Date   
Re: Searching for IMD

Glenn
 

Ashhar, I basically did this visually, using the Scope as a quick check between the two versions.

 I am aware of the Rule of Thumb about the IIP3 being 15-16dB above the 1db compression point.  

I will do a more accurate check using the SA tomorrow when i have more time available.

glenn


On Sat, Sep 15, 2018 at 04:05 PM, Ashhar Farhan wrote:
glen, you can do this,
 
find out, accurately, the gain of the amps at very low input levels.
Now, keep increasing the drive level until you see the gain dip by 1 db.
that is the compression point. For bipolar device amplifiers, the IIP3 will be about 15 above that point.
 
- f

On Sat, Sep 15, 2018 at 10:14 AM, Glenn <glennp@...> wrote:
Post 59439 is partly incorrect.  Just after I posted mentioning the visible clipping I realised, stupid me, was measuring gain during clipping which of course compresses the result.

I deleted that post. And have attached the new plots where you can see the  gain difference between uBITX and Hayward version. This obviously partly accounts for the difference in input levels before output clipping occurs. The biasing arrangement gives different Iq also.  Gain is reduced about  4dB in the Hayward version I built over uBITX. It now accords more closely also with  his test results of 15.5dB I get 16dB at 30MHz.

Haywards paper gives some values for varying the gain to other values also.







deleted this:-
On Sat, Sep 15, 2018 at 12:16 PM, Glenn wrote:
Hi Ashhur,
I just built up a proto of both versions on vero board.

As a rough check of IP3, since I am not set up to do proper measurement of IP3, I found that the 'visible distortion' of the Hayward version occurs about 10dB higher than the uBITX version.  ie the point of clipping (negative side in this case)  
~-22dBm for uBITX
~ -13dBm for Hayward.   This would then imply IMD is better.

In my set-up I found gain to be similar and pretty flat. I used junk-box parts of mixed tolerances. I built only one side of the Bi-Amps.
uBITX:-   ~ 12dB gain, flat over the range 3-45MHz flat within 0.8dB
Hayward:- ~ 10db gain, flat over same range within 0.6db

glenn

 

 

Re: Searching for IMD

Gordon Gibby <ggibby@...>
 

Thanks, Henning !


On Sep 15, 2018, at 03:03, Henning Weddig via Groups.Io <hweddig@...> wrote:

Glenn,

please compare the schematics of the Wes Hayward BiDI amp and Ashars version.

As Wes states his version is designed for 15 dB gain, resulting that he has a series feedback (680 ohms + cap) from collector to base. The biasing is done with two extra resistors.

Ashar uses only the biasing and feedback with the two resistors.

The result is that Ashars amp has about 20 dB gain, worse freqeuncy response (due to the limited ft of the 2N3904) and worse input reflection (S11). Due to the higher gain IMD must be worse at the same input level. If the textbook curve applies (3 dB for every 1 dB of input power change) the IMD will be 15 dB worse.

73

Henning Weddig

DK5LV



Am 15.09.2018 um 06:44 schrieb Glenn:

Post 59439 is partly incorrect.  Just after I posted mentioning the visible clipping I realised, stupid me, was measuring gain during clipping which of course compresses the result.

I deleted that post. And have attached the new plots where you can see the  gain difference between uBITX and Hayward version. This obviously partly accounts for the difference in input levels before output clipping occurs. The biasing arrangement gives different Iq also.  Gain is reduced about  4dB in the Hayward version I built over uBITX. It now accords more closely also with  his test results of 15.5dB I get 16dB at 30MHz.

Haywards paper gives some values for varying the gain to other values also.

<uBITX_Bi_Amp_150910.jpg>

<HAYWARD_Bi_Amp_150910.jpg>



deleted this:-
On Sat, Sep 15, 2018 at 12:16 PM, Glenn wrote:
Hi Ashhur,
I just built up a proto of both versions on vero board.

As a rough check of IP3, since I am not set up to do proper measurement of IP3, I found that the 'visible distortion' of the Hayward version occurs about 10dB higher than the uBITX version.  ie the point of clipping (negative side in this case)  
~-22dBm for uBITX
~ -13dBm for Hayward.   This would then imply IMD is better.

