# The ALERT



## GW3OQK (Jun 10, 2010)

Now's your chance; there's an ALERT on the auction site!
That's Marconi's 500 kc/s watchkeeping receiver for those fortunate enough to work for other companies. I always had it on when working HF. 
73


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## pippin (May 13, 2008)

The name ALERT was an oxymoron!


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## sparks69 (Dec 18, 2005)

It dried socks very well.......


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## Varley (Oct 1, 2006)

pippin said:


> The name ALERT was an oxymoron!


You are unkind. It may well have been very alert, just a little hard of hearing,


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## trotterdotpom (Apr 29, 2005)

In the days when, for some reason, we had to memorise circuit diagrams, I loved the Alert.

John T


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## R651400 (Jun 18, 2005)

well well... 12 bids so far and here's one who'd happily turn back the clock to the first day I clapped eyes on it's pristine GTZM grey case.. Leith Nautical College 1st September 1956.








VINTAGE MARCONI (ALERT) VALVE RADIO RECEIVER | eBay


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www.ebay.co.uk


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## Ron Stringer (Mar 15, 2005)

R651400 said:


> well well... 12 bids so far and here's one who'd happily turn back the clock to the first day I clapped eyes on it's pristine GTZM grey case.. Leith Nautical College 1st September 1956.
> 
> 
> 
> ...


The official description of the GTZM grey paint was "oyster hammer".


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## sparks69 (Dec 18, 2005)

trotterdotpom said:


> In the days when, for some reason, we had to memorise circuit diagrams, I loved the Alert.
> 
> John T


I must admit I can second that.......


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## pippin (May 13, 2008)

I have an ALERT, pristine - unlike that one for auction.
A couple of years ago I took it to the local radio club for a demonstration.
More of a brain-teaser evening really as I asked them lots of questions.
On what design for a single frequency Rx with a wide bandwidth.
They seem never to have heard of a TRF Rx!
Of course the power supply gave lots of opportunity to wield Herr Ohm and his formula.
They were either shy or incredibly inept as stunned silence abounded!
I had to prod their grey cells into action.

I reckon some MIMCCo or MWT Co engineers devised the cct on the back of a *** packet over a pint or two!!


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## trotterdotpom (Apr 29, 2005)

pippin said:


> I have an ALERT, pristine - unlike that one for auction.
> A couple of years ago I took it to the local radio club for a demonstration.
> More of a brain-teaser evening really as I asked them lots of questions.
> On what design for a single frequency Rx with a wide bandwidth.
> ...


Haw haw. That diode in the middle must have spun them out!

John T


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## GW3OQK (Jun 10, 2010)

How's you memory Trotter and Sparks?
Q1. What is the function of the Watchkeeping/Emergency switch?
Q2. Describe the audio output amplifier circuit


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## sparks69 (Dec 18, 2005)

Q1. Pass
Q2. Pathetic


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## Mad Landsman (Dec 1, 2005)

Here you go chaps. Previously posted by 'Marconi Sahib' in 2008.
Excuse my ignorance but it does not seem to fit with what you are describing


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## pippin (May 13, 2008)

Q1}
A1} 
That switch was used if the mains I/P failed, allowing operation direct from the 24V emergency battery supply.
It also did complicated things with the audio O/P.

The diode in the PSU was obviously to rectify if used on AC mains. It could easily have been left in cct on DC mains to prevent inadvertant reverse connection!


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## Ron Stringer (Mar 15, 2005)

pippin said:


> Q1}
> A1}
> That switch was used if the mains I/P failed, allowing operation direct from the 24V emergency battery supply.
> It also did complicated things with the audio O/P.
> ...


Since I can't remember what I had for lunch yesterday, it amazes me that over 60 years ago I was able to draw that circuit from memory when studying for PMG2. Also similarly the PA stages and tuning arrangements of the Oceanspan and the actuator arrangements of the Type M/Vigilant auto alarm and the Autokey. Oh to have the same memory today.


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## pippin (May 13, 2008)

That ALERT is nearly timed out - I reckon it might top a hundred quid.

Do you think I should tell the prospective buyers that there is nothing to listen to on 500kHz anymore?!!!!


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## R651400 (Jun 18, 2005)

Ron Stringer said:


> The official description of the GTZM grey paint was "oyster hammer".


 Right on ! Why GTZM omitted regeneration on the Alert beggars belief.


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## Mad Landsman (Dec 1, 2005)

I see that it got knocked down at £82. 
The seller also has a 'sextant' for sale - in a box and marked 'Kelvin and Hughes 1917'. Unfortunately Kelvin and Hughes as a Company only dates from 1947.


