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Author Topic: Ham vs ww2 equipment and CW skills.  (Read 3840 times)
LB5KE
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Posts: 141




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« on: May 09, 2010, 02:43:02 AM »

I am just wondering how does ww2 equipment perform compared to the average ham transceivers to day. Did they have good CW filters and receivers back then? It seems to me that HF / CW worked very well during the war. One example is that stations in UK picked up most of the HF transmissions in North Africa by the German's (and decoded them). The same goes for the U-boats and other services. Did they compensate simple equipment with CW skills and huge antennas?
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N2EY
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Posts: 3895




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« Reply #1 on: May 09, 2010, 05:04:51 AM »

I am just wondering how does ww2 equipment perform compared to the average ham transceivers to day. Did they have good CW filters and receivers back then? It seems to me that HF / CW worked very well during the war. One example is that stations in UK picked up most of the HF transmissions in North Africa by the German's (and decoded them). The same goes for the U-boats and other services. Did they compensate simple equipment with CW skills and huge antennas?

It depends on what you mean by "performance". And which WW2 equipment you look at. Do you have a specific receiver in mind?

For example, when it comes to sensitivity, many WW2-era receivers had all the sensitivity that could be used on frequencies below about 10 MHz. But as you go higher, the sensitivity drops off. Many WW2 HF sets don't go above 18 MHz, too.

As for selectivity, the single-crystal filters of the time were very sharp at the peak but had poor shape factors compared to the multi-pole filters that came later.

Military equipment tended to be designed for stability, but usually isn't as good as modern stuff. Frequency readout was much less accurate.

Of course it's really an apples-and-oranges comparison because the cost of a military radio during WW2 was very high compared to modern stuff, once you adjust for inflation. Also, the sets were usually designed for a specific task that was very different than what ham gear is used for.

Yes, they had good antennas and high power. But it must be remembered that there were a lot of times the radio just didn't work.

73 de Jim, N2EY

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N3QE
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Posts: 2288




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« Reply #2 on: May 11, 2010, 08:09:24 AM »

I think that in general way too much emphasis is put on equipment and filters by the crowd who post about CW to the internet.

I am continually astonished by the people who think that a 25Hz filter and a digital display tuned to the "right number" is the only way to receive CW.

Equipment back then could be "pretty decent" but that was before true product detectors were in wide use in receivers. Most of today's appliance operators wouldn't know how to begin to use a BFO. Frequency calibration could be good but that's "good" by 1940's standards, being within a few kHz of what was on the dial was great for most purposes. The US/allied military portable and vehicle radios extensively used crystals for channelized operations but not HF CW. The expectation that a HF "net" would all fall within a few Hz of each other simply did not exist. It was far more common to tune up or down a few kHz looking for a station, not just because your receiver may not be calibrated, but because his transmitter probably wasn't calibrated either. Chirp and drift were the rule, not the exception.

Crystal filters (with accompanying "phasing controls" on the front panel) were very very common for CW reception on the good equipment of the time. These are not the fancy-pants DSP's people use today, but in the hands of a good operator they could be very effective.

Intercept operations are a whole nother class. Direction finding becomes important. Traffic counts can mean a lot even if you can't decrypt the actual content. A certain kind of "band awareness" is important, a kind of overall "what's usual" and "what's special" awareness that many folks today who point-and-click on the packet cluster to zero-beat the DX are completely missing out on.

You will notice that I am picking very very much on the laziest and worst practices common today, and contrasting them with the best practices of past decades.
« Last Edit: May 11, 2010, 08:39:30 AM by Tim Shoppa » Logged
AA4HA
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Posts: 1489




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« Reply #3 on: May 11, 2010, 03:08:43 PM »

Some of the finest war era receivers were made by HRO, RCA, Hallicrafters and Hammarlund and are still decent performers to this day.

http://www.radioblvd.com


My first receiver was a Hammarlund SP-200 that was built in 1939. For the lower bands it was a very good receiver, getting above 10-15 MHz and it was pretty insensitive.

Regenerative receivers were still made and with a good hand could dig out some very weak signals.

