| Author |
Message |
    
Chad
Junior Member
Username: Chad
Post Number: 26
Registered: 11-2004
| | Posted on Thursday, December 02, 2004 - 10:14 am: | 
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I noticed that after the recent bout of rain that my station was acting badly. SWR's through the roof at high power. Amp pulling serious current, RF Burns, generally bad stuff, I was off the air 
Yesterday after work the weather was nice so I installed the remainder of my Davis RF Bury flex from the ground point to the antenna. I now have a working station. I measured the center to sheild of the old RG8X Mini and found resistance between the two, I chuc it up to moisture in the feedline.
I am still getting higher than normal SWR readings when hitting everything with power (yes I am re-calibrating), although the station is acting normally I am still concerned. So I pose a few questions.
Could I have damaged my el-cheapo Radioshack SWR meter with too much reflected power?
Could it be that I have to tune the antenna using the higher power? The SWR without power is good! Why would the resonance change with clean power?
My dummy load only handles to 40 watts safely, It can handle peaks at 60. I feel I need another dummy load. I have built and used a gazillion loads for AF work using the gold Dale resistors. Will a high power 50 ohm resistor work for me or does it need to be rated for RF freqs? Will the larger resistors become reactive at higher freqs?
I may ask for a better SWR/combo meter from "santa" Evidently from looking at prices not all meters seem to be created equal, are there any faves out there for under $100. I would like to see SWR and "ballpark" power at the same time.
For all purposes here's the rundown on gear.
RF Path:
Galaxy DX2547 -> KL300P-> LM TVX2 filter-> Meter-> coax ground stub-> Imax2000
Jumpers are all home made with RG213 cut to length. Out of meter to ground stub is Bury-Flex. Bury-Flex to antenna.
Grounding:
8' Ground rod goes to antenna mast, coax stub, and terminal block in shack. Terminal block grounds; Radio, Amp, Power supply. Antenna mast ground wire is 4Ga direct burial. Shack main ground is 6GA, 12Ga goes to each peice of gear.
Thanks in advance for your time, I sincerely appreciate it!
Chad |
Highlander
Advanced Member
Username: Highlander
Post Number: 705
Registered: 12-2001
| | Posted on Thursday, December 02, 2004 - 2:39 pm: |
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Just how high are we talking on the SWR with power on? I have seen mine go up to around 2:1 with power, but it doesn't bother me. Most CB swr meters lose alot of accuracy above 5 watts forward power. Also, the input impedance of the amp might not be 50 ohms exactly, most aren't. If it isn't going above 2.5:1, I woudn't worry about it too much, as long as it is good with barefoot power.
David
n9rzf |
Chad
Junior Member
Username: Chad
Post Number: 30
Registered: 11-2004
| | Posted on Thursday, December 02, 2004 - 8:52 pm: |
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Oh Yeah, It's above 3:1 At least it's not pegging the meter anymore. Amp is not running hot but I really haven't been really using it for long at all. I'm going scrounging for a dummy load tomorrow to test the meter.
Chad |
Bulldog369
Intermediate Member
Username: Bulldog369
Post Number: 220
Registered: 2-2004
| | Posted on Friday, December 03, 2004 - 5:49 am: |
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you might want to check your jumpers... with a high swr that you had before an now its still high.. just take a check and make sure they are still good. |
Chad
Junior Member
Username: Chad
Post Number: 32
Registered: 11-2004
| | Posted on Friday, December 03, 2004 - 9:02 am: |
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Bulldog,
Did that, Went through everything. I know an SWR meter is a bridge, I'm looking for another quality meter today and a larger dummy load. If part of that bridge failed it would read some forward power also right? The load will tell me if the current meter had failed, if it reads high with a load then......
Thanks everyone for all your help!
Chad |
Highlander
Advanced Member
Username: Highlander
Post Number: 707
Registered: 12-2001
| | Posted on Friday, December 03, 2004 - 7:31 pm: |
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I'd try a different amp if you have access to one--if it works then you know the problem is with the 300p, and might be fixable. You might also try temporarily putting the meter between the amp and radio, that might tell you if the input impedance in the amp is off.
David
n9rzf |
Highlander
Advanced Member
Username: Highlander
Post Number: 708
Registered: 12-2001
| | Posted on Friday, December 03, 2004 - 7:35 pm: |
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I just noticed too that you have your antenna and your transmitter equipment on the same ground rod--I'm pretty sure that is a no-no, it might not have anything to do with your swr problem, but I'm pretty sure you want one ground for the antenna, and a completely seperate ground for your station equipment.
David
n9rzf |
Chad
Junior Member
Username: Chad
Post Number: 36
Registered: 11-2004
| | Posted on Saturday, December 04, 2004 - 1:22 am: |
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Highlander,
I can throw another rod down tomorrow easy, I know the "water trick." BUT if you think about it, the antenna ground is bonded to the shack ground with the coax. I was thinking one big star, central point, all good, no loops. Besides the mast is merely 12' away from the ground point. Got me thinking......
Chad |
Highlander
Advanced Member
Username: Highlander
Post Number: 709
Registered: 12-2001
| | Posted on Saturday, December 04, 2004 - 8:33 am: |
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Well, if I'm wrong, hopefully someone will step in and let us know, but I've always used a separate ground for the station, and one for the antenna. They are there to serve different purposes. Like I say, that may not have anything to do with your swr problem, but it is an easy one to check--just undo the antenna ground for a few minutes to test it.
