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Sooocool
05-23-2006, 12:56 AM
I€ve noticed that on so many WW2 era aircraft, there are one or more wires or cables linking empennage to antenna masts or wings. Maybe it€s for structural reinforcement against high G loads, or perhaps it gives high gain to the radio, or possibly a radio directional signal. Does anyone know?

Waldo.Pepper
05-23-2006, 01:36 AM
Some hints here.... 'tis VERY complex.

http://aafradio.org/NASM/B-29_antennas_starboard.JPG

Platypus_1.JaVA
05-24-2006, 02:16 PM
What Waldo said http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

It is certainly not structual reinforcement wires. I studied radio technique in school but it was a long time ago. Most wires where for communications indeed.

horseback
05-24-2006, 05:11 PM
An antenna's length is based on the physical wavelenth of the frequency of the radio it is used for. Dredging up what they taught me in Electronics Technician 'A' School at NTC Great Lakes (in 1975-6), radio waves travel at around the speed of light, or something like 186,280 miles per second.

This means that the lower a frequency is, the longer its wavelength. The best antennas are a quarter, a half, or a full wavelength long. Therefore, if a megahertz is a million cycles (or waves) per second, that gives you a wavelength one millionth of a second long, or about 983.57 feet (my calculator just wheezed) for a one Megahertz cycle.

Those antenna wires were the antenna for HF and early VHF radios.

cheers

horseback

Nimits
05-24-2006, 09:17 PM
Basic Electronics: The longer the antenna, the better the radio. World War II aviation radios generally required long antennas to make them functionall useful.

M2morris
05-24-2006, 11:12 PM
Horseback is correct, and I remember the formula for determining the lenght of each half of a dipole antenna is 234 devided by the freq. and the higher the freq, the shorter the ant.
It's been a while so I forgot the formulas for a sloping "V" or a Long-wire etc. I would have to refere to my old SF suppliments.
But I ALSO heard that those wires on the WW2 planes were most widley used by Gremlins so they could shimmy from one part of the plane to another. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Platypus_1.JaVA
05-25-2006, 12:19 AM
This discussion makes me think of the 'bad' old days. http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif

M2morris
05-25-2006, 12:24 AM
Originally posted by Platypus_1.JaVA:
This discussion makes me think of the 'bad' old days. http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif
Do you mind if I ask Why? Platypus

Platypus_1.JaVA
05-25-2006, 09:03 AM
Originally posted by M2morris:

Do you mind if I ask Why? Platypus

Just a personal trauma.

I stated before that I got some radio stuff on school. This was back in the days that I still wanted to be an aircraft technician. I started to learn for mechanic but, after two years they let you choose: go work with an airline company or study further. Since the past two years had been very easy for me, I choose the latter. This added two more years in school for me. Being a little 'creative' in making the tests, I passed the theoretical part completly. I had to learn about micro-electronics, radio and TV. I found that a difficult subject. Just because I have never really bothered with it. After the two years I had to go to 'training' (dunno the proper english word, you are still a student but go to a company to learn the trade in practice) I went to the KLM on Schiphol airport. I performed maintenance on the Boeing 737 300/400 and 800/900. I was there for about ten months and got two months at a small company on a GA airfield afterwards. In this year, it became very clear to me that aviation was not the right business for me. I did not pass the last year so I went from school without a diploma. They gave me an diploma for aircraft mechanic but, I doubt if it was a valid one. If you don't do anything with your diploma, they are not valid anymore after a year also.

Ayways, I was 21 and I stood on the streets with no diploma and with 5 years waisted for NOTHING. that was just after 9/11 too. So that was a really bad year for me. Luckily, I am now a respected electrician and my company pays for evening school, to get me further in this career. So they must believe in me I think. http://forums.ubi.com/images/smilies/25.gif

What really made me p!ssed off was that two years back, I read an article in the paper about the school I was on for 5 years. The school and the teaching was so bad that only about 10% (!) of the students actually graduates... They where not going to do anything about it for a while because they really didn't need that much aircraft mechanics and technicians. http://forums.ubi.com/images/smilies/disagree.gif

This made me very vey ANGRY!! http://forums.ubi.com/groupee_common/emoticons/icon_mad.gif

