Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
811 bias for Mod




 
The AM Forum
June 16, 2019, 05:26:26 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 ... 4 [5]   Go Down
  Print  
Author Topic: 811 bias for Mod  (Read 7174 times)
0 Members and 1 Guest are viewing this topic.
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7838


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


« Reply #100 on: January 12, 2019, 06:17:27 PM »

The right angle drives I found are millen 10000 which have a 1:48 turns ratio. Are these the correct parts or will that make the turning painfully slow? i sent a email to Chuck to see if he perhaps has some pics of the underside of that deck pic as well as some for the modulator. His QRZ page only shows the same pic as yours.

John


Hopefully Chuck took some pics from underneath the rig too.  That would give you a lot of good info to study.

500 pF vacuum caps used for HF are slow enough already at 1:1 drive ratio. No need to slow them down further. You will be rowing around the bands enough already at 1:1...  Wink Same with the 1500-2000 pF loading vac caps.  

If you vertically mount one, get a 1:1   90 degree angle 1/4" shaft drive.   You will need a separate  1/4" shaft 1:1 panel mounted turns counter too.   (Most vac variables use 1/4" shafts, but not all.)   Be sure you use an insulated 1/4" shaft to the front panel (and/or an insulated 1/4" flex coupler) because there is often RF induced onto the metal shaft coming out of the vac variable casing. Potential RF burns even though the vacuum cap "rotor " may be grounded thru internal threads and finger stock. That goes for all metal shaft variable caps coming out to the front panel on a QRO KW rig.

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."
w9jsw
Two shots of Whisky
Contributing
Member
*
Offline Offline

Posts: 217



« Reply #101 on: January 15, 2019, 08:58:10 AM »

Chuck is helping me with parts. Have right angle drives, now he is looking for caps. What a guy!
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7838


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


« Reply #102 on: January 15, 2019, 10:46:32 AM »

Chuck is helping me with parts. Have right angle drives, now he is looking for caps. What a guy!

Yep, Chuck has helped many of us over the years.  (WA1EKV / K1KW)


Some background:

There was a time when I was building a lot of rigs and I needed to call him almost every night for advice. I'll bet we spent 100 hours on the phone and email over the years. He was always easy-going and more than willing to help. He could answer the questions that nobody else knew the answers to... the practical side of homebrewing that was not in the books.   He probably doesn't realize it, but he was my mentor for many years, though my work still doesn't compare to his.  The question is: Is the ham radio world a better place because of you?  In his case, yes, he made a huge difference.

It was back in 1965 when there was a knock on the door and there was 14 year old Chuck standing on the porch with his father. We had an eyeball QSO for the first time. He had his homebrew screen modulated 6146 rig under his arm built into a Bud Shadow cabinet. He pulled the cabinet off and I was amazed that anyone could build a rig, never mind make it look like factory work.  He went on to eventually build a 4-1000A plate modulated by 833As in high school. This young whipper-snapper was louder and sounded better than the old buzzard W1's of the 1960's AM era which probably made them crazy...   Grin

He went on over the next 50 years to build many homebrew rigs, some of which are still on the air in others' hands.  He was always on the "fun" leading edge of Ham technology. His 75M rotary beam in the mid 80s, stacked HF logs, homebrew amplifers, SDR, etc., etc., were a ham's dream. He's an engineer's engineer.  

Many don't know it, but he has another serious hobby -  a 6-bay garage full of 1920's/30's restored cars that he regularly drives to events, etc.  My guess is he has helped many of those hobbyists too.

What can I say? You are in good hands. Ask questions and get the right answers.  Glad you are finding some of the hard to find parts...  Some day you will pay it forward and help others build their rigs too.


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."
w9jsw
Two shots of Whisky
Contributing
Member
*
Offline Offline

Posts: 217



« Reply #103 on: January 16, 2019, 06:36:38 AM »

Chuck came thru with the Vac Caps. Almost there. Just have to now wait for all of the stuff to arrive.
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7838


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


« Reply #104 on: January 16, 2019, 11:52:32 AM »

Chuck came thru with the Vac Caps. Almost there. Just have to now wait for all of the stuff to arrive.


That's good news. With those right angle drives, you can mount the vac caps vertically on the chassis if you want.  Better tank placement and no support bracket needed for the vac cap. Now you need turns counters. They can sometimes be found on eBay. The metal ones are best and hardest to find.

