Jump to content
Sign in to follow this  
Followers 0
BajaTaco

HAM and GPS Newbie

Recommended Posts

Hello folks

 

I am a newbie at both HAM and GPS. I have always been able to get around just fine with my maps and a compass, but the GPS was a toy that I always wanted. I finally decided on the Meridian Platinum, and it is on it's way. As soon as I get it I will post some feedback on my buying experience, as I think I got a pretty good deal on the whole package.

 

On the HAM side of things, I managed to get a Yaesu FT-2600M mobile 2 meter for $109 otd. I also got a 5/8 wave whip for my truck, but I have a question regarding the coax:

 

I am planning on using RG-8 coax. Is it ok to buy this stuff at RadioShack? I am planning to make my own connections. Also, I am trying to figure out what length of cable I should use for my mobile installation. Should the length be based on the following?

 

(assuming 5/8 wave = 615 feet)

(assuming RG-8 cable velocity factor of 66%)

(assuming radio operation at 146 MHz)

 

Length = (615 x .66) /146

 

so, length would be 2.78'. Since that is too short, the length of the cable could be any even multiple of that number? So, could I use, say, a 11.12' (4 x 2.78') antenna cable?

 

Another item to consider - because my truck has a roof rack with a spare tire, Hi-Lift jack, axe, etc etc. I am going to put the antenna on the hood channel to use the hood (or bonnet as they say icon_wink.gif ) as a radiating surface for my transmissions. However, do I need to be concerned about the radiation exposure in the cab? Do I need to measure the RF in there to make sure it is safe?

 

Any help is appreciated. icon_smile.gif

 

Thanks

 

BAJATACO.COM

Vibram or BFG - getting there on rubber and seeing it all!

Share this post


Link to post

Why RG8? With such a short run, RG58 would be fine and much easier to work with. Cable length doesn't matter as long as your antenna is well matched. I assume you can't put the antenna on the roof of the cab (ideal spot) because of the rack. You don't need to be concerned about RF exposure.

 

Poindexter

N3EF

Share this post


Link to post

Thank you for the reply icon_cool.gif

 

I am avoiding the roof for a few reasons. #1 - concern that the close proximity of the roof rack will interfere or disrupt. #2 - I don't want to drill a hole in the roof (even though I am not worried about leaks) and I don't want to use a mag-mount. #3 - I do a lot of trail driving and I would rather have the antenna mounted down lower to allow for more contact and flex where trees and brush are concerned.

 

BAJATACO.COM

Vibram or BFG - getting there on rubber and seeing it all!

Share this post


Link to post

One thing that you want to do is get the antenna up as high as you can. Look in the AES or HRO catalogs for a mount that would bolt to the rack and then would pivot down out of the way. There are also antennas that pivot. RG-58 will work fine, the shorter the better. Though you will need to leave some length for when you change equipment.

Ed

Share this post


Link to post

#1. Coax length does not matter if the antenna is properly matched. If cutting the coax makes a big difference in your SWR, you need to do more work on the antenna.

 

#2. For short runs, almost ANY coax is good enough. RG-8 is great, but HARD to work with for a mobile as it is stiff. DO NOT USE FOAM CORE COAX in your car. The center conductor will migrate through the foam at bends and wherever the coax is pinched. This will as a minimum cause impeedance lumps and higher SWR. Or at worse, it will short over time.

 

#3. A 1/4 wave on the roof is better than a 5/8 wave on the trunk. Believe it or not, for most people, a 1/4 wave is the best choice for mobile. This is true if you live in hills, mountains, or cities where the repeaters are on the skyscrapers. Now, if you live in Kansas, and you only work simplex with ground stations, the 5/8 is better. Yes, the 5/8 has more gain, but it comes from limiting the pattern. The power is concentrated at the horizon. This is not good if the repeater is a number of degrees above the pattern.

 

#4. How you install your radio is very important. Almost anything will work. But sometimes you make more trouble. Save yourself the trouble right up front! Use good power cable rated for the current. Assuming your radio draws 5 amps, 14ga wire is fine. Use stranded so it will bend easily, and route it so it is protected from damage. Connect both + and - directly to the battery. Put a fuse in both + and - leads. And last... use ring terminals and solder your connections at the battery. This helps slow down corosion.

