[Tech1] Radio microphones

Tue Sep 1 15:13:09 CDT 2020

Re the EMX in the type 5s, one of my first jobs when I
joined SCPD with Bob Smith (RIP)  was to retrofit the KBX
into a 19" rack The KBX was not keen on this as it was 22"
wide!!! A lot of custom metalwork later and all ten scanners
were done.  There was a custom designed Gelnsound unit to
convert control Ines to a form the KBX could understand. The
KBX was a very clever system and was marketed by BT as the
"Herald". We went on to install KBXs into the type 6 scanner
and a Big version into the CMCCR.   So far I have resisted
acquiring a KBX.

Radio Mics   MCR21 did start out with 2 Eddystones but they
would  have been changed for the solid state BBC  RC4/1
receivers.  I do have a matching Tx type TM3/3/139  this is
a solid state one, I don't have, so far, a valve radio mic
TX in the museum collection.  There is an awful lot of stuff
yet to find and re-make for MCR21.  

Attached is a pic of the TM3/3  and an EDI sheet for it
courtesy of Martins bbceng site.  Be interesting to see if
they get through  the system. 

Regards

Brian

From: Tech1 [mailto:tech1-bounces at tech-ops.co.uk] On Behalf
Of Alan Taylor via Tech1
Sent: 01 September 2020 11:18
To: Tech-Ops-chit-chat
Subject: [Tech1] Radio microphones

All this talk of mountaineering reminds me that it was a
type of programme which only became practical to cover live
once radio microphones were available.  The research I've
been doing has hit the buffers with regards to radio
microphones, so it seems like an opportune moment to ask the
chaps on this group what they can remember.

There is very little information about early radio mics on
the internet, in trade journals or books about broadcasting.
I clearly recall the BBC Band I radio mics which at Kendal
Avenue were operated by Eric Spanier for many years and then
by Richard Kemp.  Here's a picture of the receivers used,
but I don't recognise the two objects in the foreground, any
ideas?

I recall the 1970's transmitters as looking rather like a
hip flask with a long wire aerial, powered by a custom built
battery of triangular cross section, a black resin casing ,
maybe 10 cm long, with brass terminals at either end. John
Howell has mentioned Kalium batteries. I don't recognise
that term, but it's very likely that he is referring to the
same batteries that I'm thinking about. John also refers to
a radio mic kit known as TM3 being mentioned on equipment
booking sheets in the 1960s. Again I don't recognise that
number, but it could well be the same sort of gear that I
used at KA in the 1970s.  The gear looked like it might have
been around for a decade or more by then.

There was a later generation of BBC radio mic using a
rectangular battery with tiny plug and socket connectors.
Does anybody have any info, memories or pictures of them?

I've tried to find any BBC manuals for them or research
notes concerning radio mics, but have drawn a blank.  The
only research note I've found so far has concerned
propagation of radio signals within studios and how it is
affected by scenery.

The LO21 project have mentioned that LO21 originally
incorporated two Eddystone radio receivers, but I'm pretty
sure that they had been replaced with BBC receivers by the
time I worked on it after it's conversion to colour.  Does
anybody know what type of transmitters were used originally?

I also have vague recollections of using Vega radio mics
before Microns cornered the market.  Does anybody remember
them?

While I'm asking, there are a few other topics where more
information would be useful.

Saturday Night Live - is there anybody still around who
worked on those shows?  I know about some of the infamous
incidents.  Does anybody have any personal recollections?

Bucknell's House - What sound equipment was installed in
that dedicated scanner?  Was Barry on a radio mic, or did he
use something like a cabled, neck worn  AKG D109 ?  Did they
have a radio talkback system for the FM, or was it done on
long-lead cans?  Any memories of that series?

Radio talkback - I remember a BBC designed valve radio
talkback transmitter. John Livingstone was so infuriated
with it that he 'accidentally' dropped it down some concrete
stairs, swept up the wreckage into a bag and sent it to
sound test room with a fault label on it hoping that it
would be regarded as a write-off and end up in a skip. A
month or so later, he was exasperated to discover that one
of the engineers relished the opportunity to work with
valves again and lovingly repaired it.  I also remember the
BBC designed radio talkback system which had two separate
units for the floor manager. One was the transmitter, the
other the receiver. They walked about looking like a
gunslinger with these units fastened either side of their
belt.  Power came from a 9 Volt PP4 battery ( about the size
of a 'C' cell with a snap on stud at either end ), specially
selected so that you stood no chance of finding one in any
normal shop. There were two major problems.  One was that
the base station radiated so much spurious radiation on Band
I that when a scanner set up in a street, it blotted out
reception of 405 line BBC television signals, which didn't
do a lot to make us popular. with the locals.  Designs
Department rose to the occasion, did their sums concerning
inductors and capacitors and built a passive filter to fit
inline with  the aerial lead.  They tried it and it was
discovered that it completely cancelled out the wanted
signal, while allowing all the spurious radiation through.
That's the day when they realised the important difference
between connecting the components in series or parallel.
Fortunately it was only necessary to rewire the parts the
other way to get the intended function.  

The second major problem was that when the FM transmitted,
it blasted into his receiver making a deafening noise in his
headphones. That particular problem was trickier to resolve
and I don't think it ever got properly sorted. Fortunately
Storno radios soon replaced them and subsequently Motorolas.

PBX & EMX systems - Early scanners used telephones with
ringing generators, you could use ex-army field telephones
and wind the handle to alert the other end.  From memory, I
think that all trucks up to and including the type II
scanners used that system, but will check with North 3.
However I'm pretty sure that the type 5 scanners originally
had a BBC designed telephone system which turned out to be
something of a liability and was scrapped in favour of an
off the shelf system.  Can anybody fill in the blanks in my
memory?

Labor gun mics - They were widely used before Sennheiser 816
microphones ( Labor was part of the Sennhesier group anyway
).  Does anybody have any pictures of one in use?  The one
metre long microphone was often to be seen mounted on a 'U'
shaped cradle on top of early colour cameras.  The Labor gun
mic had a distinctive teardrop shaped thicker part at the
back and I don't think they ever had an external windshield
similar to Rycote housings.  These microphones have almost
completely vanished without trace.  On a similar subject,
does anybody have any pictures or recollections of the
Electrovoice 7 foot gun mic in use on a programme?  I
remember operating one on the centre line of the basketball
court, covering the Harlem Globe Trotters in the early
1970s.  It was the most unwieldy thing imaginable for
covering such a fast moving event. Where else was it used?

Any contributions on associated topics would also be most
welcome.

Alan Taylor

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