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#1
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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
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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. |
#3
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"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.) |
#4
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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. |
#5
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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. |
#6
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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 |
#7
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"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
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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
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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. |
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