So, the school gets a profit out of 90% of the students who will waste some of the better years of their lives and large sums of money. That is not fair I think. I'm still angry if it comes in my mind again. http://forums.ubi.com/groupee_common/emoticons/icon_mad.gif http://forums.ubi.com/groupee_common/emoticons/icon_mad.gif

mortoma1958
05-25-2006, 10:17 AM
Originally posted by Nimits:
Basic Electronics: The longer the antenna, the better the radio. World War II aviation radios generally required long antennas to make them functionall useful. No, sorry wrong. I have a degree in elecronics and am an Advanced class Amateur ( Ham ) radio operator. I doubt anyone on the forums knows more about this stuff than me. It's like the other guys said, there are basic formulas for finding the best length antenna for a given frequency. If you have a 900
ft. antenna on your cell phone ( high frequency UHF ) it would be a really bad for reception as it would be way too long for that frequency. Conversely, if you put a short cell phone antenna on your shortwave radio ( lower frequency HF ) it also would have terrible results as it would be way too short of an antenna. So a longer antenna is not always better!!!

M2morris
05-25-2006, 04:38 PM
Sorry I opened that up Platypus, I geuss I feel for ya. Man that sucks. Better luck in the future.

Platypus_1.JaVA
05-25-2006, 11:30 PM
@ M2morris, no sweat mate. Talking about it helps or so they say http://forums.ubi.com/images/smilies/25.gif http://forums.ubi.com/images/smilies/touche.gif

@ mortoma, since you are far more knowledgeable on this subject then I am, why do you see those antenna wires on WWII aircraft and why don't you see them on aircraft nowadays then? Do you know what frequencies and modulation they used back then?

M2morris
05-26-2006, 12:17 AM
Well it looks like this antanea theory and wave propagation subject is going to be started so I am going to try a long shot Platypus because I have always been curious about how they are set-up on aircraft.
Now let's say that an F4u Corsair has an antena stretching from the tip of the fin to the mast near the engine cowl in front of the wind screen. I'd say that is about 12-14 feet, so that would put the freq in about the mid-HF range. About 17.5 MGHZ or there abouts. Right?
There are alot of things about radio comms I have always been curious about with airplanes. When I used field expedient antenas in the Army on the ground I learned some tricks to get the signal to travel in the direction I wanted, I hammered a nail into a Size D battery once and connected it to the end of my ant to make a terminating resistor to pull the signal in the direction of the home station etc. So when it comes to airplanes I can imagine that if a pilot was not able to contact his home station he could change the direction of his plane and use its metal body to help direct the transmitting signal. I know I have done this with a vehicle on the ground. But it is an intersting subject and I could go on and on with commo stories from my days in SF. Sorry to but in, I am just a blubbering buffoon. But I hope you guys start in with a commo discussion, because I am listening.

mymhh
05-26-2006, 05:42 AM
Since the B-29 antenna photo came from my website (http://aafradio.org/), perhaps a few words on antennas of the era might be helpful. HF finally disappeared from aircraft comms back in the 1970s, which is why you won't see any wires on today's airplanes. The beginning of the shift to VHF actually began with commercial carriers back in 1939, with the introduction of the Western Electric 233A set, though that was necessarily focused on short range plane to plane or plane to tower comms. HF was still the primary long range tool for four more decades.

The length of the HF antenna(s) on WWII aircraft was largely based on how far they could stretch it on the airframe. I have a discussion and nomograph in the documents section of my web page for those who are interested in the characteristics of those antennas. The B-29 had two long wire HF antennas, each 74 feet long (I know because I restored the antennas on the Enola Gay a couple of years ago - see the web page if interested). One was for the liaison set (BC-348 receiver and ART-13 transmitter) and the other was for the "command" set, normally a lower power set to communicate with the rest of a squdron (though not so on the atomic weapon aircraft.) It had one VHF set (125-150MHz) and an associated two foot blade (often this was the only radio installed on the fighters because of weight and room.)

Best wishes,
Mike

BigA21
05-26-2006, 08:36 AM
Mymhh,

That is nice site. I enjoyed looking at alot of those pics. That equipment was built like tanks, and there is a certain "Beauty" to it.

It must have been an honor to be hands on the Enola Gay. http://forums.ubi.com/images/smilies/11.gif

I was curious about your blanket statement though:

"HF finally disappeared from aircraft comms back in the 1970s, which is why you won't see any wires on today's airplanes."
Maybe just military aircraft? I don't know about current Mil birds.
But commercial / business / general aviation I can say that even in this age of digital / glass flight suites, SELCAL, and dual frequency ELT's that also broadcast last known coordinates as fed from on board nav systems to satellite networks - I still see HF's installed in most medium sized+ modern aircraft.
Generally if the plane has the range it has the HF's. Some with wire antennas, some without (Typically an embedded antenna in the leading edge piece of a stab surface).
Most have 2 HF's and can not dispatch with only one working.
Whether the wires are there or not, the HF's are still there, and they are still that important.

