| Author |
Message |
    
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 175
Registered: 4-2006
| | Posted on Monday, June 05, 2006 - 9:28 pm: | 
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OK, instead of using a 3 foot jumper from the amp to the meter, I decided to use a double male barrel. Well, here is something that was driving me nuts that I finally figured out.
When using the double male barrel, I would key down and for the first 10 seconds of the key down the SWR was 1:3, then all of a sudden, after about 10 seconds, it would jump instantly to 2:5, another 5 seconds 3:1. After going nuts, changing meters, changing barrels, and the problem still there, I simply inserted a 3 foot coax. Problem gone. Any idea why using a double male barrel would do these wacky things? It is a 667v amp. Thanks. |
Dale
Intermediate Member
Username: Dale
Post Number: 451
Registered: 12-2002
| | Posted on Tuesday, June 06, 2006 - 10:14 am: |
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was this done with amp on?if yes sounds to me like the double connectors cant handle the power
no good leave them off and use the jumper |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 176
Registered: 4-2006
| | Posted on Tuesday, June 06, 2006 - 12:20 pm: |
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OK. I use the 3 foot jumper and problem solved. Well kinda. With the amp off, I have literally flat SWR across the board, as soon as I put the amp on, even at only 40 watts, the SWR's are 1:6. I know, not that bad, but then they go to 2:3 when I put the 667v all the way up. AHHH...this is killing me.
PS--I am getting about 500 watts from the 667v at max. Is this right? |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1432
Registered: 1-2005
| | Posted on Tuesday, June 06, 2006 - 12:24 pm: |
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SWR and SWR meters are tricky and can be very confusing at times. What may have occured was that the meter was just showing inacurate readings. Now we know swr readings are to be taken at the antenna end of the coax for the best reading possible.If the coax length is anything other than odd multiples of a half wave length you are going to get 2 differrent SWR readings at each end of the coax. So when you replaced your 3 foot jumper you got a lot closer to the odd multiple wavelength than that barrel connector did. SWR actually stayed the same cause no changes to the antenna was made. As far as the reading jumpimg around could be due to possible a cheap barrel. I have been taught that if I must use a barrel ESPECIALLY WITH AN AMP to alaways use the good qaulity barrels such as Amphenal brand. RF and the way it is reflected back down the coax, multiple half wavelengths, SWR, and all the hundreds of good and bad meters can be a pain in the rear at times! The best advice I can give ya is to always check SWR at the antenna for the best most accurate reading possible.73 |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 177
Registered: 4-2006
| | Posted on Tuesday, June 06, 2006 - 2:30 pm: |
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OK, here it is. Radio to amp is 9 feet. amp to meter is 3 feet. meter to antenna is 14.8 feet (Something like that. it is 1/2 wave based on formula, etc..). Am I correct in thinking that the SWR reading between the meter and antenna should alwyas stay constant regardless of what size jumper I use from radio amp and amp to meter? |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1767
Registered: 9-2004
| | Posted on Tuesday, June 06, 2006 - 10:18 pm: |
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who did the coax ends?
were they done at the factory, or did you have to add PL-259's?
i am pretty sure that the coax length is going to play a role in the SWR reading no matter which jumper you are changing.
if the SWR is rising with heat, you need to check both the radio and the amp to see which one is causing the problem.
good luck,
matt |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1581
Registered: 7-2004
| | Posted on Wednesday, June 07, 2006 - 6:36 am: |
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Just curious: Is this a base or mobile set-up?
 |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 180
Registered: 4-2006
| | Posted on Wednesday, June 07, 2006 - 10:24 am: |
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Mobile setup. LMR400 coax from cable xperts. I did all the calculations. At channel 1, the SWR is literally flat. When I put the amp on, it goes up to about 2:1 with the 667 v at full power. I know it is not horrible, but it still bothers me. O yeah, where can I get good double male barrels? Thanks. |
Tech808
Moderator
Username: Tech808
Post Number: 10206
Registered: 8-2002
| | Posted on Wednesday, June 07, 2006 - 10:35 am: |
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Let's see now Copper Forum sponsored by Copper Eectronics maybe from Copper Electronics! 
