Request for help to understand my plots from "first light" with my AD8302 interferometer board without aerials

[andrew....@googlemail.com]

Please can someone help me understand what I am seeing here!

 

https://astronomy.me.uk/first-light-of-ad8302-interferometer-board-without-aerials

 

Andy

[Marcus D. Leech]

Those boards have a fair amount of gain internally, so unless the board is well shielded from outside influence, it's
  going to be "seeing" a whack of "stuff".  These things have useful analog bandwidth up to about 2.7GHz, and there's
  an awful lot of "stuff" that the board can be seeing over this frequency range even with nothing connected to the inputs
  if it isn't shielded.

Even if the board is shielded, with gain ahead of it (the LaNAs), but without any band-limiting, it's going to be reacting
  to huge swaths of environmental noise.

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[Andrew Thornett]

There are 30MHz 1420Mhz filters just before the inputs go into the AD8302 board, which is itself surrounded by metal box

Andy

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Marcus D. Leech <patchv...@gmail.com>
Sent: Thursday, November 23, 2023 9:46:10 PM
To: andrew.thornett via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] Request for help to understand my plots from "first light" with my AD8302 interferometer board without aerials

 

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[Marcus D. Leech]

On 23/11/2023 20:09, 'Andrew Thornett' via Society of Amateur Radio Astronomers wrote:

There are 30MHz 1420Mhz filters just before the inputs go into the AD8302 board, which is itself surrounded by metal box

Andy

Hmmm.  That's a bit odd.  Might be useful to stick an RTLSDR on the back of those filters, with the LNAs turned on, etc, to
  look at the band edges to see if there are strong signals present.

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[Marcus D. Leech]

On 23/11/2023 20:09, 'Andrew Thornett' via Society of Amateur Radio Astronomers wrote:

There are 30MHz 1420Mhz filters just before the inputs go into the AD8302 board, which is itself surrounded by metal box

Andy

The other possibility is that your LNAs are oscillating with no antenna on the input.    Although I think you said you'd tried
  a terminal on the input of the LNAs and that didn't calm anything down?

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[duncan campbell-wilson]

My thoughts are terminate both inputs at the correlation board . Establish that phase is noisey and  all phase values are equally represented. Connect one arm of the interferometer to  a terminated LNA. What you need to look for is a discernible phase . If this is seen the then their is a signal leak into the other side of the interferometer.  The testing can be a painful process.

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[duncan campbell-wilson]

Power supply isolation maybe a source of internal cross correlation signal. Cross correlation is a very powerful investigative tool so systems need to be very clean in terms of RF leakage. 

[Andrew Thornett]

Thank you Duncan.

So.when you say terminate both inputs at phase board, do you mean put 50 Ohm dummy loads on both?

When you say "Establish that phase is noisey and  all phase values are equally represented", do.you mean thst the maximum amplitude on peaks on trace will be same?

And my apologies please could this further too "What you need to look for is a discernible phase . If this is seen the then their is a signal leak into the other side of the interferometer."?

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of duncan campbell-wilson <duncan.cam...@gmail.com>
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[Dave Typinski]

Hi Andrew,

The AD8302 spec sheet says the inputs need to be between -60 dBm and 0 dBm (at
50 ohms).

Leaving the inputs unterminated or terminated with dummy loads isn't going to
supply anywhere near -60 dBm to to the 8302. Perhaps the thing is just
freewheeling, having no signal strong enough to work with.

Suggest using a sig gen and power splitter to place a -50 dBm sine wave direct
to both 8302 inputs and see if you get a nice flat phase output voltage from the
device.

Then, try that same test with the amps & filters connected after reducing the
sig gen output to make up for the net gain of the amps & filters.
--
Dave

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[Andrew Thornett]

Grest info, Dave! Helps me understand it.

Can you recommend a cheap signal generator on amazon.co.uk that would do the job?

Andy

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Dave Typinski <dav...@typnet.net>
Sent: Friday, November 24, 2023 8:06:04 AM

To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Request for help to understand my plots from "first light" with my AD8302 interferometer board without aerials

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[Andrew Thornett]

And Dave can you point me to appropriate power splitter on amazon.co.uk?

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Dave Typinski <dav...@typnet.net>
Sent: Friday, November 24, 2023 8:06:04 AM
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Request for help to understand my plots from "first light" with my AD8302 interferometer board without aerials

 

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[Dave Typinski]

Not sure one can find that stuff on Amazon.

Suggest looking for a used HP 8648B or similar sig gen on ebay or a used
equipment dealer in the UK.

