need help with antennas

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bluestallion

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Hello everyone. I may be buying a icom 706 for mobile use, and was wondering if i could put a 102 on the car to use for 10m, but use the antenna also for 6m without cutting it if i used a tuner. I will be using the 706 for 10m 6m and 2m mostly till i upgrade to my general. Wondering what options i could do. Thank you
 
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Get the companion Icom AH-4 auto tuner and you can use the antenna with no problems and after you upgrade the same setup will work from 40M to 6M. A word of advice install the tuner near the base of the whip and DO NOT use coax to connect the output of the tuner to the base of the antenna, use a shprt pice of HV antenna cable in place of the coax, you can normally find the HVcable at larger Marine stores such as West Marine.
 

WA0CBW

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A short piece of RG-8 coax stripped of its outer cover and shield braid can be used in place of HV cable.

I use an AH4 automatic tuner and a 102" whip and spring on my SUV with my 706, As mentioned it will operate from 40 to 6 meters. And yes I drilled the big hole and three small ones to install the ball mount. It is mounted on the left side just behind the fuel door. The tuner is mounted in the wheel well space and grounded to the main car frame.

BB

BB
 

LtDoc

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In short, what you suggest can be made to work. Just depends on the tuner, really. If the tuner will work on 6 meters and has the required capacity it should do okay.
- 'Doc
 

roadranger

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What ever you do...

In short, what you suggest can be made to work. Just depends on the tuner, really. If the tuner will work on 6 meters and has the required capacity it should do okay.
- 'Doc
...don't leave out that spring. Even tuned, that's the only way to length it for Ten.
 

W3DMV

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Antenna option

Another option you can use which does not need a tuner.

Get a Hustler 52 inch mast with the RM-10 resonator coil.. This works great on 10 meters
and on 6 meters, the coil presents a high impedance, thus the mast resonates on 6 meters.
I have used this combo for years and it works great.... SWR < 1.5 on both bands without
a tuner...
 

bluestallion

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A short piece of RG-8 coax stripped of its outer cover and shield braid can be used in place of HV cable.
Wouldnt stripping the coax of its shielding cause more interference? do you leave the plastic insulation that covers the center?
 

prcguy

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The AH-4 might have trouble tuning a 9ft whip on 6m since it will be right around a half wavelength and very high impedance on 6. If it tunes it should otherwise work fine on 6m.

A 9ft whip with no loading works ok down to about 20m then it gets pretty grim on 40m and almost useless on 80m.

If the AH-4 is outside the vehicle and near the base of the antenna you don't specifically need high voltage wire. The connecting wire is part of the antenna and the antenna is bare metal so it only needs to be insulated if its running near something where it may make contact.

If the AH-4 is inside the vehicle make the connecting wire very short and provide a fairly large hole for it to exit. In this case the connecting wire is part of the antenna which is inside the vehicle and if its say 3ft long, then about 25% of your antenna is inside the vehicle and not radiating.
prcguy
 

bluestallion

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I think i will be using a ldg z100 autotuner. So put it was close to the antenna hookup as possible? Does anyone have any pics they can share? 73s
 

WA0CBW

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As prcguy stated "as close as possible." The antenna starts at the output terminal on the tuner. Oh, make sure the tuner has a single ended output or random length wire output. The cable between the output of the tuner and the antenna should only be a couple of inches at the most and not shielded. The tuner needs to be well grounded directly to the car frame, not with a ground wire or braid. If you have to use a wire ground use a piece of copper flashing several inches wide instead.

Hope that helps.

Bill - WA0CBW
ARRL Technical Coordinator - Kansas Section
 

WA0CBW

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Most mobile tuners have mounting lugs that are used to bolt to the tuner to the chassis. If you have to use the copper flashing punch holes in each end and connect to the chassis at one end and the tuner at the other with the shortest run possible. The flat copper flashing presents the least impedance to ground. Do not use copper braid or the braid from a used piece of coax. The braid offers a very high impedance and can cause excessive radiation inside the vehicle.

Bill
 

bluestallion

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ok. I got the 706 mounted in the trunk as well as the tuner. The jumper from the radio to the tuner is around 3ft. The jumper i used from tuner to antenna lug is about 4-5inches. I cut the outer rubber, and shield braiding off, but left the plastic insulater that covers the center wire. I havnt got copper flashing yet, but when i pressed the tune button on the radio, nothing happened. Any thoughts? is the tuner not wanting to tune because i have no shielding on the coax? The tuner i am using is a ldg z100
 

jhooten

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Did you interface the Z100 control line to the transmitter or just connect the RF cable between the two?
The Z100 does not have a single wire connection for a whip antenna. You said you removed the jacket and shield. How did you hook the antenna to the tuner?

There is a reason the AH-4 was suggested. It and the radio were designed to work together and it is designed for a single wire output.
 

bluestallion

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I hooked the tuner up to the radio by the cable that hooks into the tuner part of the radio. I took a short jumper and cut the plastic and outer shield off, i left one pl 259 to screw into the tuner, and then connected the wire end to the screw on the ballmount. so i cant use my z100 or z100 plus as my tuner?
 

WA0CBW

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I'm not familiar with the z100 so you will need to read the directions to see if it will mate directly with the 706. Also it may or may not work with a single wire antenna (your whip). Check the instructions to see if it you can connect only the single wire to the antenna. Usually tuners that will tune a single wire (whip) antenna have a bananna jack for the antenna output, not an SO239. The tuner might still work but you might not be able to use the tune button on the 706.

Bill - WA0CBW
 

jhooten

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That connection to the antenna requires a very good ground at the tuner and even then the unshielded part of the coax is now part of the antenna and can radiate. If you have another section of coax with a connector on one end take about 3 inches of the jacket off the antenna end, leave the shield, un-braid the shield and twist it, cut it to about 1 inch long and crimp a ring lug on the twisted shield, unscrew one of the three nuts that hold the insulator to the car body, put the ring lug on the screw and reinstall the nut, then hook the center conductor to the antenna as you have the one now. It should look something like this:

Sorry about the crappy pic, that compartment is small and can't get the camera far enough to focus properly.


From the Manual:
read the part in bold

JUMPSTART, OR “REAL HAMS DON’T READ MANUALS!”
Ok, but at least read this one section before operating the Z-100Plus: Turn off power to your radio.
Connect the antenna jack on the transceiver to the “TX” jack on the Z-100Plus, using a 50 ohm coax cable jumper.
Connect a 50 ohm coax antenna feedline to the “ANT” jack on the Z-100Plus.
Power up the transceiver and select the desired operating frequency.
Select AM, FM, CW, or PKT mode, and then key down to transmit a carrier1.
Push and hold the TUNE button on the front of the Z-100Plus for one second (until the Tuning LED comes on), then release.
Wait for the tuning cycle to end (red LED goes out, 1 - 6 seconds) and then un-key. Restore the transceiver to the desired operating mode.

You’re ready to transmit!
 
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bluestallion

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ok everyone i got me a ah-4 tuner and got it mounted in the vehicle today. I tried tuning it for 6m but it wont even try to tune it. Guess if i want to run on 6m i'll have to stop and switch the 102 over to my whip thats cut for 6m band. radio manual says about having a switch and having a seperate 6m and hf antennas. but think it would be hard to do that when the radio is mounted in the trunk. Any suggestions??
 
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