Date   

Re: MOSFET PA RF Choke?

nm0s_qrp <ai9e_qrp@...>
 

It is difficult to speak intelligently on this design without seeing a schematic, but it is not at all unusual to have a low-inductance choke between the drain of the PA MOSFET and the supply, _if_ it is resonated against a parallel capacitor at the operating frequency to create a high impedance at the drain.  This capacitance may exist in parallel to the drain-source of the MOSFET, and have a return through a larger RF decoupling capacitor in parallel with the supply voltage.  The low value choke may let RF current pass, but as long as it is a high Q circuit, there is no RF power being dissipated.

73 Dave NM0S


Re: MOSFET PA RF Choke?

nm0s_qrp <ai9e_qrp@...>
 

Whose design is this?  Is there documentation anywhere that others could see?


Re: Magic box build, no sidetone

Jim Kortge
 

On 4/22/2019 5:03 AM, Jim Kortge wrote:

On 4/21/2019 4:28 PM, Kenneth Ketner via Groups.Io wrote:
Greetings folks.
Hello Ken,


Finally getting around to building Magic Box.
That kit is getting long in the tooth!  :-)


Can’t get a side tone at the side tone test step.
Can you send along a photo of the PCB as it currently is built, top and bottom sides so I can have a look at what you've done so far?

Can you verify that there are 2N3804 transistors at locations Q14 and Q15 and a 2N7000 at location Q16?
Sorry, 2N3904 transistors at Q14 and Q15; hands don't seem to be working at 5 AM this morning.


Replaced R46 from 10meg to 100 ohm.
That change has nothing to do with the side tone generation.
Prior tests ok.
What were your voltage readings in those tests?


Is this a known problem?
No, not at all.


Suggestions?
Send photos and answer questions and I'll try to help you.



73, Ken Ketner ka5eld

72/73,

Jim, K8IQY - The MagicBox Designer



Re: Magic box build, no sidetone

Jim Kortge
 

On 4/21/2019 4:28 PM, Kenneth Ketner via Groups.Io wrote:
Greetings folks.
Hello Ken,


Finally getting around to building Magic Box.
That kit is getting long in the tooth!  :-)


Can’t get a side tone at the side tone test step.
Can you send along a photo of the PCB as it currently is built, top and bottom sides so I can have a look at what you've done so far?

Can you verify that there are 2N3804 transistors at locations Q14 and Q15 and a 2N7000 at location Q16?


Replaced R46 from 10meg to 100 ohm.
That change has nothing to do with the side tone generation.
Prior tests ok.
What were your voltage readings in those tests?


Is this a known problem?
No, not at all.


Suggestions?
Send photos and answer questions and I'll try to help you.



73, Ken Ketner ka5eld

72/73,

Jim, K8IQY - The MagicBox Designer


Re: MOSFET PA RF Choke?

Leland L. Bahr
 

Yes, I agree with everything you said.  I also don't understand how 25 ohms could choke out RF from feeding back into the power supply. 

Lee

On 4/21/2019 5:20 PM, Curt via Groups.Io wrote:
Studying a 5 watt 40M Transmitter that uses an IRF510 for PA, what is puzzling is the RF choke is specified as a T68-2 with 10 turns.  By my calculations this presents an impedance at 7 MHz of about 20 ohms, which seems way less than the 30 times output impedance rule.  Am familiar with 10 turns on an FT37-43 which presents an impedance of about 1500 ohms, have encountered other IRF510 PAs that used that type choke.  How can the low impedance choke keep RF from leaking out of the output circuit to the power supply?

The same circuit uses a 2N3053 as a driver, the collector being coupled to the PA via a transformer that uses an FT37-43 with 14 turn primary ( 3000 ohms @ 7 MHz ) and a 4 turn secondary ( 246 ohms ). 

I am suspecting that the core types have been transposed.  If so, then the choke would be 1500 ohms and the transformer would be 49 ohm primary with a 4 ohm secondary.  These seem more what should expect?

Comments?

Curt KB5JO


MOSFET PA RF Choke?

