Imax top section made of cutdown 1/4 wave ss whip

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108EH002
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Imax top section made of cutdown 1/4 wave ss whip

Post by 108EH002 » 18 Aug 2019, 12:08

Has anyone swapped the top section of an Imax for a cut down s.steel 1/4 wave whip ?

If you have tried this did it make much difference to the tx/rx signals/swr,or was it just about the same ?

I only ask as it would help collectors install of same antenna combination on another topic,cheers.
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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by ch25 » 18 Aug 2019, 12:27

Sure you can replace it. Thicker than original, theoretically more bandwidth.
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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by The Collector » 18 Aug 2019, 15:21

108 - I've left my tank-whip at the full 108 inches and it's good with a swr of 1.6 (without the matcher switched on) all through the UKFM block. I'm going to spin the rings up just a touch to see if I can get it a bit lower without using the matcher.

I can't compare it to usage with the original top section as it was such a palaver to get it up in the trees where the Antron was, that I couldn't be arsed to hoik it up and down testing both tips and risk falling off the top of my wife's shed/outdoor gym into the brambles! ;)

I did read a couple of US posts on the interweb where they'd talked about possibly swapping to a tank-whip, but no one actually did it and reported back.

Thanks for asking about though :)

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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by 108EH002 » 21 Aug 2019, 09:56

Collector = was just incase someone might see this topic that maybe hasn't read through the "inside or out" posts elsewhere.

And it was really just to see if the mix of 2 metals now being used,has a noticeable difference on the overall performance.

I would only move the tunings rings for a lower swr after I had removed the groundplane wires that are connected at present.

When you remove the groundplane wires the swr should be far lower across 27MHz.

That's what happened to my Imax's swr anyway when I took the groundplane wires off (added just to see what if) = the swr was no higher than 1.2 > 1 = across the legal 80 channels.

All the other locals that use an Imax have the rings in the middle,but mine are closer to a 1/3 up from the bottom.

The swr on EU (CH 1) or 26.965 was 1.2 > 1,and 1.1 > 1 on UKFM (CH40) - 27.991.25 without being earthed or using a groundplane.
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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by 108EH002 » 22 Aug 2019, 08:05

The Collector wrote:
18 Aug 2019, 15:21
108 - I've left my tank-whip at the full 108 inches and it's good with a swr of 1.6 (without the matcher switched on) all through the UKFM block.
Replacement top section has to be cut to the same size as the original top section you took off the Imax for a good swr on CB.

The swr isn't too high at 1.6 but it isn't great = using a matcher or tuner on an antenna that you can easily obtain a LOW swr without any HELP is a waste of time = your amp could be in the matchers place instead with a good swr.

I would rather it was 10 - 15 minutes of hassle getting jagged to bits on they bushes,and cutting the ss whip shorter and getting jagged even more if need be to get it back in the air with a lower swr.

This will make your favourite radio's work better and help to prolong the life of your amp.

"That'll have to do" is nowhere near as good as "thats far better".= upto you.

The topic should now be =

Q = Imax top section with full 1/4 wave ss whip giving higher swr ?
A = top section far too long = cut to same length as original.You will now have a shorter whip/resulting in less flexing/more stealth and have a far lower swr.

Big work coat with hood/gloves and all the best Collector from TM1 with the jaggie bushes ;)
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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by 26VT01 » 01 Nov 2019, 23:48

Is the imax top section a standard (3/8 )fitment?

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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by The Collector » 02 Nov 2019, 08:46

Yes it is :)

Use an anti-vibration washer if you have one.

I'd also suggest using some thread-lock solution on the joint too though, but don't cover the whole thread as it may lose connectivity. When dry, seal over the joints with self-amalgamating tape. This'll stop moisture ingression (start 6 inches up the top whip and go downwards in a tight, overlapping spiral)plus it may help stop the top joint vibrating loose as a bonus.

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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by 108EH002 » 03 Nov 2019, 11:36

The Collector wrote:
02 Nov 2019, 08:46
Yes it is :)

When dry, seal over the joints with self-amalgamating tape. This'll stop moisture ingression (start 6 inches up the top whip and go downwards in a tight, overlapping spiral)plus it may help stop the top joint vibrating loose as a bonus.
If it were my antenna,I would start taping from the bottom to the top,as there is less chance of water getting in ;)
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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by The Collector » 03 Nov 2019, 13:27

108EH002 wrote:
03 Nov 2019, 11:36
The Collector wrote:
02 Nov 2019, 08:46
Yes it is :)

When dry, seal over the joints with self-amalgamating tape. This'll stop moisture ingression (start 6 inches up the top whip and go downwards in a tight, overlapping spiral)plus it may help stop the top joint vibrating loose as a bonus.
If it were my antenna,I would start taping from the bottom to the top,as there is less chance of water getting in ;)
Haha, you're right there. I was standing the other way around so yes, should start from the bottom as the overlaps will stop water sitting on the tape's edge.

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Re: Imax top section made of cutdown 1/4 wave ss whip

Post by 108EH002 » 04 Nov 2019, 16:49

All joints on vertical homebase antenna I have used,I tape 2-3"/50-75mm above and below each join = I always tape from the bottom to top,then top to bottom,then from the bottom to the top and back to the bottom again.

Proper white electrical tape is cheap (it blends in better than black on white/aluminium antenna)compared to the cost of a half decent manufactured vertical homebase CB/amateur antenna.
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