Topics

Antuino - the antenna analyzer

Ashhar Farhan
 

peeps,

while trying to measure the swr on the cubesats, i figured i couldnt use any of the analyzers i had access to. they were simply too big to be stuffed inside a 10 cm cube. my simple resistive bridge was too insensitive for any reasonable work. so, i sat down and made an antenna analyzer from a spare raduino. 

the code is wobbly and just about enough to get my work done. it works on a superhet principle. this is not my clever idea, rahul had mentioned this approach taken by a russian builder. i havent seen the original design. it would be interesting if rahul or someone can point me in the right direction.

the code and a pdf of the circuit is on https://github.com/afarhan/antuino. i am attaching the circuit for the lazy bones.

have a great holiday and get some dx !!

- f

MVS Sarma
 

I gratefully acknowledge the latest sch and firmware, Fahan jee,
I had a golden opportunity to hear the circuit explanation during the 9th Dec 2018 eyeball meet of Lamakan amateur radio club  direct from you.
regards
sarma
vu3zmv
 


On Fri, Dec 28, 2018 at 9:58 AM Ashhar Farhan <farhanbox@...> wrote:
peeps,

while trying to measure the swr on the cubesats, i figured i couldnt use any of the analyzers i had access to. they were simply too big to be stuffed inside a 10 cm cube. my simple resistive bridge was too insensitive for any reasonable work. so, i sat down and made an antenna analyzer from a spare raduino. 

the code is wobbly and just about enough to get my work done. it works on a superhet principle. this is not my clever idea, rahul had mentioned this approach taken by a russian builder. i havent seen the original design. it would be interesting if rahul or someone can point me in the right direction.

the code and a pdf of the circuit is on https://github.com/afarhan/antuino. i am attaching the circuit for the lazy bones.

have a great holiday and get some dx !!

- f

Jerry Gaffke
 

Hmm.
Someday, you will have to tell us how it works.
"works on hetrodyne principle" does not quite do it.
Nor does digging around in your code.
That thing isn't on the HF bands, is it?

Curious that it takes all three clocks from the si5351 to measure SWR.
The Bruene bridge, MoniMatch, TandemMatch, and all those other bridges they sell
do it with zero clocks, and some can be quite a bit smaller than all of this.
What do P4 and P3 connect to?  
At what frequency is the antenna system operating?
At what frequency are the three si5351 clocks?
And last but not lest, what the devil is going on around that ADE-1 mixer?

Is that spare raduino now circling the earth, waiting to drop on our heads?
If we catch it, do we get to keep it?

Regardless, very curious, and very cool.

Jerry, KE7ER



On Thu, Dec 27, 2018 at 08:28 PM, Ashhar Farhan wrote:
peeps,
 
while trying to measure the swr on the cubesats, i figured i couldnt use any of the analyzers i had access to. they were simply too big to be stuffed inside a 10 cm cube. my simple resistive bridge was too insensitive for any reasonable work. so, i sat down and made an antenna analyzer from a spare raduino. 
 
the code is wobbly and just about enough to get my work done. it works on a superhet principle. this is not my clever idea, rahul had mentioned this approach taken by a russian builder. i havent seen the original design. it would be interesting if rahul or someone can point me in the right direction.
 
the code and a pdf of the circuit is on https://github.com/afarhan/antuino. i am attaching the circuit for the lazy bones.
 
have a great holiday and get some dx !!
 

Jerry Gaffke
 

My ADE-1 document just says that pins 1,4,5 are all ground, 
3 is RF, 6 is LO, and 2 is IF. out.
Your schematic suggests that 4 is only the "ground" for the RF port,
and is not connected to the other two ground pins internally.

I suppose R21,R29,R16, and an antenna on P3 would form a balanced
bridge when the antenna is 50 ohms, CLK1 is driving the antenna and the top of the bridge.
The ADE-1 RF port sees any imbalance across the bridge.
CLK2 into the LO port is 25mhz above (or below) CLK1.

Still no idea what CLK0 and P4 are up to.