In my set-up I found gain to be similar and pretty flat. I used junk-box parts of mixed tolerances. I built only one side of the Bi-Amps.
uBITX:-   ~ 12dB gain, flat over the range 3-45MHz flat within 0.8dB
Hayward:- ~ 10db gain, flat over same range within 0.6db

glenn
<BiDi ubitx plot.pdf>
<BiDi ubitx schema.pdf>
<w7zoi original schema.pdf>
<w7zoi original plot.pdf>

Re: raduino connections on bitx40

terry hughes
 

hi
thanks for help - all working now

terry gm4dso

Re: Searching for IMD

Henning Weddig
 

Glenn,

please compare the schematics of the Wes Hayward BiDI amp and Ashars version.

As Wes states his version is designed for 15 dB gain, resulting that he has a series feedback (680 ohms + cap) from collector to base. The biasing is done with two extra resistors.

Ashar uses only the biasing and feedback with the two resistors.

The result is that Ashars amp has about 20 dB gain, worse freqeuncy response (due to the limited ft of the 2N3904) and worse input reflection (S11). Due to the higher gain IMD must be worse at the same input level. If the textbook curve applies (3 dB for every 1 dB of input power change) the IMD will be 15 dB worse.

73

Henning Weddig

DK5LV



Am 15.09.2018 um 06:44 schrieb Glenn:

Post 59439 is partly incorrect.  Just after I posted mentioning the visible clipping I realised, stupid me, was measuring gain during clipping which of course compresses the result.

I deleted that post. And have attached the new plots where you can see the  gain difference between uBITX and Hayward version. This obviously partly accounts for the difference in input levels before output clipping occurs. The biasing arrangement gives different Iq also.  Gain is reduced about  4dB in the Hayward version I built over uBITX. It now accords more closely also with  his test results of 15.5dB I get 16dB at 30MHz.

Haywards paper gives some values for varying the gain to other values also.







deleted this:-
On Sat, Sep 15, 2018 at 12:16 PM, Glenn wrote:
Hi Ashhur,
I just built up a proto of both versions on vero board.

As a rough check of IP3, since I am not set up to do proper measurement of IP3, I found that the 'visible distortion' of the Hayward version occurs about 10dB higher than the uBITX version.  ie the point of clipping (negative side in this case)  
~-22dBm for uBITX
~ -13dBm for Hayward.   This would then imply IMD is better.

In my set-up I found gain to be similar and pretty flat. I used junk-box parts of mixed tolerances. I built only one side of the Bi-Amps.
uBITX:-   ~ 12dB gain, flat over the range 3-45MHz flat within 0.8dB
Hayward:- ~ 10db gain, flat over same range within 0.6db

glenn

Re: Searching for IMD

Ashhar Farhan
 

glen, you can do this,

find out, accurately, the gain of the amps at very low input levels.
Now, keep increasing the drive level until you see the gain dip by 1 db.
that is the compression point. For bipolar device amplifiers, the IIP3 will be about 15 above that point.

- f

On Sat, Sep 15, 2018 at 10:14 AM, Glenn <glennp@...> wrote:
Post 59439 is partly incorrect.  Just after I posted mentioning the visible clipping I realised, stupid me, was measuring gain during clipping which of course compresses the result.

I deleted that post. And have attached the new plots where you can see the  gain difference between uBITX and Hayward version. This obviously partly accounts for the difference in input levels before output clipping occurs. The biasing arrangement gives different Iq also.  Gain is reduced about  4dB in the Hayward version I built over uBITX. It now accords more closely also with  his test results of 15.5dB I get 16dB at 30MHz.

Haywards paper gives some values for varying the gain to other values also.







deleted this:-
On Sat, Sep 15, 2018 at 12:16 PM, Glenn wrote:
Hi Ashhur,
I just built up a proto of both versions on vero board.

As a rough check of IP3, since I am not set up to do proper measurement of IP3, I found that the 'visible distortion' of the Hayward version occurs about 10dB higher than the uBITX version.  ie the point of clipping (negative side in this case)  
~-22dBm for uBITX
~ -13dBm for Hayward.   This would then imply IMD is better.

