More 1928 Hartley

With (plexi)glass rods ordered and one additional National DX capacitor in the mail from a friend the next step is some table saw time.

A 1928 Hartley

After seeing my 1934 transmitter a friend asked if I was doing anything special for the Bruce Kelley Memorial 1929 QSO Party coming up in December. Last year I put my TNT transmitter and SW3 on the air. This year it might be interesting to try a Hartley oscillator.

As ham radio approached January 1, 1929, and the more rigorous standards, the ARRL encouraged hams to improve their stations. One improved transmitter design was a single tube Hartley oscillator described by Ross Hull in the August 1928 issue of QST. Bruce Howes, W1UJR, covers this design on his web site here.

I've been searching through my junque box looking for the parts I need. The first step was a parts list and an enlarged scan/photo of the transmitter. After picking through multiple boxes and peanut butter jars I've lots of possibilities. Now it's a matter of sorting through what I have for the parts that match the original design.

Camping and Picnic Table QRP

This last weekend we planned a campout at Frontenac State Park. We've picniced there several times but have never camped over night. No camping trip packing list is complete without my K1. (This time we did forget the blankets and pillows but the K1 was loaded.)

I ended up getting several chances to ham. After a quick listen on 20 and discovering the CQ WW RTTY contest in full swing I moved to 30 mtrs for the weekend. The antenna was a 45' endfed wire (1/2 length wave on 30 mtrs) in a tree next to the campsite. It was approximately broadside to the NNE but did a great job into the northeast US. Between Saturday and Sunday I worked W3XAF (MD), KB3TJS (MD), W0IMD (CO), AA3TH (PA), WA1IIE (ME) and KD3DK (PA).

More 1934 Transmitter

Remember the safety problem with my 1934 transmitter? Two of the phone plugs is for metering and the third is for the key. If, in the heat of the moment, I get the them mixed up and plug the key into a B+ metering jack, I'll have up to 300 volts on the key.

To protect myself I tied a length of string and a plastic cable clamp to the key phone plug (any lump of plastic would work). After the key is plugged in I slide the cable clamp under the front edge of the transmitter. The string is short enough that the plug can not be removed without getting the clamp out from under the transmitter.

A 1934 transmitter - On the Air

Yesterday I set up my 1934 transmitter up with my NC101X and tried the pair out on 80 meters using my endfed 105' inverted "L" antenna only about 10'-20' off the ground. The station worked fine.

At 21:45 I had a nice QSO on 3570 with NG9D in Plainfield, IL. Lynn's signal varied from 589 to 599+. He reported that my 589 signal sounded fine/stable.

Also shown in the picture is my iambic keyer set up to key older tube rigs.

More 1934 transmitter - It Works!

I've finished wiring my 1934 transmitter, powered it up and it works! With about 300 volts on the plates of the 46s and the 47 it loads to 15-20 watts input and 7-10 watts output. It sounds great also.

One change I made from the Bill Orr design is to connect the 47 screen to regulated 150V rather than a resistor network off of B+.

This transmitter is not without some personality, though. Only the amplifier stage is keyed so the oscillator stage runs continuously. On key up any energy from the oscillator that makes it to the antenna will be heard as a faint back wave. We'll see if this is objectionable. The second personality trait is, unfortunately, pretty nasty. When using the rig, two phone jacks are for metering plate current and the third is for the key. If in the heat of the moment I get the three mixed up and plug the key into a metering jack I'll have over 300 volts on my key. To make matters even worse, keying the metering/B+ line works so I may not even be aware of what I've done until I get myself between the key and ground. I'm planning something that will keep me from accidentally removing the key plug.

Eventually I plan is to mate this transmitter with my National FB7X for a complete 1934 station that I'll use in the 2010 AWA Linc Cundall OT CW Contest.

QRP Operating at Crater Lake National Park

After three weeks, 5300 miles and 12 western states Beth and I are back in Rochester. I took along my K1 in a lunch bag so that I'd be ready for any ham opportunities.

One of our tourist stops was Crater Lake in southeastern Oregon. On August 19 I found a tree stump overlooking the lake, threw a 32' length of wire into a nearby tree and got on 20 meters. My location was on the western rim of the 5 mile wide caldera with the water around 800' below me. After a few CQs I worked Jim, W0CML, near Denver. Once he swung his beam around he was nice copy at 589 and I was 579. After supper that evening I operated on 40 from in front of our cabin at Mazama Village, 7 miles and about 1000' below the rim. Tim, AD7AN, in San Diego gave me a 529 while he was 579 for me.

"Picnic table QRP" continues to be a fun way to spend some spare time while traveling.

More 1934 Transmitter

I've gotten the components all mounted and the transmitter is ready for wiring. I learned a few things along the way...

30s vintage Sangamo mica capacitors are large enough that they don't mount well on their own leads. Each one must be mechanically supported, either by a solder strip or by screwing to the wooden sides of the chassis.

The wooden chassis takes 1 1/2 inches of available length and width. This can impact the layout. Using an all metal chassis there is space for a buffer stage between the oscillator and amplifier. With 1 1/2 taken off the length/width plus the added reinforcing across the middle it would be a challenge to fit the buffer stage in there.

Will the lead length be a problem? Certainly I wouldn't trust this spread out layout at 30MHz but it may be OK on 7MHz. Time will tell.

QRP from Frontenac State Park

Sunday afternoon, July 5, I got over to Frontenac State Park for some picnic table QRP. The picnic area there sits at the edge of a 400' bluff over looking the Mississippi River. Below the park is Lake Pepin , a naturally wide part of the upper Mississippi. To the east, across the Mississippi/Lake Pepin, is Wisconsin. The weather Sunday was sunny but not too warm in the shade, perfect for picnic table QRP.

Using my K1 running 4 watts and feeding a 67' end fed wire I worked K4BAI(Columbus, GA), WA3PAK(Marion, OH) and N7JOX(northern CO near Cheyenne, WY). All in all a satisfying and relaxing afternoon....

More 1934 Transmitter

After some quality table saw time, a bunch of drill press time and eight coats of paint (primer coat, satin black, three coats of wrinkle paint that didn't wrinkle and three more coats that did) I have a wood and aluminum chassis that looks pretty good. The layout is much like the Gross CW-25 but without the buffer stage. In place of the middle/buffer tuning dial I'm mounting a plate current meter. Across the bottom are three 1/4" phone jacks. One is the key jack. The other two are in the B+ circuits of the oscillator and final amp stages. These two jacks will have 350VDC exposed on the outside rim. For safety I recessed these jacks 1/2" behind the front panel. I also added a B+ switch on the far right.

I found two more examples of this tube lineup. One is a George Grammer construction project covered in November 1932 and February 1933 QST. The second is the Collins 4A transmitter.