Museum für Kommunikation

Museum für Kommunikation, Frankfurt, DeutschlandI’m currently on a business trip in Namibia, but on the way here, I had a six hour layover in Frankfurt, which is just enough time to hop the train downtown (S8 or S9 to Hauptewache, about 4.50€, which seemed a bit pricey). From there, it’s a fifteen minute walk through an historic area and then across the Main River to the museum district. Just past the world cultural museum, a few tempting antennae loom over the Museum für Kommunikation.

Those antennas are right above the ham radio station located in the museum, Funkstation DL0DPM. Unfortunately, my plane landed just about the time the station was closing for the day and I wasn’t able to visit the ham station, but I’ll put in on the itinerary for the next time I find myself in Frankfurt.

The permanent collection of the museum is on the lower level, while the upper floors are dedicated to rotating exhibits. Those exhibits were very family-friendly and were labelled in both German and English. Most concerned some aspect of media, although one explored number sequences. My main interest, though was in the permanent collection, which focuses on the PTT service (post telephone and telegraph, not push-to-talk).

One side of the collection is dedicated to the postal system and includes a number of postal wagons and cars, stamps, mailboxes, and so on. Another area focuses on the phone system and includes working demonstrations from several eras, with phones connected to switching racks. When you dial another phone, you can see the mechanical relays in the central exchange spinning and clicking to route the call.

My main interest, of course, was the radio equipment. Their collection does not focus on amateur radio equipment, but on commercial and consumer equipment. They have quite a collection of very early radios, including some developed for telegraphy. Most were commercial units from the 20s onward, including a good collection of war time radios including those in the Volksempfänger series. The radio collection includes some beautifully styled cabinets, both in wood and later materials like bakelite.

A screw mirrorNext to the radio equipment is an exhibit of television equipment, which I found at least as interesting as the radio equipment. In particular, they had an impressive collection of very early mechanical television gear. One item that attracted my attention was a helix composed of many thin, long mirror pieces, arranged like a stair case, with the mirrored surface facing outward. It was mounted on a motor and some other control gearing. This device was descriptively labeled “Spiegelschrauben” (mirror screw). It took me a while to get through museum’s description of the device, as descriptions in this part of the museum were written only in German. The bottom line is that this device provided the raster scan for an early television receiver by the company TeKaDa (from die Süddeutsche Telefon- Apparate-, Kabel- und Drahtwerke A.G — which through a series of corporate mergers and acquisitions eventually was acquired by AT&T, now Lucent Technologies). At the time, work was also progressing on cathode ray tubes, but it was difficult to manufacture tubes with a large surface area and to produce as bright an image on a CRT. Peter Yanczer’s website has a good description.  The museum has a number of other early television devices including parts from a Nipkow disc system and Vladimir Zworkin’s iconoscope.

A significant part of the display is given over to telegraphy, both cable and radio. A full high-power spark gap station set into a luxurious wooden desk with porcelain insulators, bright copper coils and brass fittings was a real work of art. However, I did note that the key was not far from some very high voltage junctions (for that matter, the contacts on the key itself probably had a few hundred volts running through them. Operator, beware). Of course, there were obligatory displays on Marconi and the Titanic. A lot of the exhibit was given over to commercial telegraphy, both for railway and general communication. Aside from keys, thumpers, and ticker tape units, there were  a number of inventions that would either take telegraph key or keyboard input and transmit a message along a wire. These were not quite teletypes; the message would display letter by letter, usually with a mechanical pointer.

swr van
On the way to the museum, I passed an “SWR” van.

Extending from the telegraph exhibit were collections on radio and landline teletype as well as facsimile machines. One corner is also devoted to the enigma machines of World War II, which includes mention of the work done at Bletchley Park. I had expected to find some Feld Hellscreiber equipment, but I did not see one in the museum’s collection.

The museum is well worth the 3€ price of admission, and if I’m in town again earlier in the day, I’d like to stop in on the amateur station.

As for Namibia, this conference came up quickly. I did make an attempt to contact some hams in Namibia and their IARU affiliate, but was unsuccessful. I’m sure I’ll be back here at some point and with more lead time, so hopefully I’ll get on the air on the next trip.


Field Day 2014

jack_cw_tentThis may be my last region two field day for a while, as plans are rapidly coming together for the move to Madagascar in August. I’m not writing off the possibility of field day next year as I know that I’ll be stateside in June for the American Society of Clinical Oncology meeting in early June, and there are some other meetings during the month that could reasonably keep me here. Also, I might throw in a bit of leave time since I’ll probably be wiped out after field day and want a day or two to cool off before heading back to Antananarivo.  In any event, this was a good chance to shake down some of the equipment that I will be bringing with me, particularly the hexbeam antenna from K4KIO.

As usual, field day planning started far in advance of the event. This year’s field day czar, Regis KF4PIY introduced a few innovations into this year’s FD, the most visible of which was tighter clustering of the stations. In the past, we spread over a large field near the entrance to Burke Lake Park, with some of the stations “down the hill” and some up. Having been “down the hill”, I can attest to the perception that it is better to be “up the hill” both from an antenna perspective and in terms of being nearer to the food and bulk of the social gathering. The obvious concern was that tighter clustering would lead to more interference. However, after a few antenna pow-wows, the band captains were happy the proposed layout and our RF gurus were reasonably confident that it would all work.

Equipment stacked up and awaiting transport.
Equipment stacked up and awaiting transport.