Curt
 

Studying a 5 watt 40M Transmitter that uses an IRF510 for PA, what is puzzling is the RF choke is specified as a T68-2 with 10 turns.  By my calculations this presents an impedance at 7 MHz of about 20 ohms, which seems way less than the 30 times output impedance rule.  Am familiar with 10 turns on an FT37-43 which presents an impedance of about 1500 ohms, have encountered other IRF510 PAs that used that type choke.  How can the low impedance choke keep RF from leaking out of the output circuit to the power supply?

The same circuit uses a 2N3053 as a driver, the collector being coupled to the PA via a transformer that uses an FT37-43 with 14 turn primary ( 3000 ohms @ 7 MHz ) and a 4 turn secondary ( 246 ohms ). 

I am suspecting that the core types have been transposed.  If so, then the choke would be 1500 ohms and the transformer would be 49 ohm primary with a 4 ohm secondary.  These seem more what should expect?

Comments?

Curt KB5JO


Magic box build, no sidetone

Kenneth Ketner
 

Greetings folks. Finally getting around to building Magic Box.  Can’t get a side tone at the side tone test step. Replaced R46 from 10meg to 100 ohm. Prior tests ok. Is this a known problem? Suggestions?

73, Ken Ketner ka5eld


DMR & QRP nets

Paul AI4EE
 

Well, it looks like it will be a while before I can check in to the talk
group. The only DMR repeater I can reach is on a TV tower, and the TV
people are upgrading everything. No internet for maybe months yet. I'm
not willing to shell out $$$ for a hotspot, the rig was enough.

I will be getting some wire in the air soon, so maybe I can hit the 40
or 80 nets on Wed.

Paul, AI4EE

near Raleigh, NC


Bayou Jumper For Sale

cpa599@...
 

$80 shipped.

Built - 1 xtal. Needs minor, minor fix (no power). With Hobby Lobby box.

Pics on request.

W8EJO


Re: KiCad Tutorial

Michael N6MST
 

Keep in mind the Contextual Electronics tutorials are not using the latest version of KiCad, I ran into some trouble using KiCad 5 with those videos, got frustrated, haven't gotten the motivation to go back!


Re: KiCad Tutorial

Gwen Patton
 

Oh, yes, Chris! He and Dave Jones down under do the Amp Hour podcast. They're great!


On Thu, Apr 18, 2019 at 3:12 PM davemrtn <davemrtn@...> wrote:

Never mind, I finally stumbled onto it....

Contextual Electronics at...

https://www.youtube.com/watch?v=PlDOnSHkX2c


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.
Recycle, Reuse, Re-purpose, Repair
>Professional Sports - An activity for small minds<
!! There is a reason it is called "Sports Trivia" !!
On 4/18/2019 14:08, davemrtn wrote:

Who is it that has good KiCad Tutorials on youtube ?

--
David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.
Recycle, Reuse, Re-purpose, Repair
>Professional Sports - An activity for small minds<
!! There is a reason it is called "Sports Trivia" !!



--

-+-+-+-+-
Jenny Everywhere's Infinite: Quark Time
http://quarktime.net


Re: KiCad Tutorial

davemrtn <davemrtn@...>
 

Never mind, I finally stumbled onto it....

Contextual Electronics at...

https://www.youtube.com/watch?v=PlDOnSHkX2c


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.
Recycle, Reuse, Re-purpose, Repair
>Professional Sports - An activity for small minds<
!! There is a reason it is called "Sports Trivia" !!

On 4/18/2019 14:08, davemrtn wrote:

Who is it that has good KiCad Tutorials on youtube ?

--
David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.
Recycle, Reuse, Re-purpose, Repair
>Professional Sports - An activity for small minds<
!! There is a reason it is called "Sports Trivia" !!


Re: KiCad Tutorial

John Evans
 

Not on youtube and not free but cheap.  I highly recommend this course and instructor.  Sales go on periodically and right now it is dirt cheap.

https://www.udemy.com/kicad-like-a-pro-2e/


On Thu, Apr 18, 2019 at 1:08 PM davemrtn <davemrtn@...> wrote:

Who is it that has good KiCad Tutorials on youtube ?

