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Bird reflect watts

math dont lie

you want it close, or do you want it dead on.


beetle of course this wont make anything perfect if you talk on many bands.
if you would like to have the best tuned setup for a spacific freq it can be fine tuned.
 
"DEAD ON" hmmm

what exactly are you trying to say bighammer???

the answers are right there in the link you posted :)
QUOTE
"Another use of the length of a radio signal is in using transmission line sections (1/2 wave, 1/4 wave, etc.) in order to provide various impedance transformations"


if you use the halfwave calculator to cut several different brands of lets say rg213u then i can absolutely guarantee you or anybody else that it will NOT be "DEAD ON" as i tried to explain earlier,

if you take the published vf for a particular coax as fact and use that or any other calculator to determine the EXACT correct length then you are guessing the velocity factor,

if you have the means to accurately measure the vf then you dont need any program,

let me have another go at this,,

an electrical halfwave of coaxial cable will mirror the terminating/load impedance ( your antenna ) at its source end ( the radio end ) regardles of the load impedance,

assuming we are dealing with 50ohm coax AND a 50ohm source ( your radio again ) and ignoring the naturally occuring increase in loss and return loss due to increasing coaxial length,,,,,,,,,,,,,,,,,,,,,,

cutting electrical halfwaves does 2 things,

it allows you to see the actual terminating impedance at the source when the load IS 50ohms and when the load is anything OTHER than 50ohms,
IE it will not transform a 75ohms load impedance to something other than 75ohms as seen by the source ( your radio )

it also allows you to add or remove electrical halfwaves of coaxial without upsetting the impedance as seen by the source,

IE you can take your radio from the shack add however many extra electrical halfwaves of coax it takes and go sit watching tv with the wife without upsetting the impedance seen at the source when the load IS 50ohms AND when the load is anything OTHER than 50ohms,

if the load is exactly 50 ohms then it does not matter what extra length you add/remove the source will still see 50ohms,

putting it more bluntly

"IF and only if your radio AND antenna are "DEAD ON" 50ohms and you got 50ohm coax then COAX LENGTH DONT MEAN SHIT"

now please explain exactly what you think you are achieveing by cutting your coax with a computer program that makes it "DEAD ON" because i just dont get it.
 
i dont cut it with a program. just showing length does matter per freq, to match it with the antenna is different per situation. you can try to make the biggest post you can. even if it was off it would still work fine. but if you want the best match up you can some adjustment is needed. this is for best performance which would show in a keydown. us cb'ers dont use tunners, you guys do. we could go on for hours and days about this. i have the proof it works, tested and tried, not some theary.

now befor this gets to a ham vrs cber thing again one thing we can agree on is both ways do work
 
hey hammer i never use atu's i always cut for electrical halfwaves and tune the antenna as best i can,
why do you assume im a HAM? is it not possible that a cber can have half an idea,

im a cber dude through and through had my ticket since 96/97 and only use 2mtrs/70cms to talk to my old cb buddies that went ham, its a freakin tellephone to me nowadays,

not only am i a real cber i have 15kc filters in my cb i have 7.5kc audio like godzilla down to 50hz at least directly driving the modulator with offboard processing and disabled rx agc for dynamic range and taking rx audio straight from the detector buffer
NOW find me a ham on here that does that or thinks thats acceptable even for a cber, then find somebody on here that says it cant be done and i will take great pleasure in making them look like a dick,

listen up on the bowl bro when i got conditions you will realise i aint no ham at heart :D

maybe if you can be arsed to get a decent wideband rx you will want to join the wideass crew on 025, if not then ya will hear me muffled as hell on your stock cb receiver on ch5 ch 6 and ch7 all at once,

ps you still have not explained how you gain better performance?
 
Beetle said:
If tuning an antenna involved using a specific length of coax, many hams would have cars so full of coax there wouldn't be room for passengers or themselves. Separate feedlines for 80/60/40/30/20/17/15/12/10 - and there are some hams who operate 160 mobile as well.

Tune the ANTENNA, and use enough coax to reach from the antenna to the radio. If a radio (or amplifier) can't stand some reflected power, it's poorly designed.
Click to expand...

I agree Beetle, its not different from HAM to CB, only a lot of wrong roomors of this and that from someone who dare to call themselves a TECH.

As long as the antenna is not as efficient as it perfectly can be, the readings close to the radio dont mean anything to me. If one still believe in adjusting swr by cutting coax thats their problem. But if i see that in my system i take away all coax, put a meter at the feedingpoint of my antenna and start new installation troubleshooting for bad earthing rf current flow etc, because then something is wrong.

Only exeption is for co-phased antennas.

Nice to run into you again Beetle, my handle earlyer was NORWEGIAN.
 
Hey, Norwegian! Good to hear from you again. Now where did I put my Norwegian/English translating dictionary :P ...?

