i use the 5 watt to fine tune with the 16 on. i use a 25 while driving around since stinger layback, vehicals, buildings will make it go over 5 watts. I have an old 50 watt slug. its not very acurate in the begining of the scale. but would be fine for a drive around slug. the 25 w i have is fairly acurate compared to the 5 w slug.
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Bird reflect watts
- Thread starter Skyscraper
- Start date
Cool that's a good way of doing it big hammer. Trying to use a 5 watt while driving or parked near some objects would make it hard to tell how bad the reflect really is.
bighammer said:
So you claim to have a reflect pct of 3/10 of 1% or better??????? You must know something that BB in Florida doesn't know because he uses a 50H to measure reflect. We all now know that you know more than BB. :roll:
It is impossible to get reflect that low.....you know you'll have to trim your nose after all the fibbing you've been doing.
BB has reflect pct of 1.5% and when is the last time you beat him hot shot?????????? Thought SO.
psych. we need to change your screen name to tea bag.
you have shown to have zero knowladge of a real system. you mearly quote what you have heard. i could care less what bb davemade x force fatboy mr coily monkeymade or any other person on the planet has for reflection. stop having your head up someones ass and open your eyes. their are plenty of people out there who know what they are doing, better then the people in the limelight. now young grasshopper, get in your mobile, drive to va and ill show you first hand what i have. other then that
please report to the edge of the swamp, and procede to stand knee deep in the mudd.
you have shown to have zero knowladge of a real system. you mearly quote what you have heard. i could care less what bb davemade x force fatboy mr coily monkeymade or any other person on the planet has for reflection. stop having your head up someones ass and open your eyes. their are plenty of people out there who know what they are doing, better then the people in the limelight. now young grasshopper, get in your mobile, drive to va and ill show you first hand what i have. other then that
please report to the edge of the swamp, and procede to stand knee deep in the mudd.
I haven't got a bird but I see 1/8 % reflect out of a 4 pill with 200 key. Meter shows less than 1/4 watt reflect. The MFJ 259 shows .oo reflect coefficient and flashing on -48 db. I have actually had the meter not move but a neddles width before. Cherokee meter.
Ya I know it isn't a bird but I think I am in the same ball park with concerns to looooooooow reflect.
By the way to achieve this it took some time. Mag mount with Kales top loaded 10K on a 4 runner. 20 in. bottom shaft. ring terminal lugs. Antenna location is everyting, then just touch the stinger for fine tuning. I was able to get 1/4 % in the Peterbilt with 10k dual coil, same 4 pill.
Ya I know Bird is the final word. Neverthless I 'll stand by my tuning.
Ya I know it isn't a bird but I think I am in the same ball park with concerns to looooooooow reflect.
By the way to achieve this it took some time. Mag mount with Kales top loaded 10K on a 4 runner. 20 in. bottom shaft. ring terminal lugs. Antenna location is everyting, then just touch the stinger for fine tuning. I was able to get 1/4 % in the Peterbilt with 10k dual coil, same 4 pill.
Ya I know Bird is the final word. Neverthless I 'll stand by my tuning.
good work boomer, and ill agree. birds are the best but your meter is doing uyou justice, and your attention to detail and doing it right is what got you there. glad to see you got it nice and low. its nice when the hard work pays off doesnt it?
never can ground to much
never can ground to much
bighammer said:
If you "tune the coax" for the freq by adjusting the length of the coax you may be fooling yourself. Then your coax may be acting as a part of the antenna and not as a feedline. RF current make strange things happen to high powered systems when coax act as a part of the antenna and not as a feedline.
Otherwise swr and reflect is as easy as matching impedances regardless of what power one use. If your system is correct and you have 1.1:1 on 4w of power you should have no problem with 2000w as long as the feedline and antenna are constructed to cope with it. You will only have a low rise on the swr. This is of course when everything is perfect, and very seldom it is. Most of us are very happy with our 1:1 readings.