Selectivity was through a complicated network of LC filters and in some case a crystal filter for CW operations. Even at it's best it did not have the steepness of filter curves that you see today. It was in a day when sensitivity was more difficult to come by and so much of a receivers design was in making the right choices of tubes for a first and second RF amplifier. There were aftermarket selectivity enhancement devices (Select-O-Jet) that could replace the first IF tube.

In the post-war years and up into the late 70's some of the finest receivers were still tube based. The R-390, R-390A series and the SP-600's were some of the finest made. I use an SP-600 for band cruising and an R-390A for getting dead on frequency with a real quiet noise floor.

There were some real duds as far as capability and some of those radios ended up as "morale radios" on the front lines.

Radios like the ARC-5 series and BC-348 were intended for use in aircraft. There once was a time when the ham marketplace was glutted with these models in the 50's and nearly every ham had one on his desk or used as a doorstop.

Germany had some fine radios, one of the best was the Köln E52  (  http://www.laud.no/ww2/  ). In WW II Germany pioneered NVIS to make it difficult to DF their radio operations.

Tisha Hayes, AA4HA
« Last Edit: May 11, 2010, 03:23:05 PM by Tisha Hayes » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
AD7WN
Member

Posts: 113




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« Reply #4 on: May 11, 2010, 06:16:52 PM »

I think we need to keep in mind what the equipment used in ww2 was intended for.  Rigs like the BC-375/BC-348 transmitter/receiver were intended to keep on working even while they were being shot full of holes, not merely to be convenient to use.  For this purpose, the BC-348 receiver had adequate selectivity, and it was very stable.  If you tried to copy a BC-375 on a modern receiver, lots of luck.  That transmitter would chirp way out of most modern receiver passbands.

But that pair could really take a beating and keep on running.  I still have this pair, using a much-modified ARC-5 transmitter for a transmit vfo, in order to make it legal to use.  The homebrew power supply, however, used mercury vapor rectifiers.  My xyl thinks any device that hisses and zaps like that power supply does is inherently evil.  So, the rig occupies floor space in a warehouse for the time being.  A more modern qrp solid state transceiver serves in its place.

Help this helps, 73 de John/AD7WN
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N2EY
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Posts: 3895




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« Reply #5 on: May 12, 2010, 02:02:01 AM »

I think we need to keep in mind what the equipment used in ww2 was intended for.  Rigs like the BC-375/BC-348 transmitter/receiver were intended to keep on working even while they were being shot full of holes, not merely to be convenient to use.  For this purpose, the BC-348 receiver had adequate selectivity, and it was very stable.  If you tried to copy a BC-375 on a modern receiver, lots of luck.  That transmitter would chirp way out of most modern receiver passbands.

I disagree with the details but not with the basic idea.

The BC-375/BC-348 combo were designed to withstand lots of shock and vibration, which were common in aircraft of the era. They also had to tolerate temperature extremes, because the planes they were mostly used in went from tropical heat to arctic cold - often in a few minutes. (It's COLD at 35,000 feet!)
They also had to be operable with heavy gloves on the operator's hands.

Often the reason for poor signal quality from WW2 transmitters is that they aren't being used the way they were intended. For example, the BC-191/375 was designed to operate from a particular dynamotor and DC filament supply, with the neutralization adjusted for minimum chirp, and at a power level that most hams consider very low. Same for the ARC-5 transmitters, which used a time-sequenced keying relay setup.

Most amateur adaptations of those rigs involve using a different power supply setup, adjusting for maximum ICAS power output, and a highly modified keying scheme. The results aren't the best.

The problem is usually that hams didn't have/couldn't afford the manuals and accessories, and so did their best with what they knew.

  The homebrew power supply, however, used mercury vapor rectifiers.  My xyl thinks any device that hisses and zaps like that power supply does is inherently evil. 

My rig's power supply has 866As and doesn't hiss or zap at all.

73 de Jim, N2EY
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WB2WIK
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Posts: 20611




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« Reply #6 on: May 12, 2010, 06:07:23 PM »

The equipment back then was very primitive to what we have today, but stuff made specifically for military use was robust.