mortoma1958
05-26-2006, 12:25 PM
Originally posted by Platypus_1.JaVA:
@ M2morris, no sweat mate. Talking about it helps or so they say http://forums.ubi.com/images/smilies/25.gif http://forums.ubi.com/images/smilies/touche.gif

@ mortoma, since you are far more knowledgeable on this subject then I am, why do you see those antenna wires on WWII aircraft and why don't you see them on aircraft nowadays then? Do you know what frequencies and modulation they used back then? Typical frequencies in those days were HF, which required a longer antenna than
modern aicraft comms on VHF from 108 to 137 Megahertz. That is above ( higher frequency ) than the FM broadcast band. And we all know that the FM band does not require a very long antenna. This is why modern aircraft do not usually need long antennas. The old HF frequencies, still in use today for long range "shortwave" broadcasts and and a few other things, ( even some long distance HF aircraft comms when aircraft need to cross oceans ) require longer antenna. In the case of modern aircraft using HF over the ocean, they still need longer antenna but the length is oftentimes shortened a bit by the use of loading coils. I don't think the use of loading coils to electrically reduce the length of antennas was used much in the W.W.II era, if at all. I'd have to research when loading coils came into widespread use.

mortoma1958
05-26-2006, 12:35 PM
Originally posted by mymhh:
Since the B-29 antenna photo came from my website (http://aafradio.org/), perhaps a few words on antennas of the era might be helpful. HF finally disappeared from aircraft comms back in the 1970s, which is why you won't see any wires on today's airplanes. The beginning of the shift to VHF actually began with commercial carriers back in 1939, with the introduction of the Western Electric 233A set, though that was necessarily focused on short range plane to plane or plane to tower comms. HF was still the primary long range tool for four more decades.

The length of the HF antenna(s) on WWII aircraft was largely based on how far they could stretch it on the airframe. I have a discussion and nomograph in the documents section of my web page for those who are interested in the characteristics of those antennas. The B-29 had two long wire HF antennas, each 74 feet long (I know because I restored the antennas on the Enola Gay a couple of years ago - see the web page if interested). One was for the liaison set (BC-348 receiver and ART-13 transmitter) and the other was for the "command" set, normally a lower power set to communicate with the rest of a squdron (though not so on the atomic weapon aircraft.) It had one VHF set (125-150MHz) and an associated two foot blade (often this was the only radio installed on the fighters because of weight and room.)

Best wishes,
Mike Well, as I stated in my above post, HF is indeed still in use for aircraft today.
But planes are only equipped with HF transceivers and the associated antennas if they are to be used for crossing oceans, or other remote regions. HF is still the only thing that will reach far enough since it's not "line if sight", short range as VHF and UHF comms are.
The difference is that the antenna are not mounted from the top of the fuselage to the top of the vertical stab any more. They are probably mounted along the length of the bottom of the aircrafts belly or possibly trailed out behind the plane. I am not sure if trailing antennas are still used however. They are also no doubt relying on loading coils, which electrically reduces the length of the antenna by some degree. With the coils, they may be physically shorter but still the equivalent of being a good bit longer. I don't know if loading coils had been discovered in the war era, as I already stated.

Here is a link which shows all the HF frequencies in use today, for aircraft crossing oceans. There is also a handy explaination as the why these frequencies are still used, better than I can explain it.

http://www.canairradio.com/hf.html

The frequencies are stated in Kilohertz, to convert to Megahertz equivalents, just move the decimal over to the left three spaces.
( For example; 2944.0 KHz would be 2.944 Mhz )
Same thing, just stated differently.

Blottogg
05-26-2006, 11:08 PM
Trailing wire antennas are still used, at least for specialty aircraft. On the other end of the spectrum, VLF (or Very Low Frequency) radios on the E-4B and TACAMO (TAke Charge And Move Out... Navy acronyms are often forced) use VLF to talk to boomers, or ballistic missile subs. The VLF waveform, with its very long wavelength requires an antenna five miles long(E-4B (http://en.wikipedia.org/wiki/Boeing_E-4B)). The tradeoff is that it can penetrate some distance of water to communicate with a submerged sub. The long wavelength means the data-rate for the signal is very low, amounting to not much more than morse code speeds of data transmission (AFAIK it's used to send "shoot the missiles" or "don't shoot the missiles" type messages, not voice or video.)