The reality is often between 1:3-1:7.
I have 7 quality meters of several brands, Zetagi, Avair, MFJ, Ameritron, Watson. Not one of those give the same readings when measuring swr lower than 1,8 and theese are quite expensive meters.
btw: swr is a very uncertain reason to make a quarrel of
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.
18 ft isnt even a 1/2 wave there is a formula to find 1/2 wave per freq and then have to factor in the volocity factor to get the true length.
18 ft isnt even a 1/2 wave there is a formula to find 1/2 wave per freq and then have to factor in the volocity factor to get the true length.
If changing the length of your coax is changing your SWR, then your antenna is not presenting a 50 ohm load. I am not saying that using coax length to tune the system is bad, but it does limit your frequency range, Use a good tuner instead.
Rich
Rich
DXman
Yes, that's 3100 degrees F. Nine yrs of hard work.
dont be fooled by the stated vf of coaxial cable, you will find small changed in sections from the same reel let alone different brands,
i have been cutting for electrical halfwaves for years and just recently i changed the rg58 on my magmount.
cut it as usual with some spare to trim back,
after testing several loads and t-pieces for the best match i hooked up the coax and swept it with minivna :shock: its too short way too short,
next i hooked up my base coax rg213u ( propper mil spec from our royal navy not the cheap stuff sold as 213 in our cb/ham shops it wont even fit in most cb pl259's ) wow only about 2" too long thats close to say i measured it with a tape measure over around 200ft of coax,
i am with richard on this,
if the coaxial length between either radio/amp or amp/antenna changes anything but the tiny difference in loss between different lengths of coaxial then it proves only one thing,
YOUR COAX IS NOT TERMINATED AT BOTH ENDS WITH THE CHARACTERISTIC IMPEDANCE OF THE COAX AND IT IS ACTING AS AN IMPEDANCE TRANSFORMER,
thats where people get the silly idea that you should use particular lengths of jumper between amp and antenna or amplifiers in a chain,
even their box builder will tell them they should use a particular length or the reflect will be high,
the customer changes the jumper and wow almost zero reflect my tech is the "MAN" a genius a veritable rfgod,
hmm he built you an amplifier that does not have 50ohms at either the input/output or you have parasitic oscillations at the drive levels you are using,
or much less likely your coax has the wrong characteristic impedance,
they are either too lazy to put trimmers in the box and tune it or they just dont have a clue
then they will tell you never use trimmers only fixed caps on the input /output, thats more bs,
i use trimmers and i have zero problems changing out amps with little to no change in reflect,
look in a harris c5/c10 transmitter they use compression trimmers on the input/output of each 2 transistor section within a 4 transistor module within a 8 or 16 module transmitter,
the neat trick is they are all hot pluggable interchangeable/removeable, even the drivers can be swapped with output modules while its still on air with minimal loss in output and still have a good match because they all have the near exact same 50 ohms input/output and the z-plane combiner is more than man enough for the job it is doing
IF ITS GOOD ENOUGH FOR HARRIS ITS GOOD ENOUGH FOR ME
you tune your antenna with ya 1x2 and all is well then you hook your 1x2 to ya straight8 and the reflect goes wild
, so you take it round to your buddies house and stick it on his quality dummyload and its still all screwed up,
next you call the builder and before you get chance to fully explain exactly whats happening he blurts out "wrong jumper length" what jumper you running???
"oh boy here we go again"
if that happens to you ask him exactly WHY hes telling you to change to a 3ft/6ft or whatever jumper,
if the guy does not admit that the tuning of at least one amp is off or at least admit things aint 100% with the amps then hes pulling the wool over your eyes or he just has no clue but he still has your money in his wallet,
i dont dispute that changing the jumper made it work better because the stages are happier with the coaxially transformed impedance they are seeing,
it does not make your vswr on the line go away like a magic trick,
the guys talking about cophasing stagger phasing and the like are correct too,
length or the relative difference between feedline length is what gives the phase shift/delay between elements be it a vertical stack of dipoles phased for downtilt or give you the cardiod pattern desireable in a 2hot keydown antenna,
imho equal phasing of 2 mobile antennas for use as a shootout/dx anteena is a total waste of time even if they are spaced wide enough for a figure 8 pattern when much more forward gain and back rejection can be had with the correct phasing even at half the spacing, in such cases the relative difference in line length DOES matter,
this is just my opinion so take it for what its worth, if you know better then please set me straight
i have been cutting for electrical halfwaves for years and just recently i changed the rg58 on my magmount.
