Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: QRP amplifier keying  (Read 3176 times)
K8AXW
Member

Posts: 3599




Ignore
« on: November 06, 2012, 12:33:38 PM »

Greetings all:

At the risk of causing undue health problems or for some, a stroke, I need to ask a question.

I just finished building a homebrew 50w linear amplifier to be used with either one of my QRP rigs.  QRP rig #1 is homebrew and I recently added circuitry to key the amplifier. 

However, my QRP rig #2 which is a Small Wonder Lab DSW-II-20, doesn't have a way to key an amplifier. 

I have researched for several days looking for a COR or RF actuated relay circuit and so far I've been unsuccessful.

I'd welcome any help with this problem and question from you avid homebrewers.
Logged
W9GB
Member

Posts: 2584




Ignore
« Reply #1 on: November 06, 2012, 12:47:42 PM »

Since Dave Benson, K1SWL (owner of Small Wonder Labs) designed the radio --
http://smallwonderlabs.com/about_us.htm
Did you ask him?
http://www.smallwonderlabs.com/
Logged
K8AXW
Member

Posts: 3599




Ignore
« Reply #2 on: November 06, 2012, 08:37:55 PM »

No I didn't ask Benson.  Last correspondence I had with Benson I got the distinct impression he considered anything over 5w blasphemy. 
Logged
W5FYI
Member

Posts: 1044




Ignore
« Reply #3 on: November 07, 2012, 07:47:07 AM »

In looking at the schematic, it appears that the collector of Q4 goes positive whenever you key down. You need to verify that, and if it does, that can be your method to switch on the amplifier (for shame for even thinking of going QRO!!!). I'd tap onto Q4's collector (or pin 7 of U8) to switch on a transistor switch to operate a fast relay. Actually, I'd build in a time delay of a half second or so to keep the relay energized (closed) until the end of the transmission.

You could also fabricate a COR by building a field strength meter (FSM) circuit, but substituting a transistor switch-and-relay circuit where the meter would normally go. GL
Logged
K8AXW
Member

Posts: 3599




Ignore
« Reply #4 on: November 07, 2012, 10:06:26 AM »

FYI: 
Quote
for shame for even thinking of going QRO!!!).

Claude:  Quite possibly you are joking.  I don't know.  The reason I prefaced my initial post the way I did was because I've found that QRP operators are without a doubt the most militant group in ham radio!  When I posted I expected sticks and stones to be thrown but I also believed that among this group there are reasonable people who enjoys the overall hobby as I do.

With that being said, I'd like to point out that I've tried to involve myself in as many facets of ham radio  that I can afford.  This includes satellite, VHF, FM, SSB, CW, digital, QRO and QRP.

My first and foremost love of ham radio is building.....homebrewing.  That has now included a solid state amplifier that puts out 40w with 2w drive.  This has been a fun and rewarding project.  Rewarding because it has introduced me into the world of solid state amplifiers, ugly constructions which is a first for me and has continued to help keep me away from the court house feeding pigeons!

No doubt I can eventually come up with a circuit that will key my little amplifier.  Actually, I built one a few years ago that was written up in QST that used RF keying to initiate a countdown timer for repeaters.

But, I'm looking for a better solution.  Why should I try to reinvent the wheel when there is no doubt a better circuit available for replication?  That way I can continue building instead of experimenting.

Al - K8AXW
Logged
KH2BR
Member

Posts: 98




Ignore
« Reply #5 on: November 07, 2012, 10:47:28 AM »

Don't over think it. Keep it simple. You could use pin diodes for your tr switching and a 555 timer to introduce some delay. I fall into that sometimes, so what could be better?
Why not a relay driven by a transistor switch with a RC time delay to hold the relay energized for a period of time?
I hate qsk.
Logged
AD6KA
Member

Posts: 2232




Ignore
« Reply #6 on: November 07, 2012, 01:39:31 PM »

Allen:

I have sent a simple amp COR circuit to
you at your ARRL email address (from QRZ).
If you have any questions let me know.

Keep on building!
73, Ken  AD6KA/5R8GQ
Logged
K8AXW
Member

Posts: 3599




Ignore
« Reply #7 on: November 07, 2012, 08:46:19 PM »

Hi Ken,

Got your email and I thank you!  I have all the parts necessary in my junk box so as soon as I can get the time, I'm going to have at it. 

2BR:  I never use QSK.....Because of the extensive modifications to my TAK-40 transceiver it is now even necessary to push a button to go from RX to TX.  This is regressing back to my younger days and I don't find it a big deal.

As for KISS..... this is why I now always think "relay."  I found myself falling into the solid state mumbo-jumbo BS a long time ago and went back to thinking "relay." 

Thanks guys for the help.  This old man appreciates it!!

73

Al - K8AXW
Logged
WB2WIK
Member

Posts: 20540




Ignore
« Reply #8 on: November 08, 2012, 08:34:51 AM »

Regression is cool.

If you want to really regress, use a hardware store knife switch as an antenna switch for T/R, and build a 6V6 rig on a kitchen cake pan (which turned upside down makes a nifty chassis), winding coils on toilet paper tubes.

Then you'd be back to my first Novice station, which made over 2000 contacts on 40m CW (crystal controlled, four crystals used) 1965-1966. Wink
Logged
K8AXW
Member

Posts: 3599




Ignore
« Reply #9 on: November 09, 2012, 08:40:42 PM »

WIK:  Steve, I've "regressed" as far as I need on this project!  I put a "soft feel" push on-push off button on the front of the amp. 

Now I can take my time experimenting with an RF activated relay.  Ya just can't beat the basics!

Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!