[time-nuts] AN/URQ-13 FE-15a oscillator question

[paul swed]

Well there is no doubt someone has been deep into this unit. Hint missing
screws internally.
But appears both heater windings are ok.
So inner and outer oven has a new meaning. I typically understood this to
be one oven in another oven. Think the HP CS units of old. The same in
other places HP3801.
But in the URQ13 it means there is a long tube. The Dewar flask. The inner
is deep into the flask and the outer is close to the opening. Two
completely separate heaters. Under the outer heater I will guess is the
actual oscillator for the 5 MHz. Further out from the outer heater are the
offset variable caps thermistor for the outer oven a pot and IC.
Several screws hold this outer heater on and considering the risk of taking
out the remainders to look and draw a schematic.
Regards
Paul

On Fri, Feb 12, 2021 at 11:28 AM paul swed <paulswedb at gmail.com> wrote:

> Yes Bob they could get hot. But the radio rooms I have been in circa 1970s
> were all air conditioned from destroyers to aircraft carriers. Shirt
> sleeve. The best place to actually be when we were down by the equator was
> the radio room, ET shop, CIC and radar and just maybe the Captain's
> stateroom. But if you were actually there you might still be sweating.
> Chuckle.
> This conversation has given me some good insights. Later today I will
> disable the outer oven. Just curious to see what possible temps might show
> up. Is the inner oven simply reading outer oven leakage. Is there a lead I
> can measure the current of the inner oven....
> Thanks
>
> On Fri, Feb 12, 2021 at 11:18 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>
>> Hi
>>
>> If it’s 105F “outdoors” that’s 40C. Military gear back in the days of the
>> URQ10
>> did not live in air conditioned enclosures. It did get deployed to places
>> with
>> temperatures at or above that level.
>>
>> If it’s 40C outdoors, by the time you get to a pile of electronics gear
>> *indoors*,
>> a >10C rise is pretty likely. That drives a very common 50C “upper end”
>> temperature
>> on ground gear in relatively benign installations.
>>
>> This does not just apply to military gear. If you look through test
>> equipment
>> catalogs, a lot of test gear also has the same sort of 50 to 60C upper
>> end spec.
>> The 5065A has a spec of 0 to 50C. The 5061A has the same spec. Both
>> targeted
>> pretty “normal” environments …. ( = they never get below freezing …) and
>> date
>> to the “era” of the URQ10.
>>
>> In this era of HVAC everywhere, the 5071A has a temp range of 0 to 55C.
>> If
>> anything, this would suggest that things still can get pretty hot.
>>
>> Bob
>>
>> > On Feb 12, 2021, at 10:29 AM, paul swed <paulswedb at gmail.com> wrote:
>> >
>> > Bob
>> > OK there is the math. and that all starts to line up.
>> > So most likely for other URQ units there will be an ambient max in the
>> > spec's. At least on the URQ10 in real life even in the hot tropics the
>> > radio room was shirt sleeve temps.
>> > But the question asked was 110 F correct as measured on the outside of
>> the
>> > outer oven against the dewar flask correct. It isn't. The darn thing is
>> > reasonably stable though.
>> > Since the front panel test switch is not labeled I speculate that the
>> > position for the outer oven is in the normal range. The next switch
>> > position most likely is inner and is not in the correct position. It
>> slowly
>> > moves to the high side.
>> > No real details on anything and a total guess.
>> > Really appreciate the thoughts.
>> > Regards
>> > Paul
>> > WB8TSL
>> >
>> > On Fri, Feb 12, 2021 at 10:18 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>> >
>> >> Hi
>> >>
>> >> Indeed the outer oven (as a minimum) needs to be 5 to 10 C above
>> >> the maximum ambient. If it’s not it goes out of regulation (runs away)
>> >> and you loose any benefit from it. ( = it now works against you ).
>> >>
>> >> The inner oven as a minimum needs to be 5 to 10 C above the outer
>> >> oven. Again if it is lower, you can / will get into the same runaway
>> >> issue.
>> >>
>> >> Those offsets are dependent on the way things are insulated. If you are
>> >> using a dewar flask, 5C is probably not going to work for you.
>> >>
