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fly_boy
30th Dec 2001, 12:30
Could someone with some know-how pls explain the difference or significance of the USB and LSB on the HF radio. What or when can one or the other be used?

Cat1234
30th Dec 2001, 13:02
In normal Amplitude Modulation (AM) signal generation a carrier and two side bands are produced. The side bands are designated Upper Side Band (USB) and Lower Side Band (LSB). It is actually not necessary to transmit all these signals to provide the receiver with enough information to reconstruct the original modulation, audio in this case. The carrier may be removed or attenuated, and so can one of the two sidebands. The resulting signals will require less transmitted power and will occupy less bandwidth.
USB is the norm for aeronautical HF communications, AM is used when a carrier is required such as while being checked for maintenance and as far as I am aware LSB is unused by acft.

Lefthanded_Rock_Thrower
30th Dec 2001, 13:06
LSB is usually not used as USB can be succesfully received at greater distances.

All else as per Cat1234

Cat1234
30th Dec 2001, 13:34
I left out the most intersting part, as Left Handed Rock Thrower has pointed out if the transmitters output power is used to transmit only a sideband, either one, the range is increased.
Thanks LHR.

cogwheel
30th Dec 2001, 15:15
It never ceases to amaze me that people get to fly aircraft and are not instructed on all the equipment therein. Another case of an extremely poor reflection on instructors, training pilots and CASA.

HF like other equipment does need to be understood to obtain the max efficiency out of the equipment and the medium it uses. Too many, it seems, it is all to hard (and is left OFF) and only something that should be used on a rainy day, so you don't need to know much about it till then. Hopefully you will get lucky at the time you need it most!

Of course if you are under instruction you should have asked all these questions at the time?

scud_runner
30th Dec 2001, 16:08
Gee Cogwheel I think you're being slightly harsh here. Other than avionic textbooks what other pilot material have you read this in?? I did a TAFE course and use a bit of Trevor Thom and it wasn't until I borrowed an Avionics textbook that I learnt about upper/lower sideband stuff, Amplitude Modulation, Frequency Modulation etc etc.

BTW no such this as a dumb question!!!! Better to ask now than later on!!!!

cogwheel
30th Dec 2001, 17:32
Sorry Scud, but don't agree. Have seen it far too many times when quite experienced pilots (Not just PPL's) fly aircraft that have an HF installed and don't have a clue on any HF basics or how to operate it. It is just assumed in many cases and I suspect not taught in others because the instructor/training pilot did not get taught either. How many pilots have you seen flying around with the squelch open and not knowing how to set it up?? And then they complain because of the noise they "have" to listen to all day.. Hello, anyone home!!??

A similar thing is going on with GPS. One is expected to know how to operate whatever is in the aeroplane. Sometimes it just aint that easy. (and you think the book is always in the aeroplane?)

Just another example of why the industry is going down the drain with such poor instructing standards. (and this is on the tip of the iceburg)

gaunty
30th Dec 2001, 17:59
Loooxury.

This USB digitally tuned panoramic, vistavision, stereoscope HF.

When we were boy, had to wind out 150 ft of washing line aerial, tune little light thingy, select one of three fixed crystal locked every band, middle, upper and lower side band frequencies, look outside to see if it day or night, recheck correct day/night frequency selected, light wick thing for boiler to run steam generator, then, check to see if DCA FS had selected frequency on chart then talk.
Remember to wind washing line aerial back in before landing or replace 5/- (five shilling) plastic funnel drogue when you forgot and unwind 300 yds of fence from end of aerial.

Walk to PMG phone box make Airflash call to nearest DCA FSU to cancel SAR advised over HF??just to be sure. :)

Simple really.

As for these 95,000 freq synthesised wooser USB HF bah, not like them old days. <img src="frown.gif" border="0"> :)

Islander Jock
30th Dec 2001, 18:34
Cogwheel,

Perhaps the aircraft flown by pilots you refer to did not have HF fitted during their training. We have only one aircraft out of 16 on our line which does have a HF comm.

