RF amp

[John Larkin]

We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1


I get to teach a young engineer my Dremeling secrets.



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Thu, 18 Jul 2019 12:47:50 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:
We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.

We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.




--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:

We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.

George H.
*says the man with mostly opamps in his tool box.

I get to teach a young engineer my Dremeling secrets.



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Uwe Bonnes]

John Larkin <jjlarkin@highland_snip_technology.com> wrote:

On Thu, 18 Jul 2019 12:47:50 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:
We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.


We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.

New buf634a perhaps?
--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------

 

[Lasse Langwadt Christense]

torsdag den 18. juli 2019 kl. 22.25.14 UTC+2 skrev John Larkin:

On Thu, 18 Jul 2019 12:47:50 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:
We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.


We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.

if the output doesn't have to grounded use two in a bridge?

 

[John Miles, KE5FX]

On Thursday, July 18, 2019 at 1:25:14 PM UTC-7, John Larkin wrote:

We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.

THS3491 would be the right part for that job, it sounds like.

-- john, KE5FX

 

[John Larkin]

On Thu, 18 Jul 2019 14:05:16 -0700 (PDT), "John Miles, KE5FX"
<jmiles@gmail.com> wrote:

On Thursday, July 18, 2019 at 1:25:14 PM UTC-7, John Larkin wrote:

We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.


THS3491 would be the right part for that job, it sounds like.

-- john, KE5FX

That just about works. We could push the Vccmax a volt or so if
needed. 28 p-p is right on the edge.

If we used a 50 ohm resistor to drive our short coax, and then the 500
ohm DUT load, it doesn't work again.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Lasse Langwadt Christense]

fredag den 19. juli 2019 kl. 00.18.03 UTC+2 skrev John Larkin:

On Thu, 18 Jul 2019 13:50:34 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

torsdag den 18. juli 2019 kl. 22.25.14 UTC+2 skrev John Larkin:
On Thu, 18 Jul 2019 12:47:50 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:
We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.


We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.


if the output doesn't have to grounded use two in a bridge?

The load is single-ended. A transformer could convert a bridge drive
to se.

could also give you some voltage gain

 

[John Larkin]

On Thu, 18 Jul 2019 13:50:34 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

torsdag den 18. juli 2019 kl. 22.25.14 UTC+2 skrev John Larkin:
On Thu, 18 Jul 2019 12:47:50 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:
We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.


We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.


if the output doesn't have to grounded use two in a bridge?

The load is single-ended. A transformer could convert a bridge drive
to se.

The mosfet class C isn't bad. One of my guys is Spicing it now.




--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On 18 Jul 2019 20:39:58 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:

John Larkin <jjlarkin@highland_snip_technology.com> wrote:
On Thu, 18 Jul 2019 12:47:50 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:
We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.


We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.

New buf634a perhaps?

That would drive the load nicely, but we'd still need to get the gain
from somewhere. Maybe a passive resonant circuit.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Joerg]

On 2019-07-18 12:39, John Larkin wrote:

We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

The link doesn't work here right now but if it's for a bench test you
could also use a shortwave transceiver for ham radio. They all do 14MHz
because that is one of the ham bands.

I get to teach a young engineer my Dremeling secrets.

Make sure the first aid kit is nearby when the engineer tries.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[George Herold]

On Thursday, July 18, 2019 at 6:52:48 PM UTC-4, Joerg wrote:

On 2019-07-18 12:39, John Larkin wrote:


We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1


The link doesn't work here right now but if it's for a bench test you
could also use a shortwave transceiver for ham radio. They all do 14MHz
because that is one of the ham bands.


I get to teach a young engineer my Dremeling secrets.


Make sure the first aid kit is nearby when the engineer tries.

We use to slice thin walled stainless with dremel grinding discs.
'eye protection' required!

George H.
And you should never be in the machine shop alone...
though I've broken that rule many times in my stupid
youth. (How is it most boys/ men live to reproduce?)

--
Regards, Joerg

http://www.analogconsultants.com/

 

[George Herold]

On Thursday, July 18, 2019 at 4:25:14 PM UTC-4, John Larkin wrote:

On Thu, 18 Jul 2019 12:47:50 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, July 18, 2019 at 3:39:43 PM UTC-4, John Larkin wrote:
We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1

Why not some opamp*? My rigol sig gen does ~20 Vp-p, a gain of
2... oh you probably need more current drive.


We could almost do it with an opamp. We'd need a gain of 3 from our
source. THS3091 might almost work, at its abs max Vcc.

If it's for testing and not sale, then sometimes parts
will work a few volts over the max... you'd have to test.
(I blew up an lt1013 at ~52 V... it ran fine at 50V for
~1 hr. I only 'looked' at my schematic after I blew it up.)

Well, it's in a loop driving a darlington so no power.

George H.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Thu, 18 Jul 2019 12:39:33 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1


I get to teach a young engineer my Dremeling secrets.

The class C thing has a lot of distortion in Spice.

This might be OK.

https://www.dropbox.com/s/ir1scaxxlecwh2u/TGEN_1.asc?dl=0

I think I can make the 1:1 transformer on a pot core that we have,
maybe 2 turns twisted pair wire-wrap wire, bifilar.

