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Old 7th Dec 2018, 10:04 pm   #1
vintage_8bit
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Default Aeonic screened IV

Continuing my sort out, I rediscovered this radio.
Thought I would share photos with the forum. I would just welcome any comments on it. I haven't managed to find much info on it. I had intended to keep my restoration projects to radios from the 1930's onward. But not sure now as this set seems complete. I won't be touching it for a while though. Colin
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Last edited by AC/HL; 8th Dec 2018 at 4:41 pm. Reason: As requested
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Old 9th Dec 2018, 1:36 pm   #2
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Default Re: Aeonic screened IV

I have found reference to a similar model on the Radio Museum website, called the "Blenheim", but with my version the left most valve is mounted horizontally and has a top cap.
I have only dealt with superhets up to now. How would you operate the reaction / feedback control on this TRF set. I see it's also marked "volume" on the Radio Museum circuit I have which is for the "Blenheim". Can this cause the set to oscillate. I remember reading somewhere that when this happens other sets nearby can be affected.
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Old 9th Dec 2018, 2:00 pm   #3
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Default Re: Aeonic screened IV

Love it a really nice set.Reaction is turned up to the point before it oscillates and the set then is at its most sensitive and of course backing off acts as volume control.

PS Need to alter your oldest set now on your profile.
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Old 9th Dec 2018, 7:16 pm   #4
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Default Re: Aeonic screened IV

Thank you for your comments and information. I've not restored any pre war sets yet. My last restoration was an Ekco from 1946. Due to the age of the Aeonic I will only tackle that after some research. I see the inter stage transformers can go open circuit, and I wonder how the speaker is. Does the centre nut in the speaker grill perform any important function? Anyway it's safely put away for now.

P.S. I updated my profile accordingly.
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Old 9th Dec 2018, 8:05 pm   #5
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Default Re: Aeonic screened IV

I was not being funny about the update profile,just looked and saw oldest 1946.Though what a great set to update to.
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Old 9th Dec 2018, 8:31 pm   #6
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Default Re: Aeonic screened IV

No problem it needed changing thanks. Colin
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Old 9th Dec 2018, 11:22 pm   #7
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Default Re: Aeonic screened IV

It's likely a moving iron, armature speaker. Can be 700 Ohms to 1500 Ohms. The nut needs adjusted according to bias current if in an anode. Also at a narrow spacing it's more sensitive for a weak station, but then "clatters" on sound peaks. It becomes more insensitive at a wider spacing. At least sounds better than early horns that essentially used a 2K Ohm earpiece as a driver!
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Old 10th Dec 2018, 2:18 pm   #8
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Default Re: Aeonic screened IV

Thanks for the info re speaker, and with the info from Hamishboxer this has now got my interest up so now on my to-do list. I need to retire to have time for all the restorations queueing up.
I have had another go at finding more info on this set. But the nearest one I can find, as mentioned previously is a 5 valve model, mine having only 4. I know I can trace out the circuit, but I haven’t found any useful reference to this model yet. (Aeonic screened IV) I see from my research that there were many similar types of portable suitcase radios back then, most with wonderfully worked speaker grills. Mine has some kind of leatherette covering? on the case which is embossed. Looking at the prices then, around £16 they must only have been owned by the well off.
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Old 10th Dec 2018, 3:20 pm   #9
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Default Re: Aeonic screened IV

I found this reference which puts it circa 1929 (I think the picture is just a generic one):

https://www.americanradiohistory.com...h=%22aeonic%22

Lawrence.
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Old 10th Dec 2018, 3:49 pm   #10
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Default Re: Aeonic screened IV

Quote:
Originally Posted by vintage_8bit View Post
How would you operate the reaction / feedback control on this TRF set. I see it's also marked "volume" on the Radio Museum circuit I have which is for the "Blenheim". Can this cause the set to oscillate. I remember reading somewhere that when this happens other sets nearby can be affected.
Yes, reaction is actually positive feedback to compensate for losses in the tuning circuit, so once it's more than that, it oscillates! This can be used to tune CW or SSB (poorly) on Shortwave if it's only just oscillating. At minimum the there is very poor sensitivity. Except on some sets it's ganged with a wirewound resistor in series with the RF stage (a Tetrode or "Screen Grid" valve on later sets, which then has a top cap for anode and the SG HT on the old Anode pin of 4 pin valves. Indirect valves added the cathode pin between the two heater pins, the filamentary cathode on battery types. So the signal grid is the pin opposite g2 or anode, closer to the filament pins or cathode pin).