I know there a plenty of PPRuners here who are passionate about perceived falling standards in training. Without trying to make excuses, it is the regulator who decides the standards, not the training establishments. If more detailed theory training in this or other subjects was to be introduced into say the PPL syllabus then sure, areas such as basic radio theory and RF propagation could be covered. But then you would have organisations which advocate ideologies such as "freedom to fly without unnecessary restriction" crying out that the student is being taught information that is not required and incurring extra expense. It will do no good to provide the best theory training as part of a PPL course if the student decides he can achieve the same result cheaper elsewhere.

I seem to recall the briefing offices [RIP]used to produce an HF prediction chart to show the best frequencies for various regioins and times of day. Havent had a look to see if it is part of the available ASA briefing material but I bet it isn't.

[ 30 December 2001: Message edited by: Islander Jock ]</p>

prunehead
30th Dec 2001, 18:36
CAT 1234 has provided the best explaination. Upper Sideband and Lower sideband operations are identical for operational purposes however. The reason that aviation uses USB is simply convention. Just as aviation uses the technically inferior AM for VHF comms, it's just a convention that cannot be changed.

The only services that use LSB are amateur and citizen radio services, so don't worry about them.

I think that this is a good question, and please dont be intimidated away from asking good questions here.

I don't know of any aviation radios that offer LSB as a user option, and knowing more than basic radio operation from a user perspective is unnecessary for pilots.

Even most avionics LAME's wouldn't know the answer to your question, and to this end CAT 1234 has surprised me.

prunehead
30th Dec 2001, 19:26
Cogwheel,

Although it's off topic, all GPS receivers that are fitted to aircraft are required to have a flight manual suppliment. If they don't either they are illegally installed, or the FMS is lost. it's the responsibility of the holder of the certificate of registration to ensure that it's all ok.

Regards,

PrUnIe

DivergingPhugoid
31st Dec 2001, 00:06
prunehead

Don't forget that the MIL uses both upper and lower sidbands, which is easily switchable if you have Collins HF equipment on board. Some of the better MIL equipment actually used 4 independant sidebands, but then again, we weren't restricted to the normal 150w PEP that I think is a requirement for aeronautical mobile (ie. airplane). From memory, we used a very conservative 10kW per sideband (all four of them).

Fly_boy - general rule for HF - short distance between stns, use lower frequency; long distances, use higher frequencies. Pays to listen out on a few freqs first to see what is being used. Also if you are fitted with FSS (freq synthensised system) which allows selection in .1k steps, you can easily work the international frequencies - SP6, INO3, SEA3, PAC9, etc. although I don't recommend calling UJANG PADANG on 8MHz to cancel SAR somewhere in the middle of nowhere.

HF is akin to Morse code - another lost art, along with the Q and Z codes.

Ice_man
31st Dec 2001, 00:35
Good Topic.

Another good rule of thumb is sun high - use high frequency, sun low - use low frequncy.

Cheers.

Ice.

Torres
31st Dec 2001, 00:48
The Amateur Radio service used LSB under 10 Mhz (3.5 and 7.0 Mhz band allocations) and USB above 10 Mhz (14.0, 21.0 and 28.0 Mhz band allocations). CW is used in the lower section of each band allocation.

Above 30 Mhz FM is generally used.

HF range = 3 to 30 Mhz
VHF range = 30 to 300 Mhz

The Wireless Institute of Australia <a href="http://www.wia.org.au/" target="_blank">http://www.wia.org.au/</a> have some excellent training material available on RF propogation.

ARS: VK4VEE

[ 30 December 2001: Message edited by: Torres ]</p>

Torres
31st Dec 2001, 01:16
Gee Gaunty, you are obviously old enough to know that a "cat's whisker" is neither a protuberance from a feline head, nor a measurement of fine tolerance, but indeed a term relating to wireless..... :) :)

Deaf
31st Dec 2001, 01:52
Prunehead,

Regarding the use of AM for VHF comms, the reason is partly historical in that AM was around before FM but it also gives more reliable comms. This is because the AM reciever avoids the capture effect and continues to recieve the signal rather than lock onto the interference and lose the signal which is inherent in the design of a FM reciever.

