Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Officially starting the 24 FET build




 
The AM Forum
September 19, 2019, 09:54:05 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: 1 [2]   Go Down
  Print  
Author Topic: Officially starting the 24 FET build  (Read 8345 times)
0 Members and 1 Guest are viewing this topic.
ka1tdq
Member

Offline Offline

Posts: 1262


Massachusetts Democrat


« Reply #25 on: July 24, 2019, 09:39:51 PM »

My vacuum variable arrived and this is how I mounted it.

Jon


* IMG_1420.jpg (2661.35 KB, 4032x3024 - viewed 116 times.)
Logged

Just follow the instructions, more or less.
http://www.ka1tdq.radio
PA0NVD
Member

Offline Offline

Posts: 583


Nico and Chappie (Chappie is the dog...)


« Reply #26 on: July 25, 2019, 01:15:47 PM »

Take great care with those clamps Jon. A little too much force close to the seal and the glass - metal seal will break./ I always make them of thin copper foil to prevent local force or use the original clamps. But also the original clamps should be mounted such that force near the seal is prevented. . I speak from experience... Cry
Logged
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 7287



WWW
« Reply #27 on: July 26, 2019, 11:46:10 PM »

Thank you for that tip!
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
ka1tdq
Member

Offline Offline

Posts: 1262


Massachusetts Democrat


« Reply #28 on: July 27, 2019, 09:48:24 PM »

I think I was fairly careful not to clamp too hard when I mounted it. Either way, I'm not going to touch it. Even if I broke vacuum (which I don't think I did) I'm probably not in danger of arcing over. But, definitely noted! These capacitors are expensive!

Jon
Logged

Just follow the instructions, more or less.
http://www.ka1tdq.radio
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7864


"Let's go sailing, Tommy!" - Yaz


« Reply #29 on: July 27, 2019, 11:21:01 PM »

I think I was fairly careful not to clamp too hard when I mounted it. Either way, I'm not going to touch it. Even if I broke vacuum (which I don't think I did) I'm probably not in danger of arcing over. But, definitely noted! These capacitors are expensive!
Jon


Hi Jon,

If the vacuum failed you would certainly have arcing with a 24 FET rig power level.   The vac cap spacing in very small and would barely work as a loading cap, never mind as a tuning cap once the vacuum is gone.

The mechanical set up you presently have should be fine if the stress loading is adjusted and balanced right. Because you have it supported in two places, it will have less stress than the many we see that are mounted in the front only.  As already said, much will depend on the stress you introduce. The problem comes when tightening things down and one strut is shorter (or out of alignment) than the other putting a load (like a lever) on the seals/ glass. Or, the RF connections pull on the glass, sometimes from tightening or even thermal expansion or contraction. Or the tuning shaft interface is not flexible enough.  We must baby our vac caps just like you would a vac relay or the pins on a big tube.

Also, I would get rid of the bare wire that connects the RF tuning cap and associated RF circuits. Use copper or silver plated strap for all RF connections for function and aesthetics.

I see you have a Plexiglas 1/4" rod to RF isolate the floating tuning cap rotor shaft from burning your hand... :-)   Nice machining job on that adapter assembly.

Your construction techniques have greatly improved from your first 3-500Z amplifier and other early projects. Looks very FB now.

T
Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
ka1tdq
Member

Offline Offline

Posts: 1262


Massachusetts Democrat


« Reply #30 on: July 28, 2019, 02:49:32 AM »

I wish I could claim credit for the machining job of the shaft coupler. I got it from eBay.

Noted on the copper strap. Iíll make changes.

I have a variac to bring carrier voltage slowly up. Iíll see how the vacuum variable behaves. If I get arcing, Iíll know that Iíve let the gas in. I do however plan on running this at just the 400 watt carrier level. Iíve always had a knee-jerk interest in QRP.

Thanks for the compliments too! Hopefully this rig lives up to more than just aesthetics and belches out some RF too.

Jon
Logged

Just follow the instructions, more or less.
http://www.ka1tdq.radio
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 7287



WWW
« Reply #31 on: July 28, 2019, 10:33:09 PM »

My vacuum variable arrived and this is how I mounted it.

Jon

That whole thing looks like something on a laboratory table in Star Trek TOS. Maybe it's the big vacuum cap but it all looks great.
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
ka1tdq
Member

Offline Offline

Posts: 1262


Massachusetts Democrat


« Reply #32 on: July 29, 2019, 09:03:30 PM »

Open frame construction does let the techie-ness show!

I moved the back vacuum variable mount outward so that things fit better now. I also added copper strapping on the output network and added the transformer.  All that's left is to complete the heat sink assembly and test.

I'll make future updates on the other thread.

Jon


* IMG_1448.jpg (3160.03 KB, 4032x3024 - viewed 88 times.)
Logged

Just follow the instructions, more or less.
http://www.ka1tdq.radio
N1XBM
Member

Offline Offline

Posts: 29


« Reply #33 on: August 04, 2019, 03:14:29 PM »

I was working on the project for an escape from yard work and heat. So be nice, I enjoy building, but I am not the prettiest builder.  Grin I have the heat sink mechanically attached to the box, hopefully the loading cap fits! I was just laying things in the box to see how things looked. I'm getting closer.

So I still need...
Loading cap
Mount for the tuning cap with shaft coupling and knob
Meters and switches
Rewind the 160m coil to a different diameter amd mounted out 90 degrees from 75m coil as Steve suggested.
Mount/connect T1-4
Of coarse interconnect everything
I'm sure I'm missing something.

My goal is to have this done by the end of the summer and have it tested. Then I'll start the PWM!


* 0804191506.jpg (3141.91 KB, 3264x2448 - viewed 70 times.)
Logged
steve_qix
Contributing
Member
*
Offline Offline

Posts: 2447


Bap!


WWW
« Reply #34 on: August 05, 2019, 08:14:30 AM »

Looks good!  My only suggestion is that you turn the 160 meter coil 90 degrees, and possibly put the relay directly underneath or directly next to the coil.  If underneath the coil, the relay can actually support (or help support) it.  In this way, the coil isn't directly coupling into the 75 meter coil, nor the transformers.
Logged

High Power, Broadcast Audio and Low Cost?  Check out the class E web site at: http://www.classeradio.org
Pages: 1 [2]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.061 seconds with 18 queries.