Topics

RF power chain mods and improvements..

ajparent1/KB1GMX
 

I'd like to consolidate discussion on changes and improvements to get uniform power out
here.

So it helps others please stay very close to the topic.  For example no discussion of external amps.

I will report my findings so far in the next post.

ajparent1/KB1GMX
 

First all changes are on a production uBitx not an older brassboard model.

The first findings are not about power out, I haven't fully tested.

What I did find is at 13.8V all on the 2n3904s in the power chain run very hot
with no signal.  How hot 125-130 degrees.  Measurements had the first Q90
running at 38ma and for a low level sage thats very high and for a 3904 its
near excessive.

Why is that problem?  THe bata sheet says that as we increase the device
current the HFE goes down and leads to reduced gain and, also lots of heat.

Current solution was to increase the bias resistor R81 from 1K to 2.5K but as two parts
 Its 1K +1.5K and the 1.5K gets a .1uf capacitor across that so the stage gain is maintained.
This lowers the current to about 20MA (19.6 actual).  FYI that means the device is now
dissipating 230mW of power where before it was 390mW.  The device max is 500mw
and I"ve found when you get close to that they fail.

One to the drivers.  Another noted he tried 2n2219s and they get warm.  Likely 
it was the bias level alone causing that.   The current devices in mine are 3904
and they are hot at 130-135F.  Again the bias is wrong (does not allow for
devices with higher than average HFE) and the device current is much too
high In a class AB push pull the current need not be this high.  The same
technique  of splitting the bias value so the 1K is unbypassed is used and
the same values 1k+1.5K (1.5k bypassed) are more suitable and result in a
16ma standing current per device.  

Much of this is the result of transistors being anything but uniform.  HFE
variations  for 2n3904 is around 50 to 300  and varies with device current.
This is typical.  But that also is variable across vendors.

Those changes alone have had no testing for power out at 20M and 10M yet.
That will be  the next step.  Right now I was trying to get the devices in the
range where they should behave as good as they can.

Allison


 

Ashhar Farhan
 

Allison,
We will be keenly following your experiments with the power chain. I will mod my ugly build to replicate your experiments.
I suspect that lower standing current in the push pull drivers would be alright. 
- f
- f

On Sat, 19 May 2018, 20:33 ajparent1/KB1GMX, <kb1gmx@...> wrote:
First all changes are on a production uBitx not an older brassboard model.

The first findings are not about power out, I haven't fully tested.

What I did find is at 13.8V all on the 2n3904s in the power chain run very hot
with no signal.  How hot 125-130 degrees.  Measurements had the first Q90
running at 38ma and for a low level sage thats very high and for a 3904 its
near excessive.

Why is that problem?  THe bata sheet says that as we increase the device
current the HFE goes down and leads to reduced gain and, also lots of heat.

Current solution was to increase the bias resistor R81 from 1K to 2.5K but as two parts
 Its 1K +1.5K and the 1.5K gets a .1uf capacitor across that so the stage gain is maintained.
This lowers the current to about 20MA (19.6 actual).  FYI that means the device is now
dissipating 230mW of power where before it was 390mW.  The device max is 500mw
and I"ve found when you get close to that they fail.

One to the drivers.  Another noted he tried 2n2219s and they get warm.  Likely 
it was the bias level alone causing that.   The current devices in mine are 3904
and they are hot at 130-135F.  Again the bias is wrong (does not allow for
devices with higher than average HFE) and the device current is much too
high In a class AB push pull the current need not be this high.  The same
technique  of splitting the bias value so the 1K is unbypassed is used and
the same values 1k+1.5K (1.5k bypassed) are more suitable and result in a
16ma standing current per device.  

Much of this is the result of transistors being anything but uniform.  HFE
variations  for 2n3904 is around 50 to 300  and varies with device current.
This is typical.  But that also is variable across vendors.

Those changes alone have had no testing for power out at 20M and 10M yet.
That will be  the next step.  Right now I was trying to get the devices in the
range where they should behave as good as they can.

Allison


 

ajparent1/KB1GMX
 

Farhan,

its a stepwise process and will take a bit of testing.   Whats good is In the local club there are three
other uBitx radios.  This  way the changes have a test n greater than 1.



Allison

Skip Davis
 

Thanks Allison for this information I have noticed similar heating of the driver transistors and also T11. I see a reduction of output somewhat on the order of 10 to 20 percent with increasing heat. 

