Trial Run Results for Three Types of Whip Antennas

ab cd

Senior Member
Please scroll down to see the test result graphs at the bottom.

(1) The three antennas under test were:

(a) Coiled Whip
(b) Stock Whip
(c) Optimized Whip

(2) In order to minimize number of variables, only the removable parts of Whips were interchanged. All other hardware, location, and software/gain settings were identical. Even the same mag mount base & RG174 coax cable was used for all the three whips.

(3) In order to be sure that results are not influenced due to fluctuation in traffic, test were conducted twice.

(a) First test between 2pm & 3pm
(b) Repeat test between 4pm & 5pm

Photo 1 - Three Antennas

Photo 2 - Test Setup
three whips.png

Photos 3 & 4 - Results of First Test


Photos 5 & 6 - Results of Repeat Test
dump1090-localhost-local_rate-1h-21May2016-4 to 5 pm.png

dump1090-localhost-range_imperial_nautical-1h-21May2016-4 to 5 pm.png

Is there any way to modify eBay antennas such as UT102 UT106 UT108 into something usable ?
the 102 has too many turns on its coil I think
the 106 has a 2 turn coil up from the base approx 5" near the 1/2 wave mark
the 108 (I have seen different styles) has a 2 turn coil up from the shielding near 65mm which is at or near 1/4 wave length.
Can the 108 be modified into a 1/4 plus one 5/8 or one 3/8 for a touch more gain?

I used to have a minimal knowledge of EZnec a few years back but the program has fatal error when I try to run in on Linux under wine 1.8-386

I do have a 67mm (true) whip that is a modified mini mag mount antenna which work well.
I'm testing the UT-108 (mk1, 1 coil) and trimming the top down in stages. The bottom section is 2 1/2" (including the hidden area) ~1/4wave.
My top section tests so far (using radarbox's range estimates):
Base is a VHF home made ground plane, feed by RG58U.
full length top = max range 74nm average 18nm
7 3/4" top (3/4wave) = max range 99nm, average 20nm
This is just rough hacking, so my results could be useless
This is an open forum and It is ok for anyone to post provided his posts are on the topic of the thread.

What happenned, did you trim UT-108 any further?
trimmed its top section down to 3/4wave 7 3/4" (using inches because my calipers are too short)
still waiting for more data & planes for tonight and it has started snowing.
My fr24 My stats has not had a stable connection the last 2 days; if it was the range data would be quite handy.
I'm using radarbox's range data, which seems a bit dodgy IMO
Polar view is NOT on your computer. It is on Planefinder Server. You will get it on following address

For example if you want to see Polar diagram of station number 98616, go to this address

The click "Daily breakdown for 2018-10-19"
Then scroll down

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rough tests comparing 1/4 wave whip against modified UT108 (2 variants)
to no ones surprise the 1/4w is winning
my stock base / ground plane is a 4"x4" junction box cover on a wooden beam

1/4w whip total 4 1/2" coax=RG174
max range nm: 113, 120, then moved antenna 2'=134, 143, 147, 114, 130

ut108-2coil 1st coil is up 4 1/2", big 2nd coil at (who cares) RG174
~50nm ~12nm average best coverage. results are spotty & weak
ut108-2c 1st coil 4 1/2" 2nd at ? coax now RG58
70nm~16nm average
ut108-1 coil 2 turn @ 2 1/2" near 1/4w untrimmed w RG58
77nm~21nm average
ut108-1 coil, trimmed down top 7 3/4" (3/4w)
86nmsmall 4"x4" base no GP radials
101nmw VHF GND plane, long radials oct 18th stats
ran a SWR test at a limited frequency range below 520Mhz

So I'm guessing the tuned frequency will be 1008Mhz (roughly, could be off due to capacitance) and SWR 1.6.
Antenna top is too long, needs more trimming to match RG58 coax
after trimming the UT108's top down to 175mm measured from the top of the coil, the readings are are barely changing.
anyone wish to estimate where the next low SWR point will be ?

rehabilitation of an UT108(1) has failed.
It's a roller coaster SWR vs freq with little to no chance of tuning 1090Mhz

the range is poor with spotty reception around 50nm


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I am currently using a stock whip (straight} on a shed with a metal roof. I do pretty well, but here's my question. If I trim the antenna such as depicted above, will that improve my range enough to make it worth the effort of getting on the roof and cutting it?
No, it is not worth the effort of climbing up the roof to cut it. If it was in your room at arms length, then yes, it was worth the effort.
So my first attempt was the coax spider with an f connector. Unfortunately, the results were very bad.
No aircrafts were picked up in the 8 hours that this Pi was connected.

Initially, the connection was made with a 7 metre RG6 (75 ohm) added to by a 5 metre RG 176 (which is thin enough to connect with an MCX connector).

I figured the signal loss would be significant and eliminated all but 10cm of RG176 but kept the 7 metre RG6. Still, there was nothing being picked up. What could have gone wrong? There were no line shorts - I had a multimeter to test with.

I will next attempt the cantenna and the coke can (the standard size has now been replaced for a 5cm diameter can - so I might have to actually buy something which is atleast 69mm in diameter).

In the meantime, what do you think of the following products:



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You can test connectivity for both center conductor and radials to shield at receiver.
How long is that center conductor measured from the radials?

Don't bother with the cantenna, the problem must be in your connection to the dongle.

Also it seems you can't see the horizon, that might mean you can only pick up aircraft overhead.
There also might be interference.
Make sure that it's pointing straight up as well.

Do you have the graphs running?
Could you show the signal and message graph?
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