There are plastic ones around made by a guy in OH? who has since passed on. I once bought 10 of them -  but one by one the counter gears stripped. All of my rigs use metal now. Also, try to get them with three digits. Two digits sometimes run out of range and you have to guess where you are.  IE, the vac cap requires a certain number of full turns from end to end.... be sure your turns counter is able to cover the full range without repeating itself.

What value caps do you have coming?  (uF / voltage)

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."
w9jsw
Two shots of Whisky
Contributing
Member
*
Offline Offline

Posts: 217



« Reply #105 on: January 17, 2019, 06:40:39 AM »

I have 2 5KV caps coming, one at 500pf and one at 1000pf. Chuck said the 1000pf will be perfect at my b+ level (2800v). He was cautious on the 500pf. He had some 15kv units that were too large for a 813 class unit. These are new and hipot at 5.8kv. He said if I keep my B+ nearer to 2500V they should work fine. I recalled that you doubt that the supply will do 2800v at full power. I figured backing it down nearer to 2500V will have a negligible effect on overall power output. We shall see.

If it does not work well there I can always move it to the Tuna.

I also have the right angle drives and he found 2 turns counters. I am planning to lay out the deck along the lines of his.

I will have to pad the antenna load cap for 160M. He suggested some good caps to use. I will also use some of those spst russian vac relays like he uses. He says they are excellent.

I get my iron in a week.  Grin

John
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7838


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


« Reply #106 on: January 17, 2019, 12:26:59 PM »

Excellente!

Yes, the 1000pF @ 5KV will be fine for loading.  You will need some padding on 160M.  Nico had mentioned about padding caps and 10M / VHF parasitics due to feed-thru coupling of the relay or switch used.  If the padding capacitor relay has minimum feedthrough C, it will be OK.   Measure it when you receive the relay and see what it is.  I've never had any problems with padding cap generated parasitics on 20M and lower.

The 500 pF at 5 KV for the plate tuning will have to be watched carefully during testing and operation. When ramping it up to full power, use put a tall mirror behind the rig in a dark room to watch for arcing. (careful!)  Also, monitor carefully the vac cap shiny copper plates for signs of tiny black pits which is the sign of RF arcing.

You might as well get a Russian T/R ant switching vac relay (or pair of spdt) while you're at it.

Too bad you don't have a pic of the bottom of Chuck's RF chassis. Well, just use strap to connect the grid circuit components and keep it as close to the grid as possible, as he says.  Just think in terms  of as short and thick as possible for all the RF connections and layout.  Make sure no input components can see the output components anywhere in the amplifier.   (good shielding and bypassing)

The rest of the stuff isn't really that critical - the audio, AC and DC stuff.

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."
w9jsw
Two shots of Whisky
Contributing
Member
*
Offline Offline

Posts: 217



« Reply #107 on: January 18, 2019, 10:27:20 AM »

Bandswitch showed up. It is huge! Going to throw it in the dishwasher and then test for inductance.
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7838


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


« Reply #108 on: January 19, 2019, 12:39:11 PM »

Hi John,

Well, it looks like you are really going through with this 813 project. You have reached the point of no return...  Wink  

As promised, I  packed up the four tubes, sockets and plate caps and put them in both bubble wrap and styro-pellets. Should make the trip from CT > IL  very FB, OM.

I checked my 813 tube supply and found I had only seven tubes. I forgot I gave four to another ham back in 1999 who built this same rig.   So I have three more 813 spares in case you run into any problems with these four.  They look pretty good and at one time I probably tested them in one of my rigs.

I assume your Salem, IL adr is OK on QRZ.com?

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."
w9jsw
Two shots of Whisky
Contributing
Member
*
Offline Offline

Posts: 217



« Reply #109 on: January 19, 2019, 01:36:49 PM »

Yes, the addr on QRZed is correct. Thank you so much for the parts and the help so far! This is just the start of a journey I am sure.

I am going to start a new thread directed at the build. That way we start fresh and focus just on this design. I am amazed that this thread has had so many views! I feel like I am just as famous as AOC  Roll Eyes

New thread here - http://amfone.net/Amforum/index.php?topic=44558.0

We are about 1 week out on the delivery of the iron. Hoping that the weather does not mess this up. It is very kind of Phil to haul this along on his trip south. At 180lbs for the transformer and the weight of the other components, it is not a casual undertaking. Hope it does not weigh down the back of my Yugo too much...Ha! (I have a Ford F250, actually).

John
W9JSW

Logged
Pages: 1 ... 4 [5]   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 0.05 seconds with 19 queries.