I’m going to wind a new T11 using a binocular core the single core toroid is inadequate for the power levels we are seeing. I’m running my UBITX at 13.5 volts but want to build another one in a grab and go case with batteries like you had mentioned. 

Just to let you know what I’ve done is bypass all driver emitters with 330pf caps and added 30uh inductors inline with the 1k bias resistors. I also added a 20pf across the T11 primary this increased output and flattened out the response some at the higher frequencies. I’m seeing a minimum of 4 watts on 10 meters with RV1 adjusted to 14 watts on 40 meters. 

Skip Davis, NC9O

On May 19, 2018, at 11:03, ajparent1/KB1GMX <kb1gmx@...> wrote:

First all changes are on a production uBitx not an older brassboard model.

The first findings are not about power out, I haven't fully tested.

What I did find is at 13.8V all on the 2n3904s in the power chain run very hot
with no signal.  How hot 125-130 degrees.  Measurements had the first Q90
running at 38ma and for a low level sage thats very high and for a 3904 its
near excessive.

Why is that problem?  THe bata sheet says that as we increase the device
current the HFE goes down and leads to reduced gain and, also lots of heat.

Current solution was to increase the bias resistor R81 from 1K to 2.5K but as two parts
 Its 1K +1.5K and the 1.5K gets a .1uf capacitor across that so the stage gain is maintained.
This lowers the current to about 20MA (19.6 actual).  FYI that means the device is now
dissipating 230mW of power where before it was 390mW.  The device max is 500mw
and I"ve found when you get close to that they fail.

One to the drivers.  Another noted he tried 2n2219s and they get warm.  Likely 
it was the bias level alone causing that.   The current devices in mine are 3904
and they are hot at 130-135F.  Again the bias is wrong (does not allow for
devices with higher than average HFE) and the device current is much too
high In a class AB push pull the current need not be this high.  The same
technique  of splitting the bias value so the 1K is unbypassed is used and
the same values 1k+1.5K (1.5k bypassed) are more suitable and result in a
16ma standing current per device.  

Much of this is the result of transistors being anything but uniform.  HFE
variations  for 2n3904 is around 50 to 300  and varies with device current.
This is typical.  But that also is variable across vendors.

Those changes alone have had no testing for power out at 20M and 10M yet.
That will be  the next step.  Right now I was trying to get the devices in the
range where they should behave as good as they can.

Allison


 

ajparent1/KB1GMX
 

Skip, that may be true.

A little thinking out loud, so to speak.  Stuff running in my head on why and
how of more uniform power.  Or -10dbm(.1mW) in and 40DBM(10W) out or
about 50DB of over all gain out of 4 stages (an average of about 12.5db)
where the lower level stages are about 16-17db and the finals are closer
to 13-15db (in the circuit). If we assume the last stage as 13db that means
the prior 3 must deliver 37DB and also .5W minimum.  Not a tall order
but to do that from 3 to 30mhz means every part of that must play well.

First item: Mosfets are fairly gain flat despite drive issues.  They do not exhibit FT
that bipolar devices do.  The upper limits are more lead and case parasitics than 
the silicon.  IRF510s put out serious power at 6M with gains in the 13-16db range.
So other than the impedance matching on the input and output we know they can.
Besides every device I looked at at best gave a better IMD for the same power or
cost a lot of money and are not in a package that is uBitx friendly.  So changes
here are not explored.  While RD parts offer a better IMD the cost (5x higher)
for legit parts is out of consideration save for those that have other performance
goals.

What I think is going on why some do better than others compared to the bogey unit:
Adding inductors to reduce the feedback is good but when the transistors are 
at best giving a gain of 10 maybe 11 (10 to 10.4DB) you are running against
possible gain vs desired gain (desired is about 39 (17db)!).  It only takes a
little bit more from the drivers to make that but with high Ic/Ie and only
300mhz Ft we run to the corner of diminishing gain to less than enough to
hit the feedback selected value. So that means a  edge group of 3904s are
running higher current which depresses the HFE and also lowering gain
due to FT issues and we end up with 12W at 80m and 1.4W at 10M.

