Survivalism & Self Sufficiency Topics > Amateur Radio How-To's

best practices for making coax patch cables?

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Carl:
I often use a 6 foot ,Mini 8 jumper as a way to allow movement and flexibility on my radio desk...a two foot cable prevents you from having a range of motion between radio/tuner/SWR meters/antenna switches and I find it pays to have a range of motion and organization of radio components. Losses are minimal as the length is nowhere near the 100 foot measure on the LOSS CHART.

I have found the RG8X to be far better than generic RG8 as SIZE of coax has little to do with quality or loss. I also have used 75 ohm coax many times as it is often of great quality and makes great matching harness for multi-antenna arrays and also helps with antenna mis-matches...a 75 ohm coax is well within the capability of a 50 ohm radio...

Why is it that Hams leap at the chance to use 75 ohm hardline??? While ignoring quality feedline...mating the coax to the PL259 (connectors) is the hardest part of using 75 ohm coax   and I have found adapters are not too tough to find as this has been done many times before.

I use 400 ohm ladder line as it is lower loss than the best coax and my radio likes it just fine with the addition of a balun...even when the balun does not provide the coveted 50 ohm match.

The antenna matcher (auto tuner) keeps the radio happy in most cases of mismatch and PROTECTS YOUR VALUABLE GEAR from most problems that feedline and antenna can generate.While the 'correct' item is often better,a thinking Ham can do many things that ,at first,appear to be 'against the rule' of antenna and feedline use. I ran a 2 meter antenna with a balun and two wire extension cord and have also used TV antennas for VHF (remember them?) Often you don't have the luxury of time and lives can depend on YOU.

Sorry to get off on a emergency rant...but my auto tuner allows most any antenna to work for me and my radio and we are preparing for what could be emergency comms....aren't we.

Alan Georges:

--- Quote from: armymars on March 05, 2015, 04:19:32 PM ---  In Europe hams like to use 75 ohm co-ax to match the antennas then a tuner to the radio. More later diners on the table.

--- End quote ---
Well, it would give a better match at an ideal dipole's 73 ohm feed point.  Then you match the transceiver's 50 ohm output to the feed line at the shack with a tuner, and everything's pretty smooth at every step along the way.  I can see it. 

Probably not that big a deal either way for HF.  Maybe not worth the hassle, but if the coax is free, why not.  High up the bands, do you really want to use a tuner at VHF/UHF frequencies?

Carl:

--- Quote from: Alan Georges on March 29, 2016, 06:58:49 AM ---Well, it would give a better match at an ideal dipole's 73 ohm feed point.  Then you match the transceiver's 50 ohm output to the feed line at the shack with a tuner, and everything's pretty smooth at every step along the way.  I can see it. 

Probably not that big a deal either way for HF.  Maybe not worth the hassle, but if the coax is free, why not.  High up the bands, do you really want to use a tuner at VHF/UHF frequencies?

--- End quote ---

You can use a tuner on VHF/UHF and often the antenna match is performed by a coil or shunt to obtain a reasonable match as in "J" poles and any NON 1/4 wave antenna...this is often done with antenna design rather than innovation of the Ham operator. Many antennas are designed with a shunt (SHORT at DC) that 'matches the antenna' but as most VHF/UHF are still comercial made ,the Ham seldom gives it a thought.

A lossy antenna that works is so much better than a golden yagi that refuses to pass RF. I use what I have and continually read,learn.plan.work to improve what I have. This is why my single antenna station has been heard in many parts of Europe and set the ARRL world record DISTANCE OVER LAND for VHF and it is just a simple station with a possibly simpler operator.

I am KB5WMY and it isn't bragging ,if it's true..

Hams do magic with RF.....

davidradio:

--- Quote from: Carl on March 29, 2016, 07:16:33 AM ---You can use a tuner on VHF/UHF and often the antenna match is performed by a coil or shunt to obtain a reasonable match as in "J" poles and any NON 1/4 wave antenna...this is often done with antenna design rather than innovation of the Ham operator. Many antennas are designed with a shunt (SHORT at DC) that 'matches the antenna' but as most VHF/UHF are still comercial made ,the Ham seldom gives it a thought.

A lossy antenna that works is so much better than a golden yagi that refuses to pass RF. I use what I have and continually read,learn.plan.work to improve what I have. This is why my single antenna station has been heard in many parts of Europe and set the ARRL world record DISTANCE OVER LAND for VHF and it is just a simple station with a possibly simpler operator.

I am KB5WMY and it isn't bragging ,if it's true..

Hams do magic with RF.....

--- End quote ---

This answer made 4 years ago but now it still helpful for me. Thank Carl link!

Carl:

--- Quote from: davidradio on March 24, 2018, 01:46:06 AM ---This answer made 4 years ago but now it still helpful for me. Thank Carl link!

--- End quote ---

WOW, I am even impressed with my old answer..their are many ways to do the right thing though worry about SWR on antenna systems (within acceptable range to make radio 'happy') is just folly as trimming an antenna that was cut to proper length just introduces LOSS into the system to produce the Hams desired LOW SWR that has only criteria for the radio and NOT ANTENNA CAPABILITY...any wire or conductor NEAR or over 1/4 wave will be effective...SWR ONLY EFFECTS POWER OUT WHEN SWR CAUSES THE RADIO TO LESSEN POWER OUT and the established cut lengths are the correct length (for single band antennas)...I  use RANDOM length
Though they are narrow specific lengths to provide I can run many/all HF bands with ONE ANTENNA and I use an ANTENNA MATCHER,often called tuner...though it only adjusts the antenna system (environment,feed line,antenna impedance to a level the radio expects and is safe on the radio ...remember ANY WIRE within reasonable length NEAR OR OVER 1/4 wave will put RF out effectively and SWR adjustment is NOT an improvement on signal out ,only radio out and safety.

  If you only run one band,a properly cut 1/4 wave per side does perform slightly better as it lends one more resonant component to the system and ,I think,aides in sensitivity and selectivity a small bit though at a cost to coax feed lines due to the number of antennas the typical Ham desires for the flexibility to manage propagation and conditions better (bands don't work consistently due to environment change and solar storms etc)

I have many collected articles and some of my own designs and observations for antennas and more  available on my Google drive,safe and secure ...you ,and any one with the link can read on line or download FREE ,as I found them . Take all you might want as I nor my site are forever ,though the data will be current long after I am gone. What small gift to any who may wish it.

https://drive.google.com/open?id=0B5ZIZLZV4AwIMFlYMTI5OTNlUTA

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