As for the last three years, I was band captain for the non-40m CW station. Most of the equipment that went to field day had gone the previous year. The main rig was the Elecraft K3 with 200 and 450 Hz filters, my main CW rig at home. I brought along the microphone just in case, and that turned out to have been fortuitous, as we had plenty of opportunity to jump on bands that other stations were not working, scoring the only voice contacts for six and ten meters. I gathered the equipment over the course of a few days and queued it up in the front hall. The day before field day, it all got loaded into the car and carted out to Burke Lake Park. I had considered staying out at the park that night and did pitch a tent, but so many others overnighted at the park that I decided a good night’s rest in my own bed would be the smarter decision.

Essentially all of the antennas were pitched on the afternoon before field day including the hex beam. Leon NT8B had purchased an AB577 mast system at one of the winter hamfests in the area and we decided to combine it and the hex beam. Despite being the first deployment of both pieces of equipment, it went smoothly. The AB577 is an intimidating piece of gear; it is repurposed military gear and looks it. It is painted some official shade of matte olive drab and the five foot sections come in a rack that looks like a portable rocket launcher.

Jacob KK4WJA cranks up the AB577
Jacob KK4WJA cranks up the AB577

The rack itself becomes the bottom portion of the antenna and sections are fed into it and cranked up into position, with a joining clamp added between each section. The diameter of these sections is about five or six inches, but the sections themselves are much lighter than they appear; they can be easily lifted by one person. An adapter piece goes on the top, and its outer diameter is about two and quarter inches.

We decided to set up the mast at 45 feet, which required three layers of guying, with guys in three directions at each level. Cables, stakes, and clamps to tighten the lines are all part of the AB577 kit. The lines are all attached at the start, but do not play a significant role until the mast is up fifteen or twenty feet.

When we got the first couple sections of the mast in place, it was time to add the antenna. The hexbeam comes in an unexpectedly small box, about five feet long corresponding to the length of the longest spreader section. Each spreader consists of three telescoping fiberglass segments. Loops to retain the wire elements are already in place on these segments.

In addition to the long box that contains the spreaders and central support column, a smaller box also showed up at my door. This box contained the base plate which anchors all of the spreaders and the central column and when installed sits on top of the supporting mast. I had ordered elements for all possible bands, so 6, 10, 12, 15, 17, and 20 meters. The wires for these bands were also in the box, as were support strings, ferrite rings, heat shrink and instructions. The ferrite rings must be ordered according to the intended feed line, in my case RG213. The rings go over the coax near the feed point and are held in place with the shrink wrap. These ferrites function as a choke and keep RF off the feed line.  Since 12 and 17 meters are not included in field day, I left them out of the set up this time.

Items in the accessory box: wire elements, strings, and the central hub.

Spreader segments and the central column.
Spreader segments and the central column.

Many hands made quick work of putting the hex beam together. Once we had read the instructions, it took less than fifteen minutes from crate to full assembly. It really is a dead simple antenna to put together because all of the attachment points are already set and the wires are cut to exactly the right length. For someone who never had a store-bought antenna before, this seemed almost like cheating, but I reminded myself that the next time I’d be doing this, I would be far away from the club and likely wouldn’t have as many helping hands.

Bob connects a support string to the central hub while Thor stabilizes the antenna.
Bob connects a support string to the central hub while Thor stabilizes the antenna.

John holds the antenna during rigging of the band-specific wires.
John holds the antenna during rigging of the band-specific wires.

We did run into one snag: the outer diameter of the support mast was about an inch wider than the than the flange on the antenna base plate. The sun was already low on the horizon at this point, but we were eager to find a solution that evening. I made a quick trip to Home Depot and picked up a two foot piece of one-inch black pipe, which is actually about 1 and quarter inches outer diameter. I also grabbed a bunch of U-clamps. Putting the whole thing together additionally involved a bunch of duct tape and two tent stakes that were hammered into shape as adapters.

Members working on finding a mounting solution for the hex beam.
Members working on finding a mounting solution for the hex beam.

By the time the sun set, we were convinced that our adapter was rigid. We set the hex beam down on the grass for the evening rather than attempt to attach it to the mast and raise it in suboptimal lighting.

The next morning, we were able to hand the antenna up to members on a ladder. They tightened the hex bolts on the hex beam’s flange, and the antenna stayed level. Additional sections of the AB577 were then added, and the antenna climbed skyward in five foot increments. Around twenty feet up, the guy lines began to have more and more importance. We had minders on each of the guy lines as well as spotters to assure that the tower was staying vertical in all planes. When the antenna was finally in position, the clamps on the end of each guy line were tightened.


Finally, the antenna reached 45 feet up, plus a bit for the extension.  A quick check at 5W verified that the antenna was working, with responses up and down the east coast.   An 80m dipole (the same one used in the Indiana QSO Party last year) was also erected to cover that band.

After the antennas were in place, the rest of the station was set up, based on the Elecraft K3 transceiver, N1MM running on a laptop, and trusty Bencher paddles.


The station remained in continuous operation from the start until the end of Field Day 2014, concentrating on 20m during the day and 80m in the evening and early morning. However, since we did not have a dedicated VHF station this year, on the morning of day two, we quickly ran the band on both voice and CW, chalking up about 10 local contacts. We also ran 10  meters when it was open. We started on voice and had a good run, but conditions were fading by the time we got to CW, so ironically, we made more contacts on voice than CW. We also had a chance to work on 15 meters for a while on day one, when the other CW station was doing good business on 40m. Although 15m and 40m are harmonically related, simultaneous operation did not result in interference.

Band mode qsos
3.5 cw 278
3.5 ssb 240
7 cw 718
7 ssb 676
14 cw 542
14 ssb 467
21 cw 151
21 ssb 19
28 cw 19
28 ssb 50
50 cw 3
50 ssb 7


A major difference from last year is that all four stations remained on the air around the clock; this is strongly reflected in our score for this year, which broke 10,000.

John K3US concentrates on code in the wee hours of the morning.
John K3US concentrates on code in the wee hours of the morning.