There was also a LOT less man-made noise back in those days.  I wasn't alive to witness that, but it must have been great! Smiley

Man made noise limits what a lot of hams can do today (on HF).  I can tell even from here on the outskirts of L.A. -- if I am my beams towards the city, the noise level can increase 3 S-units almost any time of day.

I'll bet it was not like that in the 1940s.
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IK0YGJ
Member

Posts: 43


WWW

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« Reply #7 on: May 13, 2010, 12:24:16 AM »

I have no experiences with ww2 rigs, I can report my experience with bugs.
In my collection, today, the best key ever is the Lionel J36, it actually outperforms in every aspect each key built today.
The second best is the Begali Intrepid, albeit it must be tuned properly, but it can sound like an electronic keyer, as you can see in this video:

http://www.youtube.com/watch?v=Df3JLHdW2Z4

73 Carlo IK0YGJ

---------------
Download your free copy of "Zen and the Art of Radiotelegraphy" here:
http://www.qsl.net/ik0ygj/enu/index.html

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N2EY
Member

Posts: 3895




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« Reply #8 on: May 13, 2010, 04:04:38 AM »

The equipment back then was very primitive to what we have today, but stuff made specifically for military use was robust.

Both military radio equipment and good amateur equipment was enormously expensive, too.

For example, the SP-200 mentioned by AA4HA cost about $300 back in 1939. The Westegg inflation calculator says that $300 in 1939 equates to about $4585 today. How many hams today could afford/would spend $4585 for a receiver?

The R-390A was developed from the R-390 because the earlier model cost so much.


There was also a LOT less man-made noise back in those days.  I wasn't alive to witness that, but it must have been great! Smiley

Man made noise limits what a lot of hams can do today (on HF).  I can tell even from here on the outskirts of L.A. -- if I am my beams towards the city, the noise level can increase 3 S-units almost any time of day.

I'll bet it was not like that in the 1940s.

I don't know if there was really less man-made noise. Yes, there weren't things like BPL and noisy switching power supplies all over the place.

But there were a lot of other noise sources which have since disappeared, or been quieted down:

- Small universal motors with commutators and sparking brushes were used for everything from vacuum cleaners to furnace blowers

- Millions of cars on the road had ignition systems that weren't noise-suppressed in any way, and made quite a racket.

- Neon signs were everywhere, buzzing away.

- The technology of electricity distribution was less developed and noisier

- There were things like trolley cars (Pacific Electric Red Car) which have all but disappeared today, all over the place making noise. Something as simple as a harmonic from the LO of the neighbors BC receiver could make considerable QRM.

- Things like directional antennas and noise blankers were a lot less common then. (Many hams were using regenerative receivers or simple superheterodynes that couldn't/didn't have such features).

Yes, there were fewer people then and they had less electrical stuff. But most of them lived in cities, in closer proximity than today.

It is reported that the reason Armstrong developed practical FM broadcasting was that Sarnoff said, in the late 1920s, that he never listened to the radio anymore because of all the "static". Armstrong's demonstration of FM included starting up various common noisemakers of the day and showing that they didn't affect FM.

Jim Lamb, of the ARRL staff, developed the IF noise blanker in the mid-1930s. I suspect that noisy conditions drove him to do it.

Maybe there was less noise back-when. But maybe not. I suspect that then, as now, it depended on where you were.

73 de Jim, N2EY

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N2UGB
Member

Posts: 179




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« Reply #9 on: May 14, 2010, 08:04:23 AM »

I believe the WW2 years coincided with a period of excellent propagation. So Mother Nature cooperated on that score.

I very highly recommend the purchase of the dvd The Battle of the Atlantic a BBC video. Perhaps Amazon still carries it. If you are interested in cryptography and communications...and heart-breaking personal experiences of merchant mariners during convoy duty, it is unbeatable.
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AE4RV
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Posts: 963


WWW

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« Reply #10 on: May 14, 2010, 09:14:59 AM »

Maybe, maybe not. I've long wished I could go back in time with a shortwave receiver though...

http://helios.gsfc.nasa.gov/cycle1.gif
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