| Author |
Message |
    
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 19
Registered: 4-2006
| | Posted on Thursday, April 13, 2006 - 4:51 pm: | 
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Hi. Yeah, I know I ask alot of questions, but you guys are the experts. Here we go.
I just finished installing a new antenna for my van. SWR's are almost flat (1:2 to 1:3 across the whole 40 channels). This is only when the radio is connected directly to the antenna. However, when I put a palomar 250 (silver color) in line, even with it off, the SWR's are 2:1. When I put it on lo, it is like 2:3, on medium 2:5, and on high 3:1. I do notice though that when I talk, the SWR does swing down slightly (maybe like to 2:1). Why are the SWR's that much higher even with the amp off? Why do they swing down slightly when I talk? Even with it off the SWR is 2:1. Does the amp need to be "tuned" for 11 meters? I checked all coax and tried different combinations, but nothing. Please help. Thanks. |
Leonard
Intermediate Member
Username: Leonard
Post Number: 213
Registered: 12-2002
| | Posted on Thursday, April 13, 2006 - 8:19 pm: |
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Try to do a search on the left side under utilities there are alot of information with this problem.
I can not help other that this sorry.
Len CEF#189 So,Minnesota |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1335
Registered: 7-2004
| | Posted on Thursday, April 13, 2006 - 8:28 pm: |
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I have never had a problem with high SWRs with
any of my set-ups, so, not sure if i can help.
Make sure jumper is good. Coax and connectors.
Check all connectors, also make sure they are
tight when screwed on radio and amp.
Make sure antenna is grounded well to the vehicle.
I hear people talk about using 6ft jumpers, 12 ft jumpers, ect., I always use 3ft and have never had a problem yet. So, someone else can fill you in on different jumper lengths.Good Luck! |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1427
Registered: 9-2004
| | Posted on Thursday, April 13, 2006 - 9:42 pm: |
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just so we can eliminate a few possibilities; would you give a detailed explanation of what your install was like, with all the where's what's and how's, etc.
as for the SWR swinging down when you talk; thats nothing more than your SWR meter showing its limitations.
everyones SWR meter does that when they talk.
thats why i always turn the mic gain all the way down when measuring SWR; makes the results easier to determine.
i have had this problem in a couple of installations, and if you can eliminate any bad grounds, connectors, coax; then trying different jumper lengths is your best bet.
if you are using 9, use 6, or 12 feet.
also, it was brought to my attention that the actual SWR meter may be showing misleading readings at high power, because it cant handle it.
is this a radio shack meter that you just bought new within the last two years or so?
if so, try and change the meter for another one, preferrably a different brand. (not vanco)
doing this did the trick in my current installation, where the SWR on the old meter was 2 to 1 and with the current one, its 1.3 to 1.
good luck,
matt |
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 22
Registered: 4-2006
| | Posted on Thursday, April 13, 2006 - 10:30 pm: |
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Antenna has a near flat SWR when plugged directly in the radio (van, roof top mounted, dead center, with mini 8). but when I add the amp in line, even with the amp off, the SWR's go to 2:1 or more. The meter I have is rated at 4000 watts. The jumpers are good (I even tried different ones and lengths). Antenna is grounded very well. Like I said, perfect SWR when hooked directly to radio. The radio is a 148 gtl modified for extra channels. With the amp inline, The SWR goes to at least 2:1 on the external meter, and 2:1 on the radio meter. I have the power leads for the amp going directly to the battery. Anyting you can recommend? Thanks. |
Marconi
Advanced Member
Username: Marconi
Post Number: 643
Registered: 11-2001
| | Posted on Friday, April 14, 2006 - 1:19 am: |
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Where do you have the meter installed in the line? |
Dx431
Senior Member
Username: Dx431
Post Number: 1166
Registered: 2-2002
| | Posted on Friday, April 14, 2006 - 1:57 am: |
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Only things I can suggest is grounding the radio and amp to the seat bolt and then grounding the chassis of the radio and amp. |
Chad
Advanced Member
Username: Chad
Post Number: 782
Registered: 11-2004
| | Posted on Friday, April 14, 2006 - 9:26 am: |
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Try putting the meter after the amp and before the antenna. The amp/short coax may be playing tricks with you. I generally worry about the SWR of the antenna SYSTEM not about the SWR of the amp to the radio.
