[JMS] Recently acquired James Millen Preamplifier Model 92101with plug-in coils

[Don Buska]

The problem with preamps is they will amplify the noise as well as the 
signals.  My feeling is if you can hear them then an amplifier probably 
won't make it a more pleasurable experience.  Often times we get 
"S-Meter Envy" (me too) and the higher the reading the better the 
receiver.  I'd prefer an S6 signal with little noise versus the same 
signal with an S9+20dB strength and an S7 noise level.  However, we do 
know that the RF related noise level in any receiver is primarily due to 
the first stage of amplification.  So if you have a low noise amplifier 
up front it could and will provide a real service in your receiving 
ability.  On VHF and above they will often put the preamplifier at the 
antenna.  That's because as you go higher in frequency the thermonic 
noise generated in the coax can be high enough to cause adverse effects 
in the whole receiving RF chain. Thus putting a low noise amplifying 
stage close to the antenna is a real benefit.

The 92101 has a pretty good Noise Figure for a tube ampilfier of it 
vintage.  On cheaper receivers of the 30's and 40's it could make the 
difference between hearing them or not.  I've found on my HRO it was 
helpful on 10 meters with weak signals.  A well tuned HRO on 20 or 15 
meters probably would not benefit much from the 92101.

On a side note, there are a few fellas who make preamps (broadband) for 
the Drake TR7 transceiver.  I have a TR7 and it is designed with no RF 
amplifier at all.  Antenna goes through some band filtering and directly 
to the mixer.  The bottom line is my TR7 can hear everything that the 
best receiver in my shack can hear.  One difference is the TR7 has a 
very low noise floor.  Adding an preamplifier may increase the S-Meter 
reading (Sensitivity), but I bet it would bring up the noise right along 
with it.

So keep the 92101 handy.  If you build a dedicated power supply for it 
you can try it on any receiver you want in short order.  You might find 
your HRO won't benefit with its use.  So then save it for that other 
cheaper receiver - naturally a non-National receiver, hi.

73
Don N9OO

Sherrill Watkins wrote:
> Hi Don: I note with interest that you state you used your 92101 Millen
> Preamplifier on 10 meters with your National HRO-5. I also have an HRO-5 that
> a friend restored but have not used it.  Did the 92101 actually improve the
> sensitivity of the HRO5 on 10 meters? Would a preampmlifier help on other
> bands? I have the 20 meter plug-in coil. Thank's a lot! - Sherrill k4own
>
>
> -----Original Message-----
> From: Don Buska [mailto:dbuska at wi.rr.com] 
> Sent: Wednesday, December 27, 2006 2:55 PM
> To: The James Millen Society Members Email Reflector
> Subject: Re: [JMS] Recently acquired a James Millen Preamplifier Model
> 92101with plug-in coils
>
>
> I can handle this too Sherrill,
>
> The preamp was based on the design from the Nov/Dec 1946 Issue of the GE 
> Ham News magazine. Called the R9'er and later variations were also built 
> under the Q5er name.  The schematic is on the JMS website.  I will scan 
> the manual and email it to you.
>
> Millen didn't make a power supply unit for it.  My guess is they figure 
> you will steal the DC and AC from the receiver.  Since it only uses one 
> tube.  I built a little standalone power supply for mine.  Yes I have 
> actually used it with my HRO-5 on ten meters.  Finding the plug-ins is a 
> hit or miss deal.  Keep watching eBay or at swapfests.  They do turn 
> up.  The preamp was delivered with the 10M plug-in and that is the one 
> you will find in 99% of the preamps you find. It was also the weak point 
> on early ham superhets. They are not rare.  Next to the dip meters it 
> was one of the highest produced equipment products from Millen.
>
> The RF connectors on the preamp are a bit unusual.  They use Amp(henol) 
> connectors that have the same body as the common two pin jobs used for 
> mic connections on many old BA radios (like Heathkit and the Collins 
> KWS1).  The difference being the insert only has the one male pin right 
> in the center (cable side).  Often you find these removed from the 92101 
> and replaced with SO-239's or BNC's.  That's to bad as I have also found 
> the correct connectors to plug into the 92101 on swapfest junk tables.
>
> I took my 92101 to the 1996 Central States VHF Conference in Bloomington 
> MN to enter into the Preamp GAIN/NOISE FIGURE contest.  As expected it 
> didn't win against the newer GASFET jobs on six meters.  It did turn a 
> few heads though, hi.
>
> 73
>
> Don N9OO
>
> Sherrill Watkins wrote:
>   
>> Hi Don: Thank's for the great information and pictures explaining the 
>> vfo. Now I know what a swing arm vfo is.
>>
>> Also, during December, I acquired a Millen Preamplifier, Model 92101 
>> with three plug-in coils.  I will be registering it on the equipment 
>> list in the near future. I now need an owners manual and schematic and 
>> additional coil(s) to cover 15 to 27 MC! Also, was a separate power 
>> supply made for this unit?
>>
>> Also, has anyone actually used the Millen Preamplifier Model 92101? If 
>> so, please give me you thoughts and comments. Many thank's!  - 
>> Sherrill k4own
>>
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