If somebody wants to concentrate on one, specific frequency and forget all the rest of the available spectrum, then fine. They'd better make very sure, however, that their frequency doesn't shift with component age, or the temperature of the crystal or other frequency-determining components, because that might throw things off by ten hertz or so, and they might have to rebuild their whole antenna system. Oh well - that will keep them off the air so others can enjoy the hobby.

Uff da! (And I didn't need the dictionary for that.)
 
final attempt,

no we dont agree at all,
i just read some of your threads and i see what the problem is,
look what you posted here,


"20cb110 thats not correct. everything has a length for a one set freq. which is the reasoning for exact coax lengths with 2 hot set ups. your antenna is a certain length for say 27.200, so is coax. now you cant change your antenna swr with coax, thats fooling it. you can fine tune the system as a whole for best efficency, and the least amout of reflection. i tried a test and proved this to be true. using the mfj 259 i had 50 ohms on ch 40, we centered the swr on 27.200 which was 57 ohms. when testing the reflection we had 4 watts with a 2x6. after trimming the coax till it was 50 ohms on 27.200, rechecking the center of the tunning. reflection was now 2 watts. now a field strength meter wasnt used so i cant tell you if the signal was any stronger, but more power can go out due to less loss and the box was happier also".

now where did you type anything in that post that contradicts what i am saying??

let me have a go at explaining my view one last time, if you still dont get it then i give in,

you tuned the antenna and ended up with 50ohms on ch40 and 57ohms on 27.200 ( you with me so far )

in this situation providing your test gear is accurate the only frequency that your coax may NOT be acting like an impedance transformer is on ch40,
BUTBUTBUT on 27.200 the impedance seen at the source is 57ohms and your coax is now acting as a transformer and the antenna feedpoint impedance is not really 57ohms but some other complex value ( not 50ohms ) you also have standing waves on the coax,

next you proceeed to trim the transformeraction coax untill the impedance looks like 50ohms at the source,

you have not altered anything at the antenna feedpoint it is still some complex impedance OTHERTHAN 50ohms,
but the coax is now transforming this feedpoint impedance to look like 50ohms to the source rather than the actual feedpoint impedance,

but its better!!! you say and you can prove it :x ,

yes it is, your radio is now able to deliver its full output into the coax,
it may well run cooler swing better maybe even be the difference between smoking on the bowl and smoking 10ohms lalala but you have not tuned the coax for 27.200,

now wassup with that??
the only thing we dont agree on if you care to reread my posts is the issue of the coax having to be a certain length for a certain frequency,

you think it MUST be tuning the coax for the frequency you want to use and i am TELLING you that is incorrect,

i will ADMIT that i may also be incorrect and want and expect those with a better understanding to set me straight,

the truth is your antenna is not 50ohms on 27.200 and you still have standing waves on the coax,

will that make it less efficient than a correctly tuned antenna hmmm,

depends on how you regard efficiency,

yes all the power from your transmitter will go to the antenna and be radiated eventually,
appart from a miniscule loss return loss as the signal bounces back and forth between the antenna and the output filter/tank in the transmitter,
i believe at this point that very nearly all the rf WILL be radiated,
but the radiation pattern of the antenna is most likely less than ideal when compared to a resonant antenna with a true 50ohm feedpoint and any old length of coax

putting TOLL_FREE and others in the same class as psycho is WAY off base,

these guys are here to help even if their delivery is not the most diplomatic way of getting their point across,

shit they may well jump allover me with this post and set me straight,
i dont mind at all i am hear to learn,
if nobody in the know pulls me up for my mistakes i will go on perpetuating info that is WRONG,

NOBODY but nobody understands everything and i admit to been a jack of all trades and master of none,
there are a few on here that have taught and still do teach me a thing or two,

i just hope that the only thing i taught others is NOT that i am a dumbass cber :twisted:

your remark about my long posts hahaha, MOLE does not have enough space on here for me to make a truely loooong post :wink:
 
man you guys are wound tight.

but one thing we can agree with is toll free is well above psycho. psycho is below the scum at the bottom of a portapotty, but thats a different post.

im going to hook the mfj to the antenna base and report back.
 
bighammer said:
man you guys are wound tight.

but one thing we can agree with is toll free is well above psycho. psycho is below the scum at the bottom of a portapotty, but thats a different post.

im going to hook the mfj to the antenna base and report back.
Click to expand...

That the only way to be sure of the swr at the antenna, put the meter at the feeding point if possible, of course you have loss in a coax, we dont argue that. But tune the antenna and then work with the rest of the system when you know the correct value at the feeding point you have the correct answer :)
 
freecell said:
"That the only way to be sure of the swr at the antenna, put the meter at the feeding point if possible........"

no it isn't.
Click to expand...

for what its worth i agree,
but you must have the means to accurately determine an exact electrical halfwave of feedline, and that does not mean use a computer program but actual physical measurement of the feedline,

that is unless you know another way????
 

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