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  #31  
Old 01-08-2011, 12:24 PM
xodeuce xodeuce is offline
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Originally Posted by rover67 View Post
pics of the antenna!

I need some input here.... do you HAM guys thing it would be OK to put a threaded joint like I did for the bottom part on the main part of the antenna to make it break down a little bit more? My only concerns are that the threaded portion is tapered so over time the overall length of the radiating element may get a bit shorter.... that and maybe the union is not cylindrical so maybe it'd make it radiate funky.

What do you guys think?

EDIT: I just reread my thread and realized that this was one of the first questions I asked!!! Sorry!
The length of pipe below the T fitting doesn't matter. It can be short, or you can U-Bolt it to a metal mast which would make it electrically much longer. The radiating element is wholly contained above the T as I understand it. I think if you're DC grounded below the T, you need a balun to keep the coax from radiating. Something like 4-5 turns of coax around a PVC pipe at the feed point of the antenna.

-Keith
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  #32  
Old 01-08-2011, 06:53 PM
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Quote:
Originally Posted by rover67 View Post
pics of the antenna!

I need some input here.... do you HAM guys thing it would be OK to put a threaded joint like I did for the bottom part on the main part of the antenna to make it break down a little bit more? My only concerns are that the threaded portion is tapered so over time the overall length of the radiating element may get a bit shorter.... that and maybe the union is not cylindrical so maybe it'd make it radiate funky.

What do you guys think?
I wouldn't over think it, just do it. The copper cactus is much more broad banded than its twin lead counterparts. Slight differences in OAL and diameter aren't going to make big changes in its resonance.

Choke baluns are never a bad idea, I like to use ferrite snap on beads (mix 43 iirc)
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  #33  
Old 01-08-2011, 07:03 PM
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I coiled the coax about 5 times near the connector.

I'll look for a ferrite snap on thinggie!

Thanks for the feedback! and it's nice to see you on here Keith!
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  #34  
Old 01-09-2011, 08:11 AM
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I coiled the coax about 5 times near the connector.

I'll look for a ferrite snap on thinggie!

Thanks for the feedback! and it's nice to see you on here Keith!
I've been lurking around your FJ40 resto page for a while. Figured I'd finally go ahead and join.

Good looking antenna you built there. We just started a 2M simplex net in B'ham, and it's got me wanting to get something outside and up high.
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  #35  
Old 01-09-2011, 08:25 AM
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[quote= Slight differences in OAL and diameter aren't going to make big changes in its resonance.

[/QUOTE]

FWIW, during construction of mine we put in a small screw on the short end to fine tune the copper j-pole. Additionally, the number of coax coils, diameter and location/orientation at the bottom of the "J" made differences in the impedance. We tuned it for the center of the 2-m band at 50 ohms. Antenna analyzer was MFJ-259B, I believe. Unfortunately I don't remember the ranges of these changes but I do remember the differences were enough for us to pursue changes.
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  #36  
Old 01-09-2011, 08:40 AM
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Originally Posted by DaveInDenver View Post
The Broomfield machine is 145.310-, 100Hz tone. It's a RX-only for the system, so if your shadow causes your reception to be scratchy then it won't help (it does not retransmit 145.310, just listens to 144.710). It's job is to help primarily Boulder hams when they TX to get into the machine.
Does 531 have multiple voting receivers?
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  #37  
Old 01-09-2011, 12:23 PM
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Marco, that antenna sounds 10x better on simplex than it does the repeater.. nice work, man, better than a soup can on a string, that's for sure.
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  #38  
Old 01-09-2011, 05:16 PM
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Got my arrow 70cm/2m up today, hooked the FT60 to it and wow! I can hit the repeaters and simplex seem to be much better signal. Low power gets in to the repeater with no problem. Ready for the weather to turn and make us have to hang around the house and monitor the radio.
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  #39  
Old 01-09-2011, 06:36 PM
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Default I agree!

I was messin' around with my new arrow setup and it is nice to have a decent antenna on an HT. sounds quite good...I made contact with KD0NIC on the connection on Saturday.
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  #40  
Old 01-09-2011, 08:34 PM
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Hey Shawn are you messing with it tonight? let me know if you want to try simplex.. send me a text or something.
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