 

#5. Don't be afraid to ask questions! I was a new ham once. No, Really... I was. I just look old! Feel free to E-mail direct if you need help. It is important to me that YOU get a good start. I hope to talk to you on H.F., or on the satellites some day.

 

Merry Christmas to all.

 

Mike. Desert_Warrior (KD9KC).

El Paso, Texas.

 

Citizens of this land may own guns. Not to threaten their neighbors, but to ensure themselves of liberty and freedom.

 

They are not assault weapons anymore... they are HOMELAND DEFENSE WEAPONS!

Share this post


Link to post

Thanks again for the replies icon_smile.gif

 

What does the L.O.S.T. stand for?

 

Desert Warrior - that sounds like, oh... 20 years of experience speaking! hehe icon_wink.gif

 

I really appreciate your helpful suggestions and your generous offer of assistance should I need it (and I'm sure I will).

 

Regarding the power connections: I already have a short, fused 8 ga. power wire supplying a fuse block mounted on the firewall, that I have dedicated to accessories. Would I be ok to connect my power lead to this fuse block, and run the ground to the chassis? Or is the direct connection to the battery still preferential? It would be much easier for me to make the connection to the fuse block and the chassis. But maybe I would get interference from my high-powered lights which are connected to the same block?

 

Thanks again!

 

Mike, that would be great to talk once I am on the air!

 

BAJATACO.COM

Vibram or BFG - getting there on rubber and seeing it all!

Share this post


Link to post

quote:
Originally posted by Desert_Warrior:

Put a fuse in both + and - leads


I was always taught to only fuse the hot side, so that you never break your ground connection...or is that only important with AC?

 

ApK

Share this post


Link to post

quote:
Originally posted by Desert_Warrior:

Put a fuse in both + and - leads


I was always taught to only fuse the hot side, so that you never break your ground connection...or is that only important with AC?

 

ApK

 

You should only fuse the possitive. Fusing the negative could mean that there's still a possibility of fault current flowing through the case of the rig to ground even if the negative is broken by the fuse in the negative. But that's just my opinion as an ex-electrical engineer. icon_wink.gif

 

Also, the correct length of coaxial cable to use is the length that will run from the antenna, and will reach the Output connector on the rig. icon_biggrin.gif

 

If by changing the length you change the match, you probably need a better VSWR meter. They are not infallable, in fact, they are pretty horrible devices when used on their own!

 

On my car I have a dual band 2M/70cm antenna mag mounted in the middle of the roof, fed with thin coax. that I have to coil up and shove under a seat. It works quite well with just 5 Watts on 2M and 70cm.

 

Oh, and the 5/8th wave antenna on VHF and UHF was given a real slagging off by D K Reynolds (K7DBA) in the ARRL Antenna Compendium Volume 1 (ISBN 0-87259-019-4) if anyone wants to have a read.

 

--... ...--

Morseman

Share this post


Link to post

Thanks for the additional comments folks icon_wink.gif

 

Slagging off? hehehe... so are you saying I would be better off with a 1/4 wave? I do live in the Southwest (not in Kansas) so maybe I should... ?

 

BAJATACO.COM

Vibram or BFG - getting there on rubber and seeing it all!

Share this post


Link to post

What Desert Warrior says is right on-- all 4 points about the installation. I have had a 2M mobile rig in my car for about 5 years and it is all as he described.

The point about a 1/4 wave length antenna is especially good. This is what I use and I believe it is better for most locations. Mine is very hilly.

 

73, de K6_ _ (not sure if I want to give my call here yet...)

Share this post


Link to post

Thanks EScout. I still have the 5/8 in the shrink wrap package, so maybe I'll swap it for the 1/4. I will probably do most of my communications in hilly, mountainous, or canyon type terrains.

 

BAJATACO.COM

Vibram or BFG - getting there on rubber and seeing it all!

Share this post


Link to post

quote:
Originally posted by Morseman:

quote:
Originally posted by Desert_Warrior:

Put a fuse in both + and - leads


quote:
Originally posted by ApK:

I was always taught to only fuse the hot side, so that you never break your ground connection...or is that only important with AC?

