Microphones

 A microphone is often an afterthought unless one arrived with your new transmitter. I usually rush around looking for something which nearly always has the wrong plug attached.

Such is the case with a recent interest in my old 19 Set. Years ago I used to have a pair of headphones and a microphone for this ex-tank transceiver. They plugged into flying leads

dangling from a control box. Really good if you're in a tank but not too practical in the average ham shack. Both were moving coil with low impedance connections. Something like tiny loudspeakers.

Here's a list of microphones that I found in my workshop.. photos to follow.

Astatic D104 with T-UG8 base

See spec and circuit diagram

 I found the following on the Net after going through zillions of old Ebay pages.

Introduced in 1933, the Astatic model D-104 was popular for its high frequency response which resulted in very intelligible audio.

Its high output voltage was characteristic of crystal elements and its high impedance allowed for direct grid input. The early D-104 mikes used a 1 inch thick case and have a large ID tag along with tapped holes for “ring & spring” mounts. The case thickness was reduced in April 1937 and smaller tags were then used and the ring holes eliminated. The “grip” switch stand (“G” Stand) was introduced in January 1938 but didn’t become popular until much later. The early “G” stand bases were gloss black with metal ID tag.

The D-104 continued in production with little change until the 1960s when a solid-state amplifier was added to the “G” stand. In 1976, an eagle and shield was added to the rear cover to commemorate the US Bicentennial. Other variations appeared from time to time until 2001, when production ceased, 68 years after the first D-104 was offered. [4]

The D-104 is often used by CB radio hobbyists and vintage amateur radio enthusiasts as part of their operating activities.

Here's useful links for those still interested..

http://www.west-techservices.com/p15.htm

http://www.w8ji.com/d104_to_low_impedance.htm

and a really useful general source of info...

http://www.qsl.net/g4wpw/date.html

 

Yaesu YD148

 This is the microphone that I got with my Yaesu FT480. It's switchable from 600 ohm to 50 kohm.

Yaesu's website appears not to recognise their YD148 so I filled in their query form for some information, promised within 48 hours. We'll see...

http://www.qsl.net/g4wpw/yd148.html

 

Philips B416

 I can't find anything about this one, but it looks useful.

It's full Philips number is LBB 9416/10 8900 941 61001 S/No 002449 but none of the usual search engines show it up so I went onto the Philips website which appears to make sincere sounding promises to support customers, Typing in either of the full codes however revealed only one product and the only connection was the slash ten at the end of the code number, so I filled in their query form and will now wait up to 48 hours to hear back.

I heard back in only an hour to tell me I'd contacted "Philips Consumer Lifestyle" dealing only with "Portable entertainment, Digital photo frames, Remote controls, PC products, VOIP Phones, Wireless Music Systems", and was to contact "Voice Recorders & Speech Processing" so I filled in an identical query to them and sent that off..

 

Shure #444

 This is fitted with a quarter inch jack socket and has a switch for "vox" use and is designed for connection to equipments with an input of 15kohm (min) to 100kohm.

Here's a spec

 


 Interfacing a microphone to a particular transmitter is not straightforward unless you bought the manufacturers recommended one.

Firstly there's the plug. This used to be a quarter inch jack plug but now is usually a "circular multipole connector" having a specific number of pins, often four, but sometimes a few more if your mike has extra push buttons.

Secondly, you need to match the impedance and output to the equipment's needs. Sometimes the designer of the mike helps out by fitting a switch so you can change its impedance, such as the YD148 above. If you're determined to use a particular mike with a particular transmitter you'll have to make a matching circuit from a transistor or two and add a battery to provide power for the new circuit.

The first step is to check the Philips mike as it has no plug fitted and might be a dynamic type easily used with the 19 set?

I removed the metal base and found it had been got at. Inside there's a small circuit board carrying a tiny transformer measuring 10-0-10 ohms input and 0.3 ohms output. There are three surface mount transistors and a cluster of resistors, capacitors and tiny chokes. The microphone itself has three thin wires red, white and black. Between the red or white to black measures 7.5 kohm and between red and white a few megohms, so perhaps it has two crystal inserts These may be connected to the 10-0-10 winding via transistors to transform the impedance to a common low impedace output? However the thing will beed a battery, although probably in its original application, power came from the amplifier or equipment for which it was designed? As all the wires are disconnected I'd have to trace the circuit.

The immediate alternative is the Yaesu switched to its 600 ohm setting.

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