Date   
Re: Antuino - the antenna analyzer

 

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 !!

Re: Antuino - the antenna analyzer

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 !!
 

Bitx40 - Not Transmitting #bitx40help #bitx40

Gary.ingle@...
 

Bitx40 - was working, but now does not transmit audio.

The device was working well with many QSOs on 40m.
All of a sudden it does not transmitt any audio.
Receiving is excellent.

To test or trouble shoot I did the following.
I attached a rf power meter to the rf out and noted that on transmission the needel jumped up initially and immediatly dropped to nil.
I suspected the microphone so I replaced it and got the same result.

It seems as though the audio is not getting into the system to trigger the carrier signal and trigger the transmitter.
(I have very limited knoledge so may be off, but this is my assumption)

I also replaced the main board (not audrino and LCD) as I had a spare - same results

Does any one have any ideas on what to test or how to trouble shoot further.

Regards
Gary
ZS5GI

Re: Antuino - the antenna analyzer

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

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Jerry Gaffke
 

That sounds like a broken mike connector.

Since it receives, the si5351 on the Raduino is doing everything it needs to on transmit.

When the Bitx40 transmits, it switches off power to the receiver audio amp
and turns on power to the transmitter audio amp for the mike.
This switching of power causes a quick surge of audio signal into the modulator
as the caps charge, and causes the characteristic Bitx pop which you see
on the meter.  So the transmitter is working from the modulator on out to the antenna.
All that's left is the mike amp, the mike, and the wires between.

Since you replaced the main board (and thus the mike amp) and also replaced the mike,
that leaves us with just the wires between.  Or perhaps you now have two bad mikes?

Could try driving the mike amp (or even the modulator directly) with some other source of audio.
Mike amp wants to see maybe 50mv pk-to-pk going in from the mike.

Jerry, KE7ER


On Thu, Dec 27, 2018 at 10:53 PM, <Gary.ingle@...> wrote:
Bitx40 - was working, but now does not transmit audio.

The device was working well with many QSOs on 40m.
All of a sudden it does not transmitt any audio.
Receiving is excellent.

To test or trouble shoot I did the following.
I attached a rf power meter to the rf out and noted that on transmission the needel jumped up initially and immediatly dropped to nil.
I suspected the microphone so I replaced it and got the same result.

It seems as though the audio is not getting into the system to trigger the carrier signal and trigger the transmitter.
(I have very limited knoledge so may be off, but this is my assumption)

I also replaced the main board (not audrino and LCD) as I had a spare - same results

Does any one have any ideas on what to test or how to trouble shoot further.

Regards
Gary
ZS5GI

Re: Antuino - the antenna analyzer

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.

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Gary.ingle@...
 

Thank you , Jerry.

I am going to try a completly new mike, including the wires to the jumper on the main board.

I also thought that I could try a CW transmission test if I wire up the CW keyer. ???

PS with regards to the Pop sound that when transmitting, it is not as loud as it used to be.
When i key the PTT it does switch off the receiving and I can hear a sort of a click sound as the speaker goes quiet.
I suppos this is because the audio transmitt is not making it through.

Thank you for your help so far.

I am a beginner on the electronics side with only self taught skills.

73
Gary
ZS5GI

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Timothy Fidler
 

Gary , JG has done a v good job of pointing out where you are at the moment. My tuppence worth and this is not very systematic is that if relay K1 has failed or the PTT line is not getting earthed properly  then you would see Rx and no Tx.  This could be from the relay not getting power or the relay failing in the coil (or mechanically) or  one of the components across the relay coil being in partial short and stealing power from the coil (unlikely as for this to be valid there would have to be a common decent resistance somewhere to cause the voltage to pull down.... but then this is all magic - it worked, it don't work. Electrons have changed their mind) .   You could first check power is avail to the relay K1 (not K2)

http://www.hfsignals.com/index.php/2017/11/23/bitx40-circuit-description/

And if it is then put a screwdriver on the case and to your ear  and listen to  hear it pull in as PTT goes low.  (this crudity  avoids probing the PCB too much ) .  My guess is it may not.  If it does then you need to check the Tx  line is getting power.  If yes, then it was a good idea at the time and the best idea is to fish around on the site in particular the repository run by Mike to see where the list of voltage test points and voltages is.  Mostly these relate to uBitx but you might find a Bitx40 one.   Good luck 

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Timothy Fidler
 

On second thoughts, you replaced the main  board ( I re read earlier post) . The chance of having two bad K1 relays seems remote - depending on what voltage you are running the thing on and how much use they have had.

