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 Post subject: Dial settings vs. frequency tuning data - Atwater Kent 20
PostPosted: Nov Tue 01, 2011 3:22 pm 
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Joined: Aug Sat 16, 2008 2:57 am
Posts: 41
Recently I finished restoration of an Atwater Kent 20 'big box'. The operation is enchanting. After recording settings for four stations, I was interested in possible mathematical relationships between settings on the dials vs. frequency. Perhaps such data hints at tuning selectivity/linearity/Q/etc. vs frequency. I'd been fiddling with a spreadsheet program, and came up with the attached chart showing frquency and dial settings. Further comparisons and ratios of these settings might be interesting.

I'd be interested in comparing data from other AK20s, or any brand/model that you may find interesting.


Attachments:
AK20 Dial Freq Data Chart.jpg
AK20 Dial Freq Data Chart.jpg [ 43.8 KiB | Viewed 2599 times ]
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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Wed 02, 2011 3:36 am 
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Joined: Apr Tue 19, 2011 6:24 am
Posts: 453
Location: 07470
That's nice work! Thanks for posting it.

The flattening of the tracking curves with increasing frequency is good guidance for me.
There's a big-box AK20, model 4640 (~ sure looks just like a 24) here awaiting work, and when I do get to it after the holidays, I'll compare my set's response(s) with yours and advise.


Perhaps another ARF reader has done similar research with an AK10, model 4700 (or even up to an AK35, etc.) having generally similar tuning arrangements. The 10/4700 and the 20/4640 are similar except for packaging.

If so, please post whatever tuning curves you might have; the more info here and the larger the population of sets, the better.


BTW, are you using an '01A or a '00 /'00A as the detector, and if so, what value(s) of grid-leak in your set? Weak-signal reception should differ.

Again, thanks.

John


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Wed 02, 2011 11:42 am 
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Joined: Aug Sat 16, 2008 2:57 am
Posts: 41
The set has 01A tubes - the grid leak is a 2.4 meg value.

What other tubes can be used? 4 of the Cunningham CX-301A tubes were good, replaced one with an 01A ST shape. I haven't tried the tube-shuffle as described in the AK manual to optimize tubes for a given placement.

I need to set out a better antenna to get other stations to fill in more data. I was thinking of plotting points into a graphing calculator and getting equations - something to do on a rainy day....


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Thu 03, 2011 8:10 am 
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Joined: Apr Tue 19, 2011 6:24 am
Posts: 453
Location: 07470
First a disclaimer: I 'm no AK expert, and do not specialize in such sets. My y own worldview is that such radeios were made in order to provide sockets for the really interesting tubes I collect and putto use. There are many genuine AK experts in these Forums, and Ihope they might join this thread and share their knowledge with us.

Here's what I think re your radio:

You are OK with the tubes you have, but doing the tube/socket dance can produce appreciable improvements. Follow A-K's procedure, and experience the thrills of 87 years ago.

The AK 20, like most TRF and neutrodynes of 1924 used the ubiquitous UV-201A in all sockets, but as some users wanted more sensitive detectors to pull in weak stations, they used a UV-200 in the detector socket (only). That gas-filled tube is very touchy and requires a low B+ voltage, no more than 22.5 volts, and better if it can be smoothly adjusted to a lower value. Likewise the 200's grid leak might require some other TBD value than 2.4 Megs, and the tube's detection sensitivity also responds to changes in filament voltage. The radio magazines of the day devoted a lot of space to such arcana. If you go to http://www.atwaterkent.info/TechData/Dr ... 04640.html you'll see a 200A in the schematic. Lots more great info on W3LNB's A-K site. Am sure we each owe him a case of "Cold 807's"...


You may note a yellow detector battery wire if you have an original-style battery cable. It runs, of course, to the "DET" connection terminal in the set Use 22.5V there, unless you are playing with an '00A , and then I'd recommend starting with 15V, and going upward until you hit the sweet spot.

My recommendation is to avoid UV/UX-200/200As unless you are inclined to experiment and enjoy masochistic fun learning what some folks back then tried in the interests of pulling in faraway stations. Stick with UV- or UX-201As (or direct equivalents), and you'll have a fine radio that works dependably well with local stations, and sometimes even with distant ones if they are strong enough. As UX based tubes fit the set, and are readily available, save any UV- based tubes you may have for earlier radios. The 4640 doesn't care. If you are interested in this matter, a web search will prove informative, and I recollect posts herein the ARF about adjusting volatges for 200's.


Likewise, an even more productive tube change places a "power tube" in the last socket. Use of a 112A or a 171A instead of a 201A/'01A there will give much better audio tone and power, if you are using a loudspeaker. The changes enatil additional wiring, higher B+ and lower bias volatges, and are well documented in AK's service manuals, all available on the web.

My own 4640 (s/n 6939) is being faithfully returned to original condition, even to using a set of 5 brass-based, tipless UV-201As which were produced in the summer of '24 when I think this set was built by A-K. Perhaps one of the AK experts reading this might comment?

However, I will play around with several UV-200s in the detector socket, just to see how the set performs. ( Almost no two '00s are alike in performance, something that lead to their demise in sets designed after the mid-'20s.


For a really nice picture that should be of interest to you , go to http://www.shorpy.com/node/3535?size=_original


Enjoy your wonderful set.
It is great to keep these jewels of ancient technology glowing into this century.

John


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Thu 03, 2011 8:19 am 
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Joined: Apr Tue 19, 2011 6:24 am
Posts: 453
Location: 07470
OOOPS! Wrong link in message above; last digits are -3534 not 3535:

Sorry the above post is full of typos; it's 0315 here and I was nodding off and accidentally hit "Submit" rather than "Preview".

The link re that most interesting photo is http://www.shorpy.com/node/3534?size=_original

You have my apology for the errors.


John


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Fri 04, 2011 11:20 pm 
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Joined: Aug Sat 16, 2008 2:57 am
Posts: 41
Thank you for the detailed information. The photo is spectacular.


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Mon 12, 2018 1:01 am 
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Joined: Nov Tue 29, 2016 6:05 am
Posts: 45
Location: Burnaby BC Cda. V5E 4A6
hi
Sacrilege?!?!?!?
Has anyone considered a Retrofit using modern electronics with a lower, safer voltage, & lower cost wall-wart power supply
thanx
73 de jordan ve7jjd


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Mon 12, 2018 1:22 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 13493
Location: S. Dartmouth MA 02748-1225 USA
Jordan Dobrikin wrote:
hi
Sacrilege?!?!?!?
Has anyone considered a Retrofit using modern electronics with a lower, safer voltage, & lower cost wall-wart power supply
thanx
73 de jordan ve7jjd
Bringing up this old nut...

Its been done:

http://www.antiqueradios.com/forums/vie ... hp?t=81553

http://www.greenhillsgf.com/Project_SS-Tubes.htm

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Smith's Ale Gives Strength, Smith Bros. Brewers, New Bedford MA


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Mon 12, 2018 1:53 pm 
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Posts: 122
Location: Monroe TWP, NJ 08831
mjmesserly wrote:
Thank you for the detailed information. The photo is spectacular.

The woman mid-picture on the line - I've seen that look before ....

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73 - Mark, KD2NOM


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 Post subject: Re: Dial settings vs. frequency tuning data - Atwater Kent 2
PostPosted: Nov Mon 12, 2018 3:42 pm 
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Joined: Sep Fri 07, 2007 2:27 am
Posts: 5741
Location: Grand Chute, Wisconsin
viewtopic.php?f=6&t=313246


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