Signal stalk tuning.

[gortex2]

I ve never found a VHF 1/4 wave to perform well on a UHF even though it will work. For TLMR and great repeater systems its ok, but for 90% of my UHF stuff a 1/4 wave UHF will outperform it. 

[kidphc]

It sounds like a step back, if I am reading it right.  Do you feel it's close, or are you not happy?

Need more testing step forward in clearance. Step forward in survivability. Step backwards in reception and transmit.

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[marcspaz]

35 minutes ago, kidphc said:

Need more testing step forward in clearance. Step forward in survivability. Step backwards in reception and transmit.

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I 100% understand that.  I am pretty sure you and I have discussed that I use a Comet SBB-1 when I am going offroad or in a known limited clearance area.  A slight performance tradeoff for survivability is definitely a smart choice.  A high performance antenna that is broken because of a tree or i-beam doesn't help at all.

[kidphc]

 
I 100% understand that.  I am pretty sure you and I have discussed that I use a Comet SBB-1 when I am going offroad or in a known limited clearance area.  A slight performance tradeoff for survivability is definitely a smart choice.  A high performance antenna that is broken because of a tree or i-beam doesn't help at all.

Yeah. When I look at pictures or around the nmo it looks like I already have some roof damage to the sheet metal.

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[Sshannon]

20 hours ago, Sshannon said:

Plus Signal Sticks are made in the USA by the guy who also runs HamStudy. 

Here’s more information about the company and products in a livestream format.  

 

 

[Lscott]

4 hours ago, gortex2 said:

I ve never found a VHF 1/4 wave to perform well on a UHF even though it will work. For TLMR and great repeater systems its ok, but for 90% of my UHF stuff a 1/4 wave UHF will outperform it. 

Not surprised. The radiation pattern is crap. Most of the power is at very high angle relative to the horizontal. I modeled a 1/4 on a ground plane operating on the third harmonic, which is what you would be doing.

[tweiss3]

Well, that's why the good ones, like the NMO2/70SH is colinear 3/4 design for 70cm. 

[kidphc]

Going to play with it a bit more. Dielectric grease and wire wheeled the paint off the antenna where the second set screw is located.

Already knew a 3/4 was not the way to go.

Also found on the coax. Center conductor strands were bent. So, soldered it back up and cleaned up.

Hopefully, signal reports get better.

If not any better I am looking at a 5/8 or 1/2 laird nmo where I will replace the whip. Past experience with tuning with a coil and a different whip was not a good experience for me or the outcome.

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[kidphc]

So another update.

Di-electric grease and fixing the center conductor on the coax/pl259 connection. Drastically improved the scratchiness.

Signal reports are slightly better then 1/4 wave. Still get you are scratchy, barely above noise floor but readable in the low spots where the 1/4 was unreadable.

Think at this point it maybe a keeper. Due to the survivability outweighing the advantages of the 5/8th over 5/8th for my normal usage.

Slightly better then 1/4 slightly worse then 5/8th over 5/8ths. Might be a different story when the xtl5k is finally installed with 70cm repeaters. The gmrs repeater is in Wheaton, md and just an absolutely incredible repeater. That puts 80% of ham repeaters to shame.



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[marcspaz]

Great to hear! Glad it's working out. This is good info for others thinking of going that route, for sure.

[kidphc]

So as expected, a 3/4 wave antenna just ain't cutting it. I tried out a Laird BB4503 (5/8 wave nmo). It out peforms the cut down signal stall in reception and transmitting everywhere (locations). This is stock and uncut.

Originally, I was planning on cutting the signal stalk whip and putting it on the BB4503 after during some NanoVNA sweeps. I am not sure if I am going to be doing that with the new radio being installed soon. It all may be replaced with a STI flexi tri-band. If I decide to keep the BB4503 installed I will sweep the antenna and see if I have enough bandwidth without going over 2.0 SWR across 440-468 Mhz, At that point i will decide if I will buy a triplexer and install 2 more NMOs. 

 

So the decision has been made to put a tri-band in the location of where my 440-470 antennas are located. I wanted to keep it seperate but good god are quality triplexers for public service expensive. Not to mention it got harder to find ones where the band pass was wide enough to let ham bands through.

The best one I could find was a Comtelco DB3 at about $192. Which was pretty wide banded. The STI-co which was another choice were 3x-4x the cost. The panorama ones averaged $160-300 were also pretty widebanded.

I may try to utilize the signal stalk whips with the Tri-bander, kinda like I was going to with the 5/8. BTW, the 5/8 antenna is really stiff, we hit a parking garage support with the antenna and it sound like it was going to rip the back half of the roof off. Enough so my wife said we are bringing my car next time we come here.