>> >> Your inner oven *also* is impacted by the turn temperature on the
>> crystal
>> >> being used. This *might* have a 20C range. That would put the maximum
>> >> inner oven temperature at 10 + 10 + 20 = 40C above the maximum ambient.
>> >>
>> >> Needless to say, if the max ambient is 85C, this will get the inner
>> oven
>> >> components up pretty hot. That’s not a real good idea. Derating the
>> heater
>> >> is pretty easy, derating *everything* in there is much more complex.
>> You
>> >> do not often see 85C upper end double ovens ….
>> >>
>> >> One *could* also ask: “is all this worth it?”. List members *have*
>> written
>> >> papers addressing that point :)
>> >>
>> >> Bob
>> >>
>> >>> On Feb 11, 2021, at 10:05 PM, Paul Alfille <paul.alfille at gmail.com>
>> >> wrote:
>> >>>
>> >>> Shouldn't the outer oven be cooler than the inner oven except during
>> >>> warmup? I would think the inner electronics would be generating heat.
>> >>>
>> >>> Paul Alfille K1PHA
>> >>>
>> >>> On Thu, Feb 11, 2021 at 9:30 PM paul swed <paulswedb at gmail.com>
>> wrote:
>> >>>
>> >>>> 50C is what I have sort of seen over the years. Just wondered could
>> >> there
>> >>>> have been a lower temp version. That made no sense. But then this
>> beast
>> >> has
>> >>>> never made a lot of sense. The $20 mystery from Frequency
>> Electronics.
>> >>>> Thanks Bob
>> >>>> Paul
>> >>>> WB8TSL
>> >>>>
>> >>>> On Thu, Feb 11, 2021 at 8:08 PM Bob kb8tq <kb8tq at n1k.org> wrote:
>> >>>>
>> >>>>> Hi
>> >>>>>
>> >>>>> Even for an outer oven, anything below 60C / 140F would be low
>> enough
>> >> to
>> >>>>> run into significant problems. On a mil device, an upper end
>> >> temperature
>> >>>>> on
>> >>>>> the equipment likely would be over 70C. The outer oven would need
>> to be
>> >>>>> 5 to 10C above that.
>> >>>>>
>> >>>>> Bob
>> >>>>>
>> >>>>>> On Feb 11, 2021, at 5:55 PM, paul swed <paulswedb at gmail.com>
>> wrote:
>> >>>>>>
>> >>>>>> OK I have had several responses and 110F is low as I expected.
>> >>>>>> Wonder if I am being faked out? Perhaps by an inner oven and I am
>> only
>> >>>>>> reading the outside of the outer oven. The Older URQ10 and newer
>> URQ23
>> >>>> do
>> >>>>>> have 2 ovens. The meter switch for test is only labeled 1-9. no
>> other
>> >>>>> clues
>> >>>>>> to the function. I noticed 2 positions change with warm up. Sort of
>> >>>>>> supports the 2 oven theory.
>> >>>>>> Really do not want to take what might be the outer oven off to put
>> the
>> >>>>>> probe in.
>> >>>>>> Thanks everyone.
>> >>>>>> Paul
>> >>>>>> WB8TSL
>> >>>>>>
>> >>>>>> On Thu, Feb 11, 2021 at 5:32 PM Bob kb8tq <kb8tq at n1k.org> wrote:
>> >>>>>>
>> >>>>>>> Hi
>> >>>>>>>
>> >>>>>>> 110 F makes very little sense unless you are in a very cold
>> climate.
>> >>>>>>> For military gear (or any gear for that matter) 43C on the oven
>> just
>> >>>>>>> doesn’t work.
>> >>>>>>>
>> >>>>>>> 110 C would make sense in a very high temperature environment.
>> >>>>>>> (think of 85C upper end ….).
>> >>>>>>>
>> >>>>>>> Bob
>> >>>>>>>
>> >>>>>>>> On Feb 11, 2021, at 2:18 PM, paul swed <paulswedb at gmail.com>
>> wrote:
>> >>>>>>>>
>> >>>>>>>> Hello to the group.
>> >>>>>>>> I have had a AN/URQ-13 or FE-15a oven oscillator for years.
>> >>>>>>>> Its never worked correctly and in reality some early alpha build.
>> >>>>> (Funny
>> >>>>>>>> that its labeled 15a)
>> >>>>>>>> Looking online there is no documentation that I have been able to
>> >>>> find
>> >>>>>>> over
>> >>>>>>>> the years.
>> >>>>>>>> However in another discussion on a AN/URQ-23 that does have a
>> manual
>> >>>>> and
>> >>>>>>>> schematics I realized my guesses on power could be totally wrong.
>> >>>> Using
>> >>>>>>>> voltages like the URQ23 the URQ13 actually behaves fairly well. I
>> >> was
>> >>>>>>> lucky
>> >>>>>>>> that I didn't destroy something with my original guess.
>> >>>>>>>> That said what I find odd is the internal crystal oven runs at
>> >>>> exactly
>> >>>>>>> 110
>> >>>>>>>> degrees. Its repeatably warms to that level with a range of
>> supply
>> >>>> from
>> >>>>>>> +/-
>> >>>>>>>> 12-15V.
>> >>>>>>>> Does 110 degrees F make any sense at all?
>> >>>>>>>> Thank you
>> >>>>>>>> Paul
>> >>>>>>>> WB8TSL
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