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Message |
    
Bridge_man
Member
Username: Bridge_man
Post Number: 56
Registered: 3-2006
| | Posted on Saturday, June 21, 2008 - 6:30 pm: | 
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i have a swr of 1.2 dk that swings to about 4, on a new i-max 2000 thats with the amp on.i know its high cause the amp on low will only do about 50 watts and my meter says its doing 200.thats telling me the pwr is being reflecting back.ive tested the meter (dosy 4001) on another station,its working right.ive changed all the ends on the coax (new rg-8 super low loss) and checked with an ohm meter,all is ok.i've run the rings up and down on the ant with no luck.can anyone give me any ideas on whats going wrong? |
1861
Advanced Member
Username: 1861
Post Number: 732
Registered: 2-2004
| | Posted on Saturday, June 21, 2008 - 7:48 pm: |
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sounds like harmonics from amp . try a low pass filter after amp and see if it straightens out |
Bridge_man
Member
Username: Bridge_man
Post Number: 57
Registered: 3-2006
| | Posted on Saturday, June 21, 2008 - 9:37 pm: |
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thanks ill give it a try when i get the $ but when i ran my antron 99 it was fine.same radio(2517),same amp(palomar 2 pill),and pwr supply(pyramid 12/14).i just got a new ant and coax.i did lower the ant from 46' to about 25' to the bottom and change the location from a light pole that i fell off of to a chimney mount thats alot safer to work on.could it not have the ground plane that it needs to run pwr?if it wont run my 2 pill on low im not even gonna think of hooking up my 6. |
1861
Advanced Member
Username: 1861
Post Number: 733
Registered: 2-2004
| | Posted on Saturday, June 21, 2008 - 10:13 pm: |
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I have 3 different amps , one a palomar 250 , that do the same thing unless I run a LP filter . I have other amps that are no problem . just something to try . no guarantees . LOL |
Bridge_man
Member
Username: Bridge_man
Post Number: 58
Registered: 3-2006
| | Posted on Sunday, June 22, 2008 - 10:51 am: |
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i've been looking at low pass filters,when they say 500 watts max is that pep or rms?i need one that will hold 1000 rms. |
1861
Advanced Member
Username: 1861
Post Number: 734
Registered: 2-2004
| | Posted on Sunday, June 22, 2008 - 11:52 am: |
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you need something like a BENCHER OR VECTRONICS |
Bridge_man
Member
Username: Bridge_man
Post Number: 59
Registered: 3-2006
| | Posted on Sunday, June 22, 2008 - 11:38 am: |
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i've found that when i raise the dk to 2 watts the swr only swings to 2 and when i raise it to 4 watts it only swings to 1.5.i dont get it but thats too much dk for my big amp.could it be my radio? |
Carolinagold
Member
Username: Carolinagold
Post Number: 90
Registered: 12-2002
| | Posted on Sunday, June 22, 2008 - 1:35 pm: |
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like 1862 said it sounds like harmonics somthing palomar is famous for. if it was working fine with your a99 on a light pole and moved it to a chimney mount for the I-MAXX then try a low pass filter because the new location is closer and lower to the ground and giving back harmonics it wont hurt to try a different amp too. maybe its your new coax location try running your coax a different way. or making a homemade choke for your coax.
but more than likely its just your new location causing some funky harmonics.
JAMES
CAROLINAGOLD
865
CEF#416
CCRC#2
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Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 407
Registered: 9-2004
| | Posted on Sunday, June 22, 2008 - 5:04 pm: |
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Harmonics are generated either from the radio and amplified by the amp.All radios generate harmonics to some degree even the big ones.High swr readings can be a result of harmonics or something in the feedline,antenna or other structures nearby.As Carolina stated you could try a lowpass filter as most cb amps don't have a built in tuned input filter and as far as I know most filters are ususlly rated pep.When using a cb amp you find the swr is good with it on then you have a combo of the right length of feedline antenna placement etc.You could try placing a coxial rf choke at the base of the antenna,this will help keep feedline radiation down to a minimum and possibly help out your situation,nothing ventured nothing gained.
Bob VE1CZ/CEF451
Robert L. Spicer The days of radio are just beginning!
