10W LInear PA: Starting build - any suggestions, thoughts, comments? #10W_PA


wa2cky
 

Just placed an order for the 10W Linear Power Amp kit - due here in a couple of days. I intend to use it as a piece of test equipment to boost the output of my bench RF signal generator to several watts to test VSWR bridges, power meters, etc. Before plunging into the build, does anyone on the forum have any hints, suggestions, ideas for improvements, etc?  I've looked in the past postings and found little (which is, in one aspect, because it would indicate that no one has had a lot of problems!). 

73
Bob Groh, WA2CKY


Curt wb8yyy
 

Check the list for recent traffic, several folk had input within the last few weeks. You may find much of what you need there. 

Also a key design advisor frequents this list. 

Curt


Albert Tatlock's Greatest Hits - Vol 1
 

On Fri, Jul 16, 2021 at 07:03 PM, @CurtisM wrote:
Check the list for recent traffic, several folk had input within the last few weeks. You may find much of what you need there. 
Even thought it's the 21st century, most users of user groups are still stuck in their "mail reflector" only ways,
and miss out on so many group resources and previous message search facilities.

It's a key factor as to why at least once a week, someone comes along and asks a question that has been answered
many times before, and the info could easily be found with either a cursory glance down the message board or a simple
keyword search.

It gets a bit tedious when you've been here for since day one.

(Note, this is a general comment, and has nothing to do with the OP question.)


wa2cky
 

Or a lack of ability to find relevant material is a function of a rather poor search function??  Yes, ladies and gentleman, I did do a search through the list and was unable to find much beyond a general discussion of how much drive was appropriate. Hence my email looking for anything more - things that are not necessarily a problem but just something along the line of '...it would have been nice....'


Bob Groh, WA2CKY

On Fri, Jul 16, 2021 at 1:24 PM Jesus Christ on Toast via groups.io <andyfoad=rocketmail.com@groups.io> wrote:
On Fri, Jul 16, 2021 at 07:03 PM, @CurtisM wrote:
Check the list for recent traffic, several folk had input within the last few weeks. You may find much of what you need there. 
Even thought it's the 21st century, most users of user groups are still stuck in their "mail reflector" only ways,
and miss out on so many group resources and previous message search facilities.

It's a key factor as to why at least once a week, someone comes along and asks a question that has been answered
many times before, and the info could easily be found with either a cursory glance down the message board or a simple
keyword search.

It gets a bit tedious when you've been here for since day one.

(Note, this is a general comment, and has nothing to do with the OP question.)


Bill Cromwell
 

Hi Bob,

I see who you were replying to because you requoted him. That guy never ever has anything useful, helpful, nor pleasant to say and always denegrates *everybody*. I have anything from him going straight to the round file. The only time ever see him is when somebody requotes him. You may want to consider that too. You probably won't miss him.

73,

Bill KU8H

bark less - wag more

On 7/16/21 3:28 PM, wa2cky wrote:
Or a lack of ability to find relevant material is a function of a rather poor search function??  Yes, ladies and gentleman, I did do a search through the list and was unable to find much beyond a general discussion of how much drive was appropriate. Hence my email looking for anything more - things that are not necessarily a problem but just something along the line of '...it would have been nice....'


Bob Groh, WA2CKY

On Fri, Jul 16, 2021 at 1:24 PM Jesus Christ on Toast via groups.io <http://groups.io> <andyfoad=rocketmail.com@groups.io <mailto:rocketmail.com@groups.io>> wrote:

On Fri, Jul 16, 2021 at 07:03 PM, @CurtisM wrote:

Check the list for recent traffic, several folk had input
within the last few weeks. You may find much of what you need
there.
Even thought it's the 21st century, most users of user groups are
still stuck in their "mail reflector" only ways,
and miss out on so many group resources and previous message
search facilities.

It's a key factor as to why at least once a week, someone comes
along and asks a question that has been answered
many times before, and the info could easily be found with either
a cursory glance down the message board or a simple
keyword search.

It gets a bit tedious when you've been here for since day one.

(Note, this is a */general/ *comment, and has nothing to do with
the OP question.)


Angel M0HDF
 

Hi Bob,

I am about to order one too.
Check out YouTube- qrp-labs 10W PA. There are some great videos with useful info.

GL & 73
Angel 
M0HDF


Mike Besemer - WM4B
 

What gets a little bit tedious is listening to you gripe and complain about most everything, denigrate people, and just be a plain old grouch.  If this is so trying for you, why don't you just leave?  Or is it that you just enjoy talking down to people?  This is ham radio and we're here to help each other; if you can't do that you have no business in the hobby.