Jerry


On Thu, Dec 27, 2018 at 09:35 PM, Jerry Gaffke wrote:
And last but not lest, what the devil is going on around that ADE-1 mixer?

 

Jerry,

I remember Farhan mentioning that the clock out of the Si chip is not clean and
will cause wrong readings due to harmonics. To solve this, mix down and pass
through a filter and then take the reading which will not have harmonics  reflection
factored in!

Raj


At 28-12-18, you wrote:
Hmm.
Someday, you will have to tell us how it works.
"works on hetrodyne principle" does not quite do it.
Nor does digging around in your code.
That thing isn't on the HF bands, is it?

Curious that it takes all three clocks from the si5351 to measure SWR.
The Bruene bridge, MoniMatch, TandemMatch, and all those other bridges they sell
do it with zero clocks, and some can be quite a bit smaller than all of this.
What do P4 and P3 connect to? 
At what frequency is the antenna system operating?
At what frequency are the three si5351 clocks?
And last but not lest, what the devil is going on around that ADE-1 mixer?

Is that spare raduino now circling the earth, waiting to drop on our heads?
If we catch it, do we get to keep it?

Regardless, very curious, and very cool.

Jerry, KE7ER



On Thu, Dec 27, 2018 at 08:28 PM, Ashhar Farhan wrote:
peeps,
 
while trying to measure the swr on the cubesats, i figured i couldnt use any of the analyzers i had access to. they were simply too big to be stuffed inside a 10 cm cube. my simple resistive bridge was too insensitive for any reasonable work. so, i sat down and made an antenna analyzer from a spare raduino.
 
the code is wobbly and just about enough to get my work done. it works on a superhet principle. this is not my clever idea, rahul had mentioned this approach taken by a russian builder. i havent seen the original design. it would be interesting if rahul or someone can point me in the right direction.
 
the code and a pdf of the circuit is on https://github.com/afarhan/antuino. i am attaching the circuit for the lazy bones.
 
have a great holiday and get some dx !!

Ashhar Farhan
 

jerry,

first, thanks. there is substantially your code in there.

second, onto the circuit. it uses two clocks. not three. the third is a spare output. more on that later.

the circuit here uses a resistive return loss bridge. the clock 1 drives the bridge through the R22 to a low level of -10dbm. If the bridge is perfectly balanced (that is, the antenna, R21, R29, R16, all the four are the same ohms), then, there will be no RF developed across pins 3 and 4 of the ADE mixer. Under ideal match conditions, there is no RF across the R26. As the mismatch increases, so does the RF across R26. 

We could directly detect the voltage across the R26 with a diode detector. This is quite a popular configuration with most of the simple resistive kind of SWR bridges (like the one designed by Dan Tayloe). This simplicity comes at a cost. The problem is that the detector responds to all the RF between the arms. For instance, if another ham down the block starts to transmit, that energy will show up across the R26 and you will get crazy SWR. I had that problem with broadcast FM showing up on my 7 MHz dipole! Even if there was no RFI from elsewhere, harmonics and spurs from your own transmission can show false readings. 

Here is an example: a 7 MHz transmitter with a 14 Mhz harmonic that is 20 db down is connected to a 7 MHz dipole. The dipole is perfectly tuned to show 1:1 SWR, hence, it should show no RF across R26. However, as the antenna is reflecting back the 14 MHz energy, the 14 MHz shows up across the R26.

What's the solution to get a clean dip?The solution is to substitute a simple detector like a diode detector with a simple receiver that is tuned exactly to the frequency that you want to measure the antenna at.

So, the ADE-1 mixer, Q2, Q1 together form a very simple superhet receiver with 25 MHz IF andCLK2 as the local oscillator. The RF at the IF is directly detected and converted to db range with the AD8307. This simple configuration makes this a very powerful instrument.

