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Foxhunter
Member
Username: Foxhunter
Post Number: 88
Registered: 4-2008
| | Posted on Wednesday, August 06, 2008 - 10:48 pm: | 
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Here's another question I had about a low-pass filter. In an effort to "clean up the neighborhood" I installed a like-new low-pass filter. SWR immediately went from 1.3:1 to 4:1 the instant I tried to transmit.
The filter looks mint and I then took it apart and everything appears nice inside.
I have currently inline:
Galaxy 99V
Texas Star 500V
Dosy TFC-3001
Low Pass Filter
Antenna
What or why would a filter (rated 1000W) go bad? I've been bleeding into everything around me and worry that nearby neighbors are listening to "Foxhunter" instead of their TV or PC.
I have it hooked up properly: "In" (from the radio/amp) and "out" to the antenna. |
Tech808
Moderator
Username: Tech808
Post Number: 15945
Registered: 8-2002
| | Posted on Wednesday, August 06, 2008 - 11:54 pm: |
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Where do you have your Power Supply for the Galaxy 99V grounded to?
Where do you have your Galaxy 99V grounded to?
Where do you have your Texas Star 500V grounded to?
Where do you have your Dosy TFC-3001 grounded to?
Where do you have your Low Pass Filter grounded to?
Where do you have your Antenna grounded to?
All or any of the above can effect your SWR
Lon~Tech808
CEF#0808/HAM#001/CVC#0002
Tech808@copperelectronics.com
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Marconi
Advanced Member
Username: Marconi
Post Number: 788
Registered: 11-2001
| | Posted on Thursday, August 07, 2008 - 1:21 am: |
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Foxhunter, I think I posted this already, but if your antenna is actually a sleeve dipole you cannot mount it close and on top of the TV antenna thinking it will serve as a ground plane without causing problems. You cannot add a GPK to a center fed dipole and expect it to work right. If it were a true end fed 1/2 wave antenna, it might be OK.
If you can check this antenna from the radio end of the feed line (shield to center) with an OHM's meter. If it is a sleeved, center fed dipole you should find an open circuit with the OHM meter showing no response. If it is an end fed dipole it will show a short circuit and the meter will show full deflection.
I would set the filter aside until you get this antenna thing figure out. Do you know if the filter has ever worked?
I still wouldn't think these type filters should affect SWR no mater where they are located in the system, and for sure not to the level of making the SWR read 4:1. |
Foxhunter
Member
Username: Foxhunter
Post Number: 90
Registered: 4-2008
| | Posted on Thursday, August 07, 2008 - 1:21 am: |
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Although it is more like a temporary station (in nature) it is still better than many of guys I know. I have the components sharing a common, heavy, welding-ground cable with heavy-duty brass clamps that goes to a large cast iron radiator 2-FT from my equipment.
The radiator system runs throughout the house and is ultimately attached to earth-ground via a cable-clamp & cable that runs from the basement radiator pipe mains to a 10-FT ground rod as required by building-code here in NJ.
So the whole radiator system is the house-to-earth ground and that is what I've attached my equipment to. Until I have a more proper and separately independant radio system ground.
My temporary (about 2 more months) radio room is in an upstairs room location which I know is at times a poor choice, but my antenna is directly located above the radio station and is very convenient right now. And the only place in the house I can set-up. |
Hotwire
Senior Member
Username: Hotwire
Post Number: 2564
Registered: 1-2005
| | Posted on Friday, August 08, 2008 - 11:58 am: |
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Probably better off not having your gear grounded to anything that runs through the house like a radiater system.
Remember once any grounds reach 9 feet in length or close to it many times they want to radiate just like an antenna.
I would start over with just the radio and antenna, see what you have and go from there.
Remember nothing you do or add to the radio and or coax is going to change the antenna SWR.Not even an antenna tuner changes antenna swr, it fools the radio and you still have reduced performance. A poor install will give incorrect swr readings. The only way you change swr is by changing the length of the antenna. Only by shortening or lengthening the antenna can you have any change in SWR. No extra coax, low pass filters grounds toys or amps does anything to change SWR. If installed wrong they will appear to change SWR.
Installing antennas and transmitters properly is no easy task. I hate it myself but through trial and error you learn things and it does get easier once you start to understand how it all works.