My thinking on what to do and why it may be a solution:
There are two ways to do this. Using 3904s we drop each stage gain down 
10-11db  that flattens the gain from 1-30mhz but we need more stages
and for a new design its reasonable to look at for a existing design 
its unreasonable to add so its out of  contention.   The other ways is
use transistors with higher FT and do not suffer diminishing Hfe with
increasing current (or less so).   Now we can get he required gain
and feedback limits it as we have enough (or nearly so) at 30mhz.
A 600mhz part give us a shot and 1ghz parts can easily do it. 
Those would be MPSH10 or similar and 2N5109 or similar.  For
production this may be too costly but there are other parts that
may be a good choice on a cost vs availability scale.  Oddly I've
looked at a classic the 2n2222A (TO18 metal part) as its been
my go to for years. It has a better HFE curve at higher currents
so it does not suffer that depression.  Its also higher power
(its the same DIE as the 2n2219A)  its FT is still only 300mhz
but experience says they do better so we have a candidate to try
as I have a bin full.  In the mean time an parts order is in order...

Optimizing the output transformer is also a factor but space and 
ease of performing the mod are a consideration.

It may take a lot or very few mods to get there.  Less is better.
I may try several routes and see what implements better, cheaper, 
and using parts that are not unobtainium.

My goal is not so much more power 10 to 12 W is fine but to make 10M near
that as well. Or constantly within 3db or less.  Also an effort to lower the
standing power drain some to make it more battery friendly.

Allison

Arv Evans
 

Allison

Has anybody looked into using an IRF510 to drive the IRF510's or IRF530's?

Arv
_._


On Sat, May 19, 2018 at 1:15 PM, ajparent1/KB1GMX <kb1gmx@...> wrote:
Skip, that may be true.

A little thinking out loud, so to speak.  Stuff running in my head on why and
how of more uniform power.  Or -10dbm(.1mW) in and 40DBM(10W) out or
about 50DB of over all gain out of 4 stages (an average of about 12.5db)
where the lower level stages are about 16-17db and the finals are closer
to 13-15db (in the circuit). If we assume the last stage as 13db that means
the prior 3 must deliver 37DB and also .5W minimum.  Not a tall order
but to do that from 3 to 30mhz means every part of that must play well.

First item: Mosfets are fairly gain flat despite drive issues.  They do not exhibit FT
that bipolar devices do.  The upper limits are more lead and case parasitics than 
the silicon.  IRF510s put out serious power at 6M with gains in the 13-16db range.
So other than the impedance matching on the input and output we know they can.
Besides every device I looked at at best gave a better IMD for the same power or
cost a lot of money and are not in a package that is uBitx friendly.  So changes
here are not explored.  While RD parts offer a better IMD the cost (5x higher)
for legit parts is out of consideration save for those that have other performance
goals.

What I think is going on why some do better than others compared to the bogey unit:
Adding inductors to reduce the feedback is good but when the transistors are 
at best giving a gain of 10 maybe 11 (10 to 10.4DB) you are running against
possible gain vs desired gain (desired is about 39 (17db)!).  It only takes a
little bit more from the drivers to make that but with high Ic/Ie and only
300mhz Ft we run to the corner of diminishing gain to less than enough to
hit the feedback selected value. So that means a  edge group of 3904s are
running higher current which depresses the HFE and also lowering gain
due to FT issues and we end up with 12W at 80m and 1.4W at 10M.

My thinking on what to do and why it may be a solution:
There are two ways to do this. Using 3904s we drop each stage gain down 
10-11db  that flattens the gain from 1-30mhz but we need more stages
and for a new design its reasonable to look at for a existing design 
its unreasonable to add so its out of  contention.   The other ways is
use transistors with higher FT and do not suffer diminishing Hfe with
increasing current (or less so).   Now we can get he required gain
and feedback limits it as we have enough (or nearly so) at 30mhz.
A 600mhz part give us a shot and 1ghz parts can easily do it. 
Those would be MPSH10 or similar and 2N5109 or similar.  For
production this may be too costly but there are other parts that
may be a good choice on a cost vs availability scale.  Oddly I've
looked at a classic the 2n2222A (TO18 metal part) as its been
my go to for years. It has a better HFE curve at higher currents
so it does not suffer that depression.  Its also higher power
(its the same DIE as the 2n2219A)  its FT is still only 300mhz
but experience says they do better so we have a candidate to try
as I have a bin full.  In the mean time an parts order is in order...

Optimizing the output transformer is also a factor but space and 
ease of performing the mod are a consideration.

It may take a lot or very few mods to get there.  Less is better.
I may try several routes and see what implements better, cheaper, 
and using parts that are not unobtainium.

My goal is not so much more power 10 to 12 W is fine but to make 10M near
that as well. Or constantly within 3db or less.  Also an effort to lower the
standing power drain some to make it more battery friendly.