cut it as usual with some spare to trim back,
after testing several loads and t-pieces for the best match i hooked up the coax and swept it with minivna :shock: its too short way too short,
next i hooked up my base coax rg213u ( propper mil spec from our royal navy not the cheap stuff sold as 213 in our cb/ham shops it wont even fit in most cb pl259's ) wow only about 2" too long thats close to say i measured it with a tape measure over around 200ft of coax,
i am with richard on this,
if the coaxial length between either radio/amp or amp/antenna changes anything but the tiny difference in loss between different lengths of coaxial then it proves only one thing,
YOUR COAX IS NOT TERMINATED AT BOTH ENDS WITH THE CHARACTERISTIC IMPEDANCE OF THE COAX AND IT IS ACTING AS AN IMPEDANCE TRANSFORMER,
thats where people get the silly idea that you should use particular lengths of jumper between amp and antenna or amplifiers in a chain,
even their box builder will tell them they should use a particular length or the reflect will be high,
the customer changes the jumper and wow almost zero reflect my tech is the "MAN" a genius a veritable rfgod,
hmm he built you an amplifier that does not have 50ohms at either the input/output or you have parasitic oscillations at the drive levels you are using,
or much less likely your coax has the wrong characteristic impedance,
they are either too lazy to put trimmers in the box and tune it or they just dont have a clue
then they will tell you never use trimmers only fixed caps on the input /output, thats more bs,
i use trimmers and i have zero problems changing out amps with little to no change in reflect,
look in a harris c5/c10 transmitter they use compression trimmers on the input/output of each 2 transistor section within a 4 transistor module within a 8 or 16 module transmitter,
the neat trick is they are all hot pluggable interchangeable/removeable, even the drivers can be swapped with output modules while its still on air with minimal loss in output and still have a good match because they all have the near exact same 50 ohms input/output and the z-plane combiner is more than man enough for the job it is doing
IF ITS GOOD ENOUGH FOR HARRIS ITS GOOD ENOUGH FOR ME
you tune your antenna with ya 1x2 and all is well then you hook your 1x2 to ya straight8 and the reflect goes wild
, so you take it round to your buddies house and stick it on his quality dummyload and its still all screwed up,next you call the builder and before you get chance to fully explain exactly whats happening he blurts out "wrong jumper length" what jumper you running???
"oh boy here we go again"
if that happens to you ask him exactly WHY hes telling you to change to a 3ft/6ft or whatever jumper,
if the guy does not admit that the tuning of at least one amp is off or at least admit things aint 100% with the amps then hes pulling the wool over your eyes or he just has no clue but he still has your money in his wallet,
i dont dispute that changing the jumper made it work better because the stages are happier with the coaxially transformed impedance they are seeing,
it does not make your vswr on the line go away like a magic trick,
the guys talking about cophasing stagger phasing and the like are correct too,
length or the relative difference between feedline length is what gives the phase shift/delay between elements be it a vertical stack of dipoles phased for downtilt or give you the cardiod pattern desireable in a 2hot keydown antenna,
imho equal phasing of 2 mobile antennas for use as a shootout/dx anteena is a total waste of time even if they are spaced wide enough for a figure 8 pattern when much more forward gain and back rejection can be had with the correct phasing even at half the spacing, in such cases the relative difference in line length DOES matter,
this is just my opinion so take it for what its worth, if you know better then please set me straight
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.
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.