Chad |
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 23
Registered: 4-2006
| | Posted on Friday, April 14, 2006 - 10:20 am: |
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I did just that. The meter was placed after the amp, before the antenna. Also, I did notice though that as I talked on the 28 MHZ freq, the SWR's went down to like 1:5. Could it be this amp is set for 10 meters? Is there any way for me to tell by looking inside? Should I check any crystals inside? the antenna SWR system is flat without the amp in line. Thanks.
PS--It's a palomar 250, silver colored. Thanks, |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1338
Registered: 7-2004
| | Posted on Friday, April 14, 2006 - 12:18 pm: |
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What channels do you have antenna set for?
28 MHZ is ham freq./ Amp should be fine if
it's transmitting on desired channels.
If you mainly talk on cb channels, set lowest
SWR on ch 20. |
Marconi
Advanced Member
Username: Marconi
Post Number: 644
Registered: 11-2001
| | Posted on Friday, April 14, 2006 - 2:56 pm: |
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The rule says if the antenna load is purely resistive (flat) at resonance, then the line will not make any difference regarding SWR readings.
Does that sound right in this case?
Kid Vicious says "as for the SWR swinging down when you talk; thats nothing more than your SWR meter showing its limitations. everyones SWR meter does that when they talk." Well none of my meters do that and I run a kw or more at times. Now if I crank up my dead key relative to my radio's total drive output then I might see some backwards movement in my meter.
Marconi |
Georgeodjungle
Member
Username: Georgeodjungle
Post Number: 56
Registered: 1-2006
| | Posted on Friday, April 14, 2006 - 3:51 pm: |
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you can tune the amp:
the easiest way it to put a trimmer in.
should cover 400pf
& or a coil about 14 gage 6 loops @ 1/2 inch dia.
that will lower swr & clean her up.
take it to your local tec he'll know what to do.
most amps are made for 10 meter....
not suppose to run them on 11. |
Georgeodjungle
Member
Username: Georgeodjungle
Post Number: 57
Registered: 1-2006
| | Posted on Friday, April 14, 2006 - 3:59 pm: |
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p.s.
to change swr @ the radio change in to the amp,
simlpy change that first resistor should be a 10 watt 35 ohm.
the only big one.
try a 40 or 48.
all amps are lil differnt... |
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 26
Registered: 4-2006
| | Posted on Friday, April 14, 2006 - 4:27 pm: |
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I have the antenna tuned for Channel 19. When plugged directly into my CB the SWR's are flat for the most part. But when I insert this amp inline, even with it off, the SWR goes to 2:1. Do I need to retune the antenna with this thing inline, even though it is off? |
Vanillagorilla
Advanced Member
Username: Vanillagorilla
Post Number: 529
Registered: 4-2005
| | Posted on Friday, April 14, 2006 - 6:42 pm: |
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Mmmmkay..lets start from scratch. Sounds like maybe your antenna is electronicly short...meaning hopefully its adjustable and you haven't cut it too much already. It looks to me that the amp (that should also have its chassis grounded as DX431 stated) is magnifying your true swr. Take the amp back out of line and reset your SWRs paying CLOSE attention to your bandwidth. If it looks even a LITTLE bit higher on ch1...raise the antenna tuning....if its a wee bit high on 40 then lower the tuning...keep going till its at least FLAT or lowest mid band...ch20 and done right this WILL take time!
Reinstall the kicker with a ground strap and recheck SWR...power on and off.
The fact that it changes with the kicker not powered throws me in the direction of coax length OR at the very least questionable integrity....its new stuff...right? Quality around 3 to 6ft long between kicker and radio?
I know you probably know how to set your antenna up and hope I don't sound insulting but my intention here is to really drive home the importance of setting the antenna's bandwidth (centering it to the most used freq) correctly most importantly with a relatively speaking, narrower bandwidth antenna. (didn't say what you were using?) Do NOT trust the radios SWR meter...although it could be true I've seen too many that just were not accurate.
You COULD go ahead right now and reset your antenna with the amp in line but I think you'll be putting a bandaid on the problem. You say the SWR falls the closer you get to 28mHz...I suppose then it'll go UP as you get closer to 25mHz?
I'd bet it does and you simply need to fine tune your system along with adding a SHORT ground strap to your kicker chassis.
The kicker may or may not amplify your readings depending on your circumstances but you should still be able to easily obtain the target SWR below 1.1:5 or better.