Best bet for a ground is a dedicated 8 foot copper rod in the ground outside the window. Ussually 6 gauge solid bare copper ground wire is used to run the ground into the radio room. Attach the 6 gauge to a buss bar and then the gear to the buss bar. Use the shortest length ground wires possible! Stranded ground wire is a poor choice, you need solid and BIG. I think you said your radio room is on a second floor level???
I have never used a ground in that situation myself. Only grounded the antenna and made sure my house wiring was up to the NEC.
Good luck and don't dispair! This is what it is all about man! You get bits and pieces of info from everyone and it all comes together. Soon you will have a station to be proud of and the best part is that you did it! I'm sure I'll hear New Jersey on timeout by the Fox hunter soon! 
You seem to have a hunger for good knowledge so I want to recommend an excellent book that Copper sells!
The Screwdriver Experts Guide
by Lou Franklin
Once you read this book cover to cover you will have more understanding of cb radio and better knowledge than 99% of the cb'ers out there!
Every REAL cb'er should own a copy of this book!
I own 2 copys! One in the shack and one in the bathroom!
KEEP IT REAL!
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Foxhunter
Member
Username: Foxhunter
Post Number: 97
Registered: 4-2008
| | Posted on Friday, August 08, 2008 - 6:13 pm: |
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Thanks for the reply and I will have a good room by October. I need to run separate service to the room w/breakers and have really alot to do. Shelving for 60 radio's & amp's will be a challenge not to mention test equipment. It will be located downstairs also.
Yes I've read that an upstairs radio-shack is a no-no in my first books about Amateur Radio (don't laugh)---"Ham Radio For Dummies" & "Two-Way Radios & Scanners For Dummies. I've seen "The screwdrivers guide" and will order it from Copper Electronics, I've been meaning to for some time.
For the very reasons Hotwire you just described, that any ground approaching 1/4 wavelength can radiate RF. My temporary station is only in place for about 2 more months. I was trying to make the best out of a bad situation and didn't want to leave things ungrounded.
Along the same lines I wonder how a tower can be grounded so high up? Alot of people I've visited have seemingly lengthy grounds from either their antennas or their shacks. How does one ground an antenna mounted up 40-FT or more? And if it is mounted not on a tower but off the roof using mounting-mast? Grounding my antenna would require either running a 25-Ft ground-cable down to a rod. That's about 3/4 wavelength. I know a number of the questions I ask could be found with more reading on my own and I do read quite a lot. Other times I've read conflicting information and ask a question to see how other Forum members might view things. I'll definitely check out Lou Franklin's book and I'll check I believe he's written more than one. Thanks----Foxhunter |
777_evergreen_state
Junior Member
Username: 777_evergreen_state
Post Number: 11
Registered: 12-2007
| | Posted on Monday, October 06, 2008 - 6:09 pm: |
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If you had an SWR of 1.3:1 prior to installing the LPF I would suspect:
A) faulty jumper wire
B) faulty LPF
Also, double check the connectors of the pre-existing coax and make sure the connections are secure.
The antenna was showing an acceptable SWR before, and since the only change was to install the LPF then it only stands to reason the problem was caused by the addition of the LPF... ;) |
Tech237
Moderator
Username: Tech237
Post Number: 1070
Registered: 4-2004
| | Posted on Tuesday, October 07, 2008 - 9:33 am: |
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Now to really muddy the waters, there is one rare situation that causes all the symptoms you have described. I say rare as in 35 years in the trade I have come across it once.
It is possible that your swr was bad prior to adding the filter but that the spurious signals created by the radio were actually cancelling out reflected power thuis giving an swr that looked good. The filter has removed/blocked those spurious signals so the real SWR shows.
Do I think this is possible yes, btu I really don't think it is likely.
Where were you checking the swr both before and after adding the filter? How long a patch cable between the radio and the filter? Remember odd lengths of coax can cause an apparent change in SWR.
Simon
Tech237
N7AUS
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Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 445
Registered: 9-2004
| | Posted on Tuesday, October 07, 2008 - 6:59 pm: |
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Now Hotwire make a valid point,sometimes a poor ground is worse than no ground at all. I would never recommend grounding anything to a radiator system or the house electrical grounding, too many variables.Try running a counterpoise ground which is simply a quarter wave length of insulated wire around the room and attach all equipment to this counterpoise at at common point.As for filters I have seen this before,try another filter and double check jumpers with swr 4-1 usually means an open circuit or a short.
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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