Wireless Mikes ?

N

N_Cook

Guest
In general ,845-865MHz and this one in particular.
What is the code-switch marked GR along side the ch sw?
I'm asuming it whould have a stub wire aerial out the bottom but that is
snapped off , what length ? 1/4 wavelength at 850MHz ? there is an internal
zigzag in the feed trace , presumably some sort of minimal radiator.
3 position switch on body , would that be off/on-low power/on- high power
or secondary ch setting ?

This is a Mascot Gemini PM64. I found the secret screw under the ch/gr
label. No LED and no output.
I was hoping it was a broken switch as the plastic slide-knob is missing and
they had been using a screwdriver, in ,to the slide-sw stub for on/off. As
it is nearer mobile phone circuitry in there, any insight as to how to go
about fault finding ? 2P3W switch action seems ok and battery connections
ok.
 
N_Cook <diverse@tcp.co.uk> wrote in message
news:hjs145$9et$1@news.eternal-september.org...
In general ,845-865MHz and this one in particular.
What is the code-switch marked GR along side the ch sw?
I'm asuming it whould have a stub wire aerial out the bottom but that is
snapped off , what length ? 1/4 wavelength at 850MHz ? there is an
internal
zigzag in the feed trace , presumably some sort of minimal radiator.
3 position switch on body , would that be off/on-low power/on- high power
or secondary ch setting ?

This is a Mascot Gemini PM64. I found the secret screw under the ch/gr
label. No LED and no output.
I was hoping it was a broken switch as the plastic slide-knob is missing
and
they had been using a screwdriver, in ,to the slide-sw stub for on/off. As
it is nearer mobile phone circuitry in there, any insight as to how to go
about fault finding ? 2P3W switch action seems ok and battery connections
ok.
Click to expand...
Looks a right mess under a 30x. They must have screwdrivered it hundreds of
times before neatly prizing off a SMD SOT23, leaving 3 non-virgin pads.
First guess topmark LG like most of them around , NPN yes, my list says UHF
BF775 - unlikely . Will try anything GP that is NPN , pin1 68K to it is
assumed base, p2 gnd E, p3 1k so C assumed.
For completeness LG = ?
Other SO23 are
SOT23 FET probably , marked XY
NPN SOT23 marked FV then sideways 18 small script, probable pinning p1 E, p2
C, p3 B if anyone has topmarks for about 2005
 
Label on the mike is worn , no wonder I could not find pics, it is an FM 64.
No bit of wire dangling so the zigzag is the antenna. So what is the bit of
multistrand thick wire, about 4mm long, inside a black housing that looks
like a 2.1mm DC power connector, if it was a solid conductor at the centre?
 
Anyone know if you can use the top end of an analogue UHF TV to check these
850MHz mikes, as far as some sort of modulated signal or at least active
carrier?
The mating receiver is in a fixed installation
 
N_Cook <diverse@tcp.co.uk> wrote in message
news:hju6jt$mp0$1@news.eternal-september.org...
Label on the mike is worn , no wonder I could not find pics, it is an FM
64.
No bit of wire dangling so the zigzag is the antenna. So what is the bit
of
multistrand thick wire, about 4mm long, inside a black housing that looks
like a 2.1mm DC power connector, if it was a solid conductor at the
centre?
Click to expand...

It would seem to be a mangled DC power connector for rechargeable batteries
option and one of the traces from it is zigzagged and UHF overlain on it for
radiating out.
 
Gemini FM 64 radio mike
Soldered in a GP SOT23, BCW31 topcode D1.
On 3V the LED flashes on switch on, goes goes continuous if V drops to 1.4V
and current goes well over 100mA before that.
With 3V, current draw is 69mA and 68mA without the electret mike plugged in
but no change in draw with tapping of mike. Nothing on the LM317 so I will
assume that is for DC feed for rechargeables, not used for the main
circuitry.

