REFLECTIVE POWER ? HOW MUCH IS TO MUCH ?

[Switch Kit]

Could somewhat explain this to me or send me in the right direction ? How much reflective power is to much ? Is it OK to have some ? and if so ? How much reflective power is not something to worry about ? .....for instints , let say I run 500 watts off a wilson 5000 drill through roof mount and reflective power on the meter reads about 3 watts when modulating , would this be concedered bad ?

 

[KingCobra_CDX882]

DUDE...

You mean to tell me...
You are Only getting 497 watts out of your 500 watts..
better tell those other 3 watts to snap to it...lol

nothing to worry about at all
if in using 500 watt amp you saw a return of 50 watts not 3 watts ..

so leave your set up alone..

Later

 

[Hamin' X]

How much reflective power is not something to worry about ? .....for instints , let say I run 500 watts off a wilson 5000 drill through roof mount and reflective power on the meter reads about 3 watts when modulating , would this be concedered bad ?

It depends on your terms. Are you really referring to reflected power or, do you mean SWR(vswr)? If you are measuring 3W reflected power using a meter such as the Bird 43, or another directional watt meter, then you have nothing to worry about. Your SWR is ~1.23:1. If however, you are using an SWR meter that you have to calibrated for each reading, then you are in trouble, with an SWR of 3:1.

It is generally accepted, that with solid state amps, you want to keep the SWR <2:1. I like to have mine at 1.5:1 or less. If you can get to 1.5:1, then you have reached the point of diminishing returns and any further reduction in the SWR will not result in any significant improvement of your performance.

In your case, you could read up to 15 watts reflected and remain under 1.5:1 and you would have to get to 50 watts reflected to reach the 2:1 threshold. These figures do not take into account any line loss and YMMV.

If you are using a true directional watt meter, you can use the following formula to calculate your SWR:

SWR= ((Sqrt of Power fwd)+(Sqrt of P ref))/((Sqrt of Pf)-(Sqrt of Pr))

Rich---Hamin' X

 

[Switch Kit]

thanks for the replies on this one gentleman. It really wasn't until these radio forums that I started to somewhat learn about what they call reflective power.IM guessing a good antenna analizer would get to the truth of the matter or as close as possible to it ? I've always just used run of the mill swr meters and always felt that I was fairly close to the mark that I was looking for in as low as I could go with the swr,especially after using 2 or 3 meters and all of them being fairly close with one another. I just got a decent cross needle meter and it pretty much told me the same thing all the other meters had told me ,other then this one reffering to reflective power as well which seems to be very low at 3 watts. I suppose if i had the extra money I would invest in a good antenna analizer but after 20 years of this stuff and only being a cb'er , I just can't see myself putting up those kinds of dollars for one of those. I've always thought if I did get one ? I might not be very happy about what I might find out ? Sometimes what I don't know in this hobby ,usually doesn't hurt me. It's just knowing that something isn't more close to perfect then not might allow me to screw with my head to much. So what really does an average CB Radio Joe have to go on ? SWR ! and know that when running power that it is surely a plus to do your best to make sure that whatever power your putting through that antenna is staying nice and low and around that 1.5 mark or lower. Thanks again for the replies on my question. S.K.

 

[Hulkster]

> http://www.cvarc.org/tech/standwave.html

 

[Switch Kit]

EXCELLENT LINK HULKSTER !! THANK YOU !!

 

[Hulkster]

No problem!

 

[Hamin' X]

> http://www.cvarc.org/tech/standwave.html

Kind of a long winded way of saying what my previous post did. :shock:

 

[Switch Kit]

come on Ham'in .it's all good dude !! Hey IM just a cb bozo anyway , I tend to appreciate any help I can get from time to time.IM just trying to screw with my own head here with reflective power and this and that , 20 years into this hobby and all that I've really ever had any concern about was my basic SWR readings on a usually crappy meter (Rat Shack Special) .....I've ran to many amps over the years to count and I've never burnt up a single one let alone a radio that went with it ......IM far from perfect when it comes to all of this stuff ,the basics have gotten me by this far.This subject can truely get rather deep )-: as I said ,I personally can't afford a antenna analzier and i doubt I would even spend the money on one if i had it ? OK then ...lets say that I do run 500 watts ? My SWR reads 1.1 around the band .....with the power on high it reads 1.3 on a few different meters (ballpark anyway) .....without the analizer guess I'll never really know whats truly going on huh ? even still if a decent cross needled meter tells me IM in the good .......Well ,in my case ,if it works thus far ? I really can't afford to find out if it's all a lie or not ? So if it has worked for 20 years for me I suppose it would be to my best ability to leave well enough alone ? In my case .....if it works ....not fix it !! (-: I figure it this way,if i was to get one of those analizers or even bother to borrow one ....I might not like what I would find out ? then I would really be screwing with my head ! )-: Just wanted to learn a little bit about reflective power ....I think i got the just of it. Thanks again

 

[Hamin' X]

Switch Kit

I was not trying to put anyone down, just making reference to the fact that there is a long version and a short version. I find that most people's eyes glaze over if given the long version. It's kinda like trying to explain about coax length and why the correct length is the amount to get from the radio to the antenna. I can give the long version, or you can trust me. Most people don't want to know why, just what works. This can lead to misconceptions when people don't know the why. I happen to have a very steep skirted BS filter and it takes a lot of research to keep the edges sharp. Glad to see that you're after the why.

Rich---Hamin' X

 

[Switch Kit]

like I said .....it's all good ? I think sometimes what is written can sometimes be taken the wrong way ? It must have some merit ......especially email type things and Forum posts , it can get deep. Some need It explained in full ,some don't and some could careless either way . And then there are those that feel that if it is spelled out to them in detail , the not so educated tend to take it the wrong way as well and think you are letting your smarts get the best of them. )-: I personally call it the Know-It-All syndrome.Even though one may mean well ? It can be a little intimadating to the lesser educated (-: It's all good. Peace.