The THS6022 amp has a power pad on the bottom, which would be tricky
to cool on a proto board. Maybe we can glue a heat sink to the top.
The dual THS would dissipate a half watt maybe, not too bad. Or we
could use two separate amps, just to spread the heat.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Jan Panteltje]

On a sunny day (Thu, 18 Jul 2019 12:39:33 -0700) it happened John Larkin
<jjlarkin@highland_snip_technology.com> wrote in
<kci1je5kige13m5cap0koiqb4tsmpg3ci0@4ax.com>:

We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1


I get to teach a young engineer my Dremeling secrets.

For that sort of thing maybe a simple NPN PNP totempole amp with feedback would do,
then 50 ohm resistors to the outputs.

I have used that for video several times up to 10 MHz.
Most transistors go much higher,
No inductors, capacitors, and wideband. low distortion.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

On Thu, 18 Jul 2019 12:39:33 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

What is the load impedance ? If 50 ohms, that is just 2 W, any
amateur radio transmitter could provide it.

If much less than 50 ohms, just use a bigger transmitter and a step
down transformer to transfer 50 ohms down to your low required
impedance.

If you insist of doing it all yourself with a few volt op-amps, use
some op-amp followed by a very beefy complementary emitter follower
and a step-up transformer to get 28 Vpp.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1


I get to teach a young engineer my Dremeling secrets.

 

[George Herold]

On Friday, July 19, 2019 at 12:35:55 AM UTC-4, John Larkin wrote:

On Thu, 18 Jul 2019 12:39:33 -0700, John Larkin
jjlarkin@highland_snip_technology.com> wrote:



We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1


I get to teach a young engineer my Dremeling secrets.

The class C thing has a lot of distortion in Spice.

This might be OK.

https://www.dropbox.com/s/ir1scaxxlecwh2u/TGEN_1.asc?dl=0

I think I can make the 1:1 transformer on a pot core that we have,
maybe 2 turns twisted pair wire-wrap wire, bifilar.

The THS6022 amp has a power pad on the bottom, which would be tricky
to cool on a proto board. Maybe we can glue a heat sink to the top.
The dual THS would dissipate a half watt maybe, not too bad. Or we
could use two separate amps, just to spread the heat.

I've flipped opamps with power pads over.. dead bug, and then
strapped a piece of copper tape front to back, soldered to copper
clad and pad. (Probably too ugly for a gold plated proto. :^)

George H.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Friday, 19 July 2019 15:09:54 UTC+1, John Larkin wrote:

I'd just buy a boxed RF power amp if I could find a decent one for a
low number of kilobucks. My frequency, 14-15 MHz, excludes a lot of
possibilities. I can find some nice stuff for $8K.

MiniCircuits make a few amplifiers that will do what you want for
a price within your budget.

ZHL-1-2W+ 2W 5-500MHz USD 560
ZHL-5W-1+ 5W 5-500MHz USD 1020

John

 

[Lasse Langwadt Christense]

fredag den 19. juli 2019 kl. 16.09.54 UTC+2 skrev John Larkin:

On Fri, 19 Jul 2019 05:58:21 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Friday, July 19, 2019 at 12:35:55 AM UTC-4, John Larkin wrote:
On Thu, 18 Jul 2019 12:39:33 -0700, John Larkin
jjlarkin@highland_snip_technology.com> wrote:



We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

https://www.dropbox.com/s/tq8qsvc7lbfirmh/Z468_WB_1.png?raw=1


I get to teach a young engineer my Dremeling secrets.

The class C thing has a lot of distortion in Spice.

This might be OK.

https://www.dropbox.com/s/ir1scaxxlecwh2u/TGEN_1.asc?dl=0

I think I can make the 1:1 transformer on a pot core that we have,
maybe 2 turns twisted pair wire-wrap wire, bifilar.

The THS6022 amp has a power pad on the bottom, which would be tricky
to cool on a proto board. Maybe we can glue a heat sink to the top.
The dual THS would dissipate a half watt maybe, not too bad. Or we
could use two separate amps, just to spread the heat.
I've flipped opamps with power pads over.. dead bug, and then
strapped a piece of copper tape front to back, soldered to copper
clad and pad. (Probably too ugly for a gold plated proto. :^)

George H.

I could put a bag on my head and do that.

I'd just buy a boxed RF power amp if I could find a decent one for a
low number of kilobucks. My frequency, 14-15 MHz, excludes a lot of
possibilities. I can find some nice stuff for $8K.

https://broadcastconcepts.com/Lab-Amplifier-10W-Class-A-1-525MHz.html

?

 

[John Larkin]

On Fri, 19 Jul 2019 11:08:50 +0300, upsidedown@downunder.com wrote:

On Thu, 18 Jul 2019 12:39:33 -0700, John Larkin
jjlarkin@highland_snip_technology.com> wrote:



We need 28 volts p-p at 14 MHz to test our IQ modulator box. I've
bought two Chinese RF amps from Amazon and both are garbage. So we're
going to build our own class C amp, as a dremel'd prototype.

What is the load impedance ? If 50 ohms, that is just 2 W, any
amateur radio transmitter could provide it.

The DUT is switchable to be 50r or HiZ. We could test it in either
mode.

If much less than 50 ohms, just use a bigger transmitter and a step
down transformer to transfer 50 ohms down to your low required
impedance.

If you insist of doing it all yourself with a few volt op-amps, use
some op-amp followed by a very beefy complementary emitter follower
and a step-up transformer to get 28 Vpp.

The problem is to get a fast, high-current opamp that has the voltage
swing. A few of the THS parts almost work.

Any suggestion for an amateur transmitter that would make maybe 2 or
so watts sinewave into 50r at 14.5 MHz?



--

John Larkin Highland Technology, Inc

lunatic fringe electronics