Dug out an ancient early portable colour TV, retained for just such a
purpose. So old it has a VHF rotary tuner built in as well as UHF. But of
course nice old mechanical rotation for VT to tuner block, so can play
around as much as you like detuning either side to try and get some sort of
audio demodulated.
At the top of the range around ch 68 a strong signal including interference
pattern on picture,from the other end of the room, all going on switching
off the radio mike. No amount of fiddling of de-tune would get even a
semblance of sound on tapping the mike nor change of interference pattern on
screen. At this stage without proper test equipment I will assume working
entirely until the owner tells me otherwise.
Still don't know what the third position of the slide switch is. Maybe only
2 positions used of the 3, going by the length of slot in the outer bezel,
but the plastic widget that extends up from the pcb slide sw is missing,
hence plenty of space to scrape a screwdriver around inside. The surround Al
of the slide sw was so randomly scraped I thought it was brush finished when
I first saw it, hence probably hundreds of screwdriver activations.
Now to bodge up a widget


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm
 
Made a widget from a bit of VHS tape cassette outer, kids plastic mosaic
bead, cutdown plastic snap rivet, hotmelt glue and some silicone paste so it
slides easily and looks almost proper-like , original never seen.

UHF TV test does work to the extent you can de-tune to a point where tapping
on the mike will modulate the interference pattern on the screen and at
another point a feint tapping in the audio.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm
 
Back in service
Sw is off/carrier on/carrier plus modulation


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm
 
On 02/02/2010 13:50, Dave Plowman (News) wrote:
In article<hk8vj4$341$1@news.eternal-september.org>,
N_Cook<diverse@tcp.co.uk> wrote:
Back in service
Sw is off/carrier on/carrier plus modulation


Think you've got the record for a one man thread. But interesting. ;-)
Click to expand...
It`s the digital equivalent of talking to yourself ;)
 
In article <hk8vj4$341$1@news.eternal-september.org>,
N_Cook <diverse@tcp.co.uk> wrote:
Back in service
Sw is off/carrier on/carrier plus modulation
Click to expand...

Think you've got the record for a one man thread. But interesting. ;-)

--
*Middle age is when work is a lot less fun - and fun a lot more work.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
Ron <ron@lunevalleyaudio.com> wrote in message
news:CtCdnQxuG7FNqvXWnZ2dnUVZ7tli4p2d@bt.com...
On 02/02/2010 13:50, Dave Plowman (News) wrote:
In article<hk8vj4$341$1@news.eternal-september.org>,
N_Cook<diverse@tcp.co.uk> wrote:
Back in service
Sw is off/carrier on/carrier plus modulation


Think you've got the record for a one man thread. But interesting. ;-)


It`s the digital equivalent of talking to yourself ;)
Click to expand...
Not when its collated together, corrections made and placed for all, gratis,
with hundreds of other such repair briefs ,
already uploaded at the weekend on
http://www.divdev.fsnet.co.uk/repair2.htm


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm
 
In article <hk8vj4$341$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

Back in service
Sw is off/carrier on/carrier plus modulation
Click to expand...
Most likely originally labeled "off/mute/on," and this (or something
roughly equivalent) is standard for most wireless microphones.
Switching the transmitter completely on and off will often cause pops
and other objectionable output, so for temporarily suspending use the
mute setting is useful. Of course, ideally a competent sound tech will
take care of muting and so forth at the sound board, but that's not
always reality.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot
 
Andrew Erickson wrote:
In article <hk8vj4$341$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

Back in service
Sw is off/carrier on/carrier plus modulation

Most likely originally labeled "off/mute/on," and this (or something
roughly equivalent) is standard for most wireless microphones.
Click to expand...

AKA: Cough Switch.


--
Greed is the root of all eBay.
 
Michael A. Terrell <mike.terrell@earthlink.net> wrote in message
news:4B68E3BB.D7C9A41A@earthlink.net...
Andrew Erickson wrote:

In article <hk8vj4$341$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

Back in service
Sw is off/carrier on/carrier plus modulation

Most likely originally labeled "off/mute/on," and this (or something
roughly equivalent) is standard for most wireless microphones.


AKA: Cough Switch.


--
Greed is the root of all eBay.
Click to expand...
Now , from being back in use, in the mid position the led on the receiver,
for that ch, goes on, then sound comes through in third posistion.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm
 
Dave Plowman (News) <dave@davenoise.co.uk> wrote in message
news:50e3b49f06dave@davenoise.co.uk...
In article <gmavt-202195.12484402022010@sn-ip.us.supernews.com>,
Andrew Erickson <gmavt@drewe.reverse2mail.net> wrote:
Most likely originally labeled "off/mute/on," and this (or something
roughly equivalent) is standard for most wireless microphones.
Switching the transmitter completely on and off will often cause pops
and other objectionable output, so for temporarily suspending use the
mute setting is useful. Of course, ideally a competent sound tech will
take care of muting and so forth at the sound board, but that's not
always reality.

