Author Topic: Siglent SVA1015X and SVA1032X 1.5, 3.2GHz Spectrum & Vector Network Analyzers  (Read 35490 times)

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Online tautech

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #125 on: July 20, 2018, 10:32:11 am »
One more thing: the angle of the radial(s) should be about 45o for an impedance of 50 Ohm.
Thanks.
hendorog sent me this link in an email:
http://www.microwavetools.com/monopole/
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Online PA0PBZ

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #126 on: July 20, 2018, 10:48:06 am »
I still think calling it a 'monopole' where your second pole is the ground plane is weird, but anyway…
Please keep in mind that the link points to a 2.4Ghz antenna, your ground plane needs to be 10 times bigger to be as effective. Also, it radiates slightly upwards and I don't think you want that? A vertical dipole radiates horizontally.
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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #127 on: July 20, 2018, 10:55:45 am »
I still think calling it a 'monopole' where your second pole is the ground plane is weird, but anyway…
Please keep in mind that the link points to a 2.4Ghz antenna, your ground plane needs to be 10 times bigger to be as effective. Also, it radiates slightly upwards and I don't think you want that? A vertical dipole radiates horizontally.
Call it a whip then and what's your advice to improve it's performance ?
Go from 1/4 wave to 1/2 or full wavelength ?

1/4" (6.25mm) copper rod is my preferred mast material. 952mm is full wavelength and this copper is reasonably stiff but the only concern is the nylon bush it's mounted in for full wavelength.
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Online PA0PBZ

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #128 on: July 20, 2018, 11:12:37 am »
The most basic antenna is an open dipole, which you can mount horizontal or vertical. Horizontal will give you a radiation pattern like the figure 8, vertical will be a circle.
So 2 1/4 wavelength elements mounted on a small isolator, coax conductor to one element and shield to the other. The problem here is to mount it on a pole, you can't tape it to a conducting pole but you should stay clear of conducting materials in the radiating direction for a few wavelengths. If you want to use a vertical dipole on the existing mast I think your best bet would be to put the dipole in a pvc tube and mount that on top of your mast, keeping it at least 20cm away from the top of the mast. The problem here is feeding the coax to the antenna without disturbing the radiation pattern.
So that is why a ground plane antenna is easier, you can simply mount it on top of the mast.



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Offline ironcurtain

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #129 on: July 20, 2018, 12:16:54 pm »
Whoops, I haven't got it shipped yet but I bought a Siglent SSA3021X....

Should I just tell them to ship a Siglent SVA1015X instead? Assuming we get to hack the SVA to expand the frequency range. It seems like a much more complete solution and I could definitely use the VNA options.

Damn!!!!
 

Online tautech

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #130 on: July 20, 2018, 07:59:30 pm »
Whoops, I haven't got it shipped yet but I bought a Siglent SSA3021X....

Should I just tell them to ship a Siglent SVA1015X instead? Assuming we get to hack the SVA to expand the frequency range. It seems like a much more complete solution and I could definitely use the VNA options.

Damn!!!!
SVA1015X is already the top BW model in this range so I'm fairly sure BW can't be improved. Owning both (as demo models) they're aimed at different markets due to their differing capability. If the VNA capabilities are of use and 1.5 GHz is enough to meet your SA BW needs the SVA1015X is the one to go for.
Happy hunting.  :)
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Online tautech

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #131 on: July 20, 2018, 10:30:18 pm »
The most basic antenna is an open dipole, which you can mount horizontal or vertical. Horizontal will give you a radiation pattern like the figure 8, vertical will be a circle.
So 2 1/4 wavelength elements mounted on a small isolator, coax conductor to one element and shield to the other. The problem here is to mount it on a pole, you can't tape it to a conducting pole but you should stay clear of conducting materials in the radiating direction for a few wavelengths. If you want to use a vertical dipole on the existing mast I think your best bet would be to put the dipole in a pvc tube and mount that on top of your mast, keeping it at least 20cm away from the top of the mast. The problem here is feeding the coax to the antenna without disturbing the radiation pattern.
So that is why a ground plane antenna is easier, you can simply mount it on top of the mast.
An issue I have is it needs to receive transmissions from ~130o different directions which is why I originally settled on a monopole/whip that don't have the same directivity constraints.
There's zero transmission requirement as only reception is needed but I do understand that T/R performance is approximately equivalent.
So I'll keep working with/on what I have for now and attempt to add a ground plane.
Thanks for your help.
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Offline G0HZU

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #132 on: July 20, 2018, 10:52:40 pm »
A basic J-Pole antenna might be the ideal choice here. Easy to make and easy to match and it gives a low angle of (omni) radiation.

