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Author Topic: Need a complete mobile vacation package  (Read 1500 times)
9V1VK
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Posts: 15




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« on: January 20, 2008, 06:35:51 PM »

I'm coming back to the US for the month of February.  I want to work HF mobile as W3LMB while I'm there.  Currently I have no equipment in the USA, so I need to build my mobile shack.

A few parameters:

1) I'll be changing between a number of rental cars and friend's cars, so I need an easy system for mounting antennae and powering the rig.

2) I'll have to take a flight while I'm there, so the antenna cannot be so physically big that it's difficult/impossible to bring along on a plane.

I tend to like ICOM rigs.  I was thinking of either the IC-706MKIIG or the IC-7000. I would not be opposed to a different model if something clever was suggested. Please note, I am interested really just in HF CW/SSB (20/40/80), not so much UHF.

What would you do in my situation?

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KG4RUL
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Posts: 2685


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« Reply #1 on: January 21, 2008, 05:37:22 AM »

Get a selection of "Ham Stick" type antennas for your desired operating bands:

http://www.hamstick.com/9106.htm

THEN

Get quick disconnects for the sticks:

http://www.hamstick.com/009hd.htm

THEN

Acquire an adequate Magnetic Mount:

http://www.hamstick.com/375.htm

OR

http://www.mfjenterprises.com/Product.php?productid=MFJ-336T

ALTERNATIVE ANTENNA

Get a small, screwdriver antenna and use it with one of the magnetic mounts above:

http://www.mfjenterprises.com/Product.php?productid=MFJ-1672

OR

http://www.tarheelantennas.com/little_tarheel_ii

FOR POWER

You CAN use the 20Amp PowerPorts in most vehicles with this accessory:

http://www.mfjenterprises.com/Product.php?productid=MFJ-4403
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K0BG
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« Reply #2 on: January 21, 2008, 06:03:55 AM »

Dennis fairly well spelled it out. However, there are a few things you want to keep in mind.

The MFJ device might allow you to operate from the accessory socket, but you still run the risk of overheating the vehicle's wiring. Although the power ports are often fused at 20 amps, the wire size is inadequate for long term use even if the draw averages 10 amps, and this doesn't address the voltage drop therein.

The connectors themselves are suspect at any current level, as the relay on spring pressure. The last thing you want to do is start an electrical fire. Others might suggest using a fuse tap, but this too is an unsafe practice.

Small spirally wound antennas aren't very efficient, and using a mag mount adds insult to injury. And there is an insurance issue with using them as well.

The old fashion notion of tossing a rig into the car, and taking a trip isn't safe or prudent. A fact everyone should consider before the fact.

Alan, KØBG
www.k0bg.com
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ARCH
Member

Posts: 17




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« Reply #3 on: January 21, 2008, 06:13:03 AM »

Probably the most popular small screwdriver antenna is the Sidekick from High Sierra.  The next most popular is the Yaesu ATAS-120.  Both of these manufacturers have dealers in the U.S.  The Yaesu can be made to work with the Icom.  I'd recommend that you stay away from MFJ.  Their stuff has a bad reputation because of the poor quality.  
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W3LK
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Posts: 5644




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« Reply #4 on: January 21, 2008, 07:36:32 AM »

<< FOR POWER

You CAN use the 20Amp PowerPorts in most vehicles with this accessory: >>

The typical 100w radio will overheat the wiring on the average 20A power port. I've seen it on several vehicles over the past couple of years. At best, they will handle a 10A load safely.

73,

Lon - W3LK
Naugatuck, Connecticut
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
9V1VK
Member

Posts: 15




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« Reply #5 on: January 21, 2008, 07:39:58 AM »

Thanks for the advice. What's the best advice for wiring in a safe, but temporary, power solution for a 100w transceiver?

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KG4RUL
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« Reply #6 on: January 21, 2008, 08:28:59 PM »

FOR POWER

You CAN use the 20Amp PowerPorts in most vehicles with this accessory:

http://www.mfjenterprises.com/Product.php?productid=MFJ-4403

I am sticking with my original suggestion.  Remember, a 100W SSB transmitter DOES NOT draw 100W+ except on voice peaks.  On CW the 100W+ is only drawn while the transmitter is actually being keyed.  Using a LARGE value capacitor to provide power during these peaks is a valid concept.  The average power draw for this setup is well withing the capabilities of a 20 Amp Power Port.  Do, however, remember to reduce power when tuning, a good practice anyhow.
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N2IK
Member

Posts: 220




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« Reply #7 on: January 22, 2008, 06:15:41 PM »

K0BG is correct about the cigarette lighter and power port wiring being inadaquate in most cases. In my 1996 Jeep Grand Cherokee, I discovered that my power port wiring, although fused at 20A, is 16 AWG wire. He is also correct that inside the cigarette lighter plug the center pin, which is beefy, is connected to the fuse by a teeny wire spring, not much bigger than a ball point pen spring. This is barely adaquate for a 25 watt FM rig. You might better run a properly fused, full size temporary cable from the battery outside the car and back in through to where you mount the radio. Perhaps to a chassis that can be secured to a seat with a seatbelt. I have a universal power cable with Anderson Powerpoles so I can interchange ring terminals, alligator clips at on end and extend it as long as needed and connect and adapter to the radio's DC connector.

73 de Walt N2IK
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AD5X
Member

Posts: 1426




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« Reply #8 on: January 23, 2008, 05:46:19 AM »

The MFJ-4403 is an interesting gadget.  I used one with the accessory socket for several months when moving an IC-706MKIIG between my two cars (primary car was brand new and I didn't want to start drilling holes yet).  The MFJ-4403 really did work well, letting me run my IC-706MKIIG at 100 watts SSB and CW (I mostly operate CW).  Basically, the 4+ farad output capacitors charge during the low power phases of your modulation, and then supply the high current requirements during your peak power times.  I now have my power cabling connected directly to the battery, which is the best way to go.  But the MFJ-4403 is something to consider for temporary mobile operation.

Phil - AD5X
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