antron 99 RG8U SWR

[loosecannon]

i can see how that might happen with the computer speakers.

could be that the speaker makes a pretty good receiver for 27mhz signals (many electronic items do), and when you spread that coil you decreased the amount of signal that is on 27 mhz and increased the amount of signal that is on 54mhz, 108 mhz etc...


or maybe the speaker was reacting to harmonics being put out by the radio, and your slight spreading of the coil actually decreased them.
this is less likely, but hey, im not going to say that its not possible.

just for your edification, that coil, along with the one next to it, and maybe another, are part of whats known as a half wave filter.
its a pi network whos purpose is to maintain the same impedance at the output as it sees at the input, while filtering out harmonics.
every CB has one in it.
when you spread one of the coils, you change the impedance of the input or the output, or both.
obviously an impedance mismatch is not a good thing, and thats why many of us try to spread the word against that practice.

now that being said, i guess its possible that you actually "improved" the impedance match of your particular radio, but its pretty hard to beat the engineers with this kind of stuff.

i do believe at this point that your antenna has a problem, but short of the tuning rings being at opposite ends of the threads, i dont know what it might be. that is unless you've been improperly calibrating the SWR meter this whole time. LOL J/K!

LC

 

[Robb]

i can see how that might happen with the computer speakers.

could be that the speaker makes a pretty good receiver for 27mhz signals (many electronic items do), and when you spread that coil you decreased the amount of signal that is on 27 mhz and increased the amount of signal that is on 54mhz, 108 mhz etc...


or maybe the speaker was reacting to harmonics being put out by the radio, and your slight spreading of the coil actually decreased them.
this is less likely, but hey, im not going to say that its not possible.

just for your edification, that coil, along with the one next to it, and maybe another, are part of whats known as a half wave filter.
its a pi network whos purpose is to maintain the same impedance at the output as it sees at the input, while filtering out harmonics.
every CB has one in it.
when you spread one of the coils, you change the impedance of the input or the output, or both.
obviously an impedance mismatch is not a good thing, and thats why many of us try to spread the word against that practice.

now that being said, i guess its possible that you actually "improved" the impedance match of your particular radio, but its pretty hard to beat the engineers with this kind of stuff.

i do believe at this point that your antenna has a problem, but short of the tuning rings being at opposite ends of the threads, i dont know what it might be. that is unless you've been improperly calibrating the SWR meter this whole time. LOL J/K!

LC

Or the coil with the slug in that circuit has been messed with too.

mkube, if your tech has a spectrum analyzer he might be able to sort that circuit out. I'm no tech, but it does appear that something might be wrong in there. Not saying that is it, but since the radio has been messed it is hard to say.

 

[KD2GOE]

ok well it is going to go in to be looked at this week. I will all so ask him to put it on the spectrum analyzer I am sure he has one.
the coil L37 with the slug in the tuning instructions it just states "Adjust for maximum output power"


as a side note my good friend 6 miles away told me I sound better then ever now. so I don't see it decreased the amount of signal that is on 27 mhz.. but ill let the tech take a look at the radio to rule it out this all started with my antenna... after he give my radio the all clear ill take it over to my friends house and put it on his antenna to compare.

ill all so look over my grounding on my mast with a ohm meter.

 

[W5LZ]

So, you are right, I did make an assumption about an amplifier. I apologize for that. I also still think what I said is very commonly applicable to those who do not use an 'export' radio, and I won't apologize for that, there's no reason to.
- 'Doc

 

[KD2GOE]

So, you are right, I did make an assumption about an amplifier. I apologize for that. I also still think what I said is very commonly applicable to those who do not use an 'export' radio, and I won't apologize for that, there's no reason to.
- 'Doc

It's ok I am just messing around with the radio. It is going to be the radio guys problem now he will get it working for me.

 

[wavrider]

Mkube,

first, you should put that coil back the way it was.
any "improvement" you are noticing is the result of a meter not knowing how to handle the complex impedance.

try this to see what i mean. while the coil is spread like it is, connect your

if anyone else has mentioned this, i missed it.
the antron 99 is a "half wave over a quarter wave mutual transductance tuned antenna".

they say that in the ads. what they dont say is that the "1/4 wave" part is made up of the shield of your coax coming out of the antenna for about the first 9 feet.

this means that if you made a choke balun right at the base of the antenna, you have ruined your counterpoise, hence the high SWR.

try making sure that you have the coax coming straight down from the base of the antenna with no loops or bends in it for the first 9 feet.
after that, you can add a choke balun or route it any way that you need to.

does this sound like something that could be happening at your installation?
LC

LC,

I am using an A99 for 10 through 15 meters with an ugly choke at the feed point.

I think the mast pipe is acting as a counterpoise, not the coax. I have no issues with VSWR.

 

[hotrod]

LC,

I am using an A99 for 10 through 15 meters with an ugly choke at the feed point.

I think the mast pipe is acting as a counterpoise, not the coax. I have no issues with VSWR.

i wouldnt even think about using a antenna without a rf choke. been there done that.
rfi nightmare

 

[loosecannon]

yes, you guys are right, a metal mast will act as the counterpoise as long as its 9 feet or longer.

i didnt know what his mounting method was, and thats why i mentioned it.

and yes, Antron 99's are an RFI nightmare for exactly that reason.

you should know that if your choke balun is right up against the mast, it will ruin its effectiveness.

Mkube, i must apologize for not reading through the thread thoroughly enough before i started giving advice.

i missed the part where you said that with your washington the SWR was 1.6:1.

that leads me right back to the 2990 being the culprit.
only way to determine that is to do comparisons.
same radio with different antenna.
same results? radio's fault.

different radio with same antenna.
same results? antenna's fault.

the fact that your two comparison radios have quite a bit of difference in power output does make those comparisons a bit more complicated, but an antenna that has an SWR of 1.6 with 4 watts in, and an SWR of 2.5 with 50-100 watts in sounds to me like it has had some rough handling, water egress, a nearby lightning strike, or who knows what.

i honestly cant stand working on those big base stations with the built in amps.
its done as cheaply as possible, and much more attention should be paid to properly matching the output of the radio to in input of the internal amp.

i also hate how heavy the damn things are.
when you are working on a radio, you end up turning it over and over, and that gets old real quick with a 2990.

i hope your tech is able to sort things out for you.
dont leave out ANY details when you are telling him whats been happening.
things that may mean nothing to you might turn on the light bulb for him.

i also am a big fan of people actually writing down what the problem is, and what they have tried so far, rather than just rattling it all off to me verbally.

please do post back whatever you find out.
LC

 

[KD2GOE]

54 mhz trap coil is back to where it needs to be and hot glued