WM4B


On Fri, Jul 16, 2021 at 02:23 PM, Jesus Christ on Toast wrote:
Even thought it's the 21st century, most users of user groups are still stuck in their "mail reflector" only ways,
and miss out on so many group resources and previous message search facilities.

It's a key factor as to why at least once a week, someone comes along and asks a question that has been answered
many times before, and the info could easily be found with either a cursory glance down the message board or a simple
keyword search.

It gets a bit tedious when you've been here for since day one.


Bill Cromwell
 

Hi Mike,

It's called a "troll". Just ignore or filter out as I do.

73,

Bill KU8H

bark less - wag more

On 7/16/21 3:59 PM, Mike Besemer - WM4B wrote:
What gets a little bit tedious is listening to you gripe and complain about most everything, denigrate people, and just be a plain old grouch.  If this is so trying for you, why don't you just leave?  Or is it that you just enjoy talking down to people? This is ham radio and we're here to help each other; if you can't do that you have no business in the hobby.

WM4B

On Fri, Jul 16, 2021 at 02:23 PM, Jesus Christ on Toast wrote:

Even thought it's the 21st century, most users of user groups are
still stuck in their "mail reflector" only ways,
and miss out on so many group resources and previous message
search facilities.

It's a key factor as to why at least once a week, someone comes
along and asks a question that has been answered
many times before, and the info could easily be found with either
a cursory glance down the message board or a simple
keyword search.

It gets a bit tedious when you've been here for since day one.


Mike Besemer - WM4B
 

I know, but people who live to make other's miserable just tweak my knob.

But, he's been added to the SPAM filter, so his crap will go in with the rest of the garbage!

Mike
WM4B

On July 16, 2021 at 4:16 PM Bill Cromwell <wrcromwell@gmail.com> wrote:


Hi Mike,

It's called a "troll". Just ignore or filter out as I do.

73,

Bill KU8H

bark less - wag more

On 7/16/21 3:59 PM, Mike Besemer - WM4B wrote:
What gets a little bit tedious is listening to you gripe and complain
about most everything, denigrate people, and just be a plain old
grouch.  If this is so trying for you, why don't you just leave?  Or
is it that you just enjoy talking down to people? This is ham radio
and we're here to help each other; if you can't do that you have no
business in the hobby.

WM4B

On Fri, Jul 16, 2021 at 02:23 PM, Jesus Christ on Toast wrote:

Even thought it's the 21st century, most users of user groups are
still stuck in their "mail reflector" only ways,
and miss out on so many group resources and previous message
search facilities.

It's a key factor as to why at least once a week, someone comes
along and asks a question that has been answered
many times before, and the info could easily be found with either
a cursory glance down the message board or a simple
keyword search.

It gets a bit tedious when you've been here for since day one.





Albert Tatlock's Greatest Hits - Vol 1
 

On Fri, Jul 16, 2021 at 08:28 PM, wa2cky wrote:
Or a lack of ability to find relevant material is a function of a rather poor search function?? 
Well yeah, it's not too bad, but not too good amazing.
But like I said, my comment was general, and it has been something that I'd been meaning to mention for a long time now.

I remember a classic example not too long ago.
It went like this -

A "problem" had been debated / investigated for months and months and ran up nearly 200 posts.

The answer was finally found and the matter concluded.

24 hours later someone with the same problem was asking for help - argghhhh!!!!

They had only just joined the group that day, and had only experienced the knowledge base via a couple of emails
sent via the reflector, which is why I made my point. (Once again, a general point, nothing to do with yourself).

If that person had even looked at the first page of the web interface then the answer would have been staring them in the face ;-)

So my point / observation is that somehow we need to break the historic cycle of user groups being simply "email reflectors"
and steer them to a richer browser based one.

But that might be an uphill struggle :-(


Albert Tatlock's Greatest Hits - Vol 1
 

On Fri, Jul 16, 2021 at 08:59 PM, Mike Besemer - WM4B wrote:
This is ham radio
Assuming you mean "amateur radio", yes it should be.

But it more like amateurish radio these days.

I read the messages, and half of the posters admit that they don't even know how to do a basic current
consumption test, let alone anything more useful.

You lot are joke.



Mark M
 

To answer the OP's question...

