Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old September 18th 03, 05:16 AM
Keith
 
Posts: n/a
Default Usage of Johnson 6N2 Transmitter and VFO

I have a Johnson Ranger linked to a Johnson 6n2 Transmitter. The owners
manual says it can do FM.
How do I set that up. The owners manual doesn't have much info on this.
Just says that I need a FM-VFO.
I have the standard VFO that hooks into the 6n2, but that is all the info
that I have.
Thanks in advance.
Keith



  #2   Report Post  
Old September 19th 03, 04:06 AM
William Warren
 
Posts: n/a
Default

"Dale Parfitt" wrote in message
...

Keith wrote:

I have a Johnson Ranger linked to a Johnson 6n2 Transmitter. The owners
manual says it can do FM.
How do I set that up. The owners manual doesn't have much info on this.
Just says that I need a FM-VFO.
I have the standard VFO that hooks into the 6n2, but that is all the

info
that I have.
Thanks in advance.
Keith


Hi Keith,
Although I have not used this particular VFO ( had the TX), the common

scheme
back then was to plug the mic into the VFO- which contained a mic preamp

and
thus FM the VFO.

Dale W4OP


The Turner +2 desk mikes are great for this use: the mike has a preamp
builtin to it, and you can hook it up directly to the varicap circuit.

However, there is a "gotcha": with the transmit switch open, the mike puts
it's preamp battery voltage out on the audio line, and it can forward-bias
your varicap, thus destroying it. You'll need a blocking cap on the input to
the varicap circuit to prevent any voltage on the mike line from damaging
the varicap diode: this is a good practice no matter what mike or preamp you
use.

BTW, most "FM" rigs are actually phase-modulated, so many receivers have
deemphasis filters in them to compensate for the 6DB/octave tonal bias of
phase-modulated rigs. Since a varicap across a VFO coil will produce "true"
FM, you might have to precompensate the audio so that it doesn't sound too
"basey" in some receivers.

HTH.

Bill


  #3   Report Post  
Old September 19th 03, 04:06 AM
William Warren
 
Posts: n/a
Default

"Dale Parfitt" wrote in message
...

Keith wrote:

I have a Johnson Ranger linked to a Johnson 6n2 Transmitter. The owners
manual says it can do FM.
How do I set that up. The owners manual doesn't have much info on this.
Just says that I need a FM-VFO.
I have the standard VFO that hooks into the 6n2, but that is all the

info
that I have.
Thanks in advance.
Keith


Hi Keith,
Although I have not used this particular VFO ( had the TX), the common

scheme
back then was to plug the mic into the VFO- which contained a mic preamp

and
thus FM the VFO.

Dale W4OP


The Turner +2 desk mikes are great for this use: the mike has a preamp
builtin to it, and you can hook it up directly to the varicap circuit.

However, there is a "gotcha": with the transmit switch open, the mike puts
it's preamp battery voltage out on the audio line, and it can forward-bias
your varicap, thus destroying it. You'll need a blocking cap on the input to
the varicap circuit to prevent any voltage on the mike line from damaging
the varicap diode: this is a good practice no matter what mike or preamp you
use.

BTW, most "FM" rigs are actually phase-modulated, so many receivers have
deemphasis filters in them to compensate for the 6DB/octave tonal bias of
phase-modulated rigs. Since a varicap across a VFO coil will produce "true"
FM, you might have to precompensate the audio so that it doesn't sound too
"basey" in some receivers.

HTH.

Bill


  #4   Report Post  
Old September 19th 03, 04:46 AM
Mike Knudsen
 
Posts: n/a
Default

In article , --exray-- writes:

I once had an Ameco VFO (VFO-621?) that had a simple little varicap
modulator circuit built in. It sounded great. I bet you could find
such mods in some of the older magazines.


Long ago, like early '70s, Popular Electronics mag had a short article on how
to FM a 6m rig with a varicap diode across the oscillator tank. Very short
parts list, and the most expensive item was probably the phone jack for the mic
input.