 

ApK


 

You should only fuse the possitive. Fusing the negative could mean that there's still a possibility of fault current flowing through the case of the rig to ground even if the negative is broken by the fuse in the negative. But that's just my opinion as an ex-electrical engineer. icon_wink.gif


 

I agree for AC systems. I will stick by my first statement for automotive DC systems. Draw the circuit yourself.

 

Connect the battery - to the vehicle chassis ground. Connect the starter to the battery + through a switch, and starter return to chassis ground. Now connect your radio to the + and - of the battery. Mount the radio chassis to the vehicle chassis ground. Everything works fine.

 

NOW.... open the lead from the battery to chassis ground, and flip the starter switch. Oops, what was that smoke? Oh-****! It is not unusual for that connection to come loose or corrode. How many amps does your starter draw? That is how many amps will use your radio chassis as a return path to the battery. There is little danger in 12 vdc faults. The fuse will save your radio. If you feel safer, fuse it 5 amps higher than the + side, but DO fuse the - side too.

 

Just my opinion, you must do what you believe in.

 

Mike. Desert_Warrior (aka KD9KC).

El Paso, Texas.

 

Citizens of this land may own guns. Not to threaten their neighbors, but to ensure themselves of liberty and freedom.

 

They are not assault weapons anymore... they are HOMELAND DEFENSE WEAPONS!

Share this post


Link to post

When you fuse the + and - side do it at the BATTERY. In case there is a fault between the radio and the batt the fuse will give you the protection you need...

 

"My gps say's it RIGHT HERE".

http://www.w6hy.org

KF6VFH

TOYOTA To Often Yuppies Overprice This Auto

Share this post


Link to post

I believe in fusing both leads at the battery. Here is another story. A friend took his motor home in for a battery replacement and the guy hooked up the leads wrong (black lead to the positive terminal) when putting it back together. Fortunately, the rig was not grounded, but the antenna mount was, resulting only in melted coax outside on roof. Since the rig was not turned on, it was OK, but a fuse would have been better.

Share this post


Link to post

Hi there, new to this GPS deal, but been a ham for a whole decade, so some advice to the new guy

Like the man said, RG-58 is your best option, RG-8 if your going to be running mondo wattage, just to protect you and keep the RF down, so I hope you went with the 58...

also, after attaching the coax, tune the antenna... makes sence, tune the antenna to the coax, not the coax to the antenna... piece of cake... your next toy should be an MFJ-259 SWR Analyser, I almost slept with mine at first, I was in love HI HI

73's and good luck

Share this post


Link to post

Update 3-20-02

 

Thanks for the replies. Well, I ended up passing the test and getting my license. icon_cool.gif

 

I got my Yaesu radio installed in my Tacoma, but I have yet to connect the power (wires are run) and will be getting my coax tomorrow. Yes, I decided on the RG-58 and I am getting my coax with the FireRing connector (from Firestik) because I really like that low profile connector on the stainless hood channel mount. The radio install came out NICE!! Solid as a rock. My center dash panel will never be stock again icon_wink.gif

 

KD7UUS

 

BAJATACO.COM

Vibram or BFG - getting there on rubber and seeing it all!

Share this post


Link to post

quote:
Originally posted by KD6SWR:

also, after attaching the coax, tune the antenna... makes sence, tune the antenna to the coax, not the coax to the antenna... piece of cake... your next toy should be an MFJ-259 SWR Analyser, I almost slept with mine at first, I was in love HI HI

73's and good luck


 

I had a MFJ-259 and, like a fool, I sold it.

 

However, it allow me to buy the MFJ-269. icon_biggrin.gif

 

The 269 has a few more bells and whistles, and it goes up to 70cm, which is great for me as a VHF/UHF enthusiast. HI.

 

--... ...--

Morseman

Share this post


Link to post

quote:
Originally posted by BajaTaco:

_Update 3-20-02_

 

Thanks for the replies. Well, I ended up passing the test and getting my license. icon_cool.gif


 

Well done, but what's a Tacoma?

 

The usual rule of thumb is to buy the best feeder you can afford at VHF/UHF. I even have a length of Andrews LDF5-50 (also known as Heliax) feeding a triband 6M/2M/70cm vertical antenna. It helps on receive as well as transmit of course.

 

--. ----- -.. .--- .-

 

--... ...--

Morseman

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  
Followers 0

×
×
  • Create New...