Radio Preppers

General Category => Licensing => Topic started by: Sunflower on October 09, 2012, 01:27:40 am

Title: Question for Technician Class:(T3B06)
Post by: Sunflower on October 09, 2012, 01:27:40 am
Reference: The No-Nonsense, Technician Class License Study Guide, by Dan Romanchik, KB6NU, PAGE 19.

Quoting part of fourth para:
"The formula for converting frequency to wavelength in meters is wavelength in meters equals 300 divided by frequency in megahertz. (T3B06)

Quoting fifth para:
"The approximate wavelength of radio waves is often used to identify the differnt frequency bands. (T3B07). For example, when we refer to the 2 meter band, we are referring to the amateur radio band that spans 144 MHz to 148 MHz. A radio wave with a frequency of 148 MHz, would have a wavelength of 2.02 meters. "

I do not understand this. Can someone please translate this into a math formula? or something to explain it better? I did not follow it at all.

....does this mean 300 divided by 144 MHz = meters? (2.08 meters)???
...or 300 divided by 148 =2.03 meters??
...Where does 2.02 come from? does it matter?

In the paragraphs directly above it, the approximate velocity of a radio wave as it travels through free space was noted as 300,000,000 meters per second.



Thank you,
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on October 09, 2012, 01:36:33 am
300/148=2.027 (2m band).

Let's try for 14.3MHz: 300/14.3=20.97 (20m band).
Title: Re: Question for Technician Class:(T3B06)
Post by: Sunflower on October 09, 2012, 01:48:43 am
That was helpful.
I need to work on how to use my calculator more precisely.
Thank you.
Title: Re: Question for Technician Class:(T3B06)
Post by: Sunflower on October 09, 2012, 01:51:13 am
Quote from: Sunflower on October 09, 2012, 01:48:43 am
That was helpful.
I need to work on how to use my calculator more precisely.
Thank you.

Now I understand the " :-["
Very good. My calculatation was off. Goodness. I will be so happy when I get through this material. It is enjoyable, but it will be a whole lot more enjoyable to pass the test. I need to rethink which calculator I drag along.

Thank you for the help.
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on October 09, 2012, 01:57:44 am
You're welcome. I suggest practice tests on QRZ.com. They helped me a lot.

Gil.
Title: Re: Question for Technician Class:(T3B06)
Post by: Sunflower on October 09, 2012, 02:03:58 am
Quote from: gil on October 09, 2012, 01:36:33 am
300/148=2.027 (2m band).

Let's try for 14.3MHz: 300/14.3=20.97 (20m band).

Not to be difficult, but why not ....call it 21 m band? or does it all get rounded up and down to the simpliest number?
Let's try for 14.3MHz: 300/14.3=20.97 (20m band).

--time for bed.
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on October 09, 2012, 02:33:58 am
Hello,

It's just rounded up for simplification. Even the 300,000,000 is rounded up. Doesn't matter...
The formula is just useful to calculate antenna length.
Say you need a half wave dipole for 7MHz: 300/7=42.85m.
In feet: 42.85*3.048=130.6ft.
Half wave: 130.6/2=65.3ft. of wire needed.

Usually, the formula used for a dipole though is 468/f
So, 468/7=66.85ft. You start with that and trim as needed.
Remember that formula for the exam.

Gil.
Title: Re: Question for Technician Class:(T3B06)
Post by: Paul on October 09, 2012, 10:30:33 pm
Converting frequency in Mhz to wave length in meters is only an approximation.  The commonly used 'band' numbers are not exact, and are a generalization.  Easier/shorter to say 2 meters than saying 2.0X meters of 14X.XXX Mhz.
The 'magic' number for finding lengths of antennas (234 or 468) are based on the 'general' numbers, 246 or 492, which are closer to lengths in 'free space'.  The other two, 234 or 468, factor in velocity factor for a small'ish conductor in air (typically used for wire antennas).  If you really want to know where all those 'numbers' come from I would suggest finding a 'Hand Book' and taking a look at the antenna section.
- Paul
Title: Re: Question for Technician Class:(T3B06)
Post by: White Tiger on October 11, 2012, 03:54:50 am
It fits that Sunflower is struggling a bit with the loose factoring going on here - I hallen to know she teaches complicated and specific topics - like Algebra - so if you give her an equation...the math is supposed to work!

