why do class C amps need certian jumper lengths ??

[W5LZ]

frankenstein 320,
Using your last post about transistors being the same, and the 'shielding factor' of coax as an example, I think you might want to go over your lecture notes again. Strictly a S.W.A.G., but I'll bet you're a freshman.
- 'Doc

 

[BOOTY MONSTER]

"CB amps only have to deal with one band so if the cheap builders can't get the input impedance right, it's easy enough for them to just tell people to fool with the coax."


so that the answer ......

thanks moleculo

 

[frankenstein 320]

tell me how it is

frankenstein 320,
Using your last post about transistors being the same, and the 'shielding factor' of coax as an example, I think you might want to go over your lecture notes again. Strictly a S.W.A.G., but I'll bet you're a freshman.
- 'Doc

im not right on everything but in a rf parts catalog thay give db shilding ratings and if you can find a watts to db couculater 10 watts is about 40 db and 1000 watts is about 60.correct me if im wrong. what i ment on the pills is that a 2290 is a 2290 and a 2879 is a 2879 and i now thay need to be matched.:headbang

 

[frankenstein 320]

coax is like politics

If the input impedance of the amp matches the output impedance of the transceiver, then it doesn't matter what length the coax jumper is. If there is a mismatch between the two impedances, then the coax can act as a matching transformer and then length of it will affect the SWR reading at the transceiver. An electrical 1/2 wave jumper will allow you to see what the input impedance of the amplifier/antenna actually is, but it will not provide any matching transformer characteristics. Don't get me wrong...using the coax as a matching transformer is a compromise.

The biggest issue with using coax to affect SWR readings is that as soon as you change bands, the coax length you were originally using is no longer valid. If I have an amp that I use on 5 bands, I need another way of matching the input impedance than messing with the coax. You can either make the input impedance broad-banded enough to handle the various bands, or you can use some sort of band switching mechanism that deals with it. CB amps only have to deal with one band so if the cheap builders can't get the input impedance right, it's easy enough for them to just tell people to fool with the coax.

sounds like you know what your talking about.im glad someone understands.I onely talk on one chanel so im not to woried about changing anything once its set.

 

[Beetle]

From Frankenstein in Post #13:

I am A student at itt-tecnical instatute in iowa geting a deegre in electricle engenearing i can back up every thing i say on paper.soon will be bulding amplifires and antanas.

-----------------------------------

It's a shame that "itt-tecnical instatute" doesn't stress spelling and grammar a bit more. I counted at least 14 errors in your post.

 

[frankenstein 320]

tell me how it is

frankenstein 320,
Using your last post about transistors being the same, and the 'shielding factor' of coax as an example, I think you might want to go over your lecture notes again. Strictly a S.W.A.G., but I'll bet you're a freshman.
- 'Doc

I am in schoole becouse books couldent talk back and people on the raidio couldent awnsere my questions anymore.I would like to know on paper that my equitment is going to work before i wast my time.do you have a degree in anything?and just becouse im geting mine dosent mean ill ever know it all.

 

[Beetle]

im not right on everything but in a rf parts catalog thay give db shilding ratings and if you can find a watts to db couculater 10 watts is about 40 db and 1000 watts is about 60.correct me if im wrong. what i ment on the pills is that a 2290 is a 2290 and a 2879 is a 2879 and i now thay need to be matched.:headbang

Not sure what a "couculater" is, but before anybody's going to be able to make sense out of your "10 watts is about 40 db and 1000 watts is about 60", you're going to have to reference those dB levels to some reference level.

 

[frankenstein 320]

gfififigfipgfigfbovhnvn;;o

thay do comp 1 and 2 but i dont realy care for them.im hear for electronics not spelling or computers.but at least you can count.:w00t:

 

[frankenstein 320]

go and find out

Not sure what a "couculater" is, but before anybody's going to be able to make sense out of your "10 watts is about 40 db and 1000 watts is about 60", you're going to have to reference those dB levels to some reference level.

go reference it for me.

 

[Captain Kilowatt]

take 468 devide by your operating freqency this will give you a physicale half wave at your freqency.then take your velosity factor of your coax like .66 depends on typ of coax type that will give you a half wave elecricly throue a conductor. this is the lengt and the onely length to run between raidio and amp. this will phase them together,same thing from amp to antana use multipls of the electricle length.remember the antana and coax is a circete and needs phased. this onely aplise for one freqency as soon as you chang the chanele it will be of a litle bit but why not be perfict on the chanle you talk on. remember that every half wave the impeadents is 0 that means 0 at your radio 0 at your amp and 0 at the antana.this is the onely way to get a true readout at every end. your swr might go up a little but that is a true reflection now you can tune up antana or amp.

Damn that was hard to read. Even harder to understand. :headbang

My good fellow you have a lot to learn about RF systems. First off what is "phasing them together"? When connecting equipment up in series like you would normally do with a radio/amp/antenna system,you are not "phasing them together". Also when using an electrical half wave of coax between two pieces of gear that has an impedance mismatch, the mismatch WILL STILL APPEAR at the radio. Using something other than an electrical half wave is what is required to transform the impedance and is not the best idea but it works if you can't/don't know how to retune the amp input.One last thing,what do you mean by "remember that every half wave the impeadents is 0 that means 0 at your radio 0 at your amp and 0 at the antana"? The impedance is not zero,if it was it would be a dead short. The impedance presented at the radio end of the electrical half wave cable is whatever the impedance is at the far end.No impedance transformation takes place. Also coaxial impedance transformers are not that narrowbanded that a channel or two either way will affect things. In fact on 11m you can cover the entire band as well as the "freeband" without an appreciable degradation of the system.

 

[W5LZ]

frankenstein 320,
All kidding aside, and I'm not trying to insult you. I think you really should check your notes and texts again.
There is a common way of expressing most of what you've tried to say. Unfortunately, what you've said just isn't making much sense as it's stated.
- 'Doc


Completely beside the point, there are a few people here who do have degrees, or the equivalent to a degree, in electronics. There are many more here who may not have the diploma, but do know something about electronics.

 

[HiDef]

If one downloads Firefox one will have spellcheck working when one posts.

Skip lines like this for the older generation many of whom have the information.

Every time decibels are used it will refer to some relative value.

This is why you see dBd for dB in reference to a dipole.

dBi in reference to an isotropic ant.

dBk in reference to 1 kilowatt.

Then you get into voltage verses power usage of dB.......

 

[BOOTY MONSTER]

frankenstein 320 , i got one word for ya .

you should show this thread to your instructor at "itt-tech" , he/she will be amazed .

 

[Beetle]

go reference it for me.

Hey, an "...A student at itt-tecnical instatute in iowa geting a deegre in electricle engenearing..." should be able to do something as basic as this.

I couldn't do it for you because, first off, you need the exercise for your practical work toward your "deegre". Secondly, I have no idea what you seem to be trying to say.

 

[Captain Kilowatt]

Hey, an "...A student at itt-tecnical instatute in iowa geting a deegre in electricle engenearing..." should be able to do something as basic as this.

I couldn't do it for you because, first off, you need the exercise for your practical work toward your "deegre". Secondly, I have no idea what you seem to be trying to say.

Audio engineers talk in dBm while electrical and electronic engineers talk in dBW. Franki seems to be talking in dBm but the "m" might stand for "maybe".