C70-05012 COAX CONN DOUBLE MALE, CLICK HERE
Hope this help's,
Lon
Tech808
CEF808
N9CEF
CVC#2 |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1435
Registered: 1-2005
| | Posted on Wednesday, June 07, 2006 - 11:08 am: |
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James, You say swr is flat and when you turn the amp on it reads 2.1? No worrys man! The amp is not raising the swr its only making your meter show false readings. Amps do that sometimes. Unless you changed the length of your antenna your swr is the same all the time no matter what you do. If it makes you feel better just use different coax lengths to make your meter read whatever you want but regardless nothing you do will change the swr at the antenna.73 |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 182
Registered: 4-2006
| | Posted on Wednesday, June 07, 2006 - 11:49 am: |
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Tech808, who makes that double barrel that Copper sells? Is it Amphenol, or some other company? I knew copper sold them, but for some reason I thought that it was NOT Amphenol. Let me know. Thanks.
PS--Where can I buy a new cb radio from? (Just kidding) |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1584
Registered: 7-2004
| | Posted on Wednesday, June 07, 2006 - 2:23 pm: |
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Just make sure from antenna to radio is
the best SWR you can achieve on your system.
It should be fine.
I'll have to measure my exact jumper length in my car someday. It's shorter than 3 ft. (Amp to radio) From radio to antenna i have 1:1:1- amp in-line shows 1:3:1 / I don't keep a SWR meter in-line. I just check them from time to time and
mostly watch and listen for any changes in recieve and transmit. Been doing it that way
since 1976. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1775
Registered: 9-2004
| | Posted on Wednesday, June 07, 2006 - 10:29 pm: |
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i second what hotwire said.
its just the meter showing weird readings because the amp is putting out some harmonics that the SWR meter doesnt know how to deal with.
if you have a low pass filter, try putting it after the amp and before the meter.
if this lowers the reading on the meter, then you know its just harmonics causing the mis-read.
you dont have to run the low pass filter in line after the test.
there's really no need for it in the mobile, unless you talk from the driveway alot. LOL
i would say that the setup is fine, just take the meter out of line if the reading bothers you. J/K.
good luck,
matt |
Chad
Advanced Member
Username: Chad
Post Number: 909
Registered: 11-2004
| | Posted on Wednesday, June 07, 2006 - 11:39 pm: |
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Woah, if the amplifier is being over-driven and producing harmonics the SWR reading is true. the harmonics are outside the radiator's bandwidth and are being reflected.
"Just harmonics" is actually a big issue, you DO NOT WANT harmonics. Run the LPF after the amp or drive it easier.
Chad |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1590
Registered: 7-2004
| | Posted on Thursday, June 08, 2006 - 12:32 pm: |
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James, my jumper in my mobile from amp to
radio measures 2' 11" from pin to pin of
connector. Just checked everything. I'm
running 3 watts into a KL-200 amp. I thought it
was 4 watts, but, it's 3 watts.
I'm running a middle-loaded 62" $6 antenna.
SWRS 1:1:1 with amp in-line, but, off.
1:3:1 with amp on. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2942
Registered: 7-2004
| | Posted on Friday, June 09, 2006 - 10:11 am: |
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Run the LPF after the amp or drive it easier as chad says. i think that 450 watt dead key is part of the issue... |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1594
Registered: 7-2004
| | Posted on Friday, June 09, 2006 - 10:38 am: |
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Oh, i somehow missed part about 450 watt
DK. That puts my 30 watt DK to shame.
James,how many DK watts and swinging watts you keying into your Amp? |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 189
Registered: 4-2006
| | Posted on Friday, June 09, 2006 - 3:14 pm: |
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I forgot to mention, this problems happens even only at 100 watts. The radio is doing 3.5 to 4. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2950
Registered: 7-2004
| | Posted on Friday, June 09, 2006 - 4:02 pm: |
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he posted on another thread here about the 450dk, |
