Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: Hardest part of the General exam?  (Read 16655 times)
KD8NYW
Member

Posts: 10




Ignore
« on: July 25, 2011, 05:54:14 PM »

While my studies have progressed well, I find the dB calculations next to impossible, and the G1C section ("What is the maximum symbol rate permitted for RTTY or data emission transmitted on the X band") has been hard to keep straight. What typically trips General students along the road?
« Last Edit: July 25, 2011, 06:51:37 PM by KD8NYW » Logged
KG4LMZ
Member

Posts: 102




Ignore
« Reply #1 on: July 26, 2011, 06:02:15 AM »

As far as the test goes, I believe that the test contains exactly one question from each section.  So if you're having trouble with a section, it's only going to hit you for one question on the test.  What part of the dB calculations are throwing you?  The symbol rate sort of stuff is just rote memorization.
Logged
KI4GTD
Member

Posts: 17




Ignore
« Reply #2 on: July 26, 2011, 07:47:11 AM »

I just took the General class on Saturday; the antenna-related ones get me because most of my operations so far have been with a little 2m HT. I've read and studied but seeing the questions out of order on a test caused a general panic amongst the brain cells and they all went elsewhere. Otherwise, the test wasn't too bad. As mentioned, there are a limited number of questions about each topic. The study method that I was using was to concentrate on areas where I was weak and count on experience and/or training to get me through the parts that I was more comfortable with. It worked, thankfully.

73 Brian KI4GTD
Logged
AC5UP
Member

Posts: 3864




Ignore
« Reply #3 on: July 26, 2011, 08:51:21 AM »

While my studies have progressed well, I find the dB calculations next to impossible...

Memorize two numbers: Three and Ten.

A 3 dB change in level will either double or halve the signal level depending on which way you're going. Assume 1 volt peak to peak. Change it by +3 dB. It's now 2 volts peak to peak. Take the same 1 volt signal and change it by -3 dB. It's now .5 volt peak to peak.

Easy so far.

Now... Let's change a 1 volt signal by +6 dB. Also easy, as the change is +3 dB plus another +3 dB for a total of +6 dB. Levels would be 1 volt, 2 volts and 4 volts. Every +3 dB step doubles the signal level. What if it was a +9 dB change? Add another +3 dB so the 4 volt signal becomes 8 volts.

That's how you work powers of 3 dB... Same as powers of 2. But what about 10 dB? Same deal except we'll go 10x instead of 2x.

Add +10 dB of gain to a 1 volt signal and it's now 10 volts. A +20 dB increase would give you 100 volts: (1 x 10) x 10 = 100 or 10x plus another 10x = 100x. Take a guess what a 30 dB change would mean to a 1 volt signal? Yup.................. 1,000x

How about 23 dB? 10x + 10x = 100x + 2X = 200X. And, in case you were wondering, 26 dB would be twice the amplification as 23 dB or 400x.

Notice how a 9 dB change = 8x and a 10 dB change = 10x? Decibels are on a logarithmic scale and that's Ohhh Kayyy.

Last item: An amplifier has a 30 dB signal to noise ratio. A very similar amplifier has a 33 dB signal to noise ratio. Which has the lower noise level, and by how much? The higher the ratio between noise and signal the better, so it's a no-brainer the 33 dB spec is better. But how much better? If three is 10% of 30 (it is) and the first amplifier has a 30 dB S/N ratio (it does) then a 33 dB S/N ratio is 10% better than 30 dB...... Right?

- WRONG - WRONG - WRONG -

Remember that every + / - 3dB either doubles or halves the raw value so the 33 dB S/N amplifier has exactly HALF the residual noise level as the 30 dB jobbie. And it doesn't matter if we're looking at the difference between 2 and 5 dB or 72 and 75 dB... The three dB change will always be a power of two. If the difference in specs was between a 100 dB S/N ratio and 110 dB it would be a 10X difference in noise, not 10%.

Once you understand 3 and 10 as the major players in calculating dB's you can ballpark it well enough to reason your way through a multiple choice test. And, whatever you do, don't go stupid and get faked out by something like the 30 / 33 dB question given above.

Now go, and flunk no more........................................!

 Grin
Logged

Never change a password on a Friday                
N2EY
Member

Posts: 3879




Ignore
« Reply #4 on: July 26, 2011, 11:00:15 AM »


A 3 dB change in level will either double or halve the signal level depending on which way you're going. Assume 1 volt peak to peak. Change it by +3 dB. It's now 2 volts peak to peak.

Nope.

3 dB is twice the power, not twice the voltage. Twice the voltage is 6 dB (four times the power).

Change a 1 volt signal to 2 volts and you have a gain of 6 dB because the current also doubles.

73 de Jim, N2EY
Logged
KD0FNR
Member

Posts: 13




Ignore
« Reply #5 on: July 26, 2011, 02:08:01 PM »

I wrote up one more take on the decibel issue at:

http://copaseticflows.appspot.com/examhelp/techdecibel.html

It's in conjunction with the free practice exams at:
http://copaseticflows.appspot.com/hamtest

The write ups here on the forum are excellent, mine is just one more perspective.

