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Reflected power readings


Riktar
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Both of my "commercial"  premade antenna cables (LMR400 - 90ft and 15ft) show a reflected power reading of 0.23 and 0.05 respectively on my Nissei RS-50 meter. The forward power is 24 watts and the swr is 1.15 between the 2.

 

I tried my hand at crimping a PL-259 connector on another cable to make a "custom" length. And since I am still waiting on the stripping tool for this I went online and used the example(s) of a box knife to prep the cable. What a pain that is. I hope the stripping tool gets here soon!

 

Anyway, after doing this and hooking up the meter I am show a minor deviation on the forward power but the reflected power has jumped to 1.68. My SWR has also increased to 1.56.

 

While connector installation looks proper on the cable I am wondering why the increase in reflected power? Could I have done a poor job on soldering the tip of the connector to finalize the connection to the center conductor? 

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As someone who is new to this hobby (and sometimes confused by his own post's as well.. I noticed I incorrectly put down SA-239 in an above post when I do know from reading other posts it is an SO-239. Ugh, I try to use correct spelling and then do that...  :unsure:) I want to ask if I am going too far in the quest to keep my coax one long continuous cable from the antenna to the radio.

 

My antenna is in the attic of a 2 story home and the cable is fed down an unused chimney into the basement and back up to a first floor room where is exits out in the corner of the room and hooks directly into my radio. And it is a single piece of coax. The only break in the whole link is where I put a SWR meter in to check on the line and the antenna.0

 

 I am assuming that when people use a tower install or have an extreme length between the antenna and the radio it is not feasible to use one continous length of cable. But I have no idea what the standard would be for when it is practical to add addtional connectors for extending or stepping down the cable size to complete the installation.

 

IE: In my case, while it was a pain, I was able to wrangle the (approx) 60' feet of LMR400 all the way from the antenna to the radio in one continuous section. If I was ever inclined to try and get an antenna up on the 40 foot silo in my yard and into my house the path would be (again, approx) 200' feet long. Aside from the sheer bulk of handling one long piece of cable to do this AND considering that a run this long would mandate using something as heavy/large as heliax cable which (I am admittedly guessing here) is not as forgiving at being bent around multiple corners as LMR400 is as LMR400 is not as "bendable" as RG8x, etc, etc.

 

So I am trying to find some type of guidance as to minimize my losses while still making my cable run a practical one.

 

As a for instance: If I were to mount an antenna on the 40 foot silo in my yard would it be adviseable to run 1/2, 7/8, etc. Heliax from the silo down to the ground, form the widest 90 degree bend (6 inch radius? 9? 12?) under the ground (If not using burial grade the cable would be fed through some type pvc for protection) to the house where it would be stepped down to LMR400 as it got close to needing severe bends to get it to the room where the radio sits? And IF I wanted to avoid having cables just running through holes in the floor or wall, are there connectors that would minimze my losses while allowing more of an "attractive" install?

 

I have been searching for some type of writeup/article online but have not come across anything that I can apply to this endeavor. 

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Agreed... SMA would be my preferred connectors

 

Marc, did you really meant to say SMA? I think perhaps you meant to say N? Not sure how well SMA would work outdoors since its doesn't seem to be sealed and SMA might not work for anything larger than LMR240...

 

LOL, wrangling with a 20' run Heliax 1/2" is already a pain, I can't imagine dealing with a 7/8" longer than that... lol. 

 

However, for those who like running radio straight to the antenna, I did found out that I get far better S21 readings on the analyzer (the transmitted power, not the return loss) ) when using two grounds and 3 segments of cable between radio and antenna than with a single (ungrounded) piece of 1/2 Heliax straight to the antenna. What that means is that I see more RF being radiated through the antenna.

 

Also, when I had the single run of Heliax ungrounded I could never match 50 ohms impedance to the correct antenna length for the frequency. Now I have 50 ohms sharp and a solid -34 dB loss (~1.04 SWR) on a 5/8th wave vertical that reaches for miles... :)

 

I've always thought that more connectors was bad for reception, so I never bothered grounding things b/c I thought it will kill the radio signal, etc... But I can safely say I was wrong: what a good ground seems to do is lower the noise threshold and improve the radiation pattern.

 

G.

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