RF amp

[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.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

John Larkin <jjlarkin@highlandtechnology.com> wrote in
news:nqj3jet4vtj3ajpmq4r6ec5fo9ffiq21um@4ax.com:

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?



Sheesh...

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=
15Mhz+rf+amp&_sacat=0

 

[John Larkin]

On Fri, 19 Jul 2019 07:33:23 -0700 (PDT), jrwalliker@gmail.com wrote:

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

The data sheets say that either can be damaged when driving an opan
load. I'd rather not have that hazard for a production test setup.

Maybe we could buy the 5W unit and always use an attenuator. It's
$1020 so we'd need to mount it and power it and heat sink and all
that.




--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Fri, 19 Jul 2019 07:26:53 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

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

?

That's interesting. "Class A" implies that they at least bias the
transistors some.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Fri, 19 Jul 2019 14:42:05 +0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

John Larkin <jjlarkin@highlandtechnology.com> wrote in
news:nqj3jet4vtj3ajpmq4r6ec5fo9ffiq21um@4ax.com:

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?



Sheesh...

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=
15Mhz+rf+amp&_sacat=0

We have already bought three of the cheap Chinese RF amps like that
from Amazon. All were junk.

They generally have balun-type transformers driving a pair of unbiased
bipolar transistors, probably fake Motorola parts, which has zero gain
at low level and gobs of nonlinearity and distortion, if they work at
all. The single-MMIC ones output a fraction of the claimed power.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Michael Terrell]

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 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.

Class C depends on the resonant LC circuits that follow to reduce the distortion. If you want a cleaner signal, use a push-pull configuration. The old Motorola Power RF handbook had a lot of good information. It should be available for download on Bitsavers or Archive.org.

 

[John Larkin]

On Fri, 19 Jul 2019 12:52:33 -0500, amdx <nojunk@knology.net> wrote:

On 7/19/2019 9:15 AM, John Larkin wrote:
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?



https://www.kitsandparts.com/5W-A1-Amp.php

Kit Sold Out...PCB available only
Build this 2-30 MHz 5 Watt Output Class-C Amplifier for $29.

I have no idea if this will fit your need, also it has some circuitry
you don't need, but just don't put the parts in.

Mikek

That seems to be a common circuit. Q2 and Q3 are bipolars running
unbiased, which I would expect to have lots of distortion and
nonlinearity. They do suggest that the user can add their own lowpass
filter, which would help over a narrow frequency range.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[amdx]

On 7/19/2019 9:15 AM, John Larkin wrote:

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?



https://www.kitsandparts.com/5W-A1-Amp.php

Kit Sold Out...PCB available only
Build this 2-30 MHz 5 Watt Output Class-C Amplifier for $29.

I have no idea if this will fit your need, also it has some circuitry
you don't need, but just don't put the parts in.

Mikek

 

[Tauno Voipio]

On 19.7.19 21:34, John Larkin wrote:

On Fri, 19 Jul 2019 12:52:33 -0500, amdx <nojunk@knology.net> wrote:

On 7/19/2019 9:15 AM, John Larkin wrote:
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?



https://www.kitsandparts.com/5W-A1-Amp.php

Kit Sold Out...PCB available only
Build this 2-30 MHz 5 Watt Output Class-C Amplifier for $29.

I have no idea if this will fit your need, also it has some circuitry
you don't need, but just don't put the parts in.

Mikek

That seems to be a common circuit. Q2 and Q3 are bipolars running
unbiased, which I would expect to have lots of distortion and
nonlinearity. They do suggest that the user can add their own lowpass
filter, which would help over a narrow frequency range.

You may need to prepare for an attenuator between the amplifier
and the DUT because of the varying load impedance. Nearly all
semiconductor RF amplifiers I know about dislike bad SWR at load.

A way out could also be a 6CL6 with suitable tanks, as it gets red
in good time before blowing up.

Have you thought of a switchable load for termination in the time
of Hi-Z load tsting?

--

-TV

 

[John Miles, KE5FX]

On Friday, July 19, 2019 at 8:26:18 AM UTC-7, John Larkin wrote:

The data sheets say that either can be damaged when driving an opan
load. I'd rather not have that hazard for a production test setup.

Could be worth checking out this part:
https://www.minicircuits.com/WebStore/dashboard.html?model=PHA-13HLN%2B

Its demo board (with part mounted) is $99.95, good for +28 dBm into
50 ohms. Since you need to drive 500 ohms you could use a transformer to
get some more voltage.

For a while they were selling HELA-10 eval boards for $50. These were great
because they ran on a single +12V supply and could put out 1W at 1 GHz. They
arrived fully populated in a milled aluminum block with tapped 2-56 holes,
ready to bolt into onto whatever.

Eventually Mini-Circuits realized what they were selling and jacked up
the price, and their amplifier demo boards are no longer sold as finished
assemblies. I bought 3 of those HELA amps and I wish I'd bought 10 more.

As far as running into an open circuit is concerned, that should be safe
enough with a broadband amp as long as the open circuit in question isn't
at the end of a transmission line. Most of their MMIC parts are
unconditionally stable, so it's just a matter of not sending a lot of
reflected voltage back at them.

-- john, KE5FX

 

[George Herold]

On Friday, July 19, 2019 at 7:48:18 PM UTC-4, George Herold wrote:

On Friday, July 19, 2019 at 10:09:54 AM UTC-4, John Larkin wrote:
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.
Well cut some eye holes in it or you might burn yourself.
:^)

If the copper clad is double sided, you could drill some holes
and them with solder or something.

oops ^then fill... I'm equally bad at speaking.
GH

(two holes is nice 'cause you can see when the solder wets the pad,
down one hole. I've done that with plated through holes.)