Here are things you can do with it:
1. Switch off the CLK1, now you have a receiver that can very accurately measure RF levels at any specific frequency in db range. For instance, you connected your transmitter with a suitable RF attenuator to P3, you can tune to various harmonics and measure them very accurately. If you inject a two tone signal into an amplifier, you could easily measure the IMD and IIP3. 
2. With the CLK1 on, the instrument now measures the return loss. you can measure the SWR of an antenna, S11 parameters of an amplifier, filter, etc.
3. With CLK1 off, CLK 2 on, the CLK2 can now tune to the frequency tuned in by the receiver's LO (CLK0). By connecting a device/filter between P3 and P4, you can sweep it to measure the gain, frequency reponse.
4. As the diode mixer (ADE-1) has harmonic response, a local oscillator at 135 MHz, will also convert a 430 MHz signal into 25 MHz IF (430 - (135 x 3)). This is possible because we are driving the diode mixer with a square wave from the Si5351 and the local oscillator at 135 MHz also has a 405 Mhz harmonic in it. Hence, the range of this instrument extends to UHF.

The ADE-1 mixer is quite similar to the ubitx mixers. You could even use ubitx kind of discrete version of a diode mixer, it doesn't work too well beyond 50 MHz. The pins 4 and 3 of the ADE-1 are the primary winding of the RF-input side transformer. The documentation recommends that we must ground 4, but that is not essential. We need a differential drive between those two pins, that is what the bridge provides anyway. 

73, f

On Fri, Dec 28, 2018 at 11:05 AM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Hmm.
Someday, you will have to tell us how it works.
"works on hetrodyne principle" does not quite do it.
Nor does digging around in your code.
That thing isn't on the HF bands, is it?

Curious that it takes all three clocks from the si5351 to measure SWR.
The Bruene bridge, MoniMatch, TandemMatch, and all those other bridges they sell
do it with zero clocks, and some can be quite a bit smaller than all of this.
What do P4 and P3 connect to?  
At what frequency is the antenna system operating?
At what frequency are the three si5351 clocks?
And last but not lest, what the devil is going on around that ADE-1 mixer?

Is that spare raduino now circling the earth, waiting to drop on our heads?
If we catch it, do we get to keep it?

Regardless, very curious, and very cool.

Jerry, KE7ER



On Thu, Dec 27, 2018 at 08:28 PM, Ashhar Farhan wrote:
peeps,
 
while trying to measure the swr on the cubesats, i figured i couldnt use any of the analyzers i had access to. they were simply too big to be stuffed inside a 10 cm cube. my simple resistive bridge was too insensitive for any reasonable work. so, i sat down and made an antenna analyzer from a spare raduino. 
 
the code is wobbly and just about enough to get my work done. it works on a superhet principle. this is not my clever idea, rahul had mentioned this approach taken by a russian builder. i havent seen the original design. it would be interesting if rahul or someone can point me in the right direction.
 
the code and a pdf of the circuit is on https://github.com/afarhan/antuino. i am attaching the circuit for the lazy bones.
 
have a great holiday and get some dx !!
 

Jerry Gaffke
 

The AQRP Vector Impedance Analyzer, kit #25 towards the bottom of this webpage:
    https://www.qsl.net/k5bcq/Kits/Kits.html
does something similar, but at audio frequencies. 
K5BCQ also did the AGC and PopFix kits for us.

Drives the antenna with a square wave  from an si5351 at the target frequency, detects the
voltage and current at the antenna port using two SA612 mixers with a local oscillator
that is 4khz away from the target frequency.  The two resulting audio channels (for voltage
and current, relative phase is important) are digitized and inspected by DSP algorithms
on an ARM processor.  The algorithms filter the 4khz audio for inspection, discarding 
all the crud due to harmonics and other random signals.

The W5BIG AIM VIA does much the same thing, and comes with a very clear description:
     http://w5big.com/QST_Article.pdf
Used DDS chips because the precise PLL tuning at reasonable cost offered by the si5351
and friends was not yet available.  

The AQRP VIA has managed to extend the technique for use as a 2 port network analyzer.
And uses si5351 harmonics to operate up through 440mhz, similar to your creation.

