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The Band Edge- How Close is Too Close?
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by ZS6EZ on April 25, 2001
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An extension to the logic that hasn't been mentioned, is that one could actually operate with the dial outside the band. For example, sitting on 28 299,7 would be perfectly legal if one had sufficiently sharp filter cutoff at 300 Hz. That being the case, sitting on 28 300,000 is actually perfectly acceptable, as it actually provides a 300 Hz guard band. From halfway around the world, it is very difficult to hold down a frequency when short skip is present, or when there is good propagation between the major centres. We are almost invariably in an antenna null to anyone in the major centres. The band edge is a very valuable resource in that regard, as it cleans up QRM at least on one side. For that reason, I've had my fair share of lectures from anonymous advisers, most of whom have been ill-informed.
For CW signals, the keying baud rate is around 83% of the speed in wpm. A popular contesting speed such as 35 wpm is just under 30 Bd. With well-shaped waveforms, the sidebands would not extend much more than 30 Hz either side of the carrier. However, waveforms are generally rather "hard", requiring a bit more bandwidth. W4ZV's rule of thumb (4 x wpm) is probably not far off the mark, leading to a guard band of around 150 Hz. Some big M/M entrants stretch this limit somewhat!
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RE: The Band Edge- How Close is Too Close?
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by w8ji on April 28, 2001
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We all better read the rules again. The rules do not say we are allowed to be close if the emissions are down 40 dB.
The rules say we are not allowed to have ANY emissions outside the band. It means exactly what they say. If you have ANY emissions at ANY level outside the band or segment you are allowed to use it is illegal.
The same is true for harmonics that cause interference.
-40 dB is not even a spec for this, it probably has been extracted by well-intentioned people from type-acceptance rules fo the minimum attenuation we must have at HF for spurious emissions. That actual rule is 50mW or -40dB (above certain mean power levels)....but that is a minimum for type-acceptance. It is NOT what can get us "busted".
What will get us busted is if we have ANYTHING they can hear outside the band or authorized segment.
97.303(b) kicks in at any time. It says "Emissions resulting from modulation MUST be confined to the band or segment available to the control operator. Emissions outside the necessary bandwidth must not cause splatter or keyclick interference to operations on adjacent frequiencies."
It does NOT say, "but if you are 40dB down it is OK".
The rules are not "pick the one you like", and the rules for type-acceptance are not the same rules for preventing interference. If we violate any subpart, it is a violation. The rule is, none of our clicks or sidebands can extend outside the band or segment we are allowed to use.
73 Tom
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The Band Edge- How Close is Too Close?
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by KL7HF on May 10, 2001
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Good comments, but need to go further to meet the
Commission's R&Rs.
There are 2 types of emmissions that are involved.
1) Those within the information envelope that are
necessary for communications.
2) Those not necessary for communications, referred to
as "Spurius Emmissions".
Your comments apply very well to the first.
The requirements for the second is that they not only
must be contained entirely within the Amateur bands, but must meet stringent attenuation standards. These
are quite often outside the bands, even thought the
carrier frequency is far enough inside to eliminate
out of band envelope information.
Cranking the mic gain up one more notch to get
through puts you in violation, as well as irritating
other contesters nearby.
By the way - those with the carrier oscillator set
quite far up the filter passband to get higher pitched
audio may very well exceed the 3 kHz rule. Remember,
a 2.1 kHz filter is rated only at the 6 dB attenuation
point. Setting the oscillator at 800 Hertz into the
filter passband means that you are only 6 dB down at 2.9 kHz.
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RE: The Band Edge- How Close is Too Close?
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by lu9ay on May 29, 2001
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1. For CW you should add roughly a minimum of 4 times your keying speed to the band edge due the the additional bandwidth CW keying consumes. If you are sending at 40 WPM,
.. ok I will try to remember to bring a calculator when looking for a clear frequency near the edge and do the math.. hopefully when I finish , the contest wont be over :)
matt
w1/lu9ay
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RE: The Band Edge- How Close is Too Close?
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by VE2DC on May 30, 2001
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Perhaps the contest rules should specify a minimum guard band. A few disqualifications would go a long way to curing the problem and end the pointless discussions of EXACTLY how wide an SSB or CW signal is. How high is UP anyway?
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The Band Edge- How Close is Too Close?
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Anonymous post on June 9, 2001
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Good point but it doesn't address the bottom band edge, on USB, as others have mentioned. I believe leading contesters believe you can go right down to just above 14.150, for instance.
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RE: The Band Edge- How Close is Too Close?
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by k3ko on June 10, 2001
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There has to be some limit describe the acceptable amount of suppression.
If one does a fourier transform of a single dit, he finds that there are frequency components which extend to almost light frequencies. Thus, there is no way for any time varying waveform to have zero energy beyond the fundamental and normal sidebands. Given this fact, zero can't mean zero. No technical way to achieve it other than QRTing.
Clearly the FCC knows this and won't hold a gun to the head of anyone who radiates a nanowatt outside his allocated frequencies. I doubt that they will persue anybody with properly operating type-approved equipment. Inteference with another service is perhaps the one exception.
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The Band Edge- How Close is Too Close?
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by W5JLJH on July 26, 2008
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I think the reason there is so much confusion is this;
1. All amateur radios - Factory or modified will trans
mit on say 7300 khz. If this is considered out of band then why do they work there?
2. If 7300 khz is out of band then make the darn things
stop transmitting at 7297? they work fine as intended from the factory.
3. Also the broadcast bands (AM that is) the new segment goes to 1700 KHZ, if you tune to 1700 KHZ AM on any night, you will hear more than one station transmitting on 1700 KHZ amd and is more than 5 khz wide! Do they majically end up as legal?
4. I Hate people who jump in on any frequency without identifying themselves. That is certainly a worse violation and is stated so and "is" in the rules.
5. Strap on a pair, spin the dial and use 7300 khz
and wait for the new icom and yaesu's to come out with more band clipped off the ends GEEESE! ??
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RE: The Band Edge- How Close is Too Close?
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by W5JLJH on July 26, 2008
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P.S. Also just to add another note.
If you tune to 7302 KHZ USB on any Saturday and listen to Air Force Mars, you clearly hear them down as far as 7297 Khz (even if you use 1.6 Khz filters. This is clearly another radio service, breaking the Law as you call it. Wheres the ruling there?
Time would be better spent donating your efforts to one of the ARRL organizations rather than running scared and bashing other operators for the shortcomings of the Laws of physics and radio design limits?
Don't constantly sit or the fence as it makes your neighbors nervous.
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