You advance reaction slowly till background noise is just audible. Often the aerial coil (or frame aerial on a suitcase model) is tuned separately to the detector & feedback stage RF tuning and the reaction is on the detector stage.
Hence many models had scales you could pencil in the stations, or a card on the panel for station name and both log number settings (sometimes 0 to 180 degrees).
Later TRFs had dual or even triple ganged tuning with end vanes adjustable for tracking as well as presets for the high frequency end of the band. Then it became practical to have the wavelength or frequency. Station names appeared when there was international agreement. This was revised several times, so the frequencies of stations can indicate period.
Also up to about 1930, the Medium Wave was called Short wave, because the Marine & Aeronautical band, about 280 KHz to 530 KHz, was called "Medium Wave". In North America most of the LW was also part of the Marine & Aeronautical band, hence MW was the sole "Broadcast Band" there. That's why hardly any sets from 1935 to today for the USA market have LW.
Also LW is no use in the Tropics. Perhaps North Africa being the most southerly area with LW.
The band between MW and SW, was the Marine Band in Europe but Tropical Band in Africa, parts of the Americas and Southern Asia. About 1.6KHz to 5MHz. The USA extended their "Broadcast Band" mostly for Sports up to about 1.7MHz
Amateurs were at 1.8MHz to 2MHz and 3.5MHz to 3.8MHz (higher in USA) from early on and still today.
Parts of the 5MHz to 5.6MHz are still used for emergency Aeronautical transatlantic. You can hear Shanwick on the VHF airband giving 5MHz band channnels and sel call codes to passing aircraft, and then hear the test on SW. There is a higher band too.
My 1929 McMichael suitcase with replica batteries astounds people. Only MW at night here (Short wave on its selector), but the RTE & R4 are fine on LW during the day. The RF filament rheostat is duplicated with a centre off to vary volume and select band. It only switches the LT which is several NiMH wired series parallel to give the Lead Acid 1.8V to 2.1V in a jar with replica lead acid pack labels. The combining diodes give the additional voltage drop needed. The pack must be unplugged to charge, which would have been mandatory on all Lead Acid LT systems as the float voltage would rise too high.
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Old 10th Dec 2018, 6:41 pm   #11
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Default Re: Aeonic screened IV

Hello vintage 8bit. Your radio is typical of the "suitcase set", which quite a few manufacturers seem to have offered for a brief period around 1929. This coincided with motoring becoming more affordable, and one can imagine some chap loading up this heavy incumbrance along with the hamper for a picnic in the country. Quite a few turn up, because their construction meant that when they were put away in the loft and forgotten, the internals were protected.

The example I own was made by Halcyon in London, and has 5 valves (one in a screening box), frame aerial and moving iron speaker in the lid. Wavebands are marked Long and Short but correspond to Longwave and Medium Wave. Two separate tuning controls with 0-100 scales have to be altered in unison. The set still works well with rechargeable batteries housed in MDF enclosures with replica paper artwork pasted around their sides.

During restoration I had the commonly found problem of open-circuit interstage transformers. Their windings are extremely fine and prone to breakage. My solution was the use of universal microphone transformers sourced from RS components, hidden inside the original bakelite housings.
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Old 10th Dec 2018, 10:54 pm   #12
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Default Re: Aeonic screened IV

Some lovely examples in the link, thank you Lawrence. Yes, late 20's it seems.

Mike and Mr 1936 thank you for your input, all very interesting, I will read all again, and try and take all that information in.

I have another set which I think is home made, and a 3 valve TRF. This has 3 pairs of plug in coils you mount on a base. You can then vary the distance between the coils. Is this the aerial tuning that you mentioned Mike.
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Old 12th Dec 2018, 11:58 am   #13
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Default Re: Aeonic screened IV

So in the photo of another TRF (Not yet touched) radio I have, I can see the tuning and reactance controls? What is the affect of adjusting the distance, which is adjustable, between the 2 plug in coils on the left hand side of image. I assume they should both be the same type, but that’s just how they were when I was given the set. I do have 3 matched pairs of coils for this set, which I assume are for different bands.
This radio could probably start a new thread, but I was just trying to understand a bit more now about the workings of the TRF.
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Old 13th Dec 2018, 11:01 am   #14
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Default Re: Aeonic screened IV

The top coil is the aerial coil and is tuned to the desired frequency using the tuning capacitor. The bottom coil is the reaction coil which in this case has variable capacitor coupling to the anode of the RF amplifier valve. The reaction coil is coupled to the aerial coil providing the positive feedback to make this a regenerative receiver.

This is a home built set. More often these plugin coils are on a mechanism that allows the reaction coil to be rotated away from the aerial coil obviating the need for the variable capacitor.
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Old 13th Dec 2018, 1:57 pm   #15
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Default Re: Aeonic screened IV

In a box of several spares that came with that receiver there is a mechanism for adjusting the distance between the plug in coils. From memory I think they move away in an arc from parallel. The adjustment in that last receiver image is rather crude. Anyway thanks for your reply. Colin
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