For the splitter, perhaps the Mini-Circuits ZESC-2-11 would do the job. Pretty
sure they will ship internationally.
--
Dave

On 11/24/23 04:21, 'Andrew Thornett' via Society of Amateur Radio Astronomers wrote:
> And Dave can you point me to appropriate power splitter on amazon.co.uk?
>

> Sent from Outlook for Android <https://aka.ms/AAb9ysg>
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> *From:* sara...@googlegroups.com <sara...@googlegroups.com> on behalf of
> Dave Typinski <dav...@typnet.net>
> *Sent:* Friday, November 24, 2023 8:06:04 AM
> *To:* sara...@googlegroups.com <sara...@googlegroups.com>
> *Subject:* Re: [SARA] Request for help to understand my plots from "first light"

> https://groups.google.com/d/msgid/sara-list/CWXP123MB3653569CC17C25F7F2FAEB38FFB8A%40CWXP123MB3653.GBRP123.PROD.OUTLOOK.COM
> <https://groups.google.com/d/msgid/sara-list/CWXP123MB3653569CC17C25F7F2FAEB38FFB8A%40CWXP123MB3653.GBRP123.PROD.OUTLOOK.COM?utm_medium=email&utm_source=footer>.

[Marcus D. Leech]

On 24/11/2023 10:04, Dave Typinski wrote:
> Not sure one can find that stuff on Amazon.
>
> Suggest looking for a used HP 8648B or similar sig gen on ebay or a
> used equipment dealer in the UK.
>
> For the splitter, perhaps the Mini-Circuits ZESC-2-11 would do the
> job.  Pretty sure they will ship internationally.
> --
> Dave

For this application a TV splitter will work just fine, TBH.

[Dave Typinski]

On 11/24/23 10:40, Marcus D. Leech wrote:
> On 24/11/2023 10:04, Dave Typinski wrote:
>> Not sure one can find that stuff on Amazon.
>>
>> Suggest looking for a used HP 8648B or similar sig gen on ebay or a used
>> equipment dealer in the UK.
>>
>> For the splitter, perhaps the Mini-Circuits ZESC-2-11 would do the job.
>> Pretty sure they will ship internationally.
>> --
>> Dave
> For this application a TV splitter will work just fine, TBH.

Good point. Normally one wouldn't want to mix 50 and 75 ohm parts, but for this
quick single-frequency test, the 20X more expensive 50 ohm splitter isn't
absolutely required.

On the other hand, if one us buying a $1k 50 ohm sig gen, one may as well get a
nice 50 ohm splitter to go with it.
--
Dave

[Andrew Thornett]

I think £1000 is too much for me

Andy

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Dave Typinski <dav...@typnet.net>

Sent: Friday, November 24, 2023 5:31:15 PM
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Request for help to understand my plots from "first light" with my AD8302 interferometer board without aerials

 

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[Lester Veenstra]

There are quite a number signal sources based on the  Analog Devices MAX2870 chip  that will serve as a much lower cost generator. These can be found on Amazon, and AliExpress for much less than an HP or R&S lab device.  Combine one of these sources with step attenuator, also low cost, same sources will allow bench testing of systems, and for that matter, antenna patterns.

 

For example:  MAX2870 Signal Generator 23.5MHz-6000MHz PLL Frequency Touching Screen LCD Display Radio Frequency Signal Source PC Software Controls  US$49.99

And

BECEN 60db SMA Push-Button Step attenuator,50 ohm ,DC to 2.5GHz  US$66

 

 

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)

les...@veenstras.com

 

452 Stable Ln

Keyser WV 26726 USA

 

GPS: 39.336826 N  78.982287 W (Google)

GPS: 39.33682 N  78.9823741 W (GPSDO)

 

 

Telephones:

Home:            +1-304-289-6057

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[Andrew Thornett]

Thanks - have ordered!

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Sent: Saturday, November 25, 2023 1:39:28 AM
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: RE: [SARA] Request for help to understand my plots from "first light" with my AD8302 interferometer board without aerials

 

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[Andrew Thornett]

Hi Lester,

Can I ask you about item below- is that in any way a better choice than the ones you suggest?

LATNEX RF-SG6 RF Explorer Signal Generator High Frequency HF FM Modulation Radio Frequency Oscillator Source CW Sweep Tracking Generator 6GHZ (24MHz - 6000MHz)

https://www.amazon.co.uk/dp/B07Z2RZ9HS/ref=sspa_mw_detail_0?ie=UTF8&psc=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWwp13NParams

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From: Andrew Thornett <andrew....@googlemail.com>
Sent: Saturday, November 25, 2023 1:48:27 AM
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[Jim Sky]

Andy, do you have one of the TinySA spectrum analyzers by chance? It has a mode allowing it to be used as a signal generator, something I only recently tried out, but was impressed with. If you don't have a TinySA, and decide to buy one get the Ultra model with bigger screen and wider range of frequency. 

Jim

On Friday, November 24, 2023 at 7:16:05 PM UTC-5 Andrew Thornett wrote:

I think £1000 is too much for me

Andy

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[andrew....@googlemail.com]

Hi Jim

Thanks for advice – didn’t have one but got one on order now! I can save £70 if happy to wait 3 weeks for it so I am waiting……

Andy

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[Lester Veenstra]

Contrary to title, to not see any modulation capability (FM)  so it noting more than the CW and sweeping sources below with more user friendly attenuator.  It was out of stock, so I could not see a UK price to judge value but the US  offer of USD 206

Is a bit steep for nice case.

Greetings from Negril Jamaica

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