2. Bear in mind ONLY a electret,  aka ceramic mike insert will work with this Bitx40 board as it stands.  If you replaced the microphone with a dynamic microphone as part of the testing ,  it won't work. (The circuit feeds out a low dc voltage to the microphone insert which the Dynamic Microphone does NOT want to see.) If you went.  Problem - > change to Dyna mike,  Problem remains,  ->change out PCB but retain second mike , I can see  where this is heading. (?)

Re: Antuino - the antenna analyzer

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.

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Gary.ingle@...
 

Thank you , Timothy

I am not using a Dynamic mike, I am using the small electret mike as was supplied with the kit.
I make up the mic with a plastic enclosure and a switch for the PTT.
4 wires, 2 for the PTT and 2 for the Mic.

Just a thought - how important is polarity on the mic ? (could it be that I have switched the Pos and Neg ??)

Have been running the rig on a 13.8 DCV regulated power supply with a 2amp fuse.

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Jakobus van der Merwe
 

Yes it is polarity concious. If you look at the capsule 2 connection pads, you will see that one of them have tracks to the casing. That is the negative one. The one that has no tracks to the casing is the positive one. 


On Fri, 28 Dec 2018, 11:16 Gary.ingle via Groups.Io <Gary.ingle=icloud.com@groups.io> wrote:
Thank you , Timothy

I am not using a Dynamic mike, I am using the small electret mike as was supplied with the kit.
I make up the mic with a plastic enclosure and a switch for the PTT.
4 wires, 2 for the PTT and 2 for the Mic.

Just a thought - how important is polarity on the mic ? (could it be that I have switched the Pos and Neg ??)

Have been running the rig on a 13.8 DCV regulated power supply with a 2amp fuse.

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Gary.ingle@...
 

Thank you, Jakobus

I am at the office at the moment.
I will check polarity as soon as i get home

Regards

Gary
ZS5GI

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Timothy Fidler
 

Polarity it critical.

There is a small Linear IC equiv approx to  a u741 built into the mic insert.   Generally one of the mic solder tabs on the back will  be marked with a posittive to show correct polarity. Your mileage may vary.

If the mic insert has been reverse powered it may be toasted (there are ways to test this depending on what test gear you have) .  It may well depend on the manufacturer. Some may install a protection diode, some not.

If you wired it  exactly the same way as the previous insert assuming the back solder tabs looked the same you should be fine - they are generally build to the same pattern.  Unless you have photos of what you did originally Red to which terminal etc,  it is surprising how tricky memory can be. 

 

Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 CB #2885, 
Telephone Whangarei   022  691 8405
e: Engstr@...



----- Original Message -----
From:
BITX20@groups.io

To:
<BITX20@groups.io>
Cc:

Sent:
Fri, 28 Dec 2018 01:16:00 -0800
Subject:
Re: [BITX20] Bitx40 - Not Transmitting #bitx40help #bitx40


Thank you , Timothy

I am not using a Dynamic mike, I am using the small electret mike as was supplied with the kit.
I make up the mic with a plastic enclosure and a switch for the PTT.
4 wires, 2 for the PTT and 2 for the Mic.

Just a thought - how important is polarity on the mic ? (could it be that I have switched the Pos and Neg ??)

Have been running the rig on a 13.8 DCV regulated power supply with a 2amp fuse.

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Timothy Fidler
 

On a related matter, the  heat sink of the IRF 510 on this tcvr and also on the uBitx  is live to ground ( It's a feature !!) Bear that in mind when working on it or casing it.  The Fuse on the supply line is good but it is likely the IRF will be destroyed first if the heat sink touches ground (current will flow  from the PSU to the Drain , out the tab on the case ,the Heat sink and to GND).  

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

Gary.ingle@...
 

Thank you, Timothy

It seems that the mic may be the underlying cause and if I have connected it in reverse polarity I may have damaged it.
Then testing with a damaged mic has invalidated all the tests performed
I will go and purchase a new one as they are quite cheap (ZAR 12)
I will double check the polarity on connecting it up.

