Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Questions about the Harvey Wells Bandmaster




 
The AM Forum
October 01, 2023, 06:38:29 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 [3] 4   Go Down
  Print  
Author Topic: Questions about the Harvey Wells Bandmaster  (Read 54809 times)
0 Members and 1 Guest are viewing this topic.
n0tjl
Member

Offline Offline

Posts: 44


« Reply #50 on: March 26, 2015, 10:34:53 AM »

Is there any flexibility in the value of the capacitor?
Thanks,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #51 on: March 26, 2015, 12:15:50 PM »

yes ... calculate the value of cap reactance :   Xc = 1 / (2 x pi x freq x c ) so for 10pF at 7 mHz this equals about 2.2 kOhm and this will double to 4.4 KOhm on 80 mtrs ... this sets up a desirable condition for 80 or 40 mtr op as this tends compensate for the increased output on 80 mtrs of the CFC exciter

the 6aq5 has around 13V of bias generated by the cathode ckt which is class a operation and is ready to amplify (or oscillate with the inductor in the ckt) ... as you drive it as a buffer ... swings larger than this will swing the grid into grid current which will cause grid rectification and gen negative grid bias so the circuit tends to be somewhat self regulating, at least to a point ... the output spectrum will be richer in harmonics with overdrive and could possibly tune up on one of those .... by the way the HW manual suggests 80 mtr crystals for both 80 and 40 mtr operation .... both will probably work but again could have trashy output
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #52 on: March 27, 2015, 12:21:15 PM »

Can I get away with two 18pf capacitors in series? Using the formula for capacitors in series I get 9pf. Is that close enough? The CFC is only a two band exciter (80 & 40) and I intend to work 20M initially. So I will tune up with the HW set to 20M and the switch set to VFO. I shouldn't exceed 2ma grid drive. Is that correct?
Thanks,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #53 on: March 27, 2015, 01:30:43 PM »

sounds like a plan to me .... the series caps should be fb .... nothing seems to be critical with the 47k biasing resistor ... check the note at bottom of schismatic for vfo freq / band .... grid current staying close sounds like happy happy happy to me
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #54 on: March 28, 2015, 11:49:16 AM »

In adjusting the attenuator, do I remove resistors on the ground leg or the hot leg?
Thanks a lot for all of the info and patience.
Regards,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #55 on: March 28, 2015, 02:08:51 PM »

don't remove resistors, just move the tap point ...start at the first junction between the grounded resistor and the next one in line

no sweat .... I used to teach electronics for the state of Tennessee in an adult  vocational program
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #56 on: March 28, 2015, 05:20:35 PM »

You know your stuff. I worked as a microbiologist for 43 years - not much exposure to electronics other than physics class. Nothing practical there.
Thanks,
Tom N0TJL
Logged
KA2DZT
Member

Offline Offline

Posts: 2191


« Reply #57 on: March 28, 2015, 08:28:34 PM »

You know your stuff. I worked as a microbiologist for 43 years - not much exposure to electronics other than physics class. Nothing practical there.
Thanks,
Tom N0TJL

Hang around on this Forum for the next 43 years and you'll be an expert Grin

Fred
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #58 on: March 29, 2015, 10:17:47 AM »

I'd be 113 years old.
Tom
Logged
MikeKE0ZUinkcmo
Member

Offline Offline

Posts: 438



« Reply #59 on: March 29, 2015, 10:44:58 AM »

Quote
I'd be 113 years old.
Tom

Just keep the dust off, and the bugs out, you'll be fine. Grin
Logged

Mike KE0ZU

Bold Text and PICS are usually links

https://mikeharrison.smugmug.com/
n0tjl
Member

Offline Offline

Posts: 44


« Reply #60 on: April 01, 2015, 09:58:42 AM »

Does anyone know anything about use of the tuning control on a Barker and Williamson model 381C TR switch? I found a manual for the Model 381 on BAMA but the 381 has only the band switch and no tuning control. I would like to use this unit with my r390a and the HW Bandmaster.
Thanks,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #61 on: April 01, 2015, 10:30:25 AM »

new thread
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #62 on: April 08, 2015, 07:20:54 PM »

Hello again guys,
Another HW/Sonar CFC question. I intend to key the CFC and run that output through the attenuator into the crystal socket of the HW with the switch set to VFO. Do I need to short out the key jack on the HW in order to complete the circuit?
Thanks,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #63 on: April 08, 2015, 09:27:08 PM »

looking at HW schizmatic the key line takes both 6aq5 and 807 cathodes to gnd .... with sw6 in phone position all are grounded .... to avoid having the exciter going while in receive, you may need another ptt relay contact to key the CFC
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #64 on: April 09, 2015, 10:39:12 AM »

