[Amps] Millen dipper

[W1GOR]

After owning various Millen 90651 Grid Dip Oscillators for more than 50 
years, I've discovered that calibration errors are sometimes due to the 
instrument being furnished with a different set of coils than originally 
supplied by Millen.   I hadn't considered that as a significant issue until 
buying a Measurements model 59 GDO at auction.  In the case of the 
Measurements 59, each individual coil was serial numbered with the same 
serial number as the tuning head/oscillator.  Although Millen did not 
individually number the coils, the coil set that was originally supplied 
with each GDO provided 'reasonable' frequency accuracy.  As mentioned by 
others, these instruments are not intended to provide 'laboratory accuracy', 
but are sufficiently accurate to determine the 'ball-park' frequency of a 
resonant circuit.

By the way, the first Measurements 59 that I bought at auction had coils 
that were obviously taken from several sets.  None of the coils had the same 
number as the tuning head... Overall, the accuracy was very far out of spec. 
I returned the GDO and received a refund, albeit not without a 
fight...<grin>  Since then, I have purchased several other Measurements 
model 59 GDO's and refurbed them for resale.  With matching coil sets, their 
accuracy is well within original specifications.

The Millen 90651 and 90652 GDO's are 'reasonably' accurate when furnished 
with their individual coil sets, although there is no way to determine the 
accuracy until you compare each unit against a known signal source. 
Occasionally, replacing the 9002 oscillator tube in the 90651 will improve 
accuracy, but I haven't done this to enough units to claim this as a 
universal 'fix'.  90651A's are slightly more accurate than the original 
90651's.  The solid-state Millen 90652's that I've worked-on seem to be much 
more accurate and stable than the older tube-type 90651's.

vy 73, Larry - W1GOR




----- Original Message ----- 
From: "Floyd Sense" <fsense at charter.net>
To: "carl seyersdahl" <carlseye at tampabay.rr.com>; <Amps at contesting.com>
Sent: Friday, September 30, 2005 7:24 PM
Subject: Re: [Amps] Millen dipper


> An interesting question.  I bought a nice one last year, only to find out
> that the dial calibration was off by 500 KHz at 10 MHz.  When I asked the
> remaining person at Millen about the calibration procedure, you'd think I
> was asking for the family jewels.  When I asked a question about 
> calibrating
> it myself on one of the eHam forums, I was chastised for not knowing that 
> it
> "wasn't a frequency counter" and could not be expected to be accurate.  At
> that point, I sold the damned thing to someone who was looking for a 
> "shelf
> queen" and bought a Kenwood DM-81.  It's dial was accurate to 50 KHz at 10
> MHz.  The Kenwood is superior in all ways to the Millen and I guess that's
> to be expected with the difference in technology.  I wonder how accurate 
> the
> Millens were when new.
>
> K8AC
>
> ----- Original Message ----- 
> From: "carl seyersdahl" <carlseye at tampabay.rr.com>
> To: <Amps at contesting.com>
> Sent: Friday, September 30, 2005 7:09 PM
> Subject: [Amps] Millen dipper
>
>
>>        Can anyone here tell me how well the dial calib. is on the Millen
>> Grid dip meter!!???
>>    carl / kz5ca
>>
>>
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