Allison


ajparent1/KB1GMX
 

Hi Arv,

Yes. But there is no need for that.  We need under 1W to drive a IRF510
to 10 ore more watts.  Actually I've used 2W in the WA1EBY (pp pair of
IRF510s at 28V) for more than 50W.  To get 2W I used a 2SC779 and it
as not working hard at all.

Work backwards if you want 10W assume worst case 10DB (Likely 13-16)
so to get 1 you only need 1W if its 13DB its .5W, and so on.  The trick is
to load the gate so the IRF510 is stable  and make it up with drive power.

The bigger parts like the IRF520 and 530 are sill power limited due to heat transfer
though it is better the problem is efficiency keeping it above 45% so your not
equally heating the device for every watt you put out as the dissipated power is
your limit. And IRF510 at 3A 12V is handling 36W, if the efficieny is 50%
your seeing 18W.  Save for its needs 24V to do that and then you are at 72W
input and 36 out (eff=.5).  The part is 4+ amp capable so that not a limit. The
limit is the 36W of heat.  One must deliver that power to the load not as heat.

Allison

M Garza <mgarza896@...>
 

What about using (2) 2SC1973s for the drivers and BF199s as the pre-drivers?

Marco - KG5PRT 

On Sat, May 19, 2018, 5:08 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Hi Arv,

Yes. But there is no need for that.  We need under 1W to drive a IRF510
to 10 ore more watts.  Actually I've used 2W in the WA1EBY (pp pair of
IRF510s at 28V) for more than 50W.  To get 2W I used a 2SC779 and it
as not working hard at all.

Work backwards if you want 10W assume worst case 10DB (Likely 13-16)
so to get 1 you only need 1W if its 13DB its .5W, and so on.  The trick is
to load the gate so the IRF510 is stable  and make it up with drive power.

The bigger parts like the IRF520 and 530 are sill power limited due to heat transfer
though it is better the problem is efficiency keeping it above 45% so your not
equally heating the device for every watt you put out as the dissipated power is
your limit. And IRF510 at 3A 12V is handling 36W, if the efficieny is 50%
your seeing 18W.  Save for its needs 24V to do that and then you are at 72W
input and 36 out (eff=.5).  The part is 4+ amp capable so that not a limit. The
limit is the 36W of heat.  One must deliver that power to the load not as heat.

Allison

ajparent1/KB1GMX
 

Problem with 2sc1973 is they may be hard to get and its still a 300mhs ft.  Might as well use 2n2222a.
The Bf199 is likely better save for its 25V CE breakdown is kinda low but the 1100mhz FT would be better.
I'd not use it for the 25V breakdown spec.

RIght now I'm not pulling transistors at random.

Q90 a 2n2963A in a smt form is being tried at 19 ma I think the current is too
high and I may reduce it further to 10-15ma. It only has to produce 2mw of power
max so running more than 200mw of power is excessive. At 15ma its about 185mw
being dissipated.  Why waste power.

Q911/912:
What I think we should use for pre-driver something with a 500 to 1ghz FT, .6 w or
better per device.   The HFE at higher current (30-50ma) must not sag. Even at
that the stage only need produce less than 100mw (more like 70).   One device
is not stressed doing that.  

Q92/93/96/97:
What I think we should use for driver something with a 500 to 1ghz FT, 1 w or 
better per device.   The HFE at higher current (50-100ma) must not sag.
THis stage is push pull and two need to be able to push about 1 watt
and there are many that can do that as two rather than 4.  It also can run
class AB1 at about 10 to 20ma per device since its push pull.  The
device current as is with 3904s is 27ma (very high) per device on mine.

Candidates I know of but not tested are: 
MPSH10 but I have to try them.
2n2222A  its worked in the past but the FT is barely enough.
2n3553//2n3866/2n5109 are likely good for driver (2 not four).

And no, don't go out and buy them unless your experimenting on your own.  Do report
your results!  More data points may be important.

Before the CW key oddity happened  I was testing a lone (1 not wo) and the predriver
and was getting the same or more power. makes sense as we only need maybe
70 mw of power there.  Not tested enough so everyone sit down please till it is.

I have  no reason to change the IRF510s.  For 10-12W its just right.


Allison

MVS Sarma
 

Even a BS170 (TO92) would work as a pre driver. However perhaps MPSH10 (MMBTH10 in sot23) just sits on the uBITX board and would do well i suppose

Regards
MVS Sarma
 

On Sun, May 20, 2018 at 9:02 AM, ajparent1/KB1GMX <kb1gmx@...> wrote:
Problem with 2sc1973 is they may be hard to get and its still a 300mhs ft.  Might as well use 2n2222a.
The Bf199 is likely better save for its 25V CE breakdown is kinda low but the 1100mhz FT would be better.
I'd not use it for the 25V breakdown spec.