Hey if an opamp is not enough then some opamp driving some
fet class A, would be my next try.
(Mind you I have no idea which opamp or FET, and 14 MHz,
well you've gotta start thinking about wavelenghts and
impedances. TBH I wish I had more RF wisdom.)

George H.


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.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[George Herold]

On Friday, July 19, 2019 at 10:09:54 AM UTC-4, John Larkin wrote:

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.

Well cut some eye holes in it or you might burn yourself.
:^)

If the copper clad is double sided, you could drill some holes
and them with solder or something.
(two holes is nice 'cause you can see when the solder wets the pad,
down one hole. I've done that with plated through holes.)

Hey if an opamp is not enough then some opamp driving some
fet class A, would be my next try.
(Mind you I have no idea which opamp or FET, and 14 MHz,
well you've gotta start thinking about wavelenghts and
impedances. TBH I wish I had more RF wisdom.)

George H.

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.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Arie de Muynck]

On 2019-07-18 21:39, 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


I get to teach a young engineer my Dremeling secrets.

I just got an offer for this kit:

https://www.nxp.com/products/rf/rf-power/rf-ism-and-broadcast/1-600-mhz-broadcast-and-ism/mrf101an-rf-essentials-kit:MRF101AN-START-KIT

Comes with two transistors, just in case you blow one.
$50, now 50% off with code NXP40IFU until end of august.
But maybe 100W is a bit of overkill...

Arie

 

[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.

Here's another idea: make a big square wave and bandpass filter it.

https://www.dropbox.com/s/1j4cum8sjpbw7rk/P348_Sine_Source_1.JPG?raw=1

which simulates a very nice sine with a 2-pole bandpass.

The T577 is a little totem-pole switch board that I did as an
experiment. I may have found a use for it.

We were thinking that we could use a mosfet gate driver chip to get
the square wave, but none of them seem to like to switch at 14 MHz.
The cute little T577 will switch 60 volts or so rail-to-rail in about
a nanosecond.

https://www.dropbox.com/s/thsls58qv2m4gmi/T577_lores_2.jpg?raw=1

It's a mouse-bite component that can be used on bigger boards.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Fri, 19 Jul 2019 16:48:15 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Friday, July 19, 2019 at 10:09:54 AM UTC-4, John Larkin wrote:
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.
Well cut some eye holes in it or you might burn yourself.
:^)

If the copper clad is double sided, you could drill some holes
and them with solder or something.

I should maybe make some power-pad SO adapter boards, with lots of
thermal vias and a big pour on the bottom. Next proto board!


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

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

 

[Phil Hobbs]

On 7/19/19 12:35 AM, 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.

Drill a hole and dispense cold spray on the pad.

(I've done that sort of thing occasionally.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Piotr Wyderski]

John Larkin wrote:

> I get to teach a young engineer my Dremeling secrets.

I am not able to produce decent PCBs that way, but I became quite
versed in dremeling ferrite when I was experimenting with multiaperture
cores.

Best regards, Piotr

 

[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.

Here's one way we could do it.

https://www.dropbox.com/s/aga3fq00n0g5b3y/28S772A1.pdf?raw=1

The T577 is my little totem-pole ganfet switch board.

If we lay this out to fit into one of our standard enclosures, we
could call it a product. The output filter could be a bandpass for the
sine generator function, or a lowpass, or nothing, for a pulse output.

Input could be AC or DC coupled, and there are lots of possibilities
for the power and amplitude programming bits.

I might add a crystal oscillator just for fun. Digikey will program an
XO to basically any frequency one wants.

This one only needs 3 mA of supply current:

https://www.digikey.com/product-detail/en/epson/SG-8018CA-TJHPA/SG-8018CA-TJHPA-ND/7784056

I would be linear regulating from up to 56 volts!




--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Clifford Heath]

On 21/7/19 9:56 am, Piotr Wyderski wrote:

John Larkin wrote:
I get to teach a young engineer my Dremeling secrets.
I am not able to produce decent PCBs that way, but ...

I grew up using a dental drill we had at home, so I'm ok freehand, but...

I've set a Dremel drill press up with the minimum bit height just at the
bottom of the copper. It's trivial to slide the PCB under it in nice
straight lines, but it really needs two hands. I'm considering attaching
a foot pedal to the lever that drops the bit down, to free the second
hand. It would be trivial to achieve results better than John's
freehand, that way.

Clifford Heath.

 

[John Larkin]

On Mon, 22 Jul 2019 11:15:57 +1000, Clifford Heath
<no.spam@please.net> wrote:

On 21/7/19 9:56 am, Piotr Wyderski wrote:
John Larkin wrote:
I get to teach a young engineer my Dremeling secrets.
I am not able to produce decent PCBs that way, but ...

I grew up using a dental drill we had at home, so I'm ok freehand, but...

I've set a Dremel drill press up with the minimum bit height just at the
bottom of the copper. It's trivial to slide the PCB under it in nice
straight lines, but it really needs two hands. I'm considering attaching
a foot pedal to the lever that drops the bit down, to free the second
hand. It would be trivial to achieve results better than John's
freehand, that way.

Clifford Heath.

The copper carving is artistic but fundamentally insignificant. The
"results" that matter are the circuit performance.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics