| Author |
Message |
    
738
Member
Username: 738
Post Number: 79
Registered: 7-2003
| | Posted on Tuesday, May 30, 2006 - 7:44 pm: | 
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I have always used a TVI filter as the last item in the chain before the antenna. I was reading another post that mentioned using the TVI filter before the Amp. so that Harmonics are not amplified by the Amp. I had never thought about Harmonics coming from the radio. I have always understood that they are generated within the Amp. if they are generated by the radio and the amp. then would it be a good idea to run a filter before and after the amp. to filter the radios, and the amp.s output? |
1861
Advanced Member
Username: 1861
Post Number: 508
Registered: 2-2004
| | Posted on Tuesday, May 30, 2006 - 9:24 pm: |
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I RUN ONE STRAIGHT TO RADIO AND ONE STRAIGHT TO AMP -- NO COAX . IF I WAS JUST RUNNING ONE , IT WOULD BE ON RADIO . |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1730
Registered: 9-2004
| | Posted on Tuesday, May 30, 2006 - 9:48 pm: |
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yes, if your goal is to eliminate TVI.
if the radio is bone stock and tuned properly, then its probably not a big deal, but couldnt hurt.
if, however, your radio has been peaked, modded, or had the AMC removed (your 142GTL), then it is putting out spurious emissions, which should be attenuated before they get amplified by the linear right along with your 27mhz signal.
the amplified harmonics are harder to filter out than they would be had they been dealt with before amplification.
if possible, try to use a double male or right angle connector on the back of the radio and linear rather than add another jumper into the mix.
if you cant, jumpers will work.
good luck,
matt |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1559
Registered: 7-2004
| | Posted on Tuesday, May 30, 2006 - 10:03 pm: |
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I'm not sure about this situation. ARRL
RFI handbook says to put filter after amp.
Says short leads (jumpers) should be used.
Also using jumpers it's possible some spurious energy may be radiated from the jumpers.
So, it's a touchy thing... LOL...
I personally just run a 2995dx capable of 150 watts PEP. I use a double male connector and
installed filter right to radio. And i have
nothing else in-line. No jumpers.
I will have to do some more research on this subject. |
Chad
Advanced Member
Username: Chad
Post Number: 876
Registered: 11-2004
| | Posted on Tuesday, May 30, 2006 - 10:24 pm: |
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I filter after the amp, the radio is un-modded. It really is just there to catch anything coming out of the amp if I do something stupid. Overdriven amplifiers are a cause of TVI too, a filter after the radio will not help this scenario. The meter is last in line, so I can read real power 
Chad |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1560
Registered: 7-2004
| | Posted on Tuesday, May 30, 2006 - 11:02 pm: |
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Every article i read tonight said,
if using a amp, it goes after amp.
if you have tuner in-line, filter goes
after amp, then place your tuner after filter.
Tuner should be last in-line.
If not using Tuner, filter is last in-line.
Swrs have to be low or filter will not work
as it's suppose to.
Boy, glad i do it the simple way...LOL
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738
Member
Username: 738
Post Number: 80
Registered: 7-2003
| | Posted on Wednesday, May 31, 2006 - 5:08 pm: |
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Thought this would be an interesting question. Thanks for the replies! Think I will keep a eye open for another, I am to old now-just want to relax and enjoy a little DX without people knocking on my door like when I was young, ha., ha.. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1562
Registered: 7-2004
| | Posted on Wednesday, May 31, 2006 - 9:58 pm: |
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I know what you mean 738! |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1737
Registered: 9-2004
| | Posted on Thursday, June 01, 2006 - 12:10 am: |
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most articles you will find on low pass filters assume that you are not running a "dirty" CB radio.
738, the most important things you can do to eliminate interference are to get your antenna up high in the air away from everything, and use good quality coax (new) with properly soldered ends (all four holes).
also, do a search on this forum for "choke balun" and build one.
just doing these things, even with no low pass filter should keep the neighbors happy.
hey, wait a minute, dont you live out in the middle of nowhere now?
are you worried about interfering with the cows?LOL
matt |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1563
Registered: 7-2004
| | Posted on Thursday, June 01, 2006 - 11:45 am: |
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Harmonics will make a cow stop giving milk
for weeks. Also causes chickens to lay square eggs...
From reading: amps cause harmonics and it's
even possible for a SWR meter to create harmonics.
Don't understand about SWR meter, but, that's
what they say... Radio-SWR meter-Amp- TVI filter.
