Στις 06/12/2012 03:07 πμ, ο/η doug Î*γÏ�αψε:
On Dec 3, 8:22 pm, Kosmas Anastasiadis wrote:
I found the schematic of icom's HM-7 hand powered mic.
One of the resistors inside is 18KOhm or 1.8KOhm ???

Thanks
SV2BFI


Hello Kosmas, I looked inside my HM7 mic. which
came with my Icom 740, the resistor is one point eight K.
(1.8k), and is in parallel with the 4.7uf. capacitor as shown
in the schematic. I checked the value of this resistor with
digital meter,and it confirmed this resistance value.

HTH, Doug. GM3OAV


I found a schematic at an japanese site too.
The resistor is 1.8Kohm.
I finish it and it is working loud and clear.
I have an icom ic-738 transceiver. I have both
hm-36 and sm-20 microphones. The hm-326 has very
low output and can't drive the transceiver to full
output on ssb. The sm-20 has enough power but it
picks up any surround noise (blowers, my children,
telephon rings, TV etc etc). So i need a
dynamic microphone with enough power to drive well
my transceiver without too much sensitivity.
I have an old dynamic handy microphone from a CB
transceiver and I put inside a preamplifier on a
small pcboard and it works fine.

Thanks to all for your help.

73
SV2BFI