The good part (for me) is that after reading this thread, I no longer have to rely on memorization for this part of the exam!
Title: Re: Question for Technician Class:(T3B06)
Post by: Sunflower on October 19, 2012, 09:45:33 pm
Quote from: gil on October 09, 2012, 01:57:44 am
You're welcome. I suggest practice tests on QRZ.com. They helped me a lot.

Gil.

Finally got on QRZ tonight. Wow. Went from 40 to 55 percent. Not very good.

I also spoke with the exam man for our area. Next test date is Nov 14th. I hope to be there. Much will depend on how the progress I make on QRZ.com.
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on October 19, 2012, 09:52:46 pm
Keep doing them Tess, the same questions are going to come up over and over, and you'll remember them...

Gil.
Title: Re: Question for Technician Class:(T3B06)
Post by: White Tiger on October 20, 2012, 12:55:46 am
Gil's right Tess, take them OVER and OVER! That is how I passed Tech and General.

I am currently using this same strategy for the Extra exam (except there are 50 questions in the Extra class, question pool). When I first started taking the practice exams for Extra Class a few weeks ago, I was at 40%, Gil gave me the Extra class study book, and then I started taking the practice tests on www.hamtestonline.com (the non-study practice exams are free) - and I am now at 65%!

You can do it!
Title: Re: Question for Technician Class:(T3B06)
Post by: cockpitbob on October 20, 2012, 11:41:55 pm
Yes, keep grinding the QRZ.com practice tests over and over.  My son got his Tech and his General when he was 11 using this method.  At that age kids have a great memory.  No, he didn't understand the theory, but that's OK.  Learn the rules and procedures enough to stay out of trouble, and get on the air.  If ham radio is something you stick with, the theory will come with time.
Title: Question for Technician Class:(T3B06)
Post by: White Tiger on October 21, 2012, 02:06:29 am
It's actually surprising how much you retain - and then as you assemble your gear - how much you begin to associate between what you memorized and the practical application of putting it all together.

I can only imagine how much more you would learn actually operating for a couple of years - especially if you find someone that can help explain around some of the hindrances.

If I could teach the teacher - as I believe you are Tess - I'd say don't try to learn it - just memorize it.
Title: Re: Question for Technician Class:(T3B06)
Post by: buckeye43210 on September 28, 2013, 10:28:18 am
Here's a tip to help you solve problems of this type on the exams:

Draw a circle, then draw a horizontal line dividing the circle into an upper and lower half. Next draw a vertical line dividing the lower half of the circle into two parts. Write 300 in the upper half of the circle, then write 'f' in the lower left section of the circle followed by 'm' in the lower right half of the circle.

Now cover up the symbol you are trying to solve for. Suppose you are given the frequency in MHz and are asked to find wave length in meters. Cover up the m and you get m = 300 over f or 300 divided by f. Now suppose you are given the wavelength in meters and want to find the frequency in MHz. Cover up the f and you get f = 300 over m or 300 divided by m.

The same technique works for Ohm's Law, Power in Watts, etc. You can draw your memory aids on your scratch paper at the beginning of your exam.

An example using Ohm's law can be found here. (http://hvacwebtech.com/Ohm's%20Law.htm)
Title: Re: Question for Technician Class:(T3B06)
Post by: KK0G on September 28, 2013, 11:04:56 am
Quote from: buckeye43210 on September 28, 2013, 10:28:18 am
Here's a tip to help you solve problems of this type on the exams:

Draw a circle, then draw a horizontal line dividing the circle into an upper and lower half. Next draw a vertical line dividing the lower half of the circle into two parts. Write 300 in the upper half of the circle, then write 'f' in the lower left section of the circle followed by 'm' in the lower right half of the circle.

Now cover up the symbol you are trying to solve for. Suppose you are given the frequency in MHz and are asked to find wave length in meters. Cover up the m and you get m = 300 over f or 300 divided by f. Now suppose you are given the wavelength in meters and want to find the frequency in MHz. Cover up the f and you get f = 300 over m or 300 divided by m.

