[ARC5] HS-33

[Michael Hanz]

For those interested, several years ago I posted a summary at 
http://aafradio.org/docs/NDRC_Division_17_excerpts.pdf  that goes into a 
lot of the work that Harvard and others accomplished under the NDRC 
banner, overall entitled Transmission and Reception of Sounds Under 
Combat Conditions.  The excerpt is Chapter 9, The Interphone.  The 
headphone research is covered under pp135-138 of the pdf.

- Mike  KC4TOS

On 8/9/2019 4:46 PM, Richard Knoppow wrote:
> The ANBH-1A (Army, Navy, British, Headphone) was designed to have high 
> articulation of speech in aircraft. The design originated at the 
> Harvard University laboratories. The receivers are low impedance 
> moving coil types. Some have Bakelized cloth diaphragms and some have 
> metal diaphragms. The phones were made by several suppliers. Permoflux 
> made a commercial version offering a standard and high fidelity 
> version, I suspect they are the same but the hi-fi ones may have been 
> selected. Basic element has a voice coil impedance of about 20 ohms, 
> the military version has a built in transformer to make it 300 ohms. 
> This is for single units, usually they are supplied in pairs with the 
> two in series so the impedance is either 50 ohms or 600 ohms. Higher 
> impedance is gotten by an external transformer. There were a number of 
> previous designs. The original magnetic type just was not clear enough 
> under high noise conditions. None of the magnetic phones were good 
> enough. Another type of similar headphone has a small diaphragm, I 
> think they might also be magnetic but I've never disassembled one. 
> These are the ANBH-1 (not A) version. Same impedances. They do not 
> have the wide frequency range of the A but are pretty flat in 
> response. Most magnetic headphones are quite strongly resonant 
> typically at around 1Khz. Work fine for CW but not for voice. In fact, 
> the flat response phones may be better even for CW because noise 
> doesn't make them "ring".
>     Some of these came on headbands, at least two types, some came in 
> pairs with a short cable for use in pilots helmets or perhaps for use 
> in tanks. Aircraft and tanks have similar ambient noise problems.
>     A similar headphone to the ANBH-1A is made for audiology by 
> Telephonics.
> On 8/9/2019 12:33 PM, Kenneth G. Gordon wrote:
>> On 9 Aug 2019 at 18:36, D C _Mac_ Macdonald wrote:
>>
>>> Receivers are Utah ANB-H-1.
>>
>> As I understand it, if you have the ANB-H1 receivers, it is an HS-33.
>>
>> Doesn't really matter in practical terms for most mil radios, but I 
>> prefer the older HS-23 types
>> with their higher impedance.
>>
>> However, the only set I have has one intermittant receiver. Gotta fix 
>> that some day.
>>
>> Ken W7EKB