It is about 3/4 wavelength long and you can make a skinny version from 300R ribbon feeder (this is the Slim Jim folded dipole version) and hide it inside a hollow plastic tube. So you could replace the hockey stick with a longer plastic tube and put the antenna in the top section and feed the coax up the bottom of the hollow tube.

Note that the J Pole (or the Slim Jim variant) doesn't need a ground plane so this is why it might be a good choice for you here.
« Last Edit: July 20, 2018, 10:59:58 pm by G0HZU »
 
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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #133 on: July 20, 2018, 10:58:17 pm »
A basic J-Pole antenna might be the ideal choice here. Easy to make and easy to match and it gives a low angle of (omni) radiation.

It is about 3/4 wavelength long but you can make one from 300R ribbon feeder (this is the Slim Jim folded dipole version) and hide it inside a hollow plastic tube. So you could replace the hockey stick with a longer plastic tube and put the antenna in the top section and feed the coax up the bottom of the hollow tube.

Note that the J Pole (or the Slim Jim variant) doesn't need a ground plane so this is why it might be a good choice for you here.
Thanks, yes maybe.
I'll run some numbers through this:
https://m0ukd.com/calculators/slim-jim-and-j-pole-calculator/


Edit
First look seems real good for 315 MHz with a leg separation of 21mm and total length of 686mm.
Might just fit inside some 32mm waste pipe with an end cap on the top. 40mm would give a bit more certainty of fitting but at the risk of higher wind loads on the base mount.
Maybe I'll thread the top of the 1/2" galv pipe hockey stick and use 'off the shelf' adapters to fit the waste pipe.....or build it again from 3/4" galv pipe for additional strength as there'll be a bit more windage to deal with as opposed to just a bare element.

Hmmm, off to do some measurements and scavenge though my numerous bits and bobs stashed away.
« Last Edit: July 20, 2018, 11:22:06 pm by tautech »
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Offline G0HZU

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #134 on: July 20, 2018, 11:23:36 pm »
They are easy to make although many people tend to scrimp on the RF connections and end up with something with (soldered) RF connections that will fall apart over time. Also, it's worth fitting something at the antenna feedpoint to choke RF away from the outer of the coax feedline. If it ends up inside a skinny plastic water pipe then you might as well just make the basic J Pole version as there's little/no performance advantage with the folded (Slim Jim) version. They should both radiate as an omni vertical dipole with no need for a ground plane.

I guess the alternative would be to attach ground radials to your existing monopole antenna. I don't think there will be much difference in RF performance between any of these options and it really is a case of which version you prefer to build (and look at). However, if you build it well, the J Pole version inside a plastic pipe should be the most weatherproof... but you do have to make solid connections from the coax to the antenna if you want something you can fit and forget for many years.

You should be able to fit it inside a 18mm or 22mm diameter plastic pipe. 32mm is very wide!
« Last Edit: July 20, 2018, 11:31:32 pm by G0HZU »
 

Online TK

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #135 on: July 20, 2018, 11:48:50 pm »
@tautech, I am enjoying the discussion about antennas, and I see how it is related to a VNA, but it should be more productive to move it to a new thread and keep this thread exclusively for SVA1015X discussions...
 
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Offline bicycleguy

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #136 on: July 21, 2018, 01:24:30 am »
@tautech, I am enjoying the discussion about antennas, and I see how it is related to a VNA, but it should be more productive to move it to a new thread and keep this thread exclusively for SVA1015X discussions...
I'm kind of a noob with respect to VNAs and before your post was thinking of commenting what a great idea it was for @tautech, on this sales oriented thread (or his knowledgable posters ^-^) to do this little teaching moment of what the VNA can be used for.  Maybe over time I will learn enough to think I need to buy one :-+
 

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #137 on: July 21, 2018, 01:50:38 am »
They are easy to make although many people tend to scrimp on the RF connections and end up with something with (soldered) RF connections that will fall apart over time. Also, it's worth fitting something at the antenna feedpoint to choke RF away from the outer of the coax feedline. If it ends up inside a skinny plastic water pipe then you might as well just make the basic J Pole version as there's little/no performance advantage with the folded (Slim Jim) version. They should both radiate as an omni vertical dipole with no need for a ground plane.

