N1201SA/N1201SA+ Antenna Analyzer discussion

[Skibox]

@aldoir

No surprises here, the 9dBi is obviously fake and have no electrical principles to work

Most likely it’s a 2.4 GHz WLAN antenna.

/M

[inoc]

…actually, since the VSWR is about 1.02 at about 1840 MHz it’s probably designed for Mobile Communications since the other (legal) possibility of “Space Operations - Ground to Space” would be using a large dish.

[rwinterhoff]

Had the same problem with the ebay 9dbi antenna. It does not work at 1090MHZ. Took it apart and here is what is inside.

The supplier refunded my $8.99.

[aldoir]

Could you pls disassemble this tube/sleeve to see what’s inside?

[rwinterhoff]

@aldoir

Could you pls disassemble this tube/sleeve to see what’s inside?

It appears to be a solid piece of metal with crimp connection to the antenna wire(s).

[triggers]

My analyzer turned up this afternoon so I got stuck in looking at 2 antennas I’ve made.

The first is a Quad

https://img2.brain3.photobox.com/0932229035b4c751cd298ed7edd783102fce75c16cfd39f2742b6851029938f06cf26032.jpg

Here is the SWR and the sweep
https://img2.brain3.photobox.com/988336328de3585adb091f9c5b865978757e2e8ee7e8c93f500163291db93ff73c3741b9.jpghttps://img2.brain3.photobox.com/81446130d2eaa40744f5c93c72a7df46302db4d102e584d896ae5f2b10bf9905a32b879b.jpg

This one is a 12 element CoCo

https://img2.brain3.photobox.com/2561648712c4743d91807df520c7c8486e92d648c0b08deb4a4631e04fafd8f2bf7bcae6.jpghttps://img2.brain3.photobox.com/61637879b5eaf03dfa9e9870e84d63df43210e1eca99adf897609f5281651f27c614c41d.jpg

I don’t understand the sweep graph. Has anyone else done a sweep of a CoCo?

Many thanks

[k6rtm]

VSWR and Antenna Performance–

(Low) VSWR does NOT indicate good antenna performance! It only tells you about the impedance matching between the antenna and the load (source).

I have a Bird Precision Dummy Load that has a VSWR of under 1.1 from pretty much DC up to around 4200 MHz (while taking 100 Watts) – very flat. Doesn’t “antenna” worth a damn.

VSWR is very important when you’re transmitting. For most hams, anything under 1.3 (or 1.5) is fine. For QRO (high power), yeah, 1.1 is better.

For receiving, the change in VSWR over frequency is more interesting as an indicator of antenna performance. But a VSWR of 2 in a receiving system isn’t the end of the world.

An indication of this is the number of our colleagues who are getting hammered by energy in the 960 MHz region, even though the FA antennas they’re using have a relatively high VSWR at those frequencies.

The noted American RF and Antenna researcher H.L. Mencken summed it up nicely:

For every complex problem, there is an answer that is clear, simple, and wrong.

(ok, he wasn’t an RF and antenna researcher, but his comment holds over many fields of endeavor)

respectfully submitted,

bob k6rtm

[triggers]

Hi Bob,

Many thanks for your sage words. Being a novice at all this antenna stuff, I find it difficult to fathom how the different parameters relate to each other. I’m getting there slowly

Have you done any testing with the N1201SA?

[abcd567]

I posted trigger’s question on eHam.net, and got following 3 responses:

RESPONSE #1

@WB6BYU

My immediate thought is a poor connection, or a wobbly antenna, such that the actual SWR doesn’t remain stable as the measurements are plotted.

Repeat the sweep over a smaller range (but still wide enough to hit several of the peaks) and see if you get consistent results. Even repeating the measurement as is might give you some information based on whether the peaks are always in exactly the same place (which would suggest the actual behavior of the antenna) or whether they move around (likely due to some other source of variation.)

