Re: [Drakelist] PTO/VFO
Until the advent of synthesizer IC's capable of working at 130 MHz and all electric tuning schemes, all automotive radios used PTO's, along with Permeability Tuned RF stages. There were typically three P-tuned coils per band, one for the LO, the other two the RF stages. They could easily be set up to track across the AM or FM band. The production tuning was actually done by machines in the later years when the capability became available. The other reason for the PTO was that, especially in a mobile environment, there were fewer pressure based connections (think variable capacitors and trimmers) to become corroded and noisy. Microphonics are typically lower as well, so bumpy roads would not appear to affect the radio. Another benefit was much smoother tuning than could be accomplished with a rotary capacitor, and simple mechanicals, unless you had one of the signal seeker jobs! What does this have to do with Drake's? My guess is that Drake, Collins, et all, appreciated the same benefits, as they were also interested in mobile applications. Tom Holmes, N8ZM Tipp City, OH EM79 > -Original Message- > From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] > On Behalf Of Richard Knoppow > Sent: Friday, February 18, 2011 9:08 PM > To: K9sqg > Cc: Drakelist@zerobeat.net > Subject: Re: [Drakelist] PTO/VFO > > > - Original Message - > From: "K9sqg" > To: ; > Cc: > Sent: Friday, February 18, 2011 3:56 PM > Subject: Re: [Drakelist] PTO/VFO > > > Typically, a PTO refers to a permeability tuned oscillator. > In other words, it tunes the inductor with a core that moves > in and out of the coil. A VFO typically refers to an > oscillator that varies a capacitor to vary the frequency. > However, VFO is sometimes used to refer to a traditional > VFO, a PTO, and even VCO. > > Collins also seems to use both terms although theirs > _is_ a PTO. I've also seen other confusing terms used, I > think Hallicrafters called theirs a LMO (Linear Master > Oscillator) or something of the sort. > The advantage of a permeability tuned oscillator is that > its fairly easy to get a linear frequency scale by shaping > the coil so that the inductance has a square-law relation to > linear movment of the core. Its possible to shape the plates > of a variable air capacitor to achieve the same thing but > the plates become extreme in shape and are hard to make. > Such "straight-line-frequency" capacitors were offered by > Cardwell and Hammarlund, maybe also National, in the early > 1930's but I think they proved to cause more problems than > they solved. > There have also been oscillators with simultaneous > variation of inductance and capacitance, mostly for VHF/UHF > applications. This has the advantage of more linear dial > calibration and probably also higher Q. General Radio used > this in one or more of its instruments and I think had a > patent on it. > A problem with the PTO is that its difficult to get the > coils to be exactly square-law so some means of correcting > them is needed if the dial calibration is to be accurate > without individual calibration. Collins used a "corrector > stack" consisting of a series of thin washers clamped by a > bolt. The washers could be slid to make a cam surface > according to the correction needed. The surface was followed > by a roller attached to a lever which could move the > position of the nut driving the core just a little. the > result was that the exact frequency could be adjusted > continuously along the working length of the coil. Other > manufacturers made similar arrangements that accomplished > the same end without infringing on the Collins patent. I > don't think Drake uses any such arrangement. > > > -- > Richard Knoppow > Los Angeles > WB6KBL > dickb...@ix.netcom.com > > > ___ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] PTO/VFO
Hi Richard: Great Info. THe Drake PTO coil is wound in the way you describe. It also has a core stack that is made from multiple pcs attached to the brass rod. I always thought that by altering the spacing of the cores on the shaft, that linearity could be tweaked. I have never attempted to verify this but think it might have been a possible solution. The pictures of the original Drake Mfg test fixture where the PTO's were adjusted is interesting but it was never actually described as to how they were adjusted. Perhaps just moving the windings around. Would be an interesting weekend I think :) Curt KU8L Richard Knoppow wrote: - Original Message - From: "K9sqg" To: ; Cc: Sent: Friday, February 18, 2011 3:56 PM Subject: Re: [Drakelist] PTO/VFO Typically, a PTO refers to a permeability tuned oscillator. In other words, it tunes the inductor with a core that moves in and out of the coil. A VFO typically refers to an oscillator that varies a capacitor to vary the frequency. However, VFO is sometimes used to refer to a traditional VFO, a PTO, and even VCO. Collins also seems to use both terms although theirs _is_ a PTO. I've also seen other confusing terms used, I think Hallicrafters called theirs a LMO (Linear Master Oscillator) or something of the sort. The advantage of a permeability tuned oscillator is that its fairly easy to get a linear frequency scale by shaping the coil so that the inductance has a square-law relation to linear movment of the core. Its possible to shape the plates of a variable air capacitor to achieve the same thing but the plates become extreme in shape and are hard to make. Such "straight-line-frequency" capacitors were offered by Cardwell and Hammarlund, maybe also National, in the early 1930's but I think they proved to cause more problems than they solved. There