RIght now I'm not pulling transistors at random.

Q90 a 2n2963A in a smt form is being tried at 19 ma I think the current is too
high and I may reduce it further to 10-15ma. It only has to produce 2mw of power
max so running more than 200mw of power is excessive. At 15ma its about 185mw
being dissipated.  Why waste power.

Q911/912:
What I think we should use for pre-driver something with a 500 to 1ghz FT, .6 w or
better per device.   The HFE at higher current (30-50ma) must not sag. Even at
that the stage only need produce less than 100mw (more like 70).   One device
is not stressed doing that.  

Q92/93/96/97:
What I think we should use for driver something with a 500 to 1ghz FT, 1 w or 
better per device.   The HFE at higher current (50-100ma) must not sag.
THis stage is push pull and two need to be able to push about 1 watt
and there are many that can do that as two rather than 4.  It also can run
class AB1 at about 10 to 20ma per device since its push pull.  The
device current as is with 3904s is 27ma (very high) per device on mine.

Candidates I know of but not tested are: 
MPSH10 but I have to try them.
2n2222A  its worked in the past but the FT is barely enough.
2n3553//2n3866/2n5109 are likely good for driver (2 not four).

And no, don't go out and buy them unless your experimenting on your own.  Do report
your results!  More data points may be important.

Before the CW key oddity happened  I was testing a lone (1 not wo) and the predriver
and was getting the same or more power. makes sense as we only need maybe
70 mw of power there.  Not tested enough so everyone sit down please till it is.

I have  no reason to change the IRF510s.  For 10-12W its just right.


Allison


ajparent1/KB1GMX
 

BS170 thats a MOSFET 60pf input capacitance adds complications and would require a
bias adjustment for every one.  Not  a good choice.  A 2n7000 is a similar device
and I have 2n6661 that I"ve used in the past at RF.  There is no plan to use mosfets
in the driver or predriver stages.  Generally the gate to drain capacitance is problematic
for stability.

I've already listed MPSH10/MMBTH10 as candidates.  I am waiting on sot and to92 from supplier.


Allison

 

This is a Flir image of one of my BITX40 boards

At 19-05-18, you wrote:
First all changes are on a production uBitx not an older brassboard model.

The first findings are not about power out, I haven't fully tested.

What I did find is at 13.8V all on the 2n3904s in the power chain run very hot
with no signal. How hot 125-130 degrees. Measurements had the first Q90
running at 38ma and for a low level sage thats very high and for a 3904 its
near excessive.

Why is that problem? THe bata sheet says that as we increase the device
current the HFE goes down and leads to reduced gain and, also lots of heat.

Current solution was to increase the bias resistor R81 from 1K to 2.5K but as two parts
Its 1K +1.5K and the 1.5K gets a .1uf capacitor across that so the stage gain is maintained.
This lowers the current to about 20MA (19.6 actual). FYI that means the device is now
dissipating 230mW of power where before it was 390mW. The device max is 500mw
and I"ve found when you get close to that they fail.

One to the drivers. Another noted he tried 2n2219s and they get warm. Likely
it was the bias level alone causing that. The current devices in mine are 3904
and they are hot at 130-135F. Again the bias is wrong (does not allow for
devices with higher than average HFE) and the device current is much too
high In a class AB push pull the current need not be this high. The same
technique of splitting the bias value so the 1K is unbypassed is used and
the same values 1k+1.5K (1.5k bypassed) are more suitable and result in a
16ma standing current per device.

Much of this is the result of transistors being anything but uniform. HFE
variations for 2n3904 is around 50 to 300 and varies with device current.
This is typical. But that also is variable across vendors.

Those changes alone have had no testing for power out at 20M and 10M yet.
That will be the next step. Right now I was trying to get the devices in the
range where they should behave as good as they can.

Allison

ajparent1/KB1GMX
 

I have that and a IR thermometer.  I prefer the latter as then I know what I'm
actually looking at without adding an overlay.

Its a problem of some 2n3904 are hotter because they exhibit higher than average HFE.
I put one of mine on the tracer and it was hfe of 300!  The norm is around 150-180.

Allison

K5ESS
 

Allison,

The data sheet I have for the 2N5109 lists a Vceo of 20 volts.  Does this make  it risky as a candidate or do you think it’s OK?  If replacing 3904s with 5109s or 3866s would you include Q90 in this replacement?