In my set-up I found gain to be similar and pretty flat. I used junk-box parts of mixed tolerances. I built only one side of the Bi-Amps.
uBITX:-   ~ 12dB gain, flat over the range 3-45MHz flat within 0.8dB
Hayward:- ~ 10db gain, flat over same range within 0.6db

glenn


Re: Searching for IMD

Glenn
 

Post 59439 is partly incorrect.  Just after I posted mentioning the visible clipping I realised, stupid me, was measuring gain during clipping which of course compresses the result.

I deleted that post. And have attached the new plots where you can see the  gain difference between uBITX and Hayward version. This obviously partly accounts for the difference in input levels before output clipping occurs. The biasing arrangement gives different Iq also.  Gain is reduced about  4dB in the Hayward version I built over uBITX. It now accords more closely also with  his test results of 15.5dB I get 16dB at 30MHz.

Haywards paper gives some values for varying the gain to other values also.







deleted this:-

On Sat, Sep 15, 2018 at 12:16 PM, Glenn wrote:
Hi Ashhur,
I just built up a proto of both versions on vero board.

As a rough check of IP3, since I am not set up to do proper measurement of IP3, I found that the 'visible distortion' of the Hayward version occurs about 10dB higher than the uBITX version.  ie the point of clipping (negative side in this case)  
~-22dBm for uBITX
~ -13dBm for Hayward.   This would then imply IMD is better.

In my set-up I found gain to be similar and pretty flat. I used junk-box parts of mixed tolerances. I built only one side of the Bi-Amps.
uBITX:-   ~ 12dB gain, flat over the range 3-45MHz flat within 0.8dB
Hayward:- ~ 10db gain, flat over same range within 0.6db

glenn

Re: Which xmit transistor is blown?

Sean W7SKD
 

Excellent point (cw key). One of those situations where you go down a road and don’t think to step back and rethink things. I convinced myself that it was a transmit issue related to amplification and didn’t challenge tha notion. 

Re: 2N2222A vs 2N3904 sourcing

ajparent1/kb1gmx
 

Hi Jim,...High gain in small pieces with input close to output...around and around it goes,,,

12:05 today I said...
So I know its doable, but you can not fold the amp on itself and have antennas (heatsinks) with RF and hope for stability.

Lumps of gain can be stable strung together in a cramped pace is much more of a challenge.  

I have amps that work very well.  Hans has done it as well.  All of the have one thing in common the
input is as far as possible from the output. Its not magic but trying to wring out the last drop of gain
is an unsuccessful way to go as its not stable even with good layout.  The next batch may or many
not work due to nominal variations.

Allison

Re: Searching for IMD

ajparent1/kb1gmx
 

Farhan,

>>>crucial thing is bias current and feedback. The biasing method itself is irrelevant.<<<

Generally yes but its easier to have the bias independent of the feedback as one forces
possibly less optimum values.

The other is that only the gain needed is employed not a case of what the circuit can do.

Allison

Re: Searching for IMD

Glenn
 

Hi Ashhur,
I just built up a proto of both versions on vero board.

As a rough check of IP3, since I am not set up to do proper measurement of IP3, I found that the 'visible distortion' of the Hayward version occurs about 10dB higher than the uBITX version.  ie the point of clipping (negative side in this case)  
~-22dBm for uBITX
~ -13dBm for Hayward.   This would then imply IMD is better.

In my set-up I found gain to be similar and pretty flat. I used junk-box parts of mixed tolerances. I built only one side of the Bi-Amps.
uBITX:-   ~ 12dB gain, flat over the range 3-45MHz flat within 0.8dB
Hayward:- ~ 10db gain, flat over same range within 0.6db

glenn

Re: 2N2222A vs 2N3904 sourcing

jim
 

Like most devices intended to oscillate, output getting back into input ...High gain in small pieces with input close to output...around and around it goes

Jim


On Friday, September 14, 2018, 12:32:38 PM PDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


Allison, why would the MMICs oscillate and not a 2N2219A? Might screening of the mmic help?

Iz oos,

Simple the board layout is not suitable.  Screening is not effective.

Allison

Re: 2N2222A vs 2N3904 sourcing

Timothy Fidler
 

Re the bitch about RF power transistors from PRC being substandard or fake . If they are popular old CB radio PA transistors and are cheap they will most likely be fake .  " Cecil the parts place " in the US has a few RF or pushed into RF service transistors and mosfets. Most are from Fairchild  mafr ..  one hopes the real Fairchild.  Some have rather nice specs and he has links to small amps built with them.