--
David Martin - NA1MH - Mountain Home, Ar. 


KiCad Tutorial

davemrtn <davemrtn@...>
 

Who is it that has good KiCad Tutorials on youtube ?

--
David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.
Recycle, Reuse, Re-purpose, Repair
>Professional Sports - An activity for small minds<
!! There is a reason it is called "Sports Trivia" !!


40m Net

dekle <dekle@...>
 

Storms in the area so a lot of QRN but still got a couple:

WA9PWP     Paul     WI (on his HB1B)
AH6AX      LARRY    MD
WA9PWP     Paul     WI (this time on his shiny new Hilltopper 40 - which sounded great !)

C U next time
73
Bill
KV6Z


80 meter Net

Johnny AC0BQ
 

Ge Group
I have Thunderstorms nearby by, so 
I have pulled the plug.
Get on call cq see who is out there.
Cu all next week 
72
Johnny AC
--
Check out the 4SQRP website at 4sqrp.com


Wednesday Evening 40 and 80 meter Nets - Wed, 04/17/2019 #cal-notice

main@4SQRP.groups.io Calendar <noreply@...>
 

Wednesday Evening 40 and 80 meter Nets

When:
Wednesday, 17 April 2019
8:00pm to 9:00pm
(GMT-05:00) America/Chicago

Where:
40 and 80 Meters

Organizer:
jomatlock@...

Description:
The 40 Meter Net will be at 8:00 pm central time  on 7.122 +-. QRM
NCS will be Bill KV6Z.

Wednesday evening 80 Meter CW Net. will be at  (8:30PM Central Time Wednesday). 
The 80 meter net will be called on 3.564 MHz +/- QRM.
Net control operators are Johnny AC0BQ or Paul N0NBD.

* NEW *  Wednesday evening DMR Voice Net will be at (Thursday) 0300 UTC (9:00PM Central Time Wednesday/)
Four States QRP has a Brandmeister DMR Talk Group (TG31654). Join us to discuss QRP, ask questions, or just ragchew. The Wednesday net is a directed net  but any other time you may use the Talk Group to chat with other QRPers.
Net Control operator is Bert NØYJ.


Re: W5LFL, ham astronaut passes

Michael McEwen
 

Sic transit gloria mundi.


Tonight's DMR net

Robert
 


The forecast is for rain and hail during net time at my QTH tonight, it is very probable that my Satellite internet connection will fail or at least be highly compromised during our scheduled net time,  I will try to run  the net but if my connection fails someone else will have to pick up the net  control role for tonight's net.

Thanks 
Bert 
N0YJ 


Sent from my Verizon, Samsung Galaxy Tablet


Wednesday Evening 40 and 80 meter Nets - Wed, 04/17/2019 8:00pm-9:00pm #cal-reminder

main@4SQRP.groups.io Calendar <main@...>
 

Reminder:
Wednesday Evening 40 and 80 meter Nets

When:
Wednesday, 17 April 2019
8:00pm to 9:00pm
(GMT-05:00) America/Chicago

Where:
40 and 80 Meters

Organizer:
jomatlock@...

Description:
The 40 Meter Net will be at 8:00 pm central time  on 7.122 +-. QRM
NCS will be Bill KV6Z.

Wednesday evening 80 Meter CW Net. will be at  (8:30PM Central Time Wednesday). 
The 80 meter net will be called on 3.564 MHz +/- QRM.
Net control operators are Johnny AC0BQ or Paul N0NBD.

* NEW *  Wednesday evening DMR Voice Net will be at (Thursday) 0300 UTC (9:00PM Central Time Wednesday/)
Four States QRP has a Brandmeister DMR Talk Group (TG31654). Join us to discuss QRP, ask questions, or just ragchew. The Wednesday net is a directed net  but any other time you may use the Talk Group to chat with other QRPers.
Net Control operator is Bert NØYJ.

View Event