Hello BFL,
At this point in time, I intend to operate cw only. I will need to convert the HP23 ps to full wave from voltage doubler before I can get enough soup to operate AM. To avoid relay work, could I follow the info at the bottom of pg9 of the HW manual where it discusses keying the vfo? Should I add a jumper between pin 8 and pin2 of the terminal strips?
Thanks,
Tom N0TJL
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #65 on: April 09, 2015, 12:44:21 PM »

Whoops. Upon closer examination, it looks like I should connect the CFC vfo across pins 2 & 8 on the terminal strips - 8 to hot side and 2 to ground side. A  jumper wouldn't do it. Right?
Regards,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #66 on: April 09, 2015, 12:50:16 PM »

Whoops. Upon closer examination, it looks like I should connect the CFC vfo across pins 2 & 8 on the terminal strips - 8 to hot side and 2 to ground side. A  jumper wouldn't do it. Right?
Regards,
Tom N0TJL

I can't answer this because I don't know how the CFC is keyed (no schiz-o-matic) .... if it is also cathode keyed, possibly ...if something else would have to isolate/buffer somehow

n.b.  just went and looked at HW vfo schismatic ... it is also cathode keyed thru pin 2 ... lotsa drive from a 6ag7
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #67 on: April 09, 2015, 07:19:47 PM »

CFC schematic shows hot side of key jack connected to the cathode of the 6L6 tube through a 1500ohm resistor. The tube complement of the CFC is 6SK7 oscillator, 6V6 buffer and 6L6 buffer-doubler.
Regards,
Tom
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #68 on: April 09, 2015, 08:17:26 PM »

this has become interesting inasmuch as if the CFC keying line is connected to the HW keying line this would place at least 6 cathodes in common waiting to be grounded for operation .... this might be a new record and makes you wonder what the keying note will sound like

I would probably clip lead test this by measuring the cathode voltage developed by each piece by itself and then connecting them together and remeasuring the combination .... I wouldn't be surprised to see around +40V or so on each and then together .... probably will function but with a strange keying note (guessing) ... if the voltage gets much higher then some heater to cathode voltages limits may be exceeded
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #69 on: April 10, 2015, 09:30:42 AM »

Would it help if I emailed the CFC vfo schematic to you?
Regards,
Tom
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #70 on: April 10, 2015, 12:53:41 PM »

Would it help if I emailed the CFC vfo schematic to you?
Regards,
Tom

well, it might avoid an unexpected smoky surprise


n.b. 11 apr 15  .... just reviewed the CFC schizmatic that you emailed, Tom .... the buffer and final are cathode keyed with the vfo osc left free-running ... I think you could bypass the 6l6 by unplugging it and making a connection from the 6l6 grid pin 5 over to the HW thru a short piece of coax ... no antennuator needed .... would need to verfy vfo freq to HW requirements ...

of course the original plan with the attenuator is viable just check the unkeyed key line voltages for compatability (clip lead test)   
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #71 on: April 15, 2015, 06:42:47 PM »

I will remove the 6L6, insert the center conductor of the coax into pin 5 connector, ground the shield to the chassis, connect the other end of the center conductor to terminal 8 on the HW connector strip and the other end of the shield to terminal 2 of the HW connector strip, say a short prayer and key the sucker. Would RG-6 75 ohm coax be ok?
Regards,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #72 on: April 15, 2015, 07:29:19 PM »

I will remove the 6L6, insert the center conductor of the coax into pin 5 connector, ground the shield to the chassis, connect the other end of the center conductor to terminal 8 on the HW connector strip and the other end of the shield to terminal 2 of the HW connector strip, say a short prayer and key the sucker. Would RG-6 75 ohm coax be ok?
Regards,
Tom N0TJL


no, not what is in mind

the 6L6 pin 5 connection goes to the HW vfo input thru a 100 pF or so mica cap and then the short run of coax ... you will need to see which is grounded and which is 'hot' .... this is the buffered rf from the cfc vfo

the CFC key jack connection goes to the HW connector block 8 with gnd to gnd

may have to take another look at this when trying AM
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #73 on: April 17, 2015, 04:17:56 PM »

In the 6L6 tube socket, I will plug in my spare octal plug (can't believe I have one of these in my junk box) to which I will have soldered a 100pf silver mica cap to pin 5, other end of cap soldered to the center conductor of a piece of RG-6. The shield of the RG-6 will be connected to the chassis. The other end of this will be connected to the crystal socket (shield to outside jack of crystal socket) of the HW with the switch set to VFO. I will then make a connection from the key jack of the CFC - hot side of the jack to #8 on the HW connector strip and gnd side to #2 on the HW connector strip. Key will be connected to the Key jack of the HW. I will then turn it all on and key the sucker.
What do you think about this?
Regards,
Tom 
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #74 on: April 17, 2015, 08:43:24 PM »

I believe its worth a try
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
Pages: 1 2 [3] 4   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 0.077 seconds with 18 queries.