NO I am not his brother  or a schiller for him as the Yanks say. Just noticed the site which is linked to a Steve Webber  design site.

Re: Searching for IMD

Ashhar Farhan
 

The article does mention the oip3 which is a measure of IMD. The crucial thing is bias current and feedback. The biasing method itself is irrelevant.
- f

On Sat, 15 Sep 2018, 04:21 Glenn, <glennp@...> wrote:
Perhaps it's possible to improve the Bi-Amps?   The article by Wes Hayward and Bob Kopski shows a slightly different biasing arrangement and feedback in the first stage compared to that used in uBITX. As shown, gain is 15dB and flat to 100MHz within 1dB.

More conventional resistive voltage divider is used and the feedback is AC only. Two extra parts are used. The article doesn't mention IMD though specifically, as a performance target or measure it.

glenn

Re: 2N2222A vs 2N3904 sourcing

Tim Gorman
 

Back in March, 2018 I tried building up an amp section using an HP mmic
I have in the junk box. It worked very well on the desktop. Flat from
3Mhz to 30Mhz. No oscillation. I simply could find no way to add it
into the ubitx around Q90 (i.e. before and after) where it didn't break
into oscillation as soon as I tried to transmit.

At this point it would be easier to make up a new PA driver chain on a
replacement circuit board. Mount it on standoffs above the existing
board using coax in from Q90 and coax out to IRF510's. It's not a
project I want to take on. I would rather set the power out to 1w or
2w, have a clean signal, and use an external amplifier.

tim ab0wr

On Fri, 14 Sep 2018 15:23:49 -0700
"RCBoatGuy via Groups.Io" <ijnfan-HamRadio=yahoo.com@groups.io> wrote:

In response to Warren's question about why the MMIC's would be
sensitive to oscillating..  

According to the datasheets, they are very sensitive to ground
loops.  The datasheet for the HP/Aligent MMIC on the 30dB board
available on Amazon was quite clear on this, and recommended using an
ultra-thin PCB (0.032 rather than 0.0625) to keep the inductance of
the ground vias down where it needed to be to avoid oscillation. 

Given that, it would be very hard to retro-fit one of these MMIC's
into an existing board designed for transistors rather than MMIC's
and not have it oscillate.

73,

Carl, K0MWC

Re: Searching for IMD

Glenn
 

Perhaps it's possible to improve the Bi-Amps?   The article by Wes Hayward and Bob Kopski shows a slightly different biasing arrangement and feedback in the first stage compared to that used in uBITX. As shown, gain is 15dB and flat to 100MHz within 1dB.

More conventional resistive voltage divider is used and the feedback is AC only. Two extra parts are used. The article doesn't mention IMD though specifically, as a performance target or measure it.

glenn

Re: si5351 crosstalk #radiuno

MadRadioModder
 

Glenn… Now that is a sweet solution.

 

 

 


Virus-free. www.avg.com

--

…_. _._

Re: 2N2222A vs 2N3904 sourcing

RCBoatGuy
 

In response to Warren's question about why the MMIC's would be sensitive to oscillating..  

According to the datasheets, they are very sensitive to ground loops.  The datasheet for the HP/Aligent MMIC on the 30dB board available on Amazon was quite clear on this, and recommended using an ultra-thin PCB (0.032 rather than 0.0625) to keep the inductance of the ground vias down where it needed to be to avoid oscillation. 

Given that, it would be very hard to retro-fit one of these MMIC's into an existing board designed for transistors rather than MMIC's and not have it oscillate.

73,

Carl, K0MWC

Bandscan and Spectrum using I2C dsp meter

N5KBP
 

Has anyone gotten the bandscan and spectrum pages to work on KD8CEC's firmware using the standalone  I2C dspmeter? The only way I can get it to work kinda sorta is to compile the firmware to not use the dsp meter then attach the purple wire (a7) to the junction of the 2 resistors and .01 cap on the standalone dsp uno. This works but the readings on the band scan are very low and pretty much useless. What am I not understanding about this feature?
--
N5KBP

Re: 2N2222A vs 2N3904 sourcing

Trystan G0KAY
 

..and at Farnell

Re: 2N2222A vs 2N3904 sourcing

Trystan G0KAY
 

I've just had a look, and 2n222A are available readily enough at Cricklewood.