Comparison, Larsen Tri-band, Laird WPD136M6C-001, COMPACtenna Scan III - 118 to 922MHz

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prcguy

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Here is something I've been wanting to do for a long time but didn't have the COMPACtenna scanner version to test. Another RR member who shall remain anonymous purchased one and sent to me for testing (thanks vagrant!) so I spent some time yesterday running tests on these three antennas.

The test setup was my truck with center of the roof NMO mount on a hill that overlooks much of LA and Orange county in very sunny southern CA. I used an Icom IC-8600 receiver with S meter set up for dBm display and this receiver has a very accurate readout of signal strength to .1dB. I tuned in various signals then immediately swapped antennas while making sure I was receiving the exact same station in every case. Most signals were direct line of sight with maybe a few blocked slightly by the hillside I was on. Swapping antennas for each frequency adds up to more wear on the antenna mount but I trust the data more doing that over tuning in a bunch of freqs on one antenna then swapping to another antenna maybe 30 minutes later with who knows what happens within that 30 minutes.

I'm presenting the data in chart form and also the raw numbers with signal levels in dBm for 26 frequencies tested. I'm not an Excel expert and I could not get the program to do what I want so the chart is part Excel and part hand notated. The left to right frequencies are not to scale with nearly equal distance between data points whether they are a half MHz apart or many MHz apart. The key is the specific color for each antenna where you can see one doing better than the others at some frequencies then that changes at other frequencies where another antenna works better.

Another thing to consider is every frequency is a different transmitter at a different distance producing a different receive level, so don't look at the chart as an overall zig zag of gain like all frequencies came from the same transmitter and antenna. You can only compare the three scanner antennas at each given frequency and another frequency will be a separate comparison.

This is not the absolute bottom line last word on which antenna is better because there are some slight variables, but having a fixed non movable antenna mount at the edge of a high hill and line of sight to most stations and reducing the test time between antennas lowers the potential measurement error.

So which antenna is better? You will have to decide that yourself based on what you want to receive and how you might use the antenna. The Laird WPD136M6C-001 seems to be broader band than the Larsen where it has better performance at some edges of its three advertised bands. You can see this as you go below 2m into the VHF air band and in the UHF T band. The COMPACtenna pulls ahead in the 380 to 450 range then again in the 470 to 509Mhz range. The Larsen is a little better at the upper VHF range and in the 800Mhz range.

Looking at just amateur bands all three are very similar on 2m, the COMPACtenna pulls ahead on 70CM where the Larson is not so great and on 900MHz the Laird is disappointing after an otherwise good showing over most other frequencies.

Here is the data and I hope it helps you decide what your next scanner antenna will be.

scanner antennas 3.jpg

ant chart.jpg
 
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mmckenna

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Wow, thanks for doing that. Interesting.

By the way, which Larsen Tri-Band was it? The older 150-450-800 or the newer 150-450-758?
 

prcguy

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Next time I do this it will be with a vector network analyzer covering the entire frequency range feeding an amplifier to a log periodic pointed at the antennas under test. Screw on an antenna, calibrate, save a trace. Swap antennas save a trace, swap again save a trace. Display all three traces overlapped. Done.

I hope there are some usable threads left in the borrowed antenna with about 80 screw on's and take off's for each antenna.
 

prcguy

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After I've stared at the chart and data for awhile I can see the COMPACtenna is a force to reckon with across the VHF, UHF and 700/800 public service bands, the 380-420Mhz Govt band plus 2m, 70cm and 900MHz amateur. Its not that much different than the Larson or Laird across most of the VHF public service band and it receives better than the others over nearly the entire 380-512Mhz band dipping down to equal the others near 460Mhz but never dropping below them.

It also seems to be a good performer in the 700/800MHz range. If your into railroad monitoring the COMPACtenna starts to drop below the others slightly above 160MHz and also in the VHF air band. But overall for the VHF/UHF amateur and public service bands plus 900MHz amateur its surprisingly good for a 9 1/2" tall antenna.

You can't say the COMPACtenna Scan III is the absolute best of the bunch, but considering how small it is compared to the others it does earn some special recognition and my respect here. I would be interested to know if you can transmit on this version of the COMPACtenna on the 2m and 70cm amateur bands. If so its performance would be adequate on 2m and very good on 70cm plus it would give you very wide band receive for those amateur radios with wide band capability. This exercise has been a real eye opener for me and I might have to follow up with a more formal range test as described above.

scanner ants.jpg
 

mmckenna

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Would be interesting to sweep it for return loss.