Good luck and keep us posted!
Hank CEF559 |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1161
Registered: 1-2005
| | Posted on Saturday, April 15, 2006 - 1:49 pm: |
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swr is good like 1.1 without the amp and then swr goes up when you add the amp? This sometimes happens with cheap amps, I have had many and your problem is one I have had too. You can try another antenna and maybe some new coax but not much your gonna be able to do to solve your problem. I know cause I have been there! If you can obtain an swr of 2.0 then let it be. Its not gonna matter that much I promise! Your gonna get way to stressed out over this just trying to get swr down a few points. Just get some radio checks and have fun! good luck and 73 |
Georgeodjungle
Member
Username: Georgeodjungle
Post Number: 60
Registered: 1-2006
| | Posted on Tuesday, April 18, 2006 - 12:33 am: |
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ya don't worrie about it:
your only losing about 25 to 30 watts.
splatering & running hotter. |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1198
Registered: 1-2005
| | Posted on Wednesday, April 19, 2006 - 12:56 pm: |
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How do you know he is losing 25 to 30 watts and splattering? With the way these amps are made so cheaply today not to mention the SWR meters having poor readings trying to get perfection is hard to do. Even just a little reflect can cause poor readings. You can have perfect swr and not know it. I'm not even going to get into the cars of today with there awful counterpoise potential!
I'm just offering my advice. The newbies will figure it out someday. A 2.0 swr compared to a 1.5 is not that big of a difference. 1.5 compared to 1.1 is nothing really. Of course we all want 1.1 swr for the most efficent possible but you just get it as low as you can and have fun. To much time is wasted worrying about this perfect swr stuff when contacts and friends can be made. Unless you are totally mismatched and swr is like way over 2.5 or 3.0 your radio is not gonna blow up. If somebody wants to nip it all in the bud then get your hands on an antenna analyzer!73 |
Jameslarson
Member
Username: Jameslarson
Post Number: 62
Registered: 4-2006
| | Posted on Wednesday, April 19, 2006 - 3:16 pm: |
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Well, here's another piece of the puzzle. When I change the length of coax from 6' to 9' (radio to amp), the SWR's go down to 1.5 to 1 instead of 2.1. If I change it from the 9' to 18' it goes back up (Even worse than the 3'). Strange. O yeah, the cable length from the antenna is 18'. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1457
Registered: 9-2004
| | Posted on Wednesday, April 19, 2006 - 5:10 pm: |
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you've found your cure, just keep experimenting with different coax lengths until you are happy.
i would be perfectly happy with a 1.5 SWR.
matt |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1202
Registered: 1-2005
| | Posted on Thursday, April 20, 2006 - 11:40 am: |
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I would say your antenna is tuned just fine. Different length jumpers is not changing the swr. The different lengths change how the meter is effected by the reflect. For piece of mind go ahead and use the 9 foot jumper. |
Georgeodjungle
Member
Username: Georgeodjungle
Post Number: 66
Registered: 1-2006
| | Posted on Thursday, April 20, 2006 - 5:33 pm: |
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mr hotwire:
with a swr of 2 you lose at least 10%.
and with 25 watts comming back or loss,
is got to go some where. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1463
Registered: 9-2004
| | Posted on Thursday, April 20, 2006 - 7:13 pm: |
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hotwire,
i guess i should have used a different word than, "cure".
you are correct in your post.
i believe his antenna is tuned just fine too.
matt |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1353
Registered: 7-2004
| | Posted on Thursday, April 20, 2006 - 11:34 pm: |
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I 3rd the notion on being tuned just fine. |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1206
Registered: 1-2005
| | Posted on Friday, April 21, 2006 - 12:24 pm: |
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George, I know you are correct. Whos to be sure what his swr really is without using an analyzer right at the antenna? Before what was stated was that swr was flat at radio with antenna only. Add the amp and all the trouble starts. Besides trying a different antenna what more can a guy do? Maybe an antenna tuner but thats just a bandaid. Even if your swr meter says you have a perfect swr with an amp inline the meter could be lying to you. Amps can be such a pain in the rear sometimes and getting it all perfect is a crapshoot. To this day I have yet to destroy an amp or radio even when swr meter readings were kinda high. I have just gotten over the whole swr thing. I do the best I can set it and forget it.73 |