An analogy is a conversation in a pub. When all is quiet there is no difference between AM and FM both clear, as the crowd comes in FM continues to give clear reception while AM becomes difficult. When the band starts FM only picks up the band while AM still continues to give comms with assistance from the stylized language used in aviation which has a high degree of redundancy.

Kagamuga
31st Dec 2001, 02:28
My military backpack HF (Kachina) which I use for my Pacific ferry flights is indeed an intersting beast. Battery powered and fully synthesized. The gadget floats (neutral bouyancy)and is easily moved from backpack to aircraft. No external load units reqired etc. The antennae has to be tuned manually via load coils built in. Operates on USB,LSB,AM,CW,and tuning mode where it transmits its own test signal. Clarify, headphone or speaker and HI or LOW power modes.
Automatically selects AM band on International distress frequencies as required.

Loads of fun! Easy to use once you have the hang of it. Battery charges via Cig lighter. Oaklands Oceanics easy from Christmas Island, on the ground with nothing more than an 8ft antennae.

Cheers

[ 30 December 2001: Message edited by: Kagamuga ]</p>

forget
31st Dec 2001, 20:10
All you need to know about modulation modes at;

<a href="http://www.dxing.com/modesand.htm" target="_blank">http://www.dxing.com/modesand.htm</a>

QAVION
5th Jan 2002, 01:55
"LSB is usually not used as USB can be succesfully received at greater distances."

Just wondering if someone could explain this to me, as the sidebands are mirror images of each other.

Thanks.
Rgds.
Q.

Check 6
5th Jan 2002, 03:11
Assuming both sidebands have the same PEP (peak envelope power), they will have the same range at a given time/frequency.

Blacksheep
5th Jan 2002, 09:23
fly-boy,

While you're borrowing avionics text books from the tecchies ask them how they pick their frequencies for testing and the effects of the season and sunspots on the ionosphere and thus on the range obtained from the various frequencies.

Gaunty,
Come of it mate, when you had your flying washing line you also had a Radio Operator to wind it in and out for you. And he usually used CW to transmit because morsing worked better with the carrier wave included.

By the way, did you ever use the HF aerial to fly low level back across the North sea after a night of keeping Jerry awake? You know, the old trick of trailing the end in the wave tops and have the rear gunner call out "climb" if the wake became steady and "dive" if it stopped altogether? :)

Back to the subject - when I was hands-on and had to test an HF after fixing it down on the line, I'd get the best frequency from the handy frequency chart kept in the Jeppeson Nav Bag behind the Captain's seat. All the recommended numbers were there and updated to account for the current season and sunspot activities. You didn't know its there? Tut-tut!

And I wouldn't recommend calling Ujang Padang on any frequency at any time. You'll get far more sense from the good old Aussies at Darwin most times. [provided you know the frequency of course <img src="wink.gif" border="0"> ]

**********************************
Through difficulties to the cinema

Tinstaafl
5th Jan 2002, 20:35
Ah... the joys of finding where the f%^& the FISCOM has got to and then hoping like hell one of the 10 faded, handwritten frequencies listed on the equipment matches at least one of the FISCOM frequences.

Provided the list is still legible. In the dark. With turbulence. In some remote corner of the panel. <img src="eek.gif" border="0">

Loc-out
8th Jan 2002, 03:12
Kagamuga

Wouldn't mind getting my hands on one of those Mil HF's if I knew where to get one.

mcdhu
8th Jan 2002, 13:53
Good replies to a fair question! The only thing I would add is that if you are having difficulty getting the BBC World service on HF when far from home, try all 3 SB settings; sometimes, for some inexplicable reason, LSB or AM might work better than USB.
Hey Gaunty, I seem to remember that one of the landing checks on an old radial, sleeve-valve engined aircraft I used to fly went:
'Trailing Aerial....In, Ratchets Selected, Beads Clamped.'
Boy, have things got better!
Cheers
mcdhu

jbc2001
9th Jan 2002, 10:05
Just remember that use of LSB by commercial air transport is illegal in the US! Most modern HF radios also transmit a small "vestigial" carrier with the SSB that simplifies signal demodulation at the receiver.