Jerry, KE7ER

Jerry Gaffke
 

Farhan,

OK. so best thought of as a basic spectrum analyzer
Has a return loss bridge up front to measure SWR.
Not weird at all.
But does look very cheap and buildable.

I've been thinking of building a spectrum analyzer along those lines for a couple years now.
Snow on the ground here and it's darn cold, could be a good time for it.

The fact that this thing had to be small enough to fit into the cubesat
suggests it's still in there, flying madly about the earth.
And that you are using it to verify that some 440mhz antenna 
didn't get eaten by space aliens?

Jerry


On Thu, Dec 27, 2018 at 10:28 PM, Ashhar Farhan wrote:
The circuit here uses a resistive return loss bridge. the clock 1 drives the bridge through the R22 to a low level of -10dbm. If the bridge is perfectly balanced (that is, the antenna, R21, R29, R16, all the four are the same ohms), then, there will be no RF developed across pins 3 and 4 of the ADE mixer. 
..........
So, the ADE-1 mixer, Q2, Q1 together form a very simple superhet receiver with 25 MHz IF andCLK2 as the local oscillator. The RF at the IF is directly detected and converted to db range with the AD8307. This simple configuration makes this a very powerful instrument.

Ashhar Farhan
 

jerry,

i built it so i could stuff it inside the cubesat to measure the antenna. an external spectrum analyzer and its cables were upsetting the RF model hence, i needed something that could read the return loss sitting inside the cubesat. then, i borrowed by daughter's DSLR with a monsterous tele lens and sat 100 meters away to read the the LCD display as it swept through the range. 
the analyzer was removed once we knew the correct dimensions and the actual payload went inside the bird.
- f

On Fri, Dec 28, 2018 at 1:19 PM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Farhan,

OK. so best thought of as a basic spectrum analyzer
Has a return loss bridge up front to measure SWR.
Not weird at all.
But does look very cheap and buildable.

I've been thinking of building a spectrum analyzer along those lines for a couple years now.
Snow on the ground here and it's darn cold, could be a good time for it.

The fact that this thing had to be small enough to fit into the cubesat
suggests it's still in there, flying madly about the earth.
And that you are using it to verify that some 440mhz antenna 
didn't get eaten by space aliens?

Jerry

On Thu, Dec 27, 2018 at 10:28 PM, Ashhar Farhan wrote:
The circuit here uses a resistive return loss bridge. the clock 1 drives the bridge through the R22 to a low level of -10dbm. If the bridge is perfectly balanced (that is, the antenna, R21, R29, R16, all the four are the same ohms), then, there will be no RF developed across pins 3 and 4 of the ADE mixer. 
..........
So, the ADE-1 mixer, Q2, Q1 together form a very simple superhet receiver with 25 MHz IF andCLK2 as the local oscillator. The RF at the IF is directly detected and converted to db range with the AD8307. This simple configuration makes this a very powerful instrument.

K5ESS
 

Jerry,

Despite the data sheet implying that pins 1,4,and 5 are tied together internally only pins 1 and 5 are tied together.  I just examined one to confirm this.

Mike

K5ESS

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Thursday, December 27, 2018 11:55 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Antuino - the antenna analyzer

 

My ADE-1 document just says that pins 1,4,5 are all ground, 
3 is RF, 6 is LO, and 2 is IF. out.
Your schematic suggests that 4 is only the "ground" for the RF port,
and is not connected to the other two ground pins internally.

I suppose R21,R29,R16, and an antenna on P3 would form a balanced
bridge when the antenna is 50 ohms, CLK1 is driving the antenna and the top of the bridge.
The ADE-1 RF port sees any imbalance across the bridge.
CLK2 into the LO port is 25mhz above (or below) CLK1.

Still no idea what CLK0 and P4 are up to.

Jerry

On Thu, Dec 27, 2018 at 09:35 PM, Jerry Gaffke wrote:

And last but not lest, what the devil is going on around that ADE-1 mixer?

Arv Evans
 

Farhan

Very good RF analyzer design and build.  Is that going to become a BITX-Labs product
at some future time? 