BTW, this article suggested FM as a way to reduce TVI -- not clear why it would
be less messy on TV picture or sound than an AM signal. SSB was blissfully
rare on VHF back then. --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.
  #5   Report Post  
Old September 19th 03, 04:46 AM
Mike Knudsen
 
Posts: n/a
Default

In article , --exray-- writes:

I once had an Ameco VFO (VFO-621?) that had a simple little varicap
modulator circuit built in. It sounded great. I bet you could find
such mods in some of the older magazines.


Long ago, like early '70s, Popular Electronics mag had a short article on how
to FM a 6m rig with a varicap diode across the oscillator tank. Very short
parts list, and the most expensive item was probably the phone jack for the mic
input.

BTW, this article suggested FM as a way to reduce TVI -- not clear why it would
be less messy on TV picture or sound than an AM signal. SSB was blissfully
rare on VHF back then. --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.


  #6   Report Post  
Old September 19th 03, 05:24 AM
William Warren
 
Posts: n/a
Default

"Mike Knudsen" wrote in message
...

Long ago, like early '70s, Popular Electronics mag had a short article on

how
to FM a 6m rig with a varicap diode across the oscillator tank. Very

short
parts list, and the most expensive item was probably the phone jack for

the mic
input.

BTW, this article suggested FM as a way to reduce TVI -- not clear why it

would
be less messy on TV picture or sound than an AM signal. SSB was

blissfully
rare on VHF back then. --Mike K.


I never understood it, but it seemed to work: those who tried FM reported
that TVI *was* reduced. Since TV audio is FM, albeit at 25 KHz deviation, I
would have thought it'd be *easier* to cause interference by using FM.

Of course, perhaps it was a "second order" effect: perhaps it prevented
*audible* interference, and therefore prevented anyone from identifying the
source. I'd think that previous complainents might simply assume that the
local ham whom they'd heard on their TV before was causing the picture to
roll, but then again, I remember assuring neighbors that "If it was me,
you'd hear me talking", so I might be wrong there ;-J.

If anyone out there has the authoritative answer, please pass it along: did
FM cause less interference, or did it simply prevent the interference from
being in the audio chain?

Enquiring minds want to know!

Bill
(Remove ".nouce" for direct replies.)


  #7   Report Post  
Old September 19th 03, 05:24 AM
William Warren
 
Posts: n/a
Default

"Mike Knudsen" wrote in message
...

Long ago, like early '70s, Popular Electronics mag had a short article on

how
to FM a 6m rig with a varicap diode across the oscillator tank. Very

short
parts list, and the most expensive item was probably the phone jack for

the mic
input.

BTW, this article suggested FM as a way to reduce TVI -- not clear why it

would
be less messy on TV picture or sound than an AM signal. SSB was

blissfully
rare on VHF back then. --Mike K.


I never understood it, but it seemed to work: those who tried FM reported
that TVI *was* reduced. Since TV audio is FM, albeit at 25 KHz deviation, I
would have thought it'd be *easier* to cause interference by using FM.

Of course, perhaps it was a "second order" effect: perhaps it prevented
*audible* interference, and therefore prevented anyone from identifying the
source. I'd think that previous complainents might simply assume that the
local ham whom they'd heard on their TV before was causing the picture to
roll, but then again, I remember assuring neighbors that "If it was me,
you'd hear me talking", so I might be wrong there ;-J.

If anyone out there has the authoritative answer, please pass it along: did
FM cause less interference, or did it simply prevent the interference from
being in the audio chain?

Enquiring minds want to know!

Bill
(Remove ".nouce" for direct replies.)


  #8   Report Post  
Old September 19th 03, 05:25 AM
Michael Black
 
Posts: n/a
Default

Mike Knudsen ) writes:
In article , --exray-- writes:

I once had an Ameco VFO (VFO-621?) that had a simple little varicap
modulator circuit built in. It sounded great. I bet you could find
such mods in some of the older magazines.