I guess the alternative would be to attach ground radials to your existing monopole antenna. I don't think there will be much difference in RF performance between any of these options and it really is a case of which version you prefer to build (and look at). However, if you build it well, the J Pole version inside a plastic pipe should be the most weatherproof... but you do have to make solid connections from the coax to the antenna if you want something you can fit and forget for many years.

You should be able to fit it inside a 18mm or 22mm diameter plastic pipe. 32mm is very wide!
Yes and after enlarging the J type pic I see the gap (F) spec is OD so yes it will fit into something smaller.
'Gap' put me crook thinking it was the gap between elements when it's actually an outside measurement.  :phew:

The feed points I'd experiment with and maybe with two sliding brass custom terminations that can be fixed permanently once the assembly is tuned. I can easy spin something up on the lathe and drill and tap it for termination and retaining screws.

I'm gunna feed it with coax as the run is a couple on meters and I haven't got ribbon cable on hand.
I might change the existing coax to one with a more robust middle conductor that I can sleeve and bootlace terminate.
The braid will be easy to just sleeve and retain the barrel choke in the right position with two cable ties.

I'll be a while before I post anything more on this as obtaining the bits and engineering will need to be factored into any spare time I get.  :(

Yeah, I'm liking the J pole antenna more and more.  :)

@tautech, I am enjoying the discussion about antennas, and I see how it is related to a VNA, but it should be more productive to move it to a new thread and keep this thread exclusively for SVA1015X discussions...
Noted.
I'm kind of a noob with respect to VNAs and before your post was thinking of commenting what a great idea it was for @tautech, on this sales oriented thread (or his knowledgable posters ^-^) to do this little teaching moment of what the VNA can be used for.  Maybe over time I will learn enough to think I need to buy one :-+
:) Yeah it's got a bit out of hand from just a quick attempt to demonstrate how useful these VNA's can be.
If I had one years back........well everything would be remote controlled !

If it wasn't for the highly knowledgeable RF guys maybe it would've been just a single post.
So thank them not me !
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Online TK

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #138 on: July 21, 2018, 01:30:25 pm »
Smith Chart looks so cool... @tautech: please post PICTURES of your SVA1015X unit while you experiment with new antennas and the whole tuning process
 

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #139 on: July 21, 2018, 10:49:51 pm »
Smith Chart looks so cool...
Yeah and I'm still learning to use it.
I was originally confused that it had no scaling however after some thought and a first read of the manual it's then obvious you can use the Markers and read the values from them.
An example which shows early preliminary measurements from a new bare J Pole antenna.



Quote
@tautech: please post PICTURES of your SVA1015X unit while you experiment with new antennas and the whole tuning process
It's just a plain ordinary SVA using nothing that any hobbyist doesn't have in their RF box, maybe with the exception of a N-BNC adapter borrowed from my SSA3032X.
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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #140 on: July 22, 2018, 08:15:04 am »
I think Tautech exploring the SVA1015X and his antenna is great.
As an example of something closer to what you're aiming for with your antenna here are two shots of a 1/4 whip antenna designed for the 70cm(430-450MHz) ham band, displayed in SWR and on a smith chart.
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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #141 on: July 22, 2018, 09:06:21 am »
I think Tautech exploring the SVA1015X and his antenna is great.
As an example of something closer to what you're aiming for with your antenna here are two shots of a 1/4 whip antenna designed for the 70cm(430-450MHz) ham band, displayed in SWR and on a smith chart.
:)
Thanks, I hope I'm not displaying any excellence as I'm a bit out of my depth but having a pile of fun learning.

hendorog helped me get a heap closer to optimum today when he dropped by to grab the SVA for some hardcore checks against his SH and Agilent. We explored just a small bit of the total functionality and checked his SMA Cal standards against the SVA factory setup. Changed SVA Cal to hendorog's kit and back again to factory default. Easy peasy !
Log Mag mode was something he showed me today and the dip in the sweep frequency where the antenna is the most emissive can be of great assistance for tuning this J Pole. I'll document more about the HW later as it's been changed and simplified. 3.2mm brass welding rod now with custom sliding feed points. (hint; 3.5mm chocolate block inners)
Getting some more antenna project bits tomorrow.  :)
When I get time I'll carry on with just the SSA and an external bridge then park it for a bit until the SVA gets back for final antenna optimization.
Think I'll order some more SVA's.............