The same technique works for Ohm's Law, Power in Watts, etc. You can draw your memory aids on your scratch paper at the beginning of your exam.

An example using Ohm's law can be found here. (http://hvacwebtech.com/Ohm's%20Law.htm)



Yep, that's the way I was taught many years ago and I still use it to this day. After all these years I seldom physically write it down any longer but it's still how I "see" it in my mind.
Title: Re: Question for Technician Class:(T3B06)
Post by: extra_class_ham on January 12, 2014, 12:18:48 pm
Quote from: Sunflower on October 19, 2012, 09:45:33 pm
Finally got on QRZ tonight. Wow. Went from 40 to 55 percent. Not very good. ...


Another great site for practice test is eham or http://www.eham.net/exams/

Now if you dont mind spending a little money (same cost as the ARRL study guide) go to http://www.hamtestonline.com and this is interactive. It drills you after brief explanations along with links for more in depth explanation and will make certain you pass with ease. It knows you weaker areas and stronger areas and will help you advance with no unlearned material.

Just use "study" mode, and maybe "top score" to see where you stand in rank and watch is climb as you go through)

Then when you are 80% complete (it will let you know each 5% points, ie 5, 10, 15...) , start trying "practice test" and when you consistently score over 80%, you are ready for the test. This will take you 2 weeks if you put in an hour or two each night (includes weekends) and after you pass, pay again and work on the general, then extra.

My 11 yr old grandson went from no license to general in a month (over this last summer 2013). He just turned 12 and is working on his extra class. I have signed him up for extra part of the study and he is working on it now and this summer, he spends it at my place and we should do his extra class test than. 
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on January 12, 2014, 01:22:02 pm
QuoteMy 11 yr old grandson went from no license to general in a month (over this last summer 2013). He just turned 12 and is working on his extra class.


Nice to hear that some kids are interested in science in this country!  :)

Gil.
Title: Re: Question for Technician Class:(T3B06)
Post by: cockpitbob on January 12, 2014, 09:12:46 pm
Quote from: gil on January 12, 2014, 01:22:02 pm
QuoteMy 11 yr old grandson went from no license to general in a month (over this last summer 2013). He just turned 12 and is working on his extra class.


Nice to hear that some kids are interested in science in this country!  :)

Gil.
Shameless bragging alert:
My son got his Tech and General 2 weeks apart when he was 11.  I coached him on some theory, ohms law and dividing by 300 to get wave length or MHz, but it was mostly grinding through the practice tests.  They remember so well at that age.

He's now 15 and cares very little for ham radio.  He likes Field Day with our club because of the food, camping, movie Friday night after set-up and the social aspect.  I don't think he's been on the air in a year though.
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on January 12, 2014, 11:03:59 pm
He'll probably pick it up again later after his teenage phase.. Just make sure he renews his license at 21...

Gil.
Title: Re: Question for Technician Class:(T3B06)
Post by: cockpitbob on January 13, 2014, 08:58:50 am
Quote from: gil on January 12, 2014, 11:03:59 pm.. Just make sure he renews his license at 21...

Gil.
I can't remember for sure, but I was so thrilled at him getting his General that I think I promised to pay for that first renewal.
Title: Re: Question for Technician Class:(T3B06)
Post by: extra_class_ham on January 13, 2014, 01:13:00 pm
Quote from: cockpitbob on January 12, 2014, 09:12:46 pm
Shameless bragging alert:
My son got his Tech and General 2 weeks apart when he was 11.


My grandson was a tech for only 13 days before upgrading to general.  ;)

But the truth is, he took his general test the following month, and because of a legibility issue on his original form, he was slow in getting his call (tech) making i t come later.  He received it just a week before taking general. So he was only a tech for 13 days. He used hamtestonline.com and will be spending this summer again with me.

I promised him I'd buy him a new VHF rig and power supply and QSL cards if he passed tech and a new HF rig is he passed general. Well, he made me eat my words. Got him a new Yaesu FT1900, coax, MFJ 45 amp power supply and a Cushcraft AR2X 2 meter vertical.