Happy New Year!

Arv  K7HKL
_._


On Thu, Dec 27, 2018 at 9:28 PM Ashhar Farhan <farhanbox@...> wrote:
peeps,

while trying to measure the swr on the cubesats, i figured i couldnt use any of the analyzers i had access to. they were simply too big to be stuffed inside a 10 cm cube. my simple resistive bridge was too insensitive for any reasonable work. so, i sat down and made an antenna analyzer from a spare raduino. 

the code is wobbly and just about enough to get my work done. it works on a superhet principle. this is not my clever idea, rahul had mentioned this approach taken by a russian builder. i havent seen the original design. it would be interesting if rahul or someone can point me in the right direction.

the code and a pdf of the circuit is on https://github.com/afarhan/antuino. i am attaching the circuit for the lazy bones.

have a great holiday and get some dx !!

- f

MadRadioModder
 

This could easily be turned into a simple SA.  I’ll bet Kees already has the boards mocked up…

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Ashhar Farhan
Sent: Thursday, December 27, 2018 10:28 PM
To: bitx20@groups.io
Subject: [BITX20] Antuino - the antenna analyzer

 

peeps,

 

while trying to measure the swr on the cubesats, i figured i couldnt use any of the analyzers i had access to. they were simply too big to be stuffed inside a 10 cm cube. my simple resistive bridge was too insensitive for any reasonable work. so, i sat down and made an antenna analyzer from a spare raduino. 

 

the code is wobbly and just about enough to get my work done. it works on a superhet principle. this is not my clever idea, rahul had mentioned this approach taken by a russian builder. i havent seen the original design. it would be interesting if rahul or someone can point me in the right direction.

 

the code and a pdf of the circuit is on https://github.com/afarhan/antuino. i am attaching the circuit for the lazy bones.

 

have a great holiday and get some dx !!

 

- f


Virus-free. www.avg.com

--

…_. _._

Jerry Gaffke
 

It already is a simple SA.
Just shut down CLK1 coming out of the SI5351.
Includes a tracking generator at CLK0/P4.

Jerry, KE7ER


On Fri, Dec 28, 2018 at 10:41 AM, MadRadioModder wrote:
This could easily be turned into a simple SA. 

Ashhar Farhan
 

the challenge would be to eliminate the if image. this could be done when you sweep to both sides and eliminate the image reading in software. here is an example :

1. lets imagine that there is a signal at 10 mhz. for this, we set the local oscillator at 35 mhz (as the IF is at 25 mhz). how can we be certain that the signal we are resolving is not at 60mhz (60mhz - 35 mhz = 25 mhz)?
2. we can take a second reading by setting the local oscillator at 85 mhz. in this csse, thr 60 mhz response (if any) should show up. else we can confirm that the signal we resolved in step 1 is indeed a 10 mhz signal.

one has to be aware that such a system will be slow. lets imagine that you have to sweep 30 mhz. the crystal filter is 10 khz wide. hence, we will need 30,000/5 = 6000 readings. if we can get, 100 readings a second, this will take a minute to complete the scan. an alternative would be to have two filters, a crystal filter and a 4 or even 5 section LC filter at around 12 mhz. we could switch to the lc filter for large sweeps. my specan circuit has a suitable design.

you are aking what happens if there was signal at 110 mhz in step two? aaaah, you tell me!

- f

On Sat, 29 Dec 2018, 00:48 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
It already is a simple SA.
Just shut down CLK1 coming out of the SI5351.
Includes a tracking generator at CLK0/P4.

Jerry, KE7ER

On Fri, Dec 28, 2018 at 10:41 AM, MadRadioModder wrote:
This could easily be turned into a simple SA. 

Jerry Gaffke
 

I was assuming the Antuino would have a set of front end filters for each region of interest.
Though the 25mhz IF is kind of low for this to be convenient.

Arv's DC receiver as a spectrum analyzer is also worth considering. 