hendorog will show just what it's capable of far better than I can.  :(

He left here like a dog with two tails.  :D
Now I'm hoping he'll give it back. :-//
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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #142 on: July 22, 2018, 09:46:19 am »
He left here like a dog with two tails.  :D

LOL!
Tails are like antennas right?  ;)
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Offline G0HZU

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #143 on: July 22, 2018, 09:09:33 pm »
Quote
An example which shows early preliminary measurements from a new bare J Pole antenna.

Your early plots don't look right to me so I had a go at making a very basic J-Pole at about 315MHz.

I used 2mm diameter copper wire which is a bit thin but I didn't want to waste the thicker stuff. So my antenna is a bit wobbly and needed supports to keep it stable in terms of tuning and alignment. However, see below for an image showing the complex impedance and the S11 plot and VSWR. I didn't bother to trim it for 315MHz so it is showing the best VSWR at 302MHz. I didn't do anything special in terms of optimising the lengths and just went for 3/4 wavelength overall and 1/4 wavelength for the J bit and I did this very casually to something like +/- 10mm. I then optimised the feed point on the VNA for lowest VSWR.

Note that the VNA reference plane is set right at the connection point to the antenna wires so the complex impedance graph is at the far end of the coax as it connects directly to the antenna wires.

Someone with more time on their hands could optimise the various antenna dimensions better than this but the plot below would be good enough for me for a basic J-Pole lashup  at 302MHz :)
« Last Edit: July 22, 2018, 09:13:34 pm by G0HZU »
 

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #144 on: July 22, 2018, 09:38:37 pm »
Quote
An example which shows early preliminary measurements from a new bare J Pole antenna.

Your early plots don't look right to me so I had a go at making a very basic J-Pole at about 315MHz.
Yeah they're miles off mostly due to basic newbie mistakes that were explored yesterday with hendorog.
I'm using 1/8" brass now but still in a 32mm PVC tube so I can still go back and build something with the 1/4" copper rod I have lots of.
The 1/8" brass is in just 1m lengths and a trim to the 1/4 wave section (correct calculated length) came up just a few mm short of where it should've been cut.  |O  We proved it was wrong by adding a bit back with a cable strip connector. This where it seems the Log Mag mode seems great for getting onto the target frequency.

The 200mm stainless whip in the BNC socket worked fine again this morning.  :phew:
Thanks for your pointers of help guys.  :)
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Offline hendorog

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #145 on: July 22, 2018, 10:11:42 pm »
I had a play last night when I got home. I did some unscientific tests of the drift and the directivity.

So far the drift after a cal looks OK. It looks to me like it has around 40dB of 'worst case usable' directivity - I did a calibration straight after power up and then waited an hour or so.

Probably the switched time division sampling of the reference (TG output) and the measurement has something to do with this.

The out of the box directivity with no calibration seems pretty decent too. I'll test this again to make sure I am not being fooled by it saving my last cal as we did set it to restore last settings on power up.

First impressions of the VNA software is that it is basic but stable. There are definitely features that have been held back - i.e. greyed out. These will no doubt come in due course. I wonder if Siglent have intentionally gone with a limited feature set for the early release to ensure stability?

I also had a quick play with the SA features. It is much more feature rich than the VNA side right now and I don't know if I am imagining it but I think there are even more options on the trace math page than the SSA has. The power math looks useful as it can be used, with averaging, to drop the noise floor.
 

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #146 on: July 28, 2018, 04:28:06 am »
Quote
An example which shows early preliminary measurements from a new bare J Pole antenna.

Your early plots don't look right to me so I had a go at making a very basic J-Pole at about 315MHz.
Some progress.
Using SSA3032X and Siglents RBSSA3X20 reflection bridge just in some effort to get the resonant frequency to close to where it needs to be.

Old whip/monopole.


New J-Pole and 3m RG58 feeder.


