MOBILE INSTALL: 579 Peterbilt

[rabbiporkchop]

Dipole would be great on a composite body.

 

[Slowmover]

Dipole would be great on a composite body.

Thanks. There has to be something better than the current arrangement.

 

[Slowmover]

View attachment 37004

See above. Back of factory pair of cab antenna mounts uses Mini-UHF connections to the factory cophase.

I’m guessing this is going to be my best workaround for the time being:

— Reinstall the broadbanded ProComm QW-45 Quadwraps antennas as before, but with better coax. (26-30 MHz).

Followed one of our guys 300-miles across two states a few days back as he was using a pair of Francis in stock mounts with a 29.

Nice sound. Strong signal always.

I’ll find a pair of these adaptors, and run the 18’ Wilson cophase I’ve got with me.

Have doctored the harness with FT-240-31 toroids at each end of the 18’ arms. Brings each arm down to a few feet (9-passes with 2.5” loops) per this chart



SO-239 to Mini-UHF
RF-8122



Currently have the recently purchased GALAXY DX86V into a Morgan 411B, a Palomar cube coax filter; then to the KL203, then past an MFJ-945e.

Used some 3/4” woven, braided copper strap to bond device cases to a ground point as experiment.

Sitting near Baytown, TX listening to the regulars on AM-19.

Mean Green
Clamdigger
T-Bone
Mr Peckerwood
Worldwide
Jigsaw
86

and just a whole host of little quack-quack mudducks.

.

 

[Slowmover]

Left Houston too late to locally-acquire those adaptors. Ran bobtail to San Antonio to get a trailer. From there to Del Rio and on up to OKC had no luck with numerous searches of RADIO or AMATEUR Radio Supply to find a pair.

Delivered load from the border to north of OKC. As I would pass thru that city (3) times in the next 48-hours, I got on-air and asked for help.
Plenty of answers, but no luck until DR BOB mentioned someone out in Edmond. I looked at the online for that Radio Club and found COAXMAN who was not only kind enough to make a pair of jumpers on short notice, but rode to the truckstop to meet me next day after I’d reloaded in MO and was then on my way to SoCal.

 

[Slowmover]

Turned out that what I thought was easy coax routing wasn’t.

My route took me from IH40 Flagstaff to IH8 Yuma, so I checked the catalog at the Phoenix HAM RADIO OUTLET and Bob found me a pair in a drawer even though out-of-stock.

I had a feeling about it. A nudge.

E-Z IH17 on/off, and I was in business.

The Wilson Co-Phase harness I’d had for years modified to fit.

(The Peterbilt assembly of these mounts — those bolts — includes a ground strap from backing plate to cab metal).

.

 

[Slowmover]

And, had acquired the FT 240-31 toroids last year or the year before.

1). Using the chart above (see thread MOBILE COAX CHOKE) to determine number of turns thru the center; and,

2). Reading at www.K0BG.com to figure how tightly I could wrap Mini-8 coax, 3.0” looked like the safe bet.

Took a surprising amount of time (several efforts) to come up with what’s shown.

18’ legs brought down to 4’ or less. The space between the antenna mounts in the cab, with a little extra.

 

[M0GVZ]

The Wilson Co-Phase harness I’d had for years modified to fit.

What do you mean by modified to fit? They need to be a specific length for each leg in order for it to work, you can't just go cutting it to fit.

 

[Slowmover]

Using the SOTT Tiger Everhardt antenna pair I had aboard to give to another driver, the MFJ-945e Mobile Tuner got me to 90W Forward with 3.5 Reflected with about a 1.4 SWR.

Shortened the power cabling NEG and moved it to truck frame.

As the tuner asks for ground to TX be established, I used some 3/4” woven braided strap with lugs at one end and used some copper split bolts to clamp open ends together to a ground screw in the overhead console. Radio & Amp & Tuner.

Now at home, it’s time to do a better job of that. The OEM coax harness will donate its shield.

