UHF Antenna's and connections

Submitted: Sunday, Sep 01, 2002 at 00:00
ThreadID: 1870 Views:1573 Replies:4 FollowUps:3
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A mate and I recently both bought a GME 3400 with the same antenna's. The antenna's are 6db and ground independent, mounted on bullbars. We each install them ourselves and my mate gets better recption then mine. The only thing I can put it down to is that when I wired the antenna plug up I folded the screen back over the outer insulation and then screwed the outer piece of the plug over the top, where as my mate didn't. I know that if it's done incorrectly it can ruin the radio so which way is right???
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Reply By: Brian - Monday, Sep 02, 2002 at 00:00

Monday, Sep 02, 2002 at 00:00
Smithy things to consider, are the vehicles the same, same bar work,same antenna location ??? this can make a difference.
Also have you soldiered the antenna conections, soldiered connections are better. I have the 3400 and it is great, better reception than my old uniden sundowner, small and esay to remove when parked in the big smoke.
AnswerID: 6259

Follow Up By: Smithy - Monday, Sep 02, 2002 at 00:00

Monday, Sep 02, 2002 at 00:00
Brian,
Yea we've checked all these things that's why we're foxed. Both of us own SR5 Hilux's both have ARB bullbars, the inner cores are soldered to the plug.
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FollowupID: 2761

Reply By: Smutty - Monday, Sep 02, 2002 at 00:00

Monday, Sep 02, 2002 at 00:00
The shielding connection is crucial for the power to radiate out of your antenna(AE) and not be reflected back into your transmitter stage of your set. The inner wire should be soldered to the center pin and the outer sheaf should be soldered to your outer plug(read Earth). It is important that none of the sheafing comes into contact with the main wire as this will be seen as reflected wave. Solder all joints where possible and take these other things into consideration. Is the coax length the same for you and your mate? Does he recieve the same using both AEs? Can you fit his coax and AE to your set for testing? And lastly sets do some times, have different output power levels, although they are stated as 5 watts. Usually Unidens suffer form this fate and after a $30 service where they just tune the crystal for better output your back to 5 W. GME are generraly more reliable and i would say your problem lies in your coax. Hope this helps, Smutty
AnswerID: 6281

Follow Up By: Smithy - Tuesday, Sep 03, 2002 at 00:00

Tuesday, Sep 03, 2002 at 00:00
Smutty, thanks for the info, both cables are run in the same ( may be 30cm's longer than the other ) and center cores are soldered, and metered before connecting that the inner core is Mohm's to the sheild. My mate managed to pull the plug of his aerail, and when re-connecting we found that the sheild wasn't connected to anything, when I re-connected it for him I connected as I've mentioned. I think I'll take my Hilux down to where we bought them from and get him to have a look. Thanks for your help.
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FollowupID: 2785

Reply By: John - Tuesday, Sep 03, 2002 at 00:00

Tuesday, Sep 03, 2002 at 00:00
G'day Smithy,
UHF is a Funny Animal, It is Very Dificult to rate on install over another unless the Setups and Locations are Identical.
To fairly compare both setups you will need a third for tests as follows.
Get the Third Vehicle to drive away, say about 5 or 6 Kms so your signal strenght meter reads about half way, on a 3400 lets say +5 on the meter.
Make sure this third vehicle does not move an inch during the tests.
Now postion vehicle 1 and mark on the ground the tyre positions...
Now Get the Third vehicle to transmit and take note of the recieved signal strenght. Now transmit in vehicle 1 and get the third vehicle to take note of his recieved signal......this completes tests to vehicle 1.
Next move vehicle 1 and position vehicle 2 in exactly the same spot as vehicle 1 just left.....Do this as acurrately as posible as a few inches can make a big difference (Sorry no double meanings here!).
Conduct the test on vehicle 2 the same as vehicle 1.
The results will give a clear indication if one is better than the other.
This is the only fair way to compare unless of course one is always under all conditions better.
Many things will affect performance including Some of the things mentioned above.
If one only transmitts better than the other, Battery Voltage or Transmitter tuning may be a factor.
If one Recieves better than the other Reciever Tunning may be a factor.
But if one Recieves and Transmitts better than the other, Coax and antenna may be it.

Cheers
John
AnswerID: 6304

Follow Up By: Smithy - Tuesday, Sep 03, 2002 at 00:00

Tuesday, Sep 03, 2002 at 00:00
John, we tried a similar test, but not as acurate as you've described, and that's how we found out. I'll take the whole lot down to the guy we bought them from and speak to him and get him to have a look at it. The Selcal isn't working either. Thanks for your info.
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FollowupID: 2786

Reply By: Andrew - Wednesday, Sep 04, 2002 at 00:00

Wednesday, Sep 04, 2002 at 00:00
Smithy, the answer truely lies in the coax. I have the same setup as you ( but in a troopy ), and I had a problem where I just couldn't get the distance of the others. What I found was the coax that came with the aerial had a manufacturing defect in it, ( it had air bubbles all up and down the centre conductor ) which was only found once I put an SWR meter on it. It showed that I had nearly 100% of my signal being reflected back into the radio. Luckily it was a quality GME because there was no damage to the radio, even after many months of "Why are other people getting further than me" testing. I replaced the coax with a higher quality replacement cable, and have never looked back.
Cheers, Andrew
AnswerID: 6335

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