Vintage Transmitting Valves and Halls.

[paulsherwin]

Posts Split from this thread

https://www.vintage-radio.net/forum/...d.php?t=176080

Reopened by request.

[Nymrod121]

(Thank you, Paul)

Just a footnote, here are a couple of pics for interest:

(1) a view of the North Regional transmitter hall at Moorside Edge (or Pole Moor - if preferred, David ) showing the 'A' unit (that's almost out of shot) on the extreme left and in which the MT9L would have been situated;

(2) the MT9L on display at the Droitwich Broadcast Museum.

It's to be hoped that the one being despatched arrives intact! - from the O.P.s photo, it can be seen as having the original 'curved-triangular-shaped' M.W.T. logo rather than the later 'blue GEC' badge as per the D.B.M. exhibit.

If the recipient is really, really lucky ... it might even still have an intact filament ... usually, they failed "F.B.O." (Filament Burn-Out).

In operation (Class A, if memory serves), the cylindrical anode ran orange-hot

Guy

(Tx Eng. at Moorside Edge: various secondments, 1982-85)

[Nymrod121]

From my collection:

CAT6 / MT9L / DET2

The CAT6s were operated in parallel (visible inside the C1 and C2 units which are 3rd from left, 5th from left in the earlier photo - the units were annotated A, B, C1, D, C2).

The two original transmitters ('T1' and 'T2') were rated at 50kW output power in their heyday; all operational voltages being derived from DC-DC machines - filaments, grid bias, aux HT, main HT - the lot ... *seriously* good fun starting them up

Still in use as passive reserves right up to transfer of all services over to the new/automatic and unattended station in 1985 (see the 'MB21 Transmission Gallery' for more details of the latter).

Russ W-B ... you may well have played with similar stuff at Droitwich - ?

Guy

[Vintage_RC]

Guy, thanks for the interesting additional information and images
Alan

[Nymrod121]

A pleasure

[Vintage_RC]

I was taking a browse on the Web and found an interesting page which includes a colour picture of the old Moorside Edge transmitter hall. Third picture down.
http://www.microscopy-uk.org.uk/mag/...iw-radio1.html

[KeithsTV]

The picture of the transmitting hall at Droitwich brings back memories of a visit by the school radio club back in 1968. The LW transmitter comprised two 200kW transmitter in parallel with the anode current meter showing 14A at 14kV. The engineer taking us round said that if they wanted to do maintenance on one of the pair they just switched it off. I asked "don't you lose some listeners?" He replied "Only a few fringe area listeners and we're not too concerned about them".

Keith

[russell_w_b]

Originally Posted by Nymrod121

Russ W-B ... you may well have played with similar stuff at Droitwich - ?

I certainly played with the CAT27s in T7A and T7B, Guy. Brian Murton used to make we attachees polish them on night shift maintenance!

[russell_w_b]

Here's Skelton 'A' (formerly OSE8) sender hall in July 1984. Note that it is a 'trick' shot with two images merged together. The central canopy wasn't really at an angle! Nice 1970s colour scheme, though.

The other pics show the Class B audio modulator and the Class C RF Modulated amplifier tuned on 4MHz, both with push-pull output stages using BY1144L vapour-phase cooled triodes.

[Vintage_RC]

A most interesting museum, The Radio Museum, Watchet. They have some interesting old transmitting gear including equipment from the old Moorside Edge transmitter:-
http://www.orbem.co.uk/misc/washford.htm

[Viewmaster]

Here's my CAT 6 all lit up.

[Julesomega]

Originally Posted by russell_w_b

.. and the Class C RF Modulated amplifier tuned on 4MHz..

Lovely to see those, but wouldn't that be set for the HF end, like 21MHz?

[russell_w_b]

Originally Posted by Julesomega

Lovely to see those, but wouldn't that be set for the HF end, like 21MHz?

Not with those final anode coils in, Jules. Those ones were used from 4MHz to 7MHz.

On 21MHz the final anode coupling coil was a straight bar horizontally- extended from the anodes with a centre-tap HT strap connector. The truck coil was a horizontal affair rather like a shortened sardine-can opener key.

[Julesomega]

Thanks Russell - there's a lot of inductance in a bit of pipe

[russell_w_b]

Here are Senders 35 and 36 at Rampisham back in 1989: Marconi BD253 100kW dual-channel. They were scrapped a couple of years later when the two 500kW PDM B6128 sets went on-air, or just before.

The 11kV anode HT on the BD253's was derived from English Electric AR64 excitrons, also shown. Many's the time they had to be 'tapped' with a broom handle to free a 'sticky dipper'!

[russell_w_b]

Originally Posted by Julesomega

'there's a lot of inductance in a bit of pipe'

There certainly is, Jules. The 26MHz coils are even shorter and straighter!

[Nymrod121]

Great pics Russ!

[russell_w_b]

Originally Posted by Nymrod121

Great pics Russ!

Thanks, Guy. A lifetime of film-wasting has paid off! Here's a gratuitous shot of the main Rampisham sender hall in 1991. Four AEG S4005 500kW and four Marconi B6127 500kW transmitters.

[PaulM]

I wish that as a young apprentice and R&D engineer I had photographed a few more things at Marconi's in the 70s and 80s. These 'beasts' were always there in Building 46 and High Power Test but we were 'solid state' and the future (so we thought . . .).

Watching the old stagers at work designing and developing new products like these was amazing to see but at the time I guess that I just didn't appreciate what those guys did.

One of the leading lights, Ron Bradbrook, died in 2017 and what a character!
See:https://www.marconi-veterans.com/?paged=3

Where are people like that today - have they all taken up software

Best regards,

Paul M

[turretslug]

I wondered if the floor tile patterns in Russell's post #18 were intended to indicate combiner arrangements, also if the fluorescent lights were actually connected to anything....,

Colin