I've had parts here for a year or so to build a 0-55mhz spectrum analyzer 
around two of the PX1002 86.85mhz SAW filters.  
Seeing the Antuino, I'm inspired enough to have parts splayed out on my workbench,
an enclosure selected, am about to cut the bare PC board to fit. 
Will build ugly style, use 3/4" copper pipe cut into 1/4" high cylinders
to provide a shield for each section, bolt a plate over the top once it works.
Signals going off to the next shielded section will have a wire through a hole
in the board to to where it's held down to the back groundplane using copper tape. 
So almost coax, the one inch runs short enough that impedance won't be an issue.
But by selecting appropriate wire diameter and insulation thickness, might hit 50 ohms.

And if it works, maybe add another stage up front using a 915mhz SAW filter.
That first VFO would have to do something like 915 to 1500mhz.
Either a clock doubler on the 1000mhz si5340, or perhaps the si549.
But of course, I'll have a hard time looking at that stuff when it doesn't work.

Anybody have a feel for how well the cheap $200 laptop based spectrum analyzers
are doing?  Is there much reason to homebrew other than as a hobby?
How do those $200 units compare to a Rigol SA?

Jerry, KE7ER


On Fri, Dec 28, 2018 at 08:05 PM, Ashhar Farhan wrote:
the challenge would be to eliminate the if image. this could be done when you sweep to both sides and eliminate the image reading in software. here is an example :
 
1. lets imagine that there is a signal at 10 mhz. for this, we set the local oscillator at 35 mhz (as the IF is at 25 mhz). how can we be certain that the signal we are resolving is not at 60mhz (60mhz - 35 mhz = 25 mhz)?
2. we can take a second reading by setting the local oscillator at 85 mhz. in this csse, thr 60 mhz response (if any) should show up. else we can confirm that the signal we resolved in step 1 is indeed a 10 mhz signal.
 
one has to be aware that such a system will be slow. lets imagine that you have to sweep 30 mhz. the crystal filter is 10 khz wide. hence, we will need 30,000/5 = 6000 readings. if we can get, 100 readings a second, this will take a minute to complete the scan. an alternative would be to have two filters, a crystal filter and a 4 or even 5 section LC filter at around 12 mhz. we could switch to the lc filter for large sweeps. my specan circuit has a suitable design.
 
you are aking what happens if there was signal at 110 mhz in step two? aaaah, you tell me!
 
- f

Ashhar Farhan
 

jerry, 
we need 80 db dynamic range for useful work with specans. at 6db per bit, this pushes for a 14 bit dac or better. these, including thr rtl-sdr family are hardly useful.
for a radio amateur, a double conversion specan can easily be buily for less than $100 providing as good a performance as thr professional ones with limited range and bandwidth selection.
with 110 mhz as the first IF and 12 mhz as the second, onr can span 0-70 mhz easily 
- f

On Sat, 29 Dec 2018, 11:16 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
I was assuming the Antuino would have a set of front end filters for each region of interest.
Though the 25mhz IF is kind of low for this to be convenient.

Arv's DC receiver as a spectrum analyzer is also worth considering. 

I've had parts here for a year or so to build a 0-55mhz spectrum analyzer 
around two of the PX1002 86.85mhz SAW filters.  
Seeing the Antuino, I'm inspired enough to have parts splayed out on my workbench,
an enclosure selected, am about to cut the bare PC board to fit. 
Will build ugly style, use 3/4" copper pipe cut into 1/4" high cylinders
to provide a shield for each section, bolt a plate over the top once it works.
Signals going off to the next shielded section will have a wire through a hole
in the board to to where it's held down to the back groundplane using copper tape. 
So almost coax, the one inch runs short enough that impedance won't be an issue.
But by selecting appropriate wire diameter and insulation thickness, might hit 50 ohms.

And if it works, maybe add another stage up front using a 915mhz SAW filter.
That first VFO would have to do something like 915 to 1500mhz.
Either a clock doubler on the 1000mhz si5340, or perhaps the si549.
But of course, I'll have a hard time looking at that stuff when it doesn't work.

