a year, in 1962-63, I took a spur-of-the-moment trip to the FCC examination and passed both 1st Phone and Extra, studying only a Q-A manual on the way down to the exam while my friend drove.

The rig in the photo (W8BACMOPA2.jpg) is built with period components.

Regarding the coupling, interestingly, hams generally had not figured out the balanced swinging (or rotating) link system of final amplifier coupling until sometime in 1937, even though the principles of link coupling were well known long before.  In almost all the old publications before that date, the balanced tanks illustrated used a fixed link in the centre of the coil.  Coupling was accomplished by adjusting the number of turns on the link or by using  a variable capacitor or inductor in series with the link.  Some of them actually used a coupling coil split into two sections, with each half placed near the hot ends of the balanced tank coil!  Yet it was well known that the middle of the coil was a low rf voltage point and a desirable place for the link.  Swinging links were commonly used on single-ended coils, and the variometer had been in use since the 20's but few hams had figured out that the main tank coil could be split to accommodate a variable link.

There is one rig illustrated in the 1934 ARRL handbook that uses a split tank coil with adjustable coupling coil in the middle. It was really a coupling coil and not a link, because it had about a third as many turns as the tank coil itself.  But the circuit explanation did point out that the tank coil was split so that the variable coupling coil could be place at a  voltage null in the coil. Also, an issue of R-9 magazine shows a split coil and swinging link tank circuit in a rig.  So the technology was known, but most hams had not added two plus two to get four.

There was a monthly feature in QST during the mid-30's that asked hams how they would solve a given problem.  One month the topic was just that - single control variable antenna coupling for a pushpull final amplifier.  Several entries were presented, but none of them came up with the familiar balanced coil with swinging or rotating link.  As I recall, some of the suggestions were downright bizarre, but none of the proposed solutions would have given satisfactory results.

On a related issue, as often as I have belittled the appliance operator crowd, when restoring vintage equipment, I sometimes wish the previous owner(s) had been the type who wouldn't touch the inside of a rig or even change a blown fuse.  It is very rare to find a piece of pre-WW2 ham equipment, whether homebrew or commercially built, that has not been subsequently butched by some dingbat who tried to "improve" it or "modify" it by drilling extra holes in the front panel, adding oddball switches or controls, enlarging a meter hole, replacing original parts with something totally non-functional and inappropriate, or you name it and it has been done.

One example is the vintage D-104 with the thick head and ring mount.  I have acquired several of those now, and not a single one escaped some form of severe butchering.  My best one had someone apparently use a  pair of pliers or vise grip to unscrew the part at the bottom where the wire comes out and the mic may be adapted to screw into a stand without springs (the early heads didn't plug in).  They mauled the chrome finish on that part, and actually broke it loose from the mic head, and (sloppily) resoldered it back.  Another mic, someone managed to remove one of  the fasteners that holds the metal nameplate onto the head and leave it JS danglng with an empty hole. A third one, someone completely removed that bottom piece and replaced it with one about 4 inches long to screw onto a desk stand.  The most recent one (the one I picked up on e-Pay) had the threads in one of the holes for the spring eyelets stripped out, and the front piece had been replaced with one from a later version of the mic.

Another example was the 75A-4 in which someone had attempted to remove the spinner knob and vernier tuning mechanism, using the wrong  tool (apparently an Allen driver instead of the required Bristo (spline) driver.  The holes in the tips the screws were rounded out and impossible to remove, so then they apparently attempted to grip the top of the screw with diagonal cutters to turn it, and ended up cutting it off even with the bushing, leaving behind a mangled stub that was impossible to remove without destroying the entire mechanism.  In the process the  spinner knob was broken into several pieces, and then an attempt was made to piece it back together  using epoxy.  Luckily I was able to find n.o.s. replacement parts after destroying the remains of the  original vernier mechanism in order to remove it.

I am all for modifying equipment to enhance its performance, but nearly every piece of older ham gear I have ever seen has shown at least some sign of damage from attempted repairs and/or modifications by someone who obviously didn't know what they were doing, or had absolutely no regard for the aesthetics of the equipment they were modifying, or any concern about reversibility in case the modification didn't work as planned.

Excellent site, Don.  Thanks for sharing. ;D

this is true to a fault. Some of the crap I've seen has been just nothing less than butchery. I think a lot of the damage was done post ww2 around the time the urge to go ssb hit and people trying everything they could to use that "obsolete" gear on slopbucket so they could be cheap and not have to go get new gear.