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Bridge_man
Member
Username: Bridge_man
Post Number: 60
Registered: 3-2006
| | Posted on Sunday, June 22, 2008 - 9:29 pm: |
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sounds like a plan.im going to the wireman tomorrow to get some more coax so i can raise it up a little higher and make a choke.hopefully that will solve my problem.ill post back with what i come up with.thanks |
Bridge_man
Member
Username: Bridge_man
Post Number: 61
Registered: 3-2006
| | Posted on Monday, June 23, 2008 - 7:31 pm: |
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got new coax,raised it up 20',made a choke,and even got a balun.still high swr but at least its swinging backwards now. dk 2 swinging down to 1.5 guess ill turn the rings a little more. |
Marconi
Advanced Member
Username: Marconi
Post Number: 772
Registered: 11-2001
| | Posted on Tuesday, June 24, 2008 - 1:03 am: |
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I have never heard of a 4 watt dead key being too much input for an amp.
Could you tell us how your setup works without an amp in line? Forgetting about the SWR for a moment, with just the Imax, radio, and meter in line are you still getting a 4x increase in power reading compared to the A99?
Didn't you tell us that the A99 worked fine? If so, then why not just put the A99 back up and see if it still works OK? You have changed quite a few things around since it worked good, and that might make figuring out what is going on a problem. |
Bridge_man
Member
Username: Bridge_man
Post Number: 63
Registered: 3-2006
| | Posted on Tuesday, June 24, 2008 - 8:55 am: |
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After the new coax and balun the power reading seems to be right but the swr just changes with the dk.with or without the amp.as for the A99 it and the (air dielectric)coax filled up with water and shorted out.i just happend to have it unplugged and noticed the puddle of water in the floor.I've never heard of water in the coax but i seen it so i belive it.I replaced the A99 with the Imax and the coax with rg8(foam dielectric).now ive replaced the rg8 with rg8x.To sum it up i have a new Imax 2000, 40' high to the bottom of the ant,100' rg8x coax, ground directly under the ant with 6ga. copper wire,2517 radio,dosy 4001 meter,with 9' jumpers,and swr that varies with the dk. And thats with the dosy and the meter on the radio. I have an ant pro coming today with an analizer maybe i just have it out of whack.thanks for all the help,i may still need it.i'll let you know, but if you have any comments or ideas im still listening. |
Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 410
Registered: 9-2004
| | Posted on Tuesday, June 24, 2008 - 11:00 am: |
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The braid of the coax if not protected will absorb water like a sponge.You might be able to lay it out in the sun for a few days to dry out but I would replace all of it with new and use coax seal at any exposed connectors or splices.Coax seal works great but I would recommend that you tape the connections first then add the coax seal, this makes it easier to remove later on.
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Marconi
Advanced Member
Username: Marconi
Post Number: 773
Registered: 11-2001
| | Posted on Tuesday, June 24, 2008 - 11:57 am: |
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The water in the coax can surely happen when running ASPE type coax that has connectors exposed to the weather.
You say you changed your coax to RG8 when you installed the Imax, and saw a problem. Then you changed coax to RG8x, and the SWR still varied with changes in the DK. Why did you change the coax the second time to RG8x?
When I buy a long run of coax, I always check the thru-put to make sure I am not dealing with a factory made patch in the line that will affect the SWR. I also monitor my rig for RF on my feed line at all times.
Anytime you change an antenna setup or location and you see noticable differences, you must go slow with your changes if you wish to try and understand what may have produced the problem. Even so, sometimes it is impossible to find a real solution and if the happens I move the location of the antenna.
For me, the use of filters and baluns on this type of antenna are not fixes and should not be needed. Except for safety grounding, grounding should not be needed either. If such devices work at all they are at best just convering up a poorly designed, built, or installed antenna.
The first thing out of the hat is that you have changed location for your antenna and that could be the bases of your problem since you original location with the A99 worked well, or am I still confused. |
Hotwire
Senior Member
Username: Hotwire
Post Number: 2527
Registered: 1-2005
| | Posted on Tuesday, June 24, 2008 - 1:54 pm: |
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Dead keying a 1.2 SWR is very good.
What do you mean by the SWR swinging?
Are you taking SWR readings while modulating???
KEEP IT REAL!
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Bridge_man
Member
Username: Bridge_man
Post Number: 66
Registered: 3-2006
| | Posted on Wednesday, June 25, 2008 - 9:00 am: |
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had the local tech put an analizer on it and the Imax is no good.and its brand new.gonna make some calls to see if i can get it exchanged.I put up another A99 and everything is great!sorry for all the confusion and thanks for all the help but i just assumed a new ant would be a good 1. |
Marconi
Advanced Member
Username: Marconi
Post Number: 774
Registered: 11-2001
| | Posted on Thursday, June 26, 2008 - 5:49 am: |
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Hey Bridge man, I think you did tell us that you showed a good SWR with your Imax, only thing was that the SWR went to 4:1 when you modulated with a very low dead key.