BTW, what's the water trick?
David
n9rzf |
Tech808
Moderator
Username: Tech808
Post Number: 4211
Registered: 8-2002
| | Posted on Saturday, December 04, 2004 - 9:55 am: |
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Chad,
Go to the:
Ask The Tech area then click on,
» Installations
» General
» RADIO EQUIPMENT & GROUNDING
There you will see I have a picture posted of how my station equipment is grounded to prevent a ground Loop between our Equipment and Antennas as per Tech833's advice.
Hope this helps.
Lon
Tech808
CEF808
N9OSN |
Tech808
Moderator
Username: Tech808
Post Number: 4212
Registered: 8-2002
| | Posted on Saturday, December 04, 2004 - 10:21 am: |
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Chad,
This is Grounding Bar that I have ALL Radio's & Equipment connected to.
You will also notice the Short Copper ground wire jumper that I have running from the PolyPhaser's bus bar to the Equipment bus bar to avoid / cancel any possible ground loops.
This is what Tech833 suggested to prevent any ground loop effect.
The Large Flat Braid and Solid Copper Ground Wire goes directly to a 10' Copper Clad Ground Rod outside of window. Maybe less than 6 feet from the Equipment.
Hope this helps.
Lon
Tech808
CEF808
N9OSN |
Coyote
Junior Member
Username: Coyote
Post Number: 12
Registered: 11-2004
| | Posted on Saturday, December 04, 2004 - 11:18 am: |
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Holy Moly! Look at that thing! very impressive, to me anyway! I'd like to see the rest of that station. |
Chad
Junior Member
Username: Chad
Post Number: 37
Registered: 11-2004
| | Posted on Saturday, December 04, 2004 - 8:49 pm: |
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Highlander,
Water trick- As wet the soil with water, push the rod in and pull it out. as you insert it again pour water into the hole, it will go deeper. Pull up a little and pour a trickle of water at the same time, the upwards action will pull the water down the hole and when you push the hydraulic action will displace the soil. Keep doing this bringing the rod up 6" to a foot at a time and if you are strong enough you can drive the rod with one hand! It takes less than 5 gal of water and it goes in fast with no pounding. An old electricain bet me he could drive a rod with one hand and I took it, I lost, but learned a lesson that has saved me MUCH effort.
chad |
Chad
Junior Member
Username: Chad
Post Number: 39
Registered: 11-2004
| | Posted on Saturday, December 04, 2004 - 8:52 pm: |
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Lon that's beautiful!!!!! Do you have any coax grounds outside or just the polyphasers? I have a ground outside and plan to add the phasers, BTW they also make excellent telephone line protection also! I'll read the article, thanks!
Chad |
Highlander
Advanced Member
Username: Highlander
Post Number: 711
Registered: 12-2001
| | Posted on Sunday, December 05, 2004 - 8:38 am: |
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Cool on the water trick. We used a stepladder and a large drill on mine--it worked very well.
I guess my next question for Lon is are the tower leg ground rods connected to the ground rod that is outside his station? Because that is essentially what Chad has going with the ground rod that is connected to his antenna mast IS connected to the same ground system as his feedline grounding block and station ground. I think it is OK to have the feedline(polyphasers in Lon's case) and station ground tied together, but not the antenna mast or tower grounding. That issue really hasn't been addressed in the last few posts since I brought it up. Nice pictures, but what about the question at hand? The polyphasers or regular grounding stub like Chad is using ground the feedline, that is not the same as the ground used from the antenna itself or its supporting structure, as in the case with a grounded tower or mast. Or maybe I'm going crazy, lol...
David
n9rzf |
Tech808
Moderator
Username: Tech808
Post Number: 4221
Registered: 8-2002
| | Posted on Sunday, December 05, 2004 - 9:11 am: |
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Highlander,
No each tower leg has it's own ground rod on the North side of the house and the antenna mast is grounded to the tower.
I have a separate ground rod for the radios and other equipment that is located less than 6 feet out side under the window to the radio room on the South side of the house.
Lon
Tech808
CEF808
N9OSN |
Chad
Junior Member
Username: Chad
Post Number: 43
Registered: 11-2004
| | Posted on Wednesday, December 08, 2004 - 7:16 pm: |
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Well, the weather and the woman allowed me to make my last step in troubleshooting this evening on the SWR battle. I lowered the mast and attached a dummy load to the feed point and got perfect SWR at all power levels. I then atached a diople and made an inverted V to the ground (with ropes) to the feed point elevated to 20' SWR was around 1.5 (never tuned this antenna) and hit CA wnd WVA no problems with 1/3 power, good reports.
So.... Here's the skinny, The imax has low SWR at low power (less than 10 watts), less SWR than the dipole. After that it will go up to 3 or the CAL point The Dipole raised on the same metal mast as the Imax, and eyeballed and fudged for testing purposes, has a low SWR at all power and makes good contacts.
I've had this antenna (Imax)for less than three weeks and it performed for a few days. Granted it DID go through a wind/ice storm (eh lon, got that Rohn up yet ) What should I do next? Should I call Solarcon and ask? The manual says to send it in but I paid $30 to get it here and $30 to send it back, for a $70 antenna?
Is there another antenna (omni) that I should be using? I'll eat the ten bucks difference to not have to "wiggle up" another antenna for a third time in a while.
Best
Chad |
