[TMC] VOX/PMO?

[John Vendely]

I often use the term VOX and VMO interchangeably.  The model name is VOX 
(variable oscillator), but TMC often referred to it functionally as a 
VMO (variable master oscillator).  The PMO was simply a stripped down, 
portable (!) version of the VOX, which had only the basic 2-4 Mc 
oscillator section.  TMC offered portable versions of some of their HF 
transmitters, housed in a bunch of transit cases, and the PMO was often 
used with these, when only the 2-4 Mc source was required.  It was also 
used in their fixed station transmitter.  So either the VOX series or 
the PMO is perfectly suitable as the 2-4 Mc VMO for use with any SBE 
series exciter (and the GPE-1 exciter). 

As for which unit to buy, it's up to you.  The VOX series was the more 
elaborate of the two, having the aux. crystal oscillators and the 
multiplier chain, and you may find this useful for other purposes, e.g. 
an external L.O. for a GPR-90 or Hammarlund SP-600.  I would lean toward 
the VOX only for this reason. 

W2HX wrote:
> Hi John, thanks for the explanation. Just so I am sure, am I to understand
> that there are 3 possible frequency sources? VOX, PMO and VMO?  And any of
> the three will work FB for me? (I don't think I need beyond 30megs).  I have
> available to me either a VOX or PMO do you agree with Roy that I should get
> a VOX in that case?
>
> 73 Eugene W2HX
>
>
> -----Original Message-----
> From: John Vendely [mailto:jvendely at cfl.rr.com] 
> Sent: Friday, October 09, 2009 8:11 AM
> To: Eugene Hertz
> Subject: Re: [TMC] VOX/PMO?
>
> Hi Eugene,
>
> Either the VOX or the PMO will provide the 2-4 Mc injection the SBE 
> series.  However, the VMO also includes a frequency multiplier chain to 
> increase the output frequency to as high as 64 Mc, and has auxiliary 
> crystal oscillators as well.  One oscillator is used to furnish 
> additional crystal controlled channels to either an exciter or a 
> receiver, and another provides BFO injection to a receiver such as the 
> GPR-90 series.  The VMO was often used as a stable external L.O. source 
> for the rather unstable GPR-90 in the more demanding applications. 
>
> 73,
>
> John K9WT
>
> W2HX wrote:
>   
>> Hi there. I am looking to put together a TMC station using a GPR-90 and
>> SBE-2 or -3 and PAL-350.
>>
>>  
>>
>> I understand that the SBE requires a frequency source. Can either a VOX or
>> PMO satisfy this requirement? Or is one preferable over the other? Anyone
>> know the difference in how these units were used?
>>
>>  
>>
>> Many thanks!
>>
>>  
>>
>>  
>>
>> 73 Eugene W2HX
>>
>>  
>>
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