Don't those 2517's allow for a lot of low dead key drive, like maybe 25-35 or more watts out?
If you are putting that much drive ratio into an amp with an outboard SWR meter, then tell us how you are calibrating your SWR meter to check your SWR?
Do you also drive the SWR set mark?
And, then you tell us that your amp can't handle a 4 watt dead key. I'm getting more confused with your situation.
I know the analyzer shows more information about the condition of the antenna system than a SWR bridge does.
so could you give us a bit more info on exactally what the analyzer showed you guys?
What were the readings you got for R,X,SWR and at what frequency did you check?
I wonder what the analyzer showed that the SWR bridge didn't, that told you the Imax was bad?
You did tell us that your antenna showed a good SWR to start with, right?
How could the antenna be bad and still show a good SWR?
Makes me wonder about my Imax. I have seen a couple of really bad A99's over the years, but they always showed a bad (high) SWR too. |
Bridge_man
Member
Username: Bridge_man
Post Number: 67
Registered: 3-2006
| | Posted on Saturday, July 05, 2008 - 1:04 pm: |
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yes the 2517 dead keys 1/2 watt and swings 30 to 35 watts.the dosy manual says to test swr at 4 watts,so i turn the mod. knob all the way down,set the dk to 4 watts then calabrate the meter to the swr set mark.then i switch the knob to swr and got a reading of 2. then i turn the mod. knob about half way to where i 've been told it sounds the best and audio in the mic and it swings to around 4 or 5 on the swr scale.i have ran an a99 for years checking the swr the same way and got little or no swing.the ant. tech that used a mfj analyzer.the needle on the analyzer would jump from a 2 on the left to the wall on the right.he said there was probably a broken wire in it.it does rattle when you shake it and the manual says it normal to hear that.he agreed but said it should'nt rattle that much. well i have a good A99 up now and im back talking.guess im just stuck with a bad Imax.thanks Marconi |
Marconi
Advanced Member
Username: Marconi
Post Number: 778
Registered: 11-2001
| | Posted on Sunday, July 06, 2008 - 3:07 am: |
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Thanks for getting back Bridge man. I wish you had more info about the tech using the analyzer so we could maybe understand a little more about what he saw that made it obvious that your Imax was bad. If that analyzer didn't show me about the same thing my meter did, I would be about finding out why and fast. Do you trust your Dosy now?
That rattling you hear inside should only be the wire radiator that has a bit of slack in it so as to allow the solder attachment with the hub assembly at the top of the first section. But, it is for sure that things do break.
The problem is, you told us in the beginning that your antenna showed a 1.2 SWR and if that was so, then it defies logic that something was broken inside as the tech claims. It's alright, but it just don't make sense. |
Bridge_man
Member
Username: Bridge_man
Post Number: 68
Registered: 3-2006
| | Posted on Wednesday, July 09, 2008 - 9:48 pm: |
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yes the swr was 1.2 but it was swinging to about 4 with modulation.that meter has never done that before,even at 1400 watts.i do trust it,i've checked it on my setup against 2 other meters i have on all three ant. the first A99,the Imax and the new/used A99 that i have now.all 3 meters showed about the same swr and very little swing except on the Imax.even the old bad A99 that filled up with water.its swr now is about 3/4 of the scale but it doesnt swing.only the Imax.ive never had problems like this in the 10 or so years that ive really been into this hobby.The tech that made the custom amp for me (not the ant. tech) agreed that the ant. was bad and has had this problem before but nothing that a new ant did'nt cure.But he did say that if the swr swings above 2 that i would blow pills,which i did,on my setup.amp does great on his setup at his shop, A99 and on a dummy load.we hammered on it for about 2 hrs and the amp is great.looks good too, ill post a new pic if youd like to see it.All i know now is that its rocking now and im calling it a bad Imax.maybe ill try to safely take it apart if i get bored and try to see if i can find something wrong.thanks Marconi |
Marconi
Advanced Member
Username: Marconi
Post Number: 780
Registered: 11-2001
| | Posted on Friday, July 11, 2008 - 2:28 am: |
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That good, you will let us know and maybe see some snap shot of the inside, OK? |
Bridge_man
Member
Username: Bridge_man
Post Number: 69
Registered: 3-2006
| | Posted on Friday, July 11, 2008 - 10:33 pm: |
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check out the pictures section.just put 1 up with the leds in it. |
