Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Mar Sun 29, 2020 3:29 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 8 posts ] 
Author Message
 Post subject: A simple IF transformer question
PostPosted: Sep Mon 02, 2019 4:24 pm 
Member
User avatar

Joined: Oct Sat 15, 2011 12:19 am
Posts: 2172
Location: 23452
I have an IF transformer out of an Emerson AA5. it was the 1st IF, internally it has two pie-wound coils wound on a form with caps for each. One of the coils is visibly about twice the size of the other, so either step up or step down.

My question is; does the IF transformer increase the voltage of the signal (step up) or increase the current of the signal (step down)?

_________________
I would agree with you but there's no point in both of us being wrong


Last edited by cl350rr on Sep Mon 02, 2019 9:32 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: A simple IF transformer question
PostPosted: Sep Mon 02, 2019 5:50 pm 
Member
User avatar

Joined: Jul Mon 26, 2010 8:30 pm
Posts: 27586
Location: Annapolis, MD
I think you'll find a variety of designs.....Most seem to be around 1:1.

_________________
-Mark
"Measure voltage, but THINK current." --anon.


Top
 Profile  
 
 Post subject: Re: A simple IF transformer question
PostPosted: Sep Mon 02, 2019 7:17 pm 
Moderator
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 23687
Location: Somers, CT
IFT to a diode detector can be a step down... you will specific ratios between stages in higher end sets.

_________________
Just because it can be done doesn't mean it should be done.


Top
 Profile  
 
 Post subject: Re: A simple IF transformer question
PostPosted: Sep Sun 15, 2019 4:50 pm 
Member
User avatar

Joined: Sep Wed 10, 2014 2:01 am
Posts: 2054
Location: Costa Mesa, California
I think the purpose is to step up the voltage to the grid of the IF amp tube. Grids respond to voltage fluctuation. AA5’s are very simple super het radios and use the minimum number of components to produce the result. The first tube (pentode or pentagrid) is a RF amp, mixer, and LO combined. There is one IF amp tube and the detector is also the first audio. The fourth tube is the audio amp. The fifth tube is the power supply rectifier—so really these are four tube radios—where two of the tubes are multi-function.

Norm

_________________
KK6IYM


Top
 Profile  
 
 Post subject: Re: A simple IF transformer question
PostPosted: Sep Sun 15, 2019 5:55 pm 
Member
User avatar

Joined: Oct Sat 15, 2011 12:19 am
Posts: 2172
Location: 23452
Thank you for the replies. I got it working, and it supports what you just wrote Norm. I set it up with the larger winding as the secondary, boosting the voltage.

_________________
I would agree with you but there's no point in both of us being wrong


Top
 Profile  
 
 Post subject: Re: A simple IF transformer question
PostPosted: Sep Mon 16, 2019 12:39 am 
Member

Joined: Mar Sat 23, 2013 1:08 pm
Posts: 198
Location: Lunar Station 4
As well as impedance matching.


Top
 Profile  
 
 Post subject: Re: A simple IF transformer question
PostPosted: Sep Tue 17, 2019 6:29 pm 
Member

Joined: Nov Mon 06, 2017 2:35 pm
Posts: 120
Location: Texas, U.S.A.
.....

Some sources of information on intermediate frequency transformer design. Tepper and Ghirardi are introductory; Schure is recommended next along with Slurzberg and Osterheld.

Beatty, R. T., "Two-element Band-pass Filters", The Wireless Engineer and Experimental Wireless, Oct. 1932

Ghirardi, A. A., Radio Physics Course, 2nd ed., 1933, art. 360, pp. 535 - 539

Grimes and Barden, "A Study of Litz Wire Coils for I-F and R-F Transformers", Electronics, Nov. and Dec. 1933

Scheer, F. H., "Notes on Intermediate Frequency Transformer Design", Proceedings of the IRE, Vol. 23, no. 12, Dec. 1935

Sturley, K. R., "Coupled Circuit Filters", Wireless Engineer, Sept. and Oct. 1943

Espy, D., "Double-Tuned Transformer Design", Electronics, Oct. 1944

Slurzberg, M., Osterheld, W., Essentials of Radio, 1948, pp. 106 - 110, 300 - 311

Langford-Smith, F., ed., Radio Designer's Handbook, 4th ed., Iliffe & Sons, London UK, 1957, pp. 1020 - 1071

Schure, A., Transformers, New York: John F. Rider Inc., 1961, pp. 55 - 68

Williams, E., Thermionic Valve Circuits, 4th ed., 1961, pp. 84 - 93

Tepper, M., Basic Radio, Rider Publications, 1961, pp. 4-26 - 4-27

I.F. transformer wiring color code, ref. Cooke, N. M., ed., Allied's Radio Data Handbook, 1943, p. 32:
Attachment:
COLOR_CODE_INTERMEDIATE_FREQ_XFMR.jpg
COLOR_CODE_INTERMEDIATE_FREQ_XFMR.jpg [ 74.25 KiB | Viewed 1202 times ]


----------------------
WB5HDF


Last edited by infzqi on Nov Tue 19, 2019 3:40 pm, edited 8 times in total.

Top
 Profile  
 
 Post subject: Re: A simple IF transformer question
PostPosted: Sep Wed 18, 2019 6:42 pm 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 9307
Location: Long Island NY
There isn’t anything simple about an IF transformer. The immediate purpose is obvious, complete the DC circuits for the plate of the previous tube and the grid of the next, while filtering, bandwidth shaping, and coupling the IF energy from one stage to the next. When you consider the complex impedances involved, mutual coupling, and inter and intra winding capacitances, it’s little wonder many IF transformers were created by people who spent their careers in basement laboratories and didn’t come up for air very often. As soon as somebody came up with a transformer that worked really well, everybody would copy it and produce their version until the next big discovery.

Older IF transformers often had red, blue, green or yellow, and black wires. Red was B+, blue was plate of the previous tube, green or yellow was grid of the next tube, black was AVC or ground. In newer radios you’ll sometimes see a red dot near one terminal for B+ (the main purpose is to identify primary and secondary; unless there’s additional circuitry inside the can, reversing the leads makes no difference).

If you get stuck with no way to identify primary and secondary on an IF, just try it one way, then the other. If there is any difference, the connection which aligns and performs better (going by AVC voltage, not perceived volume) is the correct one.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
Post New Topic Post Reply  [ 8 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: sprman and 9 guests



Search for:
Jump to:  
































-->


Privacy Policy :: Powered by phpBB