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## GW3OQK (Jun 10, 2010)

Some years ago I called it "useless" but members came to its defence.
1. "Switch it on and leave it"
2. "Switch it off and leave it. The result will be the same."

I hope it has gone to a good home. 73, Scruggs


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## R651400 (Jun 18, 2005)

Beautifully constructed (as all GTZM gear ) Alert was a three stage broad bandwidth single frequency TRF recceiver with probably the first marine radio solid state detector ever followed by an AF amplifier to speaker or headphones yet all that came out the speaker was hash and very little else. Why?
By comparison with the WW2 Liberty ship RCA ET8510 LF/MF standby TRF regenrerative receiver that could pick up the GBR LW time signal in the Red Sea!


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## Troppo (Feb 18, 2010)

82 quid!....(shakes head)...


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## sparks69 (Dec 18, 2005)

_ WW2 Liberty ship "RCA ET8510 LF/MF standby TRF regenerative receiver" _
Its got lots more knobs too so it must be better


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## Mad Landsman (Dec 1, 2005)

R651400 said:


> Beautifully constructed (as all GTZM gear ) Alert was a three stage broad bandwidth single frequency TRF recceiver with probably the first marine radio solid state detector ever followed by an AF amplifier to speaker or headphones yet all that came out the speaker was hash and very little else.


Thank you. In light of that I have had a proper look at the circuit. - All makes sense to me now, the how that is, not the why...


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## johnvvc (Feb 8, 2008)

> >> Now's your chance; there's an ALERT on the auction site! <<<


Last week the same seller sold an Atalanta - for would you believe it - £25 !!!
According to the blurb it came complete with 'ariel' which from looking at the picture I'd say was a folded dipole for VHF !!!


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## pippin (May 13, 2008)

An ATALANTA manual sold for more than that a couple of weeks ago!


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## R651400 (Jun 18, 2005)

Mad Landsman said:


> Thank you. In light of that I have had a proper look at the circuit. - All makes sense to me now, the how that is, not the why...


Thanks ML.. Fyi. when at sea a RO carrying ship had to maintain manually or electronically a continuous watch on the (morse) distress frequency of 500 kcs. 
When on duty should the RO move to HF tfc working the 500 kcs watch was maintained by a stand by receiver eg Alert or other.


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## Baulkham Hills (Jul 11, 2008)

Would I be right in thinking that the Alert could only receive A2. I never rated it highly, it always seemed to me to barely meet requirements like a lot of marine equipment, most ships I sailed on had 2 main receivers which I preferred, one on 500 khz and one for working H/F.


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## pippin (May 13, 2008)

Yes
Me too


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## Mad Landsman (Dec 1, 2005)

Perhaps they didn't trust you not to retune both receivers..


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## Ron Stringer (Mar 15, 2005)

Baulkham Hills said:


> Would I be right in thinking that the Alert could only receive A2. I never rated it highly, it always seemed to me to barely meet requirements like a lot of marine equipment, most ships I sailed on had 2 main receivers which I preferred, one on 500 khz and one for working H/F.


The requirement in the UK carriage requirements for an emergency receiver was that it could receive A2 (MCW) transmissions on 500kHz. Presumably that was because the ITU regulations required ships over 1600 grt to be able to transmit using A2 on 500kHz for distress and safety purposes. Seems logical to me and I can think of no reason why I would want to use A1 (CW) when trying to summon assistance in a distress or emergency situation. Give me all the bandwidth I can get - now where is that spark transmitter?


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## Baulkham Hills (Jul 11, 2008)

From what I remember the auto alarm would operate on A1 or A2. I sailed with transmitters that would either A1 or A2 on 500 khz, In a dire emergency it would have been easy to transmit on 500khz A1, in which case tough luck with the Alert.


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## pippin (May 13, 2008)

The reason for sending distress messages in A2 MCW is simple.
A1 CW reception requires a BFO. 
If the Rx just happened to zero beat then the message would not be heard.
Hence the design of the ALERT.

Quod erat demonstrandum


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## R651400 (Jun 18, 2005)

Regenerative TRF receivers resolved both CW and MCW also AM. 
The Alert was TRF but not regenerative which could have eawsily been incorporated into it;s design 
Recall emergency transmitters were A2 MCW£ only but as stated previously a distress AA signal and distress message could unwittingly be transmitted on A1 from a main tx under extreme stress. .


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