Barrett hf radio earthing

Congratulations Phil,
You made the first response, it was simple, to the point and answered Peppers question.

I'll 'try' and learn from this............ Can't promise but I will try ;-)

Cheers,
PeteS

Thankyou for taking the time to reply ,your advice is appreciated.

Codan now use round also on the new 3040 autotune.

My thoughts as well. Fatigue resistance is better with flat braid.

Here you go.

Flat braid

Guys - As already said, the RF properties here are important. Flat woven cable is good for flexibility, but also provides lots of surface area which is desirable for RF. Introducing a loop is good practice for flexibility but very bad practice when handling radio frequencies, even the low rf involved here.

Cheers

John

Due to the size of the conductors being used the "skin effect" will have little effect in the earth strap in comparison to a circular.

The major consideration in an earth strap in this situation is mechanical strenght and durability.

If ya going to start arguing skin effect...lets start with the RG58 coax....if the diameter of the earth strap is bigger than the feed line...the skin effect arguement simply fails...remember the central conductor in the coax will be .9mm.....yeh there will be skin effect there and more complicated besides.

As for a loop being bad practice....a 2 inch single or part turn loop will have bugger all effect at HF frequencies..particularly in an earth strap.

In commercial radio it is common, recommended and often required practice to install loops in feeders leading to antennae and other cables.

If the idea of a loop bothers you, a dog leg, a J loop or a carefully laid bend will provide the relief required.


OH...BTW..what are you earthing too...and is that then properly bonded to other parts of the body.

SO..if you are mounting the auto tune on the spare wheel carrier....the auto tune needs to be bonded to the carrier, that in tern needs to be bonded to the chasis and the adjacent body needs to be bonded to that.

quite often the complicated earth path puts paid to any concerns about a loop in the earth wire.

cheers

I hear this skin effect beeing tossed arround so much.....sorry most of the time it is irrelivent.

If we have an RF feeder of RG58......there will be less skin in that than there is in a piece of 10mm2 plain fine stranded circular cable.

Just to confirm..I went out to the shed and checked...no contest.

That is what I would be using as an earth strap if I was running circular.

That is before you start arguing about if it is the skin of the whole cable or the individual conductors.

Even if you could buy one you would not be wise to use a braided earth strap with less than 10mm2 copper content.

the mechaical constraints will override any notion of skin effect.

cheers

OH just to complicate the matter.

Most of the higher performance coax feeders, do not use braided outer conductors...they use plain foils or tubes.....or they use plain foils with a covering braid.

Braid is used mostly for flexibility.

the argument is that because of skin effect, the braid is inferiour because the electrical path in some sutuations is longer and higher resistance than straight laid strands or a foil or tube.

Start with the skin effect argument and most of the time it is all minutia and irrelivent......there are mostly greater considerations.

cheers

Just to bang another nain in the skin effect coffin.

follow the link provided above to the braided earh strap.

It's 25mmm wide.....that would have to be 20 to 25 ish mm2......forget about skin effect there boys.....its pure weight of copper doing the work..and lots of it.

Oh yeh there will be skin effect.....but there will be more skin than the sauna of a weight loss clinic.....plain or braided with that much skin....there is no shortage.

cheers

Hi ya Bantam,

Did I incorrectly answer Pepper2's question?

Thanks,
PeteS

Braided or plain will make no difference in this case due to skin effect, as long as the conductor is of a practical and sufficiently robust size.

Depending on the situation and the frequencies involved...braided conductors may be inferiour as the braid will have a higher resistance than plain straight conductors.

Its not always a case of right or wrong.

There is so much said about skin effect....mostly incomplete information leeds to less than good conclusions.

So often skin effect is rasied as a major consideration where it is insignificant.

Sorry but the whole skin effect thing is a bit of a hobby horse.


cheers

Thanks Bantam,

Hope I didn't get under your 'skin' :-)

Sorry for the head-spin Pepper2...

Cheers mate,
PeteS

Skin effect at HF frequencies is negligible it really only becomes significant at VHF and more so at UHF. I run an auto Barrett and use a piece of 6mm wire and have had no problems. Providing the connections are good and earthed to the body of the vehicle you should not have a problem.

Cheers
Ted

Its not the battery you should be concerned about.

In place of "the greater mass of earth" if the aerial would have been ground standing , what you are connecting your antenna to is "the greater mass of car"....the whole metal mass and surface of the car is a substitute for real ground

SO
you need to ensure there is a solid bond between the autotune base and the bullbar, and between the bullbar and the chasis....and arguably there is a good bond between the chasis and the body....and it would not be excessive to make sure the bonnet is well bonded to the body.

Its about providing a well bonded ground plane, not so much a power supply issue.

cheers

Hi Allan. I made just a simple statement and then just sat back and watched peppers brain being fried.

To quote you: "Skin Effect" is however often the basis for argument by the . . . Yep Most definitely true mate.

See I behaved.

Phil