Hi Curt, When I get the chance this weekend I'm gonna run some stability tests on the 751A here, using a 100-KHz crystal calibrator / oscillator as its "umpire"...
You've got me thinking: maybe there really WAS a reason that ICOM offered for sale an optional "high-standard / ultra-stable" crystal oscillator as option for the 751A back-in-the-day...! ~73~ de Eddy VE3CUI - VE3XZ *************************************************************************************** On 2011-11-25, at 9:05 PM, Curt Nixon wrote: > Not sure anyone asked this, and I didn't see it in your initial post, but was > the 751A already warmed up when you tested the drake? > > What is the frequency reference in the 751A? > > I recently used a 751 which is essentially the same frequency determining > set-up for a freq measurement test and I can tell you, it isn't all that > stable either...and, it goes up and down with small temperature differences > over a span of only several minutes. Even when it had been running in Rx > only for over 24 hours. > > So..keep in mind that the data you recorded is the net difference from a > moving reference. > > After warm-up, I'm not so sure that the 751A is any better than the Drake. > > They are a lot better if they have the TCXO module added, but I didn't see > that mentioned. > > Anyway, just curious what the reference conditions were. > > Thanks > > Curt > KU8L > > On 11/25/2011 5:57 PM, Garey Barrell wrote: >> Steve - >> >> I think 30 minutes is a reasonable 'warm-up' time. IF the radio is in a >> controlled environment.!! Take one out of the garage in winter and plug it >> in, it's gonna take considerably longer before everything reaches >> equilibrium. You have some sizable chunks of iron and steel in there that >> can absorb quite a bit of heat. From 60 degrees to a 'nominal' 75 degree >> ambient on top of normal internal heating would take a while, perhaps an >> hour?!? :-) >> >> Plus as Evan said there will be a delta from transmitting as well. A fan >> makes a BIG difference in this if you are into long transmissions or TTY, >> etc. This is one reason why the TR-7 fan is used to exhaust hot air from >> the PA right out the back rather than blow it in all over the radio, >> including the PTO, with each transmission. >> >> 73, Garey - K4OAH >> Glen Allen, VA >> >> Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line >> and TR-4/C Service Supplement CDs >> <www.k4oah.com> >> >> >> Steve Wedge wrote: >>> I always assumed it was a 30 minute warmup, because I seem to remember the >>> alignment procedures spec 30 minutes warmup before doing an alignment. >>> >>> Steve Wedge, W1ES/4 >>> >>> "I can't complain, but sometimes I still do." >>> - Joe Walsh >>> >>> If the above message appears, it came from Steve's Son of Laptop! >>> ----- Original Message ----- From: "Eddy Swynar" <deswy...@xplornet.ca> >>> To: <drakelist@zerobeat.net> >>> Sent: Friday, November 25, 2011 2:32 PM >>> Subject: [Drakelist] T-4X Stability >>> >>> >>>> Hi All, >>>> >>>> The manual for my T-4X states that stability is "LESS THAN 100 CYCLES >>>> AFTER WARM-UP". My question is simply this: how long, exactly, is an >>>> accepted period of "....warm-up"...? >>>> >>>> After all of the hoops that I've jumped through in stabilizing the PTO in >>>> my rig (re-buiding it almost, actually!), I decided this morning to >>>> actually measure its drift. I used my ICOM 751A transceiver (in general >>>> coverage mode) as the frequency "umpire", and tuned it directly to the >>>> Drake PTO's output frequency of 5454.0-KHz. Both rigs were in the basement >>>> overnight, where the ambient room temperature was 59F. I measured the >>>> frequency a total of SIX times, i.e. (1) immediately at the start of the >>>> test, (2) 3 minutes into the test, (3) 15 minutes into the test, (4) 30 >>>> minutes into the test, (5) 1 hour into the test, and finally (6) two hours >>>> into the test... >>>> >>>> Here are my results: >>>> >>>> (1) 5454.0-KHz (cold start); >>>> >>>> (2) 5454.0-KHz (unchanged from cold start); >>>> >>>> (3) 5453.5-KHz (downward drift of 500-Hz from cold start); >>>> >>>> (4) 5453.0 KHz (downward drift of 1-KHz from cold start); >>>> >>>> (5) 5452.8-KHz (downward drift of 1.2-KHz from cold start), and, >>>> >>>> (6) 5452.8-KHz (unchanged). >>>> >>>> So---it looks like the rascal that I have here stabilizes after a good >>>> hour of steady warm-up, which leads me to suspect that maybe "warm-up" to >>>> the writer of the manual was, in fact, just that, i.e. one hour...? >>>> >>>> No matter, it was a most interesting exercise---and I sure would be >>>> curious if my rig's performance might match that of some of the other >>>> T-4Xs that are out there...although I dare say, probably not everyone has >>>> as thick a hide as I do in being able to withstand a 59F ambient room >>>> temperature...! Hi Hi. >>>> >>>> ~73~ de Eddy VE3CUI - VE3XZ >>> _______________________________________________ >>> Drakelist mailing list >>> Drakelist@zerobeat.net >>> http://mailman.zerobeat.net/mailman/listinfo/drakelist >>> >> >> _______________________________________________ >> Drakelist mailing list >> Drakelist@zerobeat.net >> http://mailman.zerobeat.net/mailman/listinfo/drakelist >> > > _______________________________________________ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