Mike

K5ESS

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of ajparent1/KB1GMX
Sent: Saturday, May 19, 2018 10:33 PM
To: BITX20@groups.io
Subject: Re: [BITX20] RF power chain mods and improvements..

 

Problem with 2sc1973 is they may be hard to get and its still a 300mhs ft.  Might as well use 2n2222a.
The Bf199 is likely better save for its 25V CE breakdown is kinda low but the 1100mhz FT would be better.
I'd not use it for the 25V breakdown spec.

RIght now I'm not pulling transistors at random.

Q90 a 2n2963A in a smt form is being tried at 19 ma I think the current is too
high and I may reduce it further to 10-15ma. It only has to produce 2mw of power
max so running more than 200mw of power is excessive. At 15ma its about 185mw
being dissipated.  Why waste power.

Q911/912:
What I think we should use for pre-driver something with a 500 to 1ghz FT, .6 w or
better per device.   The HFE at higher current (30-50ma) must not sag. Even at
that the stage only need produce less than 100mw (more like 70).   One device
is not stressed doing that.  

Q92/93/96/97:
What I think we should use for driver something with a 500 to 1ghz FT, 1 w or 
better per device.   The HFE at higher current (50-100ma) must not sag.
THis stage is push pull and two need to be able to push about 1 watt
and there are many that can do that as two rather than 4.  It also can run
class AB1 at about 10 to 20ma per device since its push pull.  The
device current as is with 3904s is 27ma (very high) per device on mine.

Candidates I know of but not tested are: 
MPSH10 but I have to try them.
2n2222A  its worked in the past but the FT is barely enough.
2n3553//2n3866/2n5109 are likely good for driver (2 not four).

And no, don't go out and buy them unless your experimenting on your own.  Do report
your results!  More data points may be important.

Before the CW key oddity happened  I was testing a lone (1 not wo) and the predriver
and was getting the same or more power. makes sense as we only need maybe
70 mw of power there.  Not tested enough so everyone sit down please till it is.

I have  no reason to change the IRF510s.  For 10-12W its just right.


Allison

ajparent1/KB1GMX
 

Mike,
Since I've been dealing with the Raduino problem I can't answer yet.

However what I feel is you are asking;  "should I use XXX or YYY?".
My answer is what do you think?   If you do let us know your results.
Why is my answer that way, I have NOT TESTED IT YET but plan to.

All of those parts are on my candidates list way back yesterday.

Q90 if biased at 10-15MA would be better served with a 2n2369A as its a 600mhz
part and I've used it elsewhere with good behaviour.  I was testing that when
Raduino burped.  So It looks ok but more testing needed.

Allison

ajparent1/KB1GMX
 

from yesterday:


Candidates I know of but not tested are: 
MPSH10 but I have to try them.
2n2222A  its worked in the past but the FT is barely enough.
2n3553//2n3866/2n5109 are likely good for driver (2 not four).

K5ESS
 

Thanks Allison.  I was assuming that the 20 volt max Vceo for the 5109 might disqualify it based on your earlier post regarding the Bf199 with its 25 volt breakdown spec.

Mike

K5ESS

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of ajparent1/KB1GMX
Sent: Sunday, May 20, 2018 2:03 PM
To: BITX20@groups.io
Subject: Re: [BITX20] RF power chain mods and improvements..

 

Mike,
Since I've been dealing with the Raduino problem I can't answer yet.

However what I feel is you are asking;  "should I use XXX or YYY?".
My answer is what do you think?   If you do let us know your results.
Why is my answer that way, I have NOT TESTED IT YET but plan to.

All of those parts are on my candidates list way back yesterday.

Q90 if biased at 10-15MA would be better served with a 2n2369A as its a 600mhz
part and I've used it elsewhere with good behaviour.  I was testing that when
Raduino burped.  So It looks ok but more testing needed.

Allison

ajparent1/KB1GMX
 

The BF199 was pulled for many reasons that was one.  Its not out of possibility but 
the list can be so long as I have this thing for getting to done.  ;)

In this case done is in the box and able to use it as i wish.

Allison

Rahul Srivastava
 

S9018 is another candidate to consider in low power stages , now days seems very popular in 27mhz cordless bell of Chinese origin and kiddies walky talkies regen type..

Bought couple of them to try out in one of my old project PCB that I had some spare the VK5JST Areial Analyser....

73

Rahul VU3WJM