Big Truck: Dipole Antenna Install

[slowmover]

9 turns through a FT-240-31 core makes a very good broad band choke for 80-10m, a good 20dB isolation at 40 and 10m with about 30dB on 20m. On CB/10m only you can do better with an FT-240-61 core but I forget how many turns to use at the moment. For a stand alone choke I use RG-142B/U Silver/Teflon coax which will handle more power than you can make. I also pun a male connector on one end and a female on the other.

The broadband common mode choke, 1:1 balun and 1:1 unun - PA9X

Choosing a common mode choke. A look at different variants, air core, ferrite beads and ferrite toroid core for ham radio HF band.

www.pa9x.com

.98/inch (25-mm) on RG-58 looks do-able.
That author recommends different coax to achieve tight winding.

Jumper Chokes - Palomar Engineers®

simplest most cost effective feed line choke

palomar-engineers.com

SKU JC-1-1500CB

Isn’t an expensive pre-made, for those who want less pain (ha!).




Will need barrel adapter to join both coax. (Double female).




(31-Mix chart reference for others).


Should mention it looks as though an 18’ coax jumper may be an ideal length (very easy to obtain already terminated; every truckstop) if one uses approx 6’ for winding toroid and the remaining approx 12’ to feed radio while allowing length for door to open & close.

This assumes radio is dashtop, center, in big truck and antenna is door or mirror-mount.

Test length beforehand (full passenger door movement to stop).


I’ll look forward to trying a 61 + high zoot coax.

Thanks.

.

 

[Trucker700]

Be careful what coax you are using. If it's foam core, the tight turns can cause the center conductor of the coax to migrate through the foam insulation over time and short out to the shield. Major disaster if you are transmitting at the time.
A good reason to follow prcguy's suggestion.
James

 

[prcguy]

The broadband common mode choke, 1:1 balun and 1:1 unun - PA9X

Choosing a common mode choke. A look at different variants, air core, ferrite beads and ferrite toroid core for ham radio HF band.

www.pa9x.com

.98/inch (25-mm) on RG-58 looks do-able.
That author recommends different coax to achieve tight winding.

Jumper Chokes - Palomar Engineers®

simplest most cost effective feed line choke

palomar-engineers.com

SKU JC-1-1500CB

Isn’t an expensive pre-made, for those who want less pain (ha!).

View attachment 149233


Will need barrel adapter to join both coax. (Double female).


View attachment 149229

(31-Mix chart reference for others).


Should mention it looks as though an 18’ coax jumper may be an ideal length (very easy to obtain already terminated; every truckstop) if one uses approx 6’ for winding toroid and the remaining approx 12’ to feed radio while allowing length for door to open & close.

This assumes radio is dashtop, center, in big truck and antenna is door or mirror-mount.

Test length beforehand (full passenger door movement to stop).


I’ll look forward to trying a 61 + high zoot coax.

Thanks.

.

8 turns on an FT-240-61 core is ideal for CB or anything 26.5 through 30MHz.

 

[slowmover]

Be careful what coax you are using. If it's foam core, the tight turns can cause the center conductor of the coax to migrate through the foam insulation over time and short out to the shield. Major disaster if you are transmitting at the time.
A good reason to follow prcguy's suggestion.
James

RG-142 or RG-400, or RG-58, all are .98/inch bend radius. Winding the toroid quite easy.

The Mini-8 I used before is 2.5” (to which I adhered). PITA.

.

 

[Trucker700]

RG-142 or RG-400, or RG-58, all are .98/inch bend radius. Winding the toroid quite easy.

The Mini-8 I used before is 2.5” (to which I adhered). PITA.

.

As long as the inner insulator between the center conductor and the shield is a solid and not foam, then you shouldn't encounter any problems.
James

 

[slowmover]

Well, thought I had RG-58 with me, but didn’t. Used RG8 with/without P-E choke to try various combinations of antenna length, but was unsuccessful in achieving decent SWR (2.0:1 or lower).

5.5’, 4.5’ & 3.5’ Francis whips. Equal length legs or not. Every combo tried.

86V + external SWR meter, or to AT5555N2 + 945e

Numerically-lowest channels came in closer, but worsened to 3.0:1 in going upwards. (Overall nailed with MFJ-945e tuner, but that item not desired for use past experiment).

Too much disassembly required for perch mount on mirror at this time.

Back on shelf for now. Analyzer needed anyway, so that’s next.

— The permanent cophase SIRIO 5000 pair isn’t done up all the way (bonds), so that antenna system goes back to being priority claim on time.

.