Some these days send out a sort of pilot tone which if not present mutes
the receiver and prevents it reacting to interference, etc with the
transmitter switched off.

--
*Marriage changes passion - suddenly you're in bed with a relative*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
Click to expand...


Would that system also work with "taxi breakthrough" of nearby high power Rf
generating a whole spectrum of harmonics, not just dealing with
mains/triac/wiring rfi noise, flourescent light starter rfi, etc


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm
 
In article <gmavt-202195.12484402022010@sn-ip.us.supernews.com>,
Andrew Erickson <gmavt@drewe.reverse2mail.net> wrote:
Most likely originally labeled "off/mute/on," and this (or something
roughly equivalent) is standard for most wireless microphones.
Switching the transmitter completely on and off will often cause pops
and other objectionable output, so for temporarily suspending use the
mute setting is useful. Of course, ideally a competent sound tech will
take care of muting and so forth at the sound board, but that's not
always reality.
Click to expand...
Some these days send out a sort of pilot tone which if not present mutes
the receiver and prevents it reacting to interference, etc with the
transmitter switched off.

--
*Marriage changes passion - suddenly you're in bed with a relative*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
In article <hkbet2$koc$1@news.eternal-september.org>,
N_Cook <diverse@tcp.co.uk> wrote:
Some these days send out a sort of pilot tone which if not present
mutes the receiver and prevents it reacting to interference, etc with
the transmitter switched off.
Click to expand...

Would that system also work with "taxi breakthrough" of nearby high
power Rf generating a whole spectrum of harmonics, not just dealing with
mains/triac/wiring rfi noise, flourescent light starter rfi, etc
Click to expand...
I believe that's what it's designed to do. I only use radio mics
professionally and would never (intentionally) have a receiver with no
input faded up - but I do realise this can happen in churches, etc.

--
*Happiness is seeing your mother-in-law on a milk carton

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
On 03/02/2010 10:37, Dave Plowman (News) wrote:
In article<hkbet2$koc$1@news.eternal-september.org>,
N_Cook<diverse@tcp.co.uk> wrote:
Some these days send out a sort of pilot tone which if not present
mutes the receiver and prevents it reacting to interference, etc with
the transmitter switched off.


Would that system also work with "taxi breakthrough" of nearby high
power Rf generating a whole spectrum of harmonics, not just dealing with
mains/triac/wiring rfi noise, flourescent light starter rfi, etc

I believe that's what it's designed to do. I only use radio mics
professionally and would never (intentionally) have a receiver with no
input faded up - but I do realise this can happen in churches, etc.
Click to expand...
Radio mikes with switches are a menace.[1] The 'talent' can't seem to
leave them alone, sometimes switching the mike off, then forgetting and
glaring at the sound engineer when it`s muted - of course there`s
nothing he can do from FoH. The mikes with hidden switches are better,
tho often the talent spots the little red light then proceeds to press
all the buttons, sometimes going as far as to inadvertently change channels!

Ron

[1] Sorry, make that ALL mikes with switches.
 
In article <NOudnS2jhrNQGPTWnZ2dnUVZ7tGdnZ2d@bt.com>,
Ron <ron@lunevalleyaudio.com> wrote:
I believe that's what it's designed to do. I only use radio mics
professionally and would never (intentionally) have a receiver with no
input faded up - but I do realise this can happen in churches, etc.


Radio mikes with switches are a menace.[1] The 'talent' can't seem to
leave them alone, sometimes switching the mike off, then forgetting and
glaring at the sound engineer when it`s muted - of course there`s
nothing he can do from FoH. The mikes with hidden switches are better,
tho often the talent spots the little red light then proceeds to press
all the buttons, sometimes going as far as to inadvertently change
channels!
Click to expand...
Sadly many churches in the UK need a radio mic for the 'preacher' these
days but cannot guarantee having an operator for even a simple mixer. So
the user has to be able to mute his mic for singing, etc. But if there's
no operator, no one to glare at. ;-)

My brother's kirk is in just this position - and he has asked for my
advice about a replacement body pack RM for the minister. The old one was
never much good and is getting worse - and it's now illegal in the UK, and
has been for some time.

But I only use pro ones - mainly Microns - which are way outside the
budget, and I have no direct experience of this end of the market which
seems to offer a bewildering choice. My first thought was Trantec as I've
used their inexpensive IEM where there is a likelihood of damage.

--
*If we weren't meant to eat animals, why are they made of meat?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
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