Long ago, like early '70s, Popular Electronics mag had a short article on how
to FM a 6m rig with a varicap diode across the oscillator tank. Very short
parts list, and the most expensive item was probably the phone jack for the mic
input.

BTW, this article suggested FM as a way to reduce TVI -- not clear why it would
be less messy on TV picture or sound than an AM signal. SSB was blissfully
rare on VHF back then. --Mike K.

They were certainly running such articles in the early sixties, if not
earlier. FM was promoted from time to time as an antidote to interference
since at least it wasn't something that would be demodulated. If strong
enough, it would bias something wrong, but the modulation would not be
recovered.

But that early, the assumption was that the ham at the other end would
be using an AM receiver, and would slope-detect the FM signal.

As someone pointed out, there were a number of commercial VFOs
in the sixties that had a jack for a microphone so you could FM it.
You'd feed it into the matching Communicator.

By the late sixties or early seventies, of course, the point shifted
so people wanted to FM their VFOs in order to get in on that newfangled
FM and repeater thing. There were various articles about converting
those old Communicators and Cleggs to FM, but this time around, not
only would they add FM to the transmitter through various schemes,
but they'd throw in an actual FM detector.

Michael VE2BVW

  #9   Report Post  
Old September 19th 03, 05:25 AM
Michael Black
 
Posts: n/a
Default

Mike Knudsen ) writes:
In article , --exray-- writes:

I once had an Ameco VFO (VFO-621?) that had a simple little varicap
modulator circuit built in. It sounded great. I bet you could find
such mods in some of the older magazines.


Long ago, like early '70s, Popular Electronics mag had a short article on how
to FM a 6m rig with a varicap diode across the oscillator tank. Very short
parts list, and the most expensive item was probably the phone jack for the mic
input.

BTW, this article suggested FM as a way to reduce TVI -- not clear why it would
be less messy on TV picture or sound than an AM signal. SSB was blissfully
rare on VHF back then. --Mike K.

They were certainly running such articles in the early sixties, if not
earlier. FM was promoted from time to time as an antidote to interference
since at least it wasn't something that would be demodulated. If strong
enough, it would bias something wrong, but the modulation would not be
recovered.

But that early, the assumption was that the ham at the other end would
be using an AM receiver, and would slope-detect the FM signal.

As someone pointed out, there were a number of commercial VFOs
in the sixties that had a jack for a microphone so you could FM it.
You'd feed it into the matching Communicator.

By the late sixties or early seventies, of course, the point shifted
so people wanted to FM their VFOs in order to get in on that newfangled
FM and repeater thing. There were various articles about converting
those old Communicators and Cleggs to FM, but this time around, not
only would they add FM to the transmitter through various schemes,
but they'd throw in an actual FM detector.

Michael VE2BVW

  #10   Report Post  
Old September 20th 03, 04:22 AM
Mike Knudsen
 
Posts: n/a
Default

In article , "William Warren"
writes:

Of course, perhaps it was a "second order" effect: perhaps it prevented
*audible* interference, and therefore prevented anyone from identifying the
source. I'd think that previous complainents might simply assume that the
local ham whom they'd heard on their TV before was causing the picture to
roll, but then again, I remember assuring neighbors that "If it was me,
you'd hear me talking", so I might be wrong there ;-J.


Yes, that was my theory too -- there'd be herringbones all over the picture,
but they couldn't hear your voice so maybe they'd think it was a doctor's
diathermy machine or whatever. At least they couldn't copy your call and look
you up, like someone did to me on 6m AM.

Also, there wouldn't be sideband splatter and other artifacts of overmodulated
AM.
73, Mike K. AA1UK

Oscar loves trash, but hates Spam! Delete him to reply to me.


Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT +1. The time now is 09:00 AM.

Powered by vBulletin® Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
Copyright 2004-2022 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017