I just finished building one. Follow Han's assembly instructions and I don't think you'll have much trouble. Keep track of the binocular forms, don't get them mixed up. Winding them is a bit tedious, one just barely had enough space for the windings but not bad. I used a different heatsink (i'm using it with a µSDX) and had some issues accurately drilling the holes in it but that's mostly just my ineptitude for machining and trying to use a hand drill. Once I got it together it works fine. I get  a good 10W out measured with my o'scope into my old Cantenna.  Another nice kit from QRPLabs, I'm thinking of ordering another.
--
73...      Mark     AA7TA


Ron Carr
 

I haven't built my 10 watt amp yet.  But I wonder if it would be useful to match the BS170's, the idea being to maintain the best linearity.  The gate threshold voltage of a BS170 is spec'ed to be somewhere between 0.8 and 3 volts.  I have a bag of 100 and I think it was in EMRFD where I saw a method to match FET's.

Ron


Albert Tatlock's Greatest Hits - Vol 1
 

On Fri, Jul 16, 2021 at 10:20 PM, Ron Carr wrote:
I haven't built my 10 watt amp yet.  But I wonder if it would be useful to match the BS170's, the idea being to maintain the best linearity.  The gate threshold voltage of a BS170 is spec'ed to be somewhere between 0.8 and 3 volts.  I have a bag of 100 and I think it was in EMRFD where I saw a method to match FET's.
https://groups.io/g/QRPLabs/files/match-test%20bs170.pdf


Curt wb8yyy
 

Bob

Click the button here to list topics. Then scroll down to July 10. Message chain about drive level has pictures and ideas, start at bottom. Jot down the ops who have built it. Trust the info is around, and Hans will field specific questions but please search here first.

73 Curt


Al Sines
 

Oh please just go away you troll 




On Jul 16, 2021, at 16:40, Jesus Christ on Toast via groups.io <andyfoad@...> wrote:

On Fri, Jul 16, 2021 at 08:59 PM, Mike Besemer - WM4B wrote:
This is ham radio
Assuming you mean "amateur radio", yes it should be.

But it more like amateurish radio these days.

I read the messages, and half of the posters admit that they don't even know how to do a basic current
consumption test, let alone anything more useful.

You lot are joke.



wa2cky
 

Ron, I like that idea (matching the BS170s) before construction or at a minimum recording the gate threshold.  Couldn't hurt. The finals also - although they have individual bias setting pots. There is some negative feedback on both the drivers and the finals - but, again, it couldn't hurt.  I'll add it to my list. 

Bob Groh

On Fri, Jul 16, 2021 at 4:31 PM Jesus Christ on Toast via groups.io <andyfoad=rocketmail.com@groups.io> wrote:
On Fri, Jul 16, 2021 at 10:20 PM, Ron Carr wrote:
I haven't built my 10 watt amp yet.  But I wonder if it would be useful to match the BS170's, the idea being to maintain the best linearity.  The gate threshold voltage of a BS170 is spec'ed to be somewhere between 0.8 and 3 volts.  I have a bag of 100 and I think it was in EMRFD where I saw a method to match FET's.
https://groups.io/g/QRPLabs/files/match-test%20bs170.pdf


wa2cky
 

Thanks for nudge!  Never even thought of looking at YouTube!  Bad Bob!!!!

73
Bob Groh, WA2CKY

On Fri, Jul 16, 2021 at 2:55 PM Angel M0HDF <aandresfer@...> wrote:
Hi Bob,

I am about to order one too.
Check out YouTube- qrp-labs 10W PA. There are some great videos with useful info.

GL & 73
Angel 
M0HDF


Alan G4ZFQ
 

I like that idea (matching the BS170s) before construction or at a minimum recording the gate threshold.  Couldn't hurt.
Bob,

I'm not sure if it is normally any advantage. Thousands of the design were used in Softrocks. The only real problems occurred if BS170s from different batches were used.
Note, if matching the 3rd BS170 in the bias circuit also needs to be matched to the others, it sets the standing current.

Some notes here https://sites.google.com/site/g4zfqradio/configuring-a-softrock-sdr/matching-bs170-for-softrock including an alternative method of matching.

73 Alan G4ZFQ


John Payne
 

Referring of course to JCOT, NOT the OP or legitimate replies!  Sorry, guys and gals.  Should have pruned before hitting send.

W4CWZ

On 7/17/2021 10:25 AM, John Payne wrote:

This troll is why I wish Hans had time to actively moderate the list.

John W4CWZ

On 7/16/2021 6:10 PM, wb8yyy via groups.io wrote:
Bob

Click the button here to list topics. Then scroll down to July 10. Message chain about drive level has pictures and ideas, start at bottom. Jot down the ops who have built it. Trust the info is around, and Hans will field specific questions but please search here first.

73 Curt