Thank you for the tip on the positive heat sink.

Re: Bitx40 - Not Transmitting #bitx40help #bitx40

 

Electret and Ceramic are two different types AFAIK. Electret is not AKA ceramic.


At 28-12-18, you wrote:

On second thoughts, you replaced the main  board ( I re read earlier post) . The chance of having two bad K1 relays seems remote - depending on what voltage you are running the thing on and how much use they have had.

2. Bear in mind ONLY a electret,  aka ceramic mike insert will work with this Bitx40 board as it stands.  If you replaced the microphone with a dynamic microphone as part of the testing ,  it won't work. (The circuit feeds out a low dc voltage to the microphone insert which the Dynamic Microphone does NOT want to see.) If you went.  Problem - > change to Dyna mike,  Problem remains,  ->change out PCB but retain second mike , I can see  where this is heading. (?)

uBITXv4 for sale #ubitx

 

I have too many radios! (like 6 transceivers, including another uBITX)  This is a version 4 uBITX in a nice case (Fry's).  It has a 2.8" Nextion display, AGC/S meter, Axicom relays, and an LM386 audio amp. (The original audio is all there, just not loud enough for me) Includes power cord and mike. I used it on FT8 and SSB.  Asking $199, which includes USPS Priority shipping CONUS only.  Thanks, Jim W0CHL

Re: uBITXv4 for sale #ubitx

Bill Cromwell <wrcromwell@...>
 

Hi Jim,

There is no need any more to restrict sales to the 48 CONtigious United States via USPS. The priority and flat rate shipping is good for ALL states and any US territories. That includes the states if Hawaii and Alaska as well as places like Guam (US Territory). Any places that as a USPS post office address (including APO and FPO addresses). You might say something like "USPS postal addresses only". Saying "CONUS only" limits your sale opportunities without any "safety" benefit to you.

I have sent parts to US personnel on Guam way out there over the Pacific Ocean in USPS Priority Mail Flat-Rate box with *NO* issues. It's 2018 - almost 2019. Not 1948. I don't want to sell or send to non US locations either.

Happy New Year and 73,

Bill KU8H

On 12/28/18 8:46 AM, Jim Reagan wrote:
I have too many radios! (like 6 transceivers, including another uBITX) This is a version 4 uBITX in a nice case (Fry's).  It has a 2.8" Nextion display, AGC/S meter, Axicom relays, and an LM386 audio amp. (The original audio is all there, just not loud enough for me) Includes power cord and mike. I used it on FT8 and SSB.  Asking $199, which includes USPS Priority shipping CONUS only.  Thanks, Jim W0CHL
--
bark less - wag more

Re: uBITXv4 for sale #ubitx

Bob Villa
 


Hi Jim:

I am outside CoNus ( Puerto Rico) and would like to buy it

Miguel WP4ZI

On Fri, Dec 28, 2018 at 10:14, Bill Cromwell
<wrcromwell@...> wrote:
Hi Jim,

There is no need any more to restrict sales to the 48 CONtigious United
States via USPS. The priority and flat rate shipping is good for ALL
states and any US territories. That includes the states if Hawaii and
Alaska as well as places like Guam (US Territory). Any places that as a
USPS post office address (including APO and FPO addresses). You might
say something like "USPS postal addresses only". Saying "CONUS only"
limits your sale opportunities without any "safety" benefit to you.

I have sent parts to US personnel on Guam way out there over the Pacific
Ocean in USPS Priority Mail Flat-Rate box with *NO* issues. It's 2018 -
almost 2019. Not 1948. I don't want to sell or send to non US locations
either.

Happy New Year and 73,

Bill  KU8H

On 12/28/18 8:46 AM, Jim Reagan wrote:
> I have too many radios! (like 6 transceivers, including another uBITX) 
> This is a version 4 uBITX in a nice case (Fry's).  It has a 2.8" Nextion
> display, AGC/S meter, Axicom relays, and an LM386 audio amp. (The
> original audio is all there, just not loud enough for me) Includes power
> cord and mike. I used it on FT8 and SSB.  Asking $199, which includes
> USPS Priority shipping CONUS only.  Thanks, Jim W0CHL


--
bark less - wag more