73 de KD0FNR Hamilton
Logged
WB2WIK
Member

Posts: 20595




Ignore
« Reply #6 on: July 26, 2011, 06:39:14 PM »


A 3 dB change in level will either double or halve the signal level depending on which way you're going. Assume 1 volt peak to peak. Change it by +3 dB. It's now 2 volts peak to peak.

Nope.

3 dB is twice the power, not twice the voltage. Twice the voltage is 6 dB (four times the power).

Yep.  Plus why bother memorizing silly stuff when they will allow you to bring a calculator to the test?  A $9.95 calculator has log functions.

Logged
KA5N
Member

Posts: 4380




Ignore
« Reply #7 on: July 27, 2011, 05:53:07 AM »

A ham friend of mine (who was also into photography) said he always had trouble with
dB's and so he always converted them into F-Stops and never was troubled again.

I think people would have less difficulty and fewer stumbling blocks if they would study math, electronics, rules and regs etc. first.  Then read over the questions in a study guide and they would find any of the tests to be a sure thing. 

Also with multiple choice questions, one can almost pass without knowing any of the answers just by learning that if you are given four answer choices, two of them will be obiviously incorrect and of the two left logic and good guessing (even coin flipping) will get half of the correct answers.

Allen
Logged
WB2WIK
Member

Posts: 20595




Ignore
« Reply #8 on: July 28, 2011, 10:21:00 AM »



Also with multiple choice questions, one can almost pass without knowing any of the answers just by learning that if you are given four answer choices, two of them will be obiviously incorrect and of the two left logic and good guessing (even coin flipping) will get half of the correct answers.



So, this blonde was taking a multiple-choice exam and her friend seated next to her saw she flipped a coin for each answer.  After about 20 minutes, she was done and put down her pencil.

Then, she started flipping the coin again.  Her friend whispered, "I thought you were done!"

The blonde replies, "I was, but now I'm checking my answers."
Logged
N0FPE
Member

Posts: 364




Ignore
« Reply #9 on: July 31, 2011, 08:20:07 PM »

The hardest part of any amateur radio exam these days is trying to decide where to go for breakfast before or lunch after the exams!  Grin
Logged
W5DQ
Member

Posts: 1209


WWW

Ignore
« Reply #10 on: August 02, 2011, 02:17:55 PM »

Just remember "PIE ARE SQUARE, CAKE ARE ROUND and APPLESAUCE ARE MESSY"
Logged

Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
K2OWK
Member

Posts: 1060




Ignore
« Reply #11 on: August 02, 2011, 09:30:53 PM »

I found the hardest part of the general exam was getting up in the morning, and getting there in time to take the test.

73s

K2OWK
Logged
W5GNB
Member

Posts: 419




Ignore
« Reply #12 on: August 06, 2011, 07:20:34 AM »

"The hardest part of any amateur radio exam these days is trying to decide where to go for breakfast before or lunch after the exams! "

HAHAHA !! How entirely CORRECT you are !!!

Actually, for me it was remembering WHICH DAY the exam was being given so that I didn't sleep in that day !!!

 73's
Gary - W5GNB
Logged
AE5JU
Member

Posts: 229




Ignore
« Reply #13 on: August 06, 2011, 04:05:06 PM »

"What typically trips General students along the road?"


Not studying for it, thinking they can only pass the Tech.

As a CVE I highly encourage new hams that have just passed the Tech to not stop.  Take the General, it won't cost you a dime more, just a little more time.

And when we give classes we highly encourage students that once they are doing 85%-90% on the practice tests to continue study for the Tech, but to begin studying for the General, too.  At the very least, look over the material.  It is really not that much harder.

On the first test session I administered I had the new Techs take the General.  One missed being a General by only 2 questions, another by just 6. 

I asked, did you study the General as we suggested?  No, they had not. 

I further asked, had you at least read over the material a few times, do you think that you could have passed those 2 more, or 6 more questions?

They replied yes.

So, that is the major impediment, failing to study for it.

As far as memorization, well, a lot of it IS memorization.  And no code, well, even our military does not use CW anymore.  If you want to learn CW, great, do so!  If that is not your interest, that's OK, there's nobody stopping you.  There's something for everyone in ham radio.  Various digital modes, IRLP, Echolink, APRS, SSTV, and more.  You never quit learning in this hobby, there's always something new right around the corner.

73,
Paul - AE5JU
Logged
KG4LMZ
Member

Posts: 102




Ignore
« Reply #14 on: August 07, 2011, 09:23:50 AM »

When I took the Tech test, I'd only studied for Tech.  Took the General test at the urging of the VECs.  Missed by one.  And had changed a correct answer to a wrong answer, to boot.  I definitely urge people taking the Tech test to go ahead and take the General test, even if they haven't studied for it.

The Extra test, on the other hand, would have been a waste of time.  I needed to refresh a lot more of the electrics, electronics, and "physics of RF" sorts of stuff to pass the Extra.  I hadn't studied for it when I took the General test, but went ahead and gave it a try.  Didn't make it this time, either, but the VECs didn't tell me my score, and I didn't ask.  I was already planning to study and take the Extra test the next month.
Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!