I promised him a new HF rig for general, well, a new Icom IC-718 and a RadioWayvz G5RV lite and an LDG auto tuner with interface cable for his radio.

I signed him up for a local repeater group, signed him up in a local ham radio club and signed him up for the ARRL. He bought himself a little Boafeng UV-5R+ radio for club activities, but he had trouble with the repeater freq programming (pain to program plus club member's gave him friendly ribbing on his radio). So for his birthday, Dec 2013, I got him a new Yaesu FT250R HT with remote mic, better antenna, a SignaLink USB for PSK31/JT65... with the correct cable to plug into the rear data port for his Icom 718 and for Christmas 2013, got him a Heil PR781 mic with the PL-2T boom, HS-1 handswitch and adapter cords to make it plug and play. Plus a nice Diawa CH801HP cross needle power meter.  I think I have spent $3500+ in radio gear for him since summer 2013, bought all of it new.  He live about 100 miles from me.  I spent a Saturday in August setting up his entire station with help from his dad. The entire family has been really helpful.  He is a roster member of the W.A.R.T.S. or Washington Amateur radio traffic system, he is their youngest member EVER by a long shot I was told.  ;D

His mom makes sure to take him to all his radio club meetings, he is volunteering for lots of activities etc and having fun. His mom has been very supportive and sets through those boring meetings (to her) with him, so he can attend.

I haven't promised him anything for extra. I may not.  ;D

He is the only one in the family that is still alive that was interested in radio.
I was excited when he all of a sudden shows huge interest in radio.

I cant get the wife to even get her tech license. Zero interest.  >:(

73 Rick
Title: Re: Question for Technician Class:(T3B06)
Post by: extra_class_ham on January 13, 2014, 01:24:38 pm
Quote from: cockpitbob on January 13, 2014, 08:58:50 am
I can't remember for sure, but I was so thrilled at him getting his General that I think I promised to pay for that first renewal.


I know the thrilled feeling. Many people at the test center was floored to find out he was doing general. He missed 2 on his tech test and one on his general.

Bob,  you know, if you go to the FCC website directly, you can renew at no cost at all, just a mouse click as long as there is no vanity call. But don't tell him that .  ;)
Title: Re: Question for Technician Class:(T3B06)
Post by: White Tiger on January 13, 2014, 02:19:05 pm
Quote from: Sunflower on October 19, 2012, 09:45:33 pm
Finally got on QRZ tonight. Wow. Went from 40 to 55 percent. Not very good.

I also spoke with the exam man for our area. Next test date is Nov 14th. I hope to be there. Much will depend on how the progress I make on QRZ.com.


Hey Tess, an update on your test? Hope all is well!


Sent from my iPad using Tapatalk HD
Title: Re: Question for Technician Class:(T3B06)
Post by: cockpitbob on January 13, 2014, 08:51:21 pm
Quote from: extra_class_ham on January 13, 2014, 01:24:38 pm
Quote from: cockpitbob on January 13, 2014, 08:58:50 am
I can't remember for sure, but I was so thrilled at him getting his General that I think I promised to pay for that first renewal.


I know the thrilled feeling. Many people at the test center was floored to find out he was doing general. He missed 2 on his tech test and one on his general.

Bob,  you know, if you go to the FCC website directly, you can renew at no cost at all, just a mouse click as long as there is no vanity call. But don't tell him that .  ;)
Thanks for the tip on the free renewal!  I'll try to remember that in 2020.
Title: Re: Question for Technician Class:(T3B06)
Post by: White Tiger on January 14, 2014, 12:14:47 pm
Quote from: extra_class_ham on January 13, 2014, 01:24:38 pm
Quote from: cockpitbob on January 13, 2014, 08:58:50 am
I can't remember for sure, but I was so thrilled at him getting his General that I think I promised to pay for that first renewal.


I know the thrilled feeling. Many people at the test center was floored to find out he was doing general. He missed 2 on his tech test and one on his general.

Bob,  you know, if you go to the FCC website directly, you can renew at no cost at all, just a mouse click as long as there is no vanity call. But don't tell him that .  ;)


and by the way - they're not the only one's floored!

