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eHam Forums => Mobile Ham => Topic started by: GOLDTR8 on March 16, 2014, 01:58:07 PM



Title: Petlowany coil for mobile counterpoise comments please
Post by: GOLDTR8 on March 16, 2014, 01:58:07 PM
Besides bonding your mobile rig, I am looking for ideas to improve the counterpoise of my Jeep.

One of my ideas is to add some Petlowany coils to act as radials.   The question is has anyone tried this idea?   If I try it out any comments suggestions on how to implement such and idea.

My other idea is to just put some hamsticks horizontal at the base of the screwdriver.

Any comments welcome for my idea.

KD8NNU
73
Don


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: W8JI on March 17, 2014, 05:43:12 AM
The "Petlowany" coil is nothing but a rather poor form factor inductor integrated into a capacitance hat the radius of the outer turn.

Performance of a ring hat with a few spokes to the center, and piece of miniductor or small air wound solenoid coil, would be better.

The important question is why do you think the Jeep is such a poor counterpoise that a Hamstick or small hat might improve it? Is the Jeep almost all fiberglass?


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: KB4QAA on March 17, 2014, 09:39:55 AM
Petlawhatchamacallit?  That's what those things are called.  LOL.

A fancy way of making a capacitance hat difficult to make and support.   

If you want a cap hat, just use a hub and spoke with a perimeter wire.  Much simpler and stronger.  For more capacitance add more spokes; but diminishing returns after about 8, IMO.

For operations while not in motion, you can always lay out radial wire on the ground and connect them to the antenna base with alligator clips or better.

As always, the best place for antenna location is probably the center of the hood, or the roof, if it is metal.  Bonding the hood, trunk, doors improves things.  Mounting an antenna on a bumper, tire rack, or low on a side panel is the worst you can do.

If you want to redesign the antenna, put a cap hat where it belongs: at the top.  You will need to retune the antenna, and it may exceed the tuning provisions it was built with, meaning you will need a tuner/matching unit.  You can always clip a wire onto the end and drape to a tree or other support.

If you haven't already, go read Alan's website  www.k0bg.com

bill


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: GOLDTR8 on March 17, 2014, 04:04:43 PM
Let me clarify my request for comments.

I am going to enter some mobile shoot out contests so I am looking to increase the radiation resistance of the entire system.   

My thoughts are you can only bond once and then its bonded.  I already have my capacity hats built and am waiting for warm weather to harden the installation to make it road worthy.

So once these items are done all I can think of is to improve the counterpoise.   I consider the jeep to be basically a vertical antenna and if you add radials to a vertical you improve the efficiency.   

Thus I am thinking about how to improve the vehicle have of the antenna.  I could add some hamsticks to act like radials on the bottom of the screwdriver antenna which I will try because I have them available, but I am wondering about these Petlowany coils to try also.

So its not that I dont think my installation is having problems but I am looking for methods to improve the system so that I can squeeze out some efficiency.   Also if the coil does work I can mount it to the spare tire and harden it for a more permanent installation.

So maybe the real question is what options besides bonding are there to improve radiation efficiency for a mobile rig.

Thanks  KD8NNU

73 Don 



Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: W8JI on March 17, 2014, 05:51:08 PM
Let me clarify my request for comments.

I am going to enter some mobile shoot out contests so I am looking to increase the radiation resistance of the entire system.   

The only possible way to increase radiation resistance is to make the ampere-feet area of the antenna larger. The ground won't do it. Two things do that;

1.) Top loading as high up as possible, especially with a hat way up high.

2.) A taller vertical.



Quote
So once these items are done all I can think of is to improve the counterpoise.   I consider the jeep to be basically a vertical antenna and if you add radials to a vertical you improve the efficiency. 
 

A radial works because it spreads the current out, and the electric and magnetic fields out. If you put 500 feet of wire in a shoebox near the Jeep body, you have a Jeep body with a shoebox on it. The difference is insignificant. You did not expand the area.

Quote
Thus I am thinking about how to improve the vehicle have of the antenna.  I could add some hamsticks to act like radials on the bottom of the screwdriver antenna which I will try because I have them available, but I am wondering about these Petlowany coils to try also.

With a Hamstick sticking out horizontally, you add a inches of effective length to the Jeep. I doubt you will have a measurable difference unless you start getting directivity.

Quote
So its not that I dont think my installation is having problems but I am looking for methods to improve the system so that I can squeeze out some efficiency.   Also if the coil does work I can mount it to the spare tire and harden it for a more permanent installation.


The objective of a ground or counterpoise is to spread the fields out away from the antenna so they are not concentrated in one small area. How will a coil on the spare tire do that?

To spread the fields out, you would have to have things sticking out horizontally away from the Jeep body. Pulling a trailer will work. Or, if you want the Jeep to be a better ground, park it on a F250 Supercab with 8 foot bed.  :)

If coiled up radials would work, broadcast stations and Hams would be using them everywhere.

73 Tom


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: GOLDTR8 on March 18, 2014, 04:29:09 PM
To spread the fields out, you would have to have things sticking out horizontally away from the Jeep body. Pulling a trailer will work. Or, if you want the Jeep to be a better ground, park it on a F250 Supercab with 8 foot bed.  :)


Thanks for the info Tom it makes sense to me.  The real answer is to bond my pull behind camper trailer and have that connected to the Jeep during the shootout.   I get 18 ft of steel rails out the back side.

I appreciate the help and clarification on how this stuff work.

73
Don
KD8NNU


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: K1DA on March 20, 2014, 10:02:58 AM
The "mobile shootout" is a "contest" involving illegal high power on the ZEEEEEEE BEEEEEEEEEEE band.  I'm sure "S9" magazine has much info. 


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: GOLDTR8 on March 20, 2014, 05:35:10 PM
The "mobile shootout" is a "contest" involving illegal high power on the ZEEEEEEE BEEEEEEEEEEE band.  I'm sure "S9" magazine has much info. 

There are mobile shootouts that are for amateur radio operators that have nothing to do with what you refer in your comment.  It takes effort to make a quality mobile installation and more effort to take the time to compete in one of the shootouts that take place in the summer months.  Do some searching on the internet and find one close to you and you might learn the right way to get your power in the air instead of heat in the air.


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: W8JI on March 21, 2014, 06:36:33 AM
The "mobile shootout" is a "contest" involving illegal high power on the ZEEEEEEE BEEEEEEEEEEE band.  I'm sure "S9" magazine has much info. 

There are mobile shootouts that are for amateur radio operators that have nothing to do with what you refer in your comment.  It takes effort to make a quality mobile installation and more effort to take the time to compete in one of the shootouts that take place in the summer months.  Do some searching on the internet and find one close to you and you might learn the right way to get your power in the air instead of heat in the air.

+1 mobile shootouts for ham radio have been around for at least 40-50 years in various form.


Title: RE: Petlowany coil for mobile counterpoise comments please
Post by: W5WSS on June 16, 2014, 09:43:26 PM
Take a look at my mobile antenna for hill topping.

Eham my call sign see the picture.

Bad to the bone! :)

73