christian_MD80
9th Jan 2002, 14:20
Propagation forecast charts:

<a href="http://www.stockholmradio.telia.com/aero/" target="_blank">http://www.stockholmradio.telia.com/aero/</a>

<a href="http://www.bernradio.ch/forecast1.htm" target="_blank">http://www.bernradio.ch/forecast1.htm</a>

Rgds

Chris

Self Loading Freight
9th Jan 2002, 16:07
Loc-Out --

There's quite a market in military HF manpacks, but they're expensive. They turn up on eBay (very expensive), on amateur radio sites (not so expensive) or at amateur radio rallies (you can get lucky, but you have to be able to cope with ham rallies. These can sometimes seem like a home for the terminally bewildered let lose at a Harrod's sale).

Have a look at

<a href="http://groups.yahoo.com/group/hfpack" target="_blank">http://groups.yahoo.com/group/hfpack</a>

or

<a href="http://groups.yahoo.com/group/armyradios" target="_blank">http://groups.yahoo.com/group/armyradios</a>

if you're keen. A much cheaper, more effective, easier and more fun alternative is to get a Yaesu FT-817 portable HF/VHF/UHF transceiver -- which in any case uses technology that Yaesu developed for its mil range. Costs £800 in the UK or £600 if you shop around on the Net (Greece recommended -- US prices and no import duty).

I'll get me anorak...

R, G6HVY and bar

radeng
9th Jan 2002, 16:18
It is said in ham radio circles that the use of LSB below 10MHz and USB above comes from an ITU recommendation. I've never found that recommendation......I believe it came about because of the design of the very early (1950's) ham radio SSB equipment.I don't think LSB gets much use in military circles these days.

gaunty
9th Jan 2002, 17:58
Blacksheep and mcdhu

Modesty prohibits me from claiming the height finding methods of WW11 or WT operator enjoyed by my father or the rare privilege of sitting behind an old radial sleeve-valve.

But in Oz from the mid sixites for me up to the early eighties crystal locked raw HF was the mode for most journeys.
You generally only carried those frequencies (3-4)for the area in which you operated as the limitation of the number of channels (10 if I recall) available on your AWA whizbang did not usually allow universal Oz coverage and the sheer expense of getting a crystal cut and fitted (I seem to recall $500 in the days when that would buy a good used car).
I have kept a souvenir FISCOM which was printed in colours that disappeared when viewed at night with the then fashionable red cockpit lights.

I seem to recall once when the dear old DCA issued about 100,000 pads of new Flight Plan forms with the same disappearing colour ink. The first experience when you picked it up after take off to enter your best guess for the next reporting point was a little bewildering.

Plastic funnels and fences, the first you new usually, was when there was a whirring noise from the HF aerial reel as it ran out to its limit then "twang" followed by the backlash. Fishing rod reels have a lot of design features derived from this experience. OR a very short arrival.

The new Codan SSB thingies were a joy, providing endless amusement with "Donald Ducking" by playing with the Clarifier and the King 93 Godzillion frequency synthesised toys miraculous indeed.

And if all that was too hard, there was what they call music from China and Koran reading competitions from Indonesia helping to while away the long nights.

Spodman
14th Jan 2002, 13:07
Great stuff Gaunty.

Sorry to disappoint, but the good ol' boys at Darwin HF have been in Brisbane for a while now, and before that they were in Perth.

Still get people transmitting AM on HF, my FS spies tell me, sounds like an enraged duck from our end. I have no idea what it sounds like when they tell them to change to USB, but it works sometimes.

The squeally-horrible stuff you hear when 2 stations transmit together on VHF is the carriers heterodyning with each other, multiple stations on USB really do sound like people talking over each other, and can be understood. It would a huge improvement to safety if we only used SSB on VHF.

Loc-out
20th Jan 2002, 02:06
Self Loading Freight

Thanks for that. Will investigate further. <img src="smile.gif" border="0">

Golden Rivet
20th Jan 2002, 15:04
slightly off the thread, but does anyone have a list of HF frequencies that can be used for ground testing HF in the UK?

Thanks