But looking at all 3 and considering the performance, I only see one that I'd be willing to put on top of my truck.
 

vagrant

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I am using the Larsen (no spring) version now, so it will be interesting to compare with my mounting location on the hood. At less than half the price, the Larsen would probably please many for mobile use.
 

alcahuete

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I had absolutely horrible luck with the Laird. In my testing, it is outperformed by every antenna I own, including standard 1/4 wave whips. I REALLY want to like that antenna (especially for $100 :ROFLMAO:) but I just can't.
 

russbrill

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After I've stared at the chart and data for awhile I can see the COMPACtenna is a force to reckon with across the VHF, UHF and 700/800 public service bands, the 380-420Mhz Govt band plus 2m, 70cm and 900MHz amateur. Its not that much different than the Larson or Laird across most of the VHF public service band and it receives better than the others over nearly the entire 380-512Mhz band dipping down to equal the others near 460Mhz but never dropping below them.

It also seems to be a good performer in the 700/800MHz range. If your into railroad monitoring the COMPACtenna starts to drop below the others slightly above 160MHz and also in the VHF air band. But overall for the VHF/UHF amateur and public service bands plus 900MHz amateur its surprisingly good for a 9 1/2" tall antenna.

You can't say the COMPACtenna Scan III is the absolute best of the bunch, but considering how small it is compared to the others it does earn some special recognition and my respect here. I would be interested to know if you can transmit on this version of the COMPACtenna on the 2m and 70cm amateur bands. If so its performance would be adequate on 2m and very good on 70cm plus it would give you very wide band receive for those amateur radios with wide band capability. This exercise has been a real eye opener for me and I might have to follow up with a more formal range test as described above.

View attachment 83884
When it comes to the COMPACtenna antenna line on HF, you need to sweep it with a broom and collect it in dust pan... Total POS..
How was the SWR Curve with the Laird on 144/440 ???
 

prcguy

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I did a quick sweep of the COMPACtenna Scan III in the center of my truck roof and on a mount at the rear of the truck just below the bed rail. On the roof the resonant points were sharp around 154 and 414Mhz with about a 2:1 VSWR then a range from about 600MHz to past 1GHz where it was above 2:1 with a lot of peaks and dips. Using the mount at the rear of the truck which is more in line with the instructions and with much less ground plane it had a very usable match for a transceiver from 145 to 163MHz, 410 to 473MHz and 691 to past 1GHz. Looking at the instructions it is rated for up to 100W on VHF and 75W on higher bands.

I also tested my 2m/220/440 version and on the roof the VSWR was well above 2:1 on all bands but at the rear of the truck it covered the three bands in their entirety with well under a 2:1 match.
 

vagrant

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Your results on the back corner are promising for the location I plan to use it (corner hood). Hell, while I'm at it, I might as well sweep and then test it on all five mount points. This going to be fun and interesting.
 

alcahuete

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How was the SWR Curve with the Laird on 144/440 ???
Here's the sweeps I have for the published ranges, including the ham bands:

83947 83948


83949

Best SWR:

VHF: 1.362 @ 160.700 MHz
UHF: 1.293 @ 385.600 MHz
800: 1.468 @ 835.900 MHz


Not terrible anywhere, but like I said, I've gotten horrible performance out of mine. No idea why. NMO mount, center of roof. Every single antenna I have outperforms it handily.
 

prcguy

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In places the COMPACtenna outperformed the others it had a pretty bad match in the center of my roof. If I had the time it would be interesting to repeat the test with all antennas at the rear bed rail on my truck. The match on the Larsen and Laird would probably get worse where the COMPACtenna gets better. Not sure how much that affects overall performance.

Here's the sweeps I have for the published ranges, including the ham bands:

Not terrible anywhere, but like I said, I've gotten horrible performance out of mine. No idea why. NMO mount, center of roof. Every single antenna I have outperforms it handily.
 

russbrill

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Here's the sweeps I have for the published ranges, including the ham bands:

View attachment 83947 View attachment 83948


View attachment 83949

Best SWR:

VHF: 1.362 @ 160.700 MHz
UHF: 1.293 @ 385.600 MHz
800: 1.468 @ 835.900 MHz


Not terrible anywhere, but like I said, I've gotten horrible performance out of mine. No idea why. NMO mount, center of roof. Every single antenna I have outperforms it handily.
So it looks like a waste of money, thanks for the info, and the cash savings :)
 

russbrill

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Sometimes simple is better and works great too... My wife's car goes in the garage every night, so clearance is an issue.. I tried a really short (13.5 inch) Diamond dual-bander... I hated the VHF performance, I can't say SUCKED loud enough..

So I went with the Larsen NMOQBLACK , trimmed it for 146.000 MHz and it works GREAT on 144/440 MHz. It does not quite clear the top of the garage entry, but the antenna is really flexible so I haven't had a problem, it bends back a little, and then snaps back into place. I've had it on her car for 3 years...
 

mmckenna

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So I went with the Larsen NMOQBLACK , trimmed it for 146.000 MHz and it works GREAT on 144/440 MHz. It does not quite clear the top of the garage entry, but the antenna is really flexible so I haven't had a problem, it bends back a little, and then snaps back into place. I've had it on her car for 3 years...
I've been saying that for a long time.
11 years of that on top of my wife's Ford Escape. Simple 1/4 wave. Also, costs less than $10.00
 
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