But, i like Kids advice on height, good coax, ect. |
738
Member
Username: 738
Post Number: 83
Registered: 7-2003
| | Posted on Thursday, June 01, 2006 - 5:03 pm: |
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To funny! Don't want to plug up a cow! No really just in the planning phase, got a few items purchased. I do have some houses close by, and some people still actually use TV antenna's, not to mention stereo's, computers, etc. Yes antenna height is important, and that is why as far as verticles I have always gone for a grond plane (except my old loved Sigma 4's!) Think I am just going to run flat off a beam this time to start. I am only interested in DX really. On the coax, there are so many choices now. Last time I was on back in 89 there was 9913/14 as the best. Now my biggest slow down is deciding on LMR400, Direct Bury, or 9913/14 sort of thinking of Bury, as I got a 45' above ground run. Thanks for all the idea's... |
Tech808
Moderator
Username: Tech808
Post Number: 10168
Registered: 8-2002
| | Posted on Thursday, June 01, 2006 - 5:24 pm: |
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738,
I have had 3 runs of RG-213 of between 75' and 125' above ground along with my rotor cable for the last 15-20 years with NO Problems.
Just never seen the need to pay more for buryflex when the RG-213 works just as well for me.
Many of the Copper Forum Member's have been here and seen that I just run all of my coax and rotor cable from the tower's thru 2" PVC and then into the house.
No Digging, No Pests, No Problems and a LOT more money in my pocket to spend on other thing's. 
Lon
Tech808
CEF808
N9CEF
CVC#2  |
738
Member
Username: 738
Post Number: 87
Registered: 7-2003
| | Posted on Thursday, June 01, 2006 - 6:17 pm: |
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Thanks for advice, have never tried 213, have you used it at 50MHz or higher? I need to run a new 6M line too (using 8x-temp.), many of my 6M contacts are at or just above the noise level. |
Tech808
Moderator
Username: Tech808
Post Number: 10171
Registered: 8-2002
| | Posted on Thursday, June 01, 2006 - 6:25 pm: |
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738,
YES, we use RG-213 for ALL of our antennas including our 2 Meter and and 6 Meter Antennas. 
Lon
Tech808
CEF808
N9CEF
CVC#2 |
738
Member
Username: 738
Post Number: 89
Registered: 7-2003
| | Posted on Thursday, June 01, 2006 - 8:43 pm: |
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Cool, just saw you have direct bury 213 for same price (@100' minus connectors). Think I will give it a shot. No insult to copper at all never saw their connectors, but I like to solder my own connectors anyway. I'm mil. spec. certified, and like to add a RFI/EMP over-braid on connector end anyway with silicone tape. Like we do on our Rocket cables. Sort of make sure there is no RF leakage, and hopefully if I take a hit the lightning will like the skin effect.
Tnx.
738 |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1748
Registered: 9-2004
| | Posted on Friday, June 02, 2006 - 12:17 am: |
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738, will you give us some details about your PL-259 shielding technique?
that sounds really neat.
YOU should definitely do your own connectors!
matt |
738
Member
Username: 738
Post Number: 93
Registered: 7-2003
| | Posted on Friday, June 02, 2006 - 6:14 pm: |
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Well the way we do all connections at connector is, well number one we mainly use multi-pin connectors, but some similar to type N. Most wires are, shielded or coax, a few twisted pair. All shielded wires are strippped back lets just say 6" and laid together. If there are any twisted pair in the group then a small braid of same lenght is placed over them, then over that bundle is placed a larger braid. After pins are inserted in connector, then braid is laced tightly over braids/shields and over backshell (banded) and then covered with silicone self sealing tape(coax seal). On a PL-259 I expose shield/braid back from connector about 4-6" and cover with braid from just behind spinning part of connector clamped tightly with lacing, hose clamp, or banding tool-whatever I have on hand. Then over stripped coax to just where insulation starts. I put at least 3 tight lacings over it to squeeze tight to shield, then wrap up nice and tight with sealing tape. This way there is a tight water sealed connection from connector to braid, over back of connector to shield. Even if your solder connection at the inner holes break from age/movement, you still have a solid connection. It will also cover more surface area all away around, rather than the solder tacks to a few shield strands on the inside. Will also carry more current without melting solder, and have a better skin effect for both RF, and lighting passing over connector from antenna. Even if you don't do this, always use coax seal. When this is screwed to antenna, then I seal over the whole conncetion area with the tape. This stuff is self sealing, have never opened one yet to find any water or even oxidation! Cool stuff. Here is a link to info. on the last rocket that went up, before that we launched the New Horizons Spacecraft on the way to Pluto. It's interesting work. http://www.ilslaunch.com/newsarchives/newsreleases/rec337/
738 |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1752
Registered: 9-2004
| | Posted on Saturday, June 03, 2006 - 9:34 pm: |
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very interesting!
thanks,
matt |
Navyrebel782003
Intermediate Member
Username: Navyrebel782003
Post Number: 181
Registered: 12-2004
| | Posted on Sunday, June 04, 2006 - 8:09 pm: |
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Hey 738, that sounds like the way we do connectors on the F-18, shielding, "stretch tape" or "cherry" tape and all. I have never thought about doing coax connectors that way though, but now I have a new project...
James
CEF#590
CVC#49
Va Beach |