have also been oscillators with simultaneous variation of inductance and capacitance, mostly for VHF/UHF applications. This has the advantage of more linear dial calibration and probably also higher Q. General Radio used this in one or more of its instruments and I think had a patent on it. A problem with the PTO is that its difficult to get the coils to be exactly square-law so some means of correcting them is needed if the dial calibration is to be accurate without individual calibration. Collins used a "corrector stack" consisting of a series of thin washers clamped by a bolt. The washers could be slid to make a cam surface according to the correction needed. The surface was followed by a roller attached to a lever which could move the position of the nut driving the core just a little. the result was that the exact frequency could be adjusted continuously along the working length of the coil. Other manufacturers made similar arrangements that accomplished the same end without infringing on the Collins patent. I don't think Drake uses any such arrangement. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] PTO/VFO
- Original Message - From: "K9sqg" To: ; Cc: Sent: Friday, February 18, 2011 3:56 PM Subject: Re: [Drakelist] PTO/VFO Typically, a PTO refers to a permeability tuned oscillator. In other words, it tunes the inductor with a core that moves in and out of the coil. A VFO typically refers to an oscillator that varies a capacitor to vary the frequency. However, VFO is sometimes used to refer to a traditional VFO, a PTO, and even VCO. Collins also seems to use both terms although theirs _is_ a PTO. I've also seen other confusing terms used, I think Hallicrafters called theirs a LMO (Linear Master Oscillator) or something of the sort. The advantage of a permeability tuned oscillator is that its fairly easy to get a linear frequency scale by shaping the coil so that the inductance has a square-law relation to linear movment of the core. Its possible to shape the plates of a variable air capacitor to achieve the same thing but the plates become extreme in shape and are hard to make. Such "straight-line-frequency" capacitors were offered by Cardwell and Hammarlund, maybe also National, in the early 1930's but I think they proved to cause more problems than they solved. There have also been oscillators with simultaneous variation of inductance and capacitance, mostly for VHF/UHF applications. This has the advantage of more linear dial calibration and probably also higher Q. General Radio used this in one or more of its instruments and I think had a patent on it. A problem with the PTO is that its difficult to get the coils to be exactly square-law so some means of correcting them is needed if the dial calibration is to be accurate without individual calibration. Collins used a "corrector stack" consisting of a series of thin washers clamped by a bolt. The washers could be slid to make a cam surface according to the correction needed. The surface was followed by a roller attached to a lever which could move the position of the nut driving the core just a little. the result was that the exact frequency could be adjusted continuously along the working length of the coil. Other manufacturers made similar arrangements that accomplished the same end without infringing on the Collins patent. I don't think Drake uses any such arrangement. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] PTO/VFO
Typically, a PTO refers to a permeability tuned oscillator. In other words, it tunes the inductor with a core that moves in and out of the coil. A VFO typically refers to an oscillator that varies a capacitor to vary the frequency. However, VFO is sometimes used to refer to a traditional VFO, a PTO, and even VCO. -Original Message- From: Nigel Gunn G8IFF/W8IFF To: Neil M Califano Cc: Drakelist@zerobeat.net Sent: Fri, Feb 18, 2011 6:10 pm Subject: Re: [Drakelist] PTO/VFO No. On 18-Feb-11 23:03, Neil M Califano wrote: > Is there any difference between a PTO and a VFO? The R-4 has a PTO and the > R-4A a VFO per the specs. > > > > > ___ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist > -- Nigel A. Gunn, 1865 El Camino Drive, Xenia, OH 45385-1115, USA. tel +1 937 825 5032 Amateur Radio G8IFF W8IFF (was KC8NHF 9H3GN), e-mail ni...@ngunn.net www http://www.ngunn.net Member of ARRL, GQRP #11396, QRPARCI #11644, SOC #548, Flying Pigs QRP Club International #385, Dayton ARA #2128, AMSAT-NA LM-1691, AMSAT-UK 0182, MKARS, ALC, GCARES, XWARN, EAA382. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] PTO/VFO
A PTO is a type or style of VFO. Drake uses them interchangebly. There is no synthesizer noise from the R4 series VFO/PFO's. They're solid state for stability. (The FS-4 accessory synthesizer is another story as to noise). 73 Lee WB6SSW ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] PTO/VFO
No. On 18-Feb-11 23:03, Neil M Califano wrote: Is there any difference between a PTO and a VFO? The R-4 has a PTO and the R-4A a VFO per the specs. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist -- Nigel A. Gunn, 1865 El Camino Drive, Xenia, OH 45385-1115, USA. tel +1 937 825 5032 Amateur Radio G8IFF W8IFF (was KC8NHF 9H3GN), e-mail ni...@ngunn.net www http://www.ngunn.net Member of ARRL, GQRP #11396, QRPARCI #11644, SOC #548, Flying Pigs QRP Club International #385, Dayton ARA #2128, AMSAT-NA LM-1691, AMSAT-UK 0182, MKARS, ALC, GCARES, XWARN, EAA382. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] PTO/VFO
Is there any difference between a PTO and a VFO? The R-4 has a PTO and the R-4A a VFO per the specs. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
