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Old 22nd Aug 2019, 11:44 pm   #1
m0cemdave
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Default Marconi NS702 / 2207E, SN 623 (Atlanta type) receiver

Split from the original offer thread: https://www.vintage-radio.net/forum/...d.php?t=159096

It's the same as an Atalanta except for the labelling. The ones on ships all seem to have been 2207C, with the bandspread scale pre-printed with the marine bands.
I assume this scale was supplied blank for the customer to mark up to their own requirements - it just has the lines, no numbers.

Last edited by AC/HL; 28th Aug 2019 at 7:51 pm. Reason: Thread split
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Old 23rd Aug 2019, 9:33 am   #2
Synchrodyne
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

As best I can determine, NS702 was the MWT designation. and 2207C Atalanta was the MIMCO designation. MWT literature and advertising did not seem to mention the Atalanta name. Possibly those units that MWT made for MIMCO carried both MWT and MIMCO nameplates.

2207E looks like a MIMCO designation. But without the HF marine bands bandspread facility, would it still have met the GPO requirements for a ship’s main receiver? As a “left-field” suggestion, might it have been used as a shipboard broadcast receiver, in which case the E suffix might mean the “entertainment” version. In the 1950s MIMCO used Dynatron receivers for this purpose, particularly the Dynatron T139/LF512 combination known as the MIMCO 2235A. But such Dynatron models only ran until c.1959-60, after which MIMCO would have needed other solutions. Pressing the Atalanta, perhaps modified, into such service may have been one pathway.


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Name:	POEEJ V49 Pt2 195607 rp.vi Marconi NS702.jpg
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Old 23rd Aug 2019, 10:37 am   #3
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Interesting I have some pictures and the knob on the front panel states push in for bandspread so I presume the facility is there.
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Old 23rd Aug 2019, 6:35 pm   #4
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Yes, the facility is there. The bandspread follows from the main tuning, so it can be labelled for whatever parts of the tuning ranges are of interest.

It looks like the Atalanta label and marine band scales were only used on the ones supplied as part of Marconi radio rooms on ships, and they all seem to be designated 2207C.

This advert promotes it as a general-purpose receiver, without the Atalanta badge:
https://www.vintage-radio.net/forum/...0&d=1382900750
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Old 24th Aug 2019, 1:57 am   #5
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

The plot thickens!

There were also 2207B, 2207D and 2207D variants:

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Name:	Marconi Atalanta 2207B,D,F.jpg
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The 2207D was the 2207C when fitted with a muting circuit.

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Name:	Marconi Atalanta 2207D.jpg
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ID:	188805

As the bandspread facility covering six marine HF bands was a “normally fitted” facility, it would appear that it was what might be called a “delete option”. That being so, perhaps the 2207E was a 2207C without the marine HF bandspread? In which case the 2207F might have been a 2207E with the added muting facility.

The above attachments are from a 2207C document dated 1967 November, so quite late in the Atalanta production run.


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Old 24th Aug 2019, 11:38 am   #6
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

If the bandspread wasn't present why would the knob still be there also the calibrate wouldn't be as much use . And to meet the GPO specs the bandspread must be present . Without it to me a pointless receiver . There must be someone out there with the same model eventhough the seem pretty scarce just a thought .

Last edited by deliverance; 24th Aug 2019 at 11:49 am. Reason: Info
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Old 24th Aug 2019, 11:56 am   #7
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

If the bandspread variable capacitor is there, the set will still do bandspread, but with a blank scale for the segments being spread, you get the slower tuning but you don't get a scale to tell you where you are.

As suggested earlier, this will work for a user who wants to use different bands to Marconi's usual marine bands, and is prepared to mark up his own bandspread scale with say an indelible pen based on pips from a crystal marker.

It's far from useless.. there is life outside the marine bands!

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Old 24th Aug 2019, 1:37 pm   #8
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Yes the variable capacitor is there David which is good I shall set about sorting the scale side of later . I am not familiar with the Atalanta .
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Old 24th Aug 2019, 1:39 pm   #9
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

I seem to remember the band-spread only spreads the tuning scale, doesn't give fine tuning. No separate capacitor.

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Old 24th Aug 2019, 1:54 pm   #10
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

There is a small variable cap on the back of the panel that is behind the front panel with a pulley on it which when the bandspread knob is engaged moves it from what I can see .
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Old 24th Aug 2019, 2:14 pm   #11
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Forget the last post that cap is for the fine tuning .
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Old 25th Aug 2019, 12:58 am   #12
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

It would appear that the bandspread facility is entirely mechanical in nature, not using a separate bandspread tuning capacitor:

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Name:	Marconi Atalanta 2207C IM p.06 Bandspread.jpg
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ID:	188854Click image for larger version

Name:	Marconi Atalanta 2207C IM p.19 Bandspread.jpg
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ID:	188855

Thus on versions not factory-equipped with marine HF bandspread, the user would be free to choose six bandspread ranges as desired and to mark the scales accordingly.