Anybody have a feel for how well the cheap $200 laptop based spectrum analyzers
are doing?  Is there much reason to homebrew other than as a hobby?
How do those $200 units compare to a Rigol SA?

Jerry, KE7ER


On Fri, Dec 28, 2018 at 08:05 PM, Ashhar Farhan wrote:
the challenge would be to eliminate the if image. this could be done when you sweep to both sides and eliminate the image reading in software. here is an example :
 
1. lets imagine that there is a signal at 10 mhz. for this, we set the local oscillator at 35 mhz (as the IF is at 25 mhz). how can we be certain that the signal we are resolving is not at 60mhz (60mhz - 35 mhz = 25 mhz)?
2. we can take a second reading by setting the local oscillator at 85 mhz. in this csse, thr 60 mhz response (if any) should show up. else we can confirm that the signal we resolved in step 1 is indeed a 10 mhz signal.
 
one has to be aware that such a system will be slow. lets imagine that you have to sweep 30 mhz. the crystal filter is 10 khz wide. hence, we will need 30,000/5 = 6000 readings. if we can get, 100 readings a second, this will take a minute to complete the scan. an alternative would be to have two filters, a crystal filter and a 4 or even 5 section LC filter at around 12 mhz. we could switch to the lc filter for large sweeps. my specan circuit has a suitable design.
 
you are aking what happens if there was signal at 110 mhz in step two? aaaah, you tell me!
 
- f

Jerry Gaffke
 

Tacking an AD8307 into a uBitx between the 12mhz crystal filter and the demodulator
could make it useful as a spectrum analyzer.  
Given the better crystal filter and the higher first IF of the uBitx,
should be a better choice than an Antuino.
Though may not fit into a cubesat.

The AD8307 is $13 each up on Mouser.
Ebay sellers have them at about $0.30 each.
The ebay parts reportedly work well enough, but may be a bit out of spec
with regard to calibration.
  
Jerry


On Fri, Dec 28, 2018 at 09:46 PM, Jerry Gaffke wrote:
I was assuming the Antuino would have a set of front end filters for each region of interest.
Though the 25mhz IF is kind of low for this to be convenient.

Ashhar Farhan
 

The SMD AD8307 was selling for two dollars on mouser, then suddenly upped the price. 

- f

On Sat, Dec 29, 2018 at 11:54 AM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Tacking an AD8307 into a uBitx between the 12mhz crystal filter and the demodulator
could make it useful as a spectrum analyzer.  
Given the better crystal filter and the higher first IF of the uBitx,
should be a better choice than an Antuino.
Though may not fit into a cubesat.

The AD8307 is $13 each up on Mouser.
Ebay sellers have them at about $0.30 each.
The ebay parts reportedly work well enough, but may be a bit out of spec
with regard to calibration.
  
Jerry

On Fri, Dec 28, 2018 at 09:46 PM, Jerry Gaffke wrote:
I was assuming the Antuino would have a set of front end filters for each region of interest.
Though the 25mhz IF is kind of low for this to be convenient.

 

Must be following this group!

Raj

At 29-12-18, you wrote:
The SMD AD8307 was selling for two dollars on mouser, then suddenly upped the price.Â

- f

On Sat, Dec 29, 2018 at 11:54 AM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io > wrote:
Tacking an AD8307 into a uBitx between the 12mhz crystal filter and the demodulator
could make it useful as a spectrum analyzer. Â
Given the better crystal filter and the higher first IF of the uBitx,
should be a better choice than an Antuino.
Though may not fit into a cubesat.

The AD8307 is $13 each up on Mouser.
Ebay sellers have them at about $0.30 each.
The ebay parts reportedly work well enough, but may be a bit out of spec
with regard to calibration.
 Â
Jerry

On Fri, Dec 28, 2018 at 09:46 PM, Jerry Gaffke wrote:
I was assuming the Antuino would have a set of front end filters for each region of interest.
Though the 25mhz IF is kind of low for this to be convenient.

Ian vk2ama
 

I see the Antuino was officially released at FDIM. Anyone know how much it will be to the rest of us?