HF isn't used much anymore, except where mentioned above. OV-10's and F-111's had HF radios, and a former OV-10 pilot would tell us about "blowing the doors off" of truckers on Citizen's Band radios (the bands overlap) while flying cross-country. The aircraft radios put out a lot more power than the FCC restricted transmitter in a Peterbilt. The loading coils would explain the lumps on CB radio antennas, and the lack of long wire antennas, both of which had me wondering if Smokey was embellishing or not.

Platypus_1.JaVA
05-27-2006, 12:23 PM
Hold your horses a bit. HF communication is disappearing rapidly. I heard that Satelite comms is now in fashion. KLM has satcom on most of their transatlantic machines.

mortoma1958
05-27-2006, 07:30 PM
Yes, but satcom in the case of KLM and other airlines is not used for air traffic control, just communication between the crew and the airline corporate headquarters. So far all flights that go over oceans and remote regions will need to have HF radios for air traffic comms. This is true for civilian aircraft, not necessarily true for military, which is a different animal in most cases. The KLM satcom is most likely digital data packets of info pertaining to aircraft mechanical/electrical status, fuel levels and geographical position for the purpose of maintaining the schedule. Also problems with passengers and crew members may be communicated.

It is not so much used for air traffic control yet, not until everybody else goes to it. This will take a long time for all the cooperation necessary between governments and airlines, so on, so forth. This digital data comms goes on in the VHF portion of aircraft allocations, mostly in the range of 128 to 130 megahertz. And has been going on for a long time. That is called ACARS ( Aircraft Communications Addressing & Reporting System ). If you listen to it, it sounds like beeps and boops like an internet modem or fax. Can be used for voice if need be too.

mortoma1958
05-27-2006, 07:33 PM
Originally posted by Blottogg:
Trailing wire antennas are still used, at least for specialty aircraft. On the other end of the spectrum, VLF (or Very Low Frequency) radios on the E-4B and TACAMO (TAke Charge And Move Out... Navy acronyms are often forced) use VLF to talk to boomers, or ballistic missile subs. The VLF waveform, with its very long wavelength requires an antenna five miles long(E-4B (http://en.wikipedia.org/wiki/Boeing_E-4B)). The tradeoff is that it can penetrate some distance of water to communicate with a submerged sub. The long wavelength means the data-rate for the signal is very low, amounting to not much more than morse code speeds of data transmission (AFAIK it's used to send "shoot the missiles" or "don't shoot the missiles" type messages, not voice or video.)

HF isn't used much anymore, except where mentioned above. OV-10's and F-111's had HF radios, and a former OV-10 pilot would tell us about "blowing the doors off" of truckers on Citizen's Band radios (the bands overlap) while flying cross-country. The aircraft radios put out a lot more power than the FCC restricted transmitter in a Peterbilt. The loading coils would explain the lumps on CB radio antennas, and the lack of long wire antennas, both of which had me wondering if Smokey was embellishing or not. You are talking military, slightly diffent world than civilain.
I can and do hear lots of civie HF aircraft radio traffic. If you have a shortwave radio, you can tune to scads of it.

Blottogg
05-27-2006, 10:47 PM
Yep, sorry about that. In our little Viper world, we just had UHF and VHF/FM, and were ignorant about the world of HF. At least we had it better than the Eagles. They just had two UHF's, and thus couldn't even talk to a lot of civilian towers.

Sooocool
05-28-2006, 09:02 PM
Thank you all!
Most interesting and educational.
Best forum going.

mymhh
05-29-2006, 02:18 PM
Mea culpa on the second sentence I wrote in haste as we were headed out the door for the holiday weekend. I'll bow to others with later experience on the date that HF did (or did not) disappear from aircraft (and which type(s)) - the later history is not my particular area of interest, and my info was from vague recollections from posts on the milsurplus radio list over the years - I should have known better than to send out something that wasn't properly researched. The rest is accurate and I'll be glad to discuss anything avionics related prior to December 1945... http://forums.ubi.com/images/smilies/35.gif

- Mike

Top_Gun_1_0_1
05-29-2006, 02:38 PM
So this Wires does not have anything to do with the reinforcement of the Airframes structural strength?

AAFRadio
05-31-2006, 06:43 PM
That's correct. The wires are what is today called Copperweld (and its equivalents) - a copper clad steel core wire. Because of the lengths involved, the differential length changes due to temperature variations between flight line and high altitude gets fairly large, and a tension unit has to be attached to the end of each wire to allow for this expansion and contraction. Total tension is typically on the order of 10-20 lbs - not enough to function as a structural aid. These antennas are occasionally lost in flight, so depending on them for structural strength would probably be a bad idea anyway. http://forums.ubi.com/images/smilies/halo.gif

- Mike