I was measuring a 2m quad in my garage with the antenna hanging by a string from the ceiling, and saw some quirky variations in the graph that turned out to be due to the antenna rotating slowly on the support string. When I spun it quickly the period of the variation decreased accordingly. Similarly, letting the antenna swing back and forth in an arc also modulated the plot.

If you set the width of the plot to something like 1 MHz, you’d expect the antenna to show a relatively constant behavior across the range. If you see a significant variation, it may be due to antenna movement, and intermittent connection, pickup of RF from a nearby transmitter (possibly on a lower frequency where the CoCo happens to have a resonance but the quad doesn’t.)

RESPONSE #2

@W9IQ

It appears to me that the antenna was picking up a relatively strong signal at the time the sweep was being conducted.

• Glenn W9IQ

RESPONSE #3

@KA5IPF

Unless you are in a Faraday Cage the antenna and analyzer are going to be picking up other signals and can give a false reading.

[triggers]

@abcd

Thanks for the responses from eHam.
https://img2.brain3.photobox.com/61637879b5eaf03dfa9e9870e84d63df43210e1eca99adf897609f5281651f27c614c41d.jpg

I’ve done a bit more investigation and found that I get the same response as above, when I just have a length (3m) of coax attached to the analyzer. Is that normal? My coax has no markings on it except SAT 100. I know the VF is 0.66 from building many CoCos

I don’t live in a noisy environment as I’m in the countryside and no masts within 2 km. I do have a Davis weather station which states it transmits by “Frequency-hopping spread spectrum radio”

I’ll do a scan with SDR Sharp or HDSDR this evening.

[abcd567]

@triggers:
The plot for Keith’s commercial Moonraker aerial is similar to your Coco’s plot. He has posted it on page 2 of this thread:

Off Designed-Frequency Behavior of 2 Types of Antennas

Keith’s plot of his commercial Moonraker aerial:

[Devonian]

The Davis Wx station should be TX’ing on 868MHz every 2.5 seconds if it’s a UK model (I have a UK VP2).
I don’t notice it on 1090

Nigel.

[triggers]

@Devonian

Thanks for your input. I thought the frequency would be well away from 1090Mhz but I wasn’t sure. It is a UK model.

[Nitr0]

@triggers

@abcd

Thanks for the responses from eHam.
https://img2.brain3.photobox.com/61637879b5eaf03dfa9e9870e84d63df43210e1eca99adf897609f5281651f27c614c41d.jpg

I’ve done a bit more investigation and found that I get the same response as above, when I just have a length (3m) of coax attached to the analyzer. Is that normal? My coax has no markings on it except SAT 100. I know the VF is 0.66 from building many CoCos

I don’t live in a noisy environment as I’m in the countryside and no masts within 2 km. I do have a Davis weather station which states it transmits by “Frequency-hopping spread spectrum radio”

I’ll do a scan with SDR Sharp or HDSDR this evening.

I get the same “fuzz” everytime when I stick any length of RG-6 between the antenna and analyzer. Swap it out with LMR400 or whatever and it’s fine again. Mismatch throws the thing for a loop.

[abcd567]

I have posted trigger’s question in the forum “ham.stackexchange.com”. Answers are slowly pouring in.

ham.stackexchange.com/questions … eep-vs-swr

[XE3N7NAT]

Mine has been ordered, last message was being shipped out this week, cant wait to give it a test on a few I made up.

[LFBDBORDEAUX]

Hello, did anyone test this antenna with the N1201 SA. Thank you

Nooelec - 1090MHz ADS-B Antenna, 5dBi (High Gain), SMA - Software Defined Radio

[keithma]

@inoc

Sometimes it’s just one press of the Ok to turn on and sometimes off.
Other times the Ok button has to be used along with the CTRL button.
Other times the above buttonologys have to be held for a couple of seconds.

Since the manual doesn’t shed any light on how it’s supposed to be turned on or off - does anyone know how it’s supposed to be turned on and off??

Huge long delay before replying. The correct way to turn it on is to hold the CTRL button and tap the OK button and then release the CTRL button. That has never failed for me.