[JMS] 90711 VFO questions

[Don Buska - The Radio Lab Works]

Hi George.

The 90801 transmitter doesn't even need the little Millen crystal 
matching unit with the 90711 VFO.  I have the banana jacks on my 
personal VFO, one side is connected directly to chassis ground, so it 
shouldn't matter if yours has the jacks or the UHF connector. I have an 
RG-58 coax cable from my banana jack into the 90711 front XTAL socket 
and then I have the switch on the 90711 set to VFO.

I'm sure Millen did change the jacks along the way.  They did that on 
much of their equipment.  I've seen several connector variants on their 
90501/505 Crystal Calibrator through it's manufacture. Reasoning - Who 
knows?

73
Don N9OO




On 10/28/24 8:35 PM, W1LSB - George via James_Millen_Society wrote:
> Hello all!
>
>   
>
> After a lengthy search, I finally acquired a 90711 VFO thanks to a tip from
> Bob - W9RAN, who knew that I was on the hunt for one  Since acquiring it, a
> few questions have come to mind that one of you may be able to answer.
>
>   
>
> I've seen that two variants of the RF output connector have been noted on
> the serial number page of the JMS web site; one with a 2 pin banana jack,
> and one with a UHF connector, like mine has.  The serial number of my unit
> is 309, however, I found a photo of the VFO with a two pin banana jack for
> the RF output; it was serial number 287.   It sounds like they may have
> changed connectors somewhere between the two units.
>
>   
>
> Another question is whether the high impedance plug-in adapter was standard
> or optional.  The manual seems to imply that it was standard, however I
> gather that not everyone has one with their VFO; I do not.  The adapter was
> used to provide a high impedance output versus the standard low impedance
> output.   Apparently, the plug-in adapter was made in both banana plug and
> UHF connector versions as well, again per info on the JMS serial number
> page.
>
>   
>
> Just curious as to whether anyone know more about these differences, and
> whether the high impedance plug-in adapter actually provides a benefit.
> Interestingly, the VFO could be used a vintage QRP rig all by itself, given
> that manual claims the RF O/P is around 1.75W
>
>   
>
> Once this VFO has been restored, I'm planning to use it with a 90801 exciter
> and 90831 modulator, and eventually a 90881 RF amplifier with a high level
> modulator.
>
>   
>
> Thanks & 73,
>
> George - W1LSB
>
>   
>
>   
>
>   
>
>   
>
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