Co phased coax for big rig set up

[Slowmover]

Xerox & Kleenex. “Co-Phase” became the word for description. Search for an assembled harness and see what word used.

 

[9C1Driver]

Thank you @BJ radionut you always come through! @Slowmover I just switched to the 97 freightshakin fld condo, so mirror mounts and I haven't bought any antennas so far thinking about the hussler whips. Currently just running a single Francis. The radio is a Galaxy dx98vhp but I'm thinking about keeping this at home and getting something like a stryker. @jdchet Roger Roger! That's the current set up I'd just like alittle bit more range up and down the road currently only reaching 5 miles out with a single stick

Your running a Galaxy 98-VHP and you can only talk 5 miles? You got some issues to work out for sure. Just adding a second antenna is probably not going to save the day.

 

[Slowmover]

Your running a Galaxy 98-VHP and you can only talk 5 miles? You got some issues to work out for sure. Just adding a second antenna is probably not going to save the day.

One would want to state conditions. Far West Texas at night is one thing. Almost all else has terrain or population-density-related handcuffs waiting. (And I’d install co-phase any day to help with trailer-related problems; highway distances really matter).

I don’t think a high-powered radio is the determinant nearly so much as big trucks with poor antenna mounts is a constant problem in need of solution.

The single biggest improvement I’ve experienced— where the install was professionally-done with ALL new gear — was on a Peterbilt 367 (west coast mirrors as with the FLD) running a DX-99V2 and I made the leap to using a West Mountain Radio CLEARSPEECH DSP Speaker.

Other men in identical trucks running installs as nice as mine or better simply couldn’t hear a number of distant others with whom I could converse as we ran the oilfield together.

That I regularly hear RX from 10-12 miles (sometimes farther) is condition dependent, but not unusual. (Haven’t said it’s all-the-time). Well past five miles IS a regular thing.

“Five miles” may just mean signals strong enough to overcome high noise levels per big truck deficiencies.

I regularly key up and try to speak to Big Radios I can hear, but who cannot hear me.

In big trucks an amp and DSP audio is employed to overcome the other guys radio rig install deficiencies. But the typical big truck “good” antenna system leaves one a bench warmer when the Skip or Sideband game is underway.

One of those devices without the other — amp & DSP — isn’t a help in communications. Get off the 4W floor, sure, but have the signal clean-up to take advantage of 50-150W range for typical road-related problem discussion.

A big amp — and wanting to play Skip or talk Sideband — is going to require an antenna mount and antenna tuning past “best” for what most smart operators typically employ.

I bumped a Sirio antenna thread where contributor fourstringburn had what may have been an antenna set-up (if I recall correctly) able to do a good job on Skip & Sideband.

There’s CB (typical AM) and there’s the rarity: SSB or Skip where to be included as a regular player in the mix requires a new antenna approach and more work. The Eleven Meter Capable Radio System versus the typical big truck amp’d CB.

— “Five miles with a DX-98VHP” isn’t uncommon in big truck mobile-to-mobile. It just doesn’t require big watts so much as an okay antenna system if RX distance is the measure.

The operator lacking DSP may not be able to hear past that (conditions).

The big wattage isn’t adding anything without the DSP ears (on one hand), and (on the other hand) one needs a much better thought-out antenna system to meet the Skip/Sideband test (as it appears to me a worthy goal).


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[freecell]

reposted from april 4, 2007.

what is required to match two 50 ohm loads to a single 50 ohm source is a harness composed of two sections, each consisting of a 1/4 section of line. (1/4 wave transformer) a 1/2 wave line mirrors impedance and a 1/4 wave line inverts impedance. in the case of dual antennas we want to invert the impedances presented by the loads to match them to the source transmitter. with polyethylene line at .66% VF the length of a 1/4 wave line at cb frequencies is approximately 6' and ANY ODD MULTIPLE.

246 / 27.205 X .66% VF = 5.968' or 5' 11.6"

so the lengths required for a 1/4 wave transformer based on VF and the frequency in question would be: 6', 18' 30' etc. for polyethylene @ .66% VF

using foam line @ .78% VF the length is approximately 7' OR ANY ODD MULTIPLE.

246 / 27.205 X .78% VF = 7.053' or 7' 0.6"

so the lengths required for a 1/4 wave transformer based on VF and the frequency in question would be 7'. 21' 35' etc. for foam @ .78% VF

since there is no feedline impedance that is close to that value and since we are matching two 50 ohm loads in parallel, (which equals 25 ohms) then two 70 - 75 ohm lines in parallel provides the necessary impedance transformation.

1/4 Matching Section = sqrt ( Z1 * Z2)
sqrt ( 25 * 50 )
sqrt (1250)
35.35 ohms

there is no such thing as "co-phased" antennas. that term is a "madison avenue," manufacturer generated advertising catch phrase. an identical pair of antennas configured in the above manner constitutes what is correctly referred to as a "phased antenna array." a phasing harness is an impedance transformer.

https://www.worldwidedx.com/threads/dual-coax-with-single-102.26351/page-2#post-86020

 

[freecell]

9C1Driver posted:

"Your running a Galaxy 98-VHP and you can only talk 5 miles? You got some issues to work out for sure. Just adding a second antenna is probably not going to save the day."

@ 200W that's 40W per mile. have you checked the position or setting of your tx power control? have you measured the power output lately? has the power amplifier circuit shut down? is the feedline open somewhere along the line? is it shorted anywhere? has anyone who knows what they're doing looked at the antenna load impedance using an antenna network analyzer?