From: Trish & Carla (wa6ube@tactical-link.com)
Date: Sun May 11 2003 - 16:51:57 PDT
The secret to microphone operation in noisy
vehicles is the use of "noise-cancelling" microphones..
The H-250 handset, and M80 microphones are examples, as
they have entry points for sound on both sides of the
mic elements ...
external noise sources tend to hit both sides of the mic
element, therefore cancelling out, while when you talk
into a handset or mic, it is from only one side ...
Shure makes commercial noise-cancelling mics, and I modified
one some years ago for a Cobra 146-GTL AM/SSB CB radio..
In order to use it, however, I had to install a relay inside
the radio in order to switch the 12-volt power from tx to rx..
I really dislike rigs like the 146-GTL where power is switched
to the receiver and transmitter via additional contacts
in the microphone switch .. YUK!!..
-- Patricia E. Gibbons & Carla Satra Tactical Link Systems In California: "She sells D-cells by the seashore" <ICQ#: 72818195> <http://www.tactical-link.com> see my comvan at: <http://www.tactical-link.com/wa6ube.htm> ...................................... My Public Key is available at: http://wwwkeys.pgp.net:11371/pks/lookup?op=index&search=0xedecb44f Key ID: 0xEDECB44F This key is RSA, NOT Diffie-Hellman !!-----Original Message----- From: Military Vehicles Mailing List [mailto:mil-veh@mil-veh.org]On Behalf Of Patrick Jankowiak Sent: Sunday, May 11, 2003 18:47 To: Military Vehicles Mailing List Subject: [MV] CB in MV
Here's some commo thoughts for long range drivers. Long winded, yes.
A CB radio is needed in the M35 becaue I like to drive the wide open roads of the great State of Texas. CB is the road language..
The antenna installed is made of MS-116, 117, and 118, with an AB-15-like base (the rubber shaft part is thicker and the base is plastic). It resonates at 22 MHz but will be fine with an antenna tuner.
I have a vanner 50 amp battery equalizer, so 12VDC is no problem
I do not like the modulation quality (transmit audio quality) of most modern (foreign-made) CB radios, and I just can't picture one of those cheap plastic things in there, even painted green. Let's face it, even a Cobra 148-GTL does not sound anything like the old plate-modulated boat-anchors of ye olde American manufacture.
I have just repaired and aligned a Sonar FS-23 tube-type CB made in 1965. 3 tubes and 4 resistors later, the CB is working.
I will have to remove its covers and front panel and give them the ol' green treatment. Replace the meter with a GRC-106 type meter.
The knobs are another issue.. They are not military-looking, but are held on by setscrews. Knobs like those on the VRC-12/RT524, or GRC106, PRC77, etc. are held on by screws put in from the front,. I don't have the means to deal with that.
For starters, a small PA speaker in the cab should provide enough volume from the CB to be heard in the M35. The issue will be the CB's mike. It will surely pick up all the noise.
This brings up the question of microphones in general. MIL aircraft and trucks are real noisy. Yet the radio operator's voice is always clear and above the noise (re: the AC130 gunship video). What's the secret? (besides the CB mike is uuuugly!)
(integration to VIC-1 is possible, another subject for later)
Now, some will say it's not right to do this, putting a CB in a military vehicle, that I should use military radios.
I agree to a point of aesthetics, but where to find a 'small' underdash military radio which is low powered and will easily do the 23 or 40 channels of the 27 MHz band?
A 27 MHz FM rig like in G. R. Baker's M5 Stuart is quite big and would have to be modified heavily for more than rudimentary AM use. I will not chop up a good military radio!
A PRC104 is too expensive.
The GRC106 won't fit under the dash and although I could mount one on the passenger seat, I would be distracted trying to change channels, fiddling with the fine tuning because CB's are often slightly off frequency and the 106 is essentially a SSB radio, forever shooting thieves in my driveway, and its 400 watts is a bit excessive for CB!
So therefore a resurrected tube type CB, saved from the junk box.
I'll have some pictures of it later when it is green.
soapbox off. flame away!
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