The AM Forum
December 10, 2023, 09:16:03 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Make SURE you size your TX / Rx relay correctly.  (Read 1690 times)
0 Members and 1 Guest are viewing this topic.
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2613


Making AM GREAT Again!


« on: January 19, 2023, 06:39:17 PM »

Friend send some pics.  Thought I'd share.

He runs legal limit AM Smiley


Size your gigavac right.  This was NOT a cheap fix.

--Shane
WP2ASS / ex KD6VXI


* Screenshot_20230119_193735_Chrome.jpg (736.11 KB, 1080x2400 - viewed 256 times.)

* Screenshot_20230119_193720_Chrome.jpg (932.7 KB, 1080x2400 - viewed 238 times.)

* Screenshot_20230119_193702_Chrome.jpg (606.46 KB, 1080x2400 - viewed 219 times.)
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2613


Making AM GREAT Again!


« Reply #1 on: January 19, 2023, 06:42:00 PM »

Yes.  The first pic of the inside of the relay, that's Cload next to it.  Sized appropriately.....  Peak currents are in the range above 75 amps on that cap.



--Shane
WP2ASS / ex KD6VXI

Logged
KD1SH
Member

Offline Offline

Posts: 656



« Reply #2 on: January 19, 2023, 07:58:31 PM »

Is he sure it wasn't a sequencing issue - hot switched it?
Logged

"Gosh, Batman, I never knew there were no punctuation marks in alphabet soup!"
—Robin, in the 1960's Batman TV series.
KD1SH
Member

Offline Offline

Posts: 656



« Reply #3 on: January 19, 2023, 08:16:00 PM »

I'm using a Greenstone VC-2 in my 8877 two-holer; specs say 50 amps. It's enclosed in a Budd die-cast box, so at least the shrapnel will be contained.
Logged

"Gosh, Batman, I never knew there were no punctuation marks in alphabet soup!"
—Robin, in the 1960's Batman TV series.
W3SLK
Member

Online Online

Posts: 2625

Just another member member.


« Reply #4 on: January 20, 2023, 11:21:01 AM »

I'll bet that will keep your panfish down! Wink
Logged

Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2613


Making AM GREAT Again!


« Reply #5 on: January 20, 2023, 09:07:54 PM »

Is he sure it wasn't a sequencing issue - hot switched it?

He uses a foot pedal for the amp and a microphone for the radio.  I do believe his amps are sequenced, I know there is more than one stage but I only saw one foot pedal.....  Didn't get into it that close / behind the scenes, other than the amplification room.

I wondered about balanced currents in the configuration used.  I would have preferred symmetric but that's a tall order for 4 vac relays that large.

--Shane
WP2ASS / ex KD6VXI
Logged
KD1SH
Member

Offline Offline

Posts: 656



« Reply #6 on: January 21, 2023, 09:21:18 AM »

Probably almost impossible to ensure balanced current through multiple relays; even less possible to ensure perfectly simultaneous closing/opening. I'm only using a single vac-relay for the output switching,  but I designed my sequencer to be almost painfully slow to make sure that everything is settled down before the final application of operating bias brings the tubes out of cutoff.
Logged

"Gosh, Batman, I never knew there were no punctuation marks in alphabet soup!"
—Robin, in the 1960's Batman TV series.
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8279



WWW
« Reply #7 on: January 24, 2023, 01:22:25 AM »

Handles noted.
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2613


Making AM GREAT Again!


« Reply #8 on: January 25, 2023, 04:34:40 AM »

Handles noted.

8 handles.

4 pairs.


--Shane
WP2ASS / ex KD6VXI
Logged
Pages: [1]   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 0.105 seconds with 19 queries.