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Old 25th Aug 2019, 3:36 am   #13
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Sounds like the bandspread button drops the tuning gearbox into a lower gear and clutches the knob to the bandspread pointer as well.

Atalantas seem rather rare in private hands. There must have been plenty made, so I assume Marconi got most of them back through contracts and destroyed them to prevent a second-hand market developing.

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Old 27th Aug 2019, 11:56 pm   #14
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Yes, pushing and pulling the knob effects a gear change and so it is effectivly a slow-motion drive, which also engages the Eddystone-lookalike scale.
The bandspread scale plate is made of Traffolyte and can be removed by undoing four screws. It can either be engraved, or written up with a drawing pen, to suit the user's requirements.

The radio is very well made, and includes a bimetallic strip capacitor for oscillator temperature compensation.

The case and front panel are isolated from the receiver chassis. The AC mains supply, built into the back of the case, uses a transformer and solid state rectifiers to supply 110V unsmoothed DC for the HT and the heater chain. The smoothing capacitors are on the receiver chassis.

The mains filter is substantial, and the 2uF capacitors will *definitely* need replacing with modern Y types. For one thing it would trip any RCD in the mains supply - and for another, in the event of a poor earth connection the case would float at 110V AC with enough current available to deliver a very nasty shock.

I will post some pictures when I have found the correct micro USB lead for my phone...it must be here somewhere...
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Old 28th Aug 2019, 7:55 am   #15
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Quote:
Originally Posted by m0cemdave View Post
The radio is very well made, and includes a bimetallic strip capacitor for oscillator temperature compensation.
Probably an Oxley Thermotrimmer.

If I remember right, the Tempatrimmer was a differential capacitor adjusting the proportions of a pair of fixed capacitors, one negative tempco, one positive, while the cheaper thermotrimmer used a bimetallic strip to move split 'stationary' plates that the rotor plates got a variable tempco. Could be somewhat vibration sensitive!

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Old 31st Aug 2019, 12:32 am   #16
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

I had a Atalanta for a while - it didn't appear to have been wired for 110V at any stage, and I guess it was from an ex-BT coast station. It's true that Marconi usually destroyed the old kit which came back from their shipboard installations - which weren't actually sold to the shipowners, as I understand it. The Post Office / BT kit was purchased outright, though, and BT scrapped kit was sometimes sold for a nominal price on local arrangements.

The Atalanta was a very nice receiver, designed primarily for easy servicing. Lovely to work on. I'd still have it but for the sheer size. I think it was a bit bigger than an AR88, but it always seemed to be huge, and I just didn't have the space to accommodate it. It had to go, sadly.

The downloadable training manual on the Boatanchors Archive came from me - it's still got some of my pencilled notes...
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Old 31st Aug 2019, 10:38 am   #17
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

I have two Atalantas but I have no idea about their history. I don't think that either has been to sea. One is a Marconi Marine and the other is MWT. Both continue to be very good and very reliable.

I started a thread some years ago on the topic, here:
https://www.vintage-radio.net/forum/...ad.php?t=99826

Compared to some of my vintage broadcast TV kit, it's quite a reasonable size and weight, but as ever with MWT products you do receive you money's worth in metal! As an ex-Marconi employee I can say that the old gag was that Marconi was really a metal-working company that did a bit of electronics, but that's not really a true analysis. They just made things 'properly' and items such as the Atalanta were made to last - unlike today's products.

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Old 1st Sep 2019, 12:26 am   #18
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Here is an early MWT advertisement for the NS702:

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Name:	POEEJ V49 Pt2 195607 rp.vi Marconi NS702.jpg
Views:	23
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ID:	189255

And here is a much later mention of the NS702 by the GPO as a representative marine receiver:

Click image for larger version

Name:	POEEJ V58 Pt2 196507 p.87 Marconi NS702.jpg
Views:	21
Size:	80.7 KB
ID:	189256

There does not seem to have been a lot of consistency when it came to the use of the mythological names. Atalanta appears to have been exclusive to Mimco. On the other hand, Hydrus and Argo were MWT names for receivers that had no Mimco versions. Apollo appears to have started as the Mimco name for the MWT N2050. It was not used by MWT in early literature for that model, but later advertising had it as N2050 (Apollo).


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Old 1st Sep 2019, 9:58 am   #19
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

There was no 700 Kc/s calibration crystal in my Atalanta. I fitted a 1 meg crystal and a 1N4001 from SKG,2 to SKF,4. That gives me 1MHz markers and brings on the BFO in the "calibrate" position.
73, Andrew
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Old 2nd Sep 2019, 5:01 pm   #20
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Default Re: Marconi NS702 / 2207E, SN 623 (Atalanta type) receiver

Good information it's definitely a well made Receiver .
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