 

[M0GVZ]

the MFJ-945e Mobile Tuner

As the tuner asks for ground to TX be established,

No it doesn't. I used one for years before getting an auto tuner. It's a good idea to connect it to a ground bus bar if you're using a random end fed wire with no counterpoise but if you've a decent RF ground and are using a RF choke then neither the tuner, the rig or the amp need any additional ground to the body of the vehicle. If putting that ground in makes a difference you need to go back to the antenna and look at what you're using there.

 

[Slowmover]

As of 08/02/2020:

1). The Galaxy DX86V acquired thru a WWDX contributor (currently with an RK-56 microphone)

2). Morgan Systems Bandpass Filter 411CB

3). Palomar Engineers Coax Filter Cube

4). RM ITALY KL203P amp that’s been hard at work the past couple of years; to,

The MFJ tuner as shown.

Of course, the West Mountain Radio ClearSpeaker as in above posts (see also that thread).


Changes from stock otherwise are

— the ANCOR 10/2 Duplex cabling to BATT (fused) and Neg to frame.

— Mini-8 Coax with chokes on Male Mini-UHF to Female (SO-239) adaptors.

— a preliminary gear case ground system

— Truck door hinges (2-ea; 2-doors) jumped with 3/4” strap.

.

 

[Slowmover]

(Same date)

Yet to come, but ready to go:

— aircraft cable to attach at rearmost frame rails as Static Control

— will cut and prep more 3/4 woven to jump Front & Rear Truck Cab/Sleeper RF Bonds.

— (same) after removing interior door panels to access mirror arm attachments.

Now, if someone will KINDLY address this 99F heat (whoa!)

.

 

[Slowmover]

What do you mean by modified to fit? They need to be a specific length for each leg in order for it to work, you can't just go cutting it to fit.

18’ legs not cut.

But now wrapped thru toroids as shown.

.

 

[Slowmover]

No it doesn't. I used one for years before getting an auto tuner. It's a good idea to connect it to a ground bus bar if you're using a random end fed wire with no counterpoise but if you've a decent RF ground and are using a RF choke then neither the tuner, the rig or the amp need any additional ground to the body of the vehicle. If putting that ground in makes a difference you need to go back to the antenna and look at what you're using there.

Yes, it does make a difference with the earlier spot mirror door mount.

Less so with what’s installed as described.

With Radio power to a minimum (no tuner) flat SWR. With 10W, just above that. With amp on, as described above (but, no tuner+power and has climbed above 2.0).

Maybe with more bonding as described it’s value (tuner) is made unnecessary.

RF Ground “system” experiment shows lower noise floor.

Experiments all of this. Hammer away. Advice welcome.

As an aside, maybe the trucks you all run over there are better factory-prepped for Radio than ours? Because these are a damned joke.

I really hope this morning that crawling around in the gravel under that tractor will make obvious some decent RF Bond points. Front brackets; and across rear airbags.

.

 

[M0GVZ]

Yeah I think you got proof that mirror mounts provide basically no RF grounding no matter what the multimeter shows. More bonding will help but ultimately it's what is right at the antenna feedpoint where the coax braid ends which makes the biggest difference. If you've got an antenna on the outer edge of a vehicle body whether it be a mirror mount, a fender mount, a bumper mount you've got at least 180 degrees of antenna with little to no RF ground. If there's enough horizontal metal on the other side of that at or very close to the antenna feedpoint (as in an inch or so) then other than directivity you'll have little issue. If though your ground plane is a far enough distance away to work as a far removed groundplane, such as if you mount it on a mirror arm, then you're going to have problems.

 

[Handy Andy]

@Slowmover - Sounds like you're making a FARADAY cage.

Might be your safest option to keep RF where it belongs.

Don't need it wandering around the Trucks' harnesses looking for a place to return.

​

It's not the first time I've seen this. I've seen HVAC hangers and Load braces used for not just holding the radio equipment but in BEHIND the console "glovebox" compartment as a means to offer a bar for counterpoise...

Use whatever works for you - Best of luck.

Caught the story of your friend.

Glad to know you spread the "love of Radio" around like that.

Hope it works out...