Impedance and Resistance Measurments
Of
Sound Powered Elements
"Balanced Armature" Elements used for crystal radio sets

Please note:
These measurements were measured at only one frequency (1 kHz. which is the industry standard).
Impedance will change as the frequency changes.
The measurements were made to show the difference in impedance within the same type and brand of element.
This list is a work in progress.

---

RCA

Manufacturer  RCA	Unit Number	Element Number	Unit Type	Element Type	AC Impedance  @ 1 kHz. with capacitor/without cap.	DC Resistance (ohms)
"Big Cans"  MI-2045	1	1	DT	mic	na / 220	7.9
"	2	2	DT	mic	na / 140	8.3
"	3	3	DT	mic	na / 220	8.3
"	4	4	DT	mic	na / 200	8.1
"	5	27	DT	mic	na / 100	9.6
"Big Cans"  MI-2045	1	5	DT	ear	na / 3900	88.1
"	1	6	DT	ear	na / 3000	81.7
"	2	7	DT	ear	na / 3600	78.5
"	2	8	DT	ear	na / 3000	81.1
"	3	9	DT	ear	na / 300*	81.5
"	5	23	DT	ear	na / 2000	91
"	5	24	DT	ear	na / 1800	95
"	6	25	DT	ear	na / 1000	99
"	6	26	DT	ear	na / 2000	86
Handsets  MI-2040	5	10	Handset	mic	na / 850	141.9
"	6	11	Handset	mic	1800 / 1420	142.2
"	7	12	Handset	mic	1000 / 600	142.4
"	8	13	Handset	mic	na / 300	70.2
"	9	14	Handset	mic	1400 / 3500	146.6
"	10	15	Handset	mic	na / 400	81.9
"	11	16	Handset	mic	na / 265	71.6
"	12	17	Handset	mic	na / 160	49.5
"	5	18	Handset	ear	na / 2250	94.2
"	6	19	Handset	ear	1800 / 1420	142.2
"	7	20	Handset	ear	910 / 150	87.2
"	8	21	Handset	ear	na / 254	48.3
"	9	22	Handset	ear	320 / 500	74.7

* Units marked with  *  may have problems.
This problem may be mechanical thus giving a bad reading.
 
 
 
 
 

---

United States Instrument (USI)

NEW !
United States Instruments (USI) Deck Talkers ("Big Cans")
Model #A-260 UA1614 (older model)
Ear Units

AC Impedance  @ 1 kHz.	DC Resistance (ohms)
780	64.8
1600	61.2
500*	60.5
260*	64.4
700	61.9
1200	56.4
1100	60.6
1100	60.4
1100	61.1
1100	57.6
1300	58.2
395*	63.4
1000	58.5
1300	60.0
1800	60.0
800	59.4
1300	58.5
1300	58.8
1200	59.9
700	59.1
900	not available
1100	not available
850	59.7
1200	not available
1200	59.5
1200	58.6
1200	57.7
1100	62.0
1220	63.5
1400	63.3

* Units marked with  *  may have problems.
This problem may be mechanical thus giving a bad reading.
 
 

NEW !
United States Instruments (USI) Deck Talkers ("Big Cans")
Model #A-260 UA1614 (older model)
Mic Units

AC Impedance  @ 1 kHz.	DC Resistance (ohms)
390	13.7
350	13.7
82	15.5
240	not available
192	15.8
150	15.8

 
 
 

United States Instruments (USI) Handsets
Models A560, A577, A257,and A333
Ear and Mic Units

Manufacturer  United States Instruments (USI)	Unit Number	Element Number	Unit Type	Element Type	AC Impedance  @ 1 kHz.	DC Resistance (ohms)	Comments
UA1614 type	na	8	Handset	ear	300	62.6	no ua #'s  "Receiver T"
"	1	11	Handset	mic	450	63.3	no ua #'s (handset 677)
"	2	13	Handset	mic	450	60.1	UA1614-1 (handset 560)
"	3	15	Handset	mic	680	64.8	UA1614-3 (Stromberg A257)
"	4	17	Handset	mic	240	61.4	UA1614-1 (Stromberg H203)
"	na	23	Handset	mic	1050	60	UA1614-1
"	na	24	Handset	ear	810	60.9	UA1614-1
"	na	1	Handset	mic	1200	63	UA1614-1
"	na	2	Handset	mic	246	61.5	UA1614-1
"	na	3	Handset	mic	750	63.1	UA1614-1
"	na	4	Handset	mic	2500	62.5	UA1614-15
"	na	6	Handset	mic	3500	65.6	UA1614-15
"	na	7	Handset	mic	1500	64.8	UA1614-15
"	1	12	Handset	mic	1450	61.5	UA1614-15 (handset 577)
"	2	14	Handset	mic	dead	dead	UA1614-1 (handset 560)
"	3	16	Handset	mic	900	92.3	UA1614-4 (Stromberg A257)
"	4	18	Handset	mic	750	62.1	UA1614-1 (Stromberg H203)
"	na	25	Handset	mic	1150	89.8	UA1614-4
UA1614 type	na	26	Handset	mic	100	86.4	UA1614-4

 
 

United States Instruments (USI) Deck Talkers
Model #A-260 UA1614 (newer style model)
Ear Units

AC Impedance  @ 1 kHz.	DC Resistance (ohms)
750	64.7
750	64.7

---

Misc. Makers

Manufacturer Misc. Makers (will be updated soon)	Unit Type	Element Type	AC Impedance @ 1 kHz.
Automatic Electric	DT	mic	14
"	DT	ear	600
"	DT	ear	610
SPC	Handset	ear / mic	310
"	Handset	ear / mic	260
"	Handset	ear / mic	310
"	Handset	ear / mic	265
Stromberg Carlson	DT	mic	120
"	DT	mic	95
"	Handset	ear	1100
"	Handset	mic	1900
"	Handset	ear	700
"	Handset	mic	1100
"	Handset	ear	250?
"	Handset	mic	900
Telephonics	Handset	ear	355
TMC (British)	DT	ear	200
TMC (Aussie)	DT	ear	145
Western Electric	DT	ear	650
"	DT	ear	655
"	Handset	mic	500
"	Handset	mic	300
Vintage Magnetic			vintage measured as a pair in series
Western Electric	509W	vintage	23000 (23k)
Baldwin	Type C	vintage	20000 (20k)
Baldwin	Type C	vintage	20000 (20k)

DT = Deck Talkers
mic = microphone or transmitter unit
ear = receiver unit

---

Notes:

1)  All measurements were taken with element removed from housing and in free air.

2)  Warming up (or cooling down) the elements up can change impedance measurments.

3)  Any obstruction at all will change the impedance. Moving the obstruction (such as a finger) closer to the
     elements, will raise the impedance. At about 1/2" from the element it will start to drop again as you get
     closer  still.

4)  1kHz. frequency was used for these tests. Impedance will change as frequency changes.

5)  Some RCA handset elements have a capacitor built into the element. You need to remove that
     capacitor in order to use the element on a crystal radio. Most all other brands of Decktalkers and handsets
     (including the RCA decktalkers) have the capacitors on the out side of the element.

---