Congratulations!


Sent from my iPad using Tapatalk HD
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on January 14, 2014, 02:38:08 pm
Fortunately (or unfortunately?) in the United States the Ham exams are very easy. Only the Extra Class poses a slight challenge. Most other countries have much harder exams. Here we have economic considerations, hence the easier exams. In socialist Europe for instance, the government doesn't care how many radios are sold. They'd rather prevent people from doing what they like... God forbid a happy population, they might get used to it, even want more!

Gil.
Title: Re: Question for Technician Class:(T3B06)
Post by: raybiker73 on January 14, 2014, 10:59:54 pm
Quote from: gil on January 14, 2014, 02:38:08 pm
Most other countries have much harder exams. Here we have economic considerations, hence the easier exams. In socialist Europe for instance, the government doesn't care how many radios are sold. They'd rather prevent people from doing what they like... God forbid a happy population, they might get used to it, even want more!


I'm hoping that the federal gubbermint passes the Affordable Radio Act ("0bamaham," for short), so that every American will have access to a free or heavily subsidized Elecraft KX-3.

Of course, if you like your current radio, you can keep it.  8)
Title: Re: Question for Technician Class:(T3B06)
Post by: gil on January 15, 2014, 12:39:27 am
Obamaphone was the first step  ::)

Gil.
Title: Re: Question for Technician Class:(T3B06)
Post by: IT Tech on January 18, 2014, 06:48:59 pm
Gil's perception of the answer is correct, however he did not explain why it was the answer.

The answer to the OP's question is the reason why we use vague terms to describe frequency is because we follow a band plan.

If you look at the band plan you will see similarities, those similarities are that some frequencies are harmonic's of other frequencies.   Like playing hop scotch when you were a kid, if you have a 10 oz glass of water and you get a 20 oz glass of water, the glass with 20oz has twice as much water it it - right.

If you have a 40 meter dipole antenna - a dipole antenna is electrically 1/2 of 1 wavelength in size.
That antenna is also 1 full wavelength @20 meters and is 2 full wavelengths long @10 meters.
Even if I am wrong, the purpose of the answer is to get you to see what they are talking about.

Now 12 meters is not a harmonic of anything
15 meters is not a harmonic of anything
30 meters is a harmonic of 15 meters
17 meters is not a harmonic of anything.

The Dipole antenna is a balanced antenna..  Think of a teeter totter , when one child sits on one end and another child of equal weight sits in the same location on the other end, the teeter totter will balance.
When the positively charged wave is on the left side the right is negatively charged, this alternates from side to side.   Because it is equal, it is very easy to tune.  When you change the length or the frequency - you have a harder time tuning it because the impedance changes with the length and the height above the ground and everything around it - which causes standing waves.  Even if you see standing waves on your meter, that does not mean that the antenna is not resonant, just that something is interfering with it.

Your best bet is to study the manual and then the questions and when you know enough of the right answers, then you can attempt to take the online quiz.   The online quiz is not designed to teach anything and those that only takes the online quiz - usually never amounts to anything because they quickly forget everything that they learned once they get their license.

The purpose of the license is to show that you know the basic requirements to operate the radio.
This has all been lost on the ham in the day people and the walkie talkie crowd.

A easy way to learn once you learn the basic's is to open the test, take each question on the online test, open another internet web page, look up the answer, then look up why it is the answer.
When you can explain to other people this is this because when you do this, this is what happens, then you will be knowledgeable.

Amateur radio encompasses Algebra, Trigonometry, Calculus, Physic's, Geography, Science, and many other arts.   It isn't just passing a 35 question multiple guess test and getting a license and getting on the air.  We work with dangerous voltages and this stuff can kill you!   It's what you don't know that will usually kill you and not what you know but forgot.

Even the most knowledgeable people sometimes makes mistakes.
That is why QST Magazine had to print a retraction last year when they told people how to bypass the interloc switch in the Ameritron Amplifier and work on live equipment.  Then they refered to a live component that would have killed someone had they touched it with their bare fingers or a screwdriver.

We all make mistakes.