No final tuning from VNA SWR or Smith charts until hendorog is finished with the SVA.
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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #147 on: August 05, 2018, 03:06:03 am »
I received my sva1015 last week and have been having fun getting to know it.  However I'm having a bit of trouble with the analog modulation analysis option and I'm wondering if anyone can provide some help/guidance.  I'm not sure if the issue is with my setup, theory, expectations or some combination thereof. 

I want to be able to do some FM deviation measurements, so I wanted to start by making sure I could get (what I believe to be) the correct values with a controlled setup. 

I've tried several different setups and I'm getting similar results from each of them, so I'll describe just one of the setups.  I have an amateur radio VHF/UHF transceiver connected to a Bird 4431 wattmeter which has an RF sample port.  The output of the bird is connected to a 50Ohm dummy load and the sample port is connected to the SVA1015.  For the modulating signal, I'm using the waveform generator on my SDS2204X scope, connected to the audio line-in on the data port of my transceiver. 

The waveform generator is sending a 1.2kHz sine wave onto a carrier at 144.41Mhz, and I used the spectrum analyzer functionality to adjust the waveform generator's amplitude until I hit the 1st order Bessel null.  This should be a modulation index of 2.4 and thus a frequency deviation of +/- 2.88kHz.  I also double-checked the deviation using the spectrum analyzer via the min/max trace differential and got the expected 2.88kHz deviation.  So I'm pretty sure the signal's FM deviation is indeed 2.88kHz. 

But when I enable the analog FM modulation mode, I can't seem to get it to give me that result.  I've tried every value of IF Bandwidth available, as well as every EqLPF.  I've tried both with and without averaging.  None of the values (min, max or average) are showing a deviation of 2.88kHz.  And the signal on screen is a bit more wonky than I'd expect.  It does sort of, mostly, show what looks like the 1.2kHz signal but it's not clean or consistent at all.  I've tried moving the SVA1015 away from the transceiver and the dummy load in case there was some noise getting into the machine from them, but that didn't seem to have any effect. 

Is there something I'm doing wrong?  Any advice/suggestions? 

BTW - I want to give some kudos to Siglent's support staff.  There were some issues getting my option licenses installed, which was exacerbated by the fact that the analog modulation analysis option was not enabled under trial license.  The tech support stayed late on friday waiting for the corrected codes to send to me so that I could do the work I was expecting to do over the weekend. 

One other side note for anyone looking at using the vector analysis functionality, their calibration kit is back-ordered and won't be available for roughly another week.  So unless you already have an appropriate calibration kit, you won't really be able to use the VA functionality for a little while.   Of course you can play around with it, but you can't *really* use it without proper calibration.


   
 

Offline hendorog

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #148 on: August 05, 2018, 03:52:36 am »
I just tried to replicate your setup quickly with a signal generator - I have to go out now, so didn't have time for screenshots etc.

Things I observed were:
* Level reading 3.4 dB when signal was 0dB. Channel power measurement on SA funciton showed 0dB.
* Not able to get a stable deviation reading in Demod mode for low FM deviation values. Above about 4 kHz I could get a stable reading using averaging, but it was always about 30% below what the signal generator was saying.
* I tried the min/max measurement in SA mode, but I'm not familiar with it and didn't have time to research it. It also read a different value but that is probably my fault.
* The Occupied bandwidth measurement function on the SA closely matched the FM deviation setting on my Sig gen.

I can look into it a bit further for you later on - let me know if there are any other tests I can do.

 
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Offline nautiboy

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Re: Siglent SVA1015X 1.5GHz Spectrum & Vector Network Analyzer
« Reply #149 on: August 05, 2018, 06:30:51 am »
Thanks for running the tests.  If it can't give stable values below 4kHz deviation, that certainly limits its functionality (at least for me).  My usage is primarily with transceivers using a max of 5kHz deviation (and it's usually a bit lower than that), and it wouldn't be helpful at all while testing in narrowband mode (2.5kHz deviation). 

But at least with my setup I still can't seem to get any stable results even at roughly 4.5kHz deviation (which is the highest deviation I can get out of my transceiver).  I was able to get a much more stable visual display if I used 4kHz as my modulating frequency, though it's showing a weird component at the start of the trace which I don't believe is part of the signal.  But I'm still not getting stable deviation numbers.  I'll try to get some screenshots in the morning in case that helps diagnose my issue. 
 


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