Restoration vs Improvements

[jsbhavsar]

Dear Members,

I own a National Ekco A731 eight band tube radio, it was a kit from Ekco UK and they were assembled in Mumbai downtown (then Bombay, India).
Model Year 1959-60

Good points about A731:
================
The radio has unique feature of "coil packs" at each stage. Total 24 bobbin type coils could be underneath and upper board.

The radio has a tuned RF stage.



Key Observations Ekco A731:
==================
MW band reception is very weak. Even the MSW band is weak.
The A731 radio set is "very selective" but not very sensitive. Weaker frequencies dont receive easily on SW. The stronger ones much stronger and the weaker ones are nulled.



Notable about Ekco A731:
=================
The radio lacks "ferrite loop" antenna even though the ferrites had been launched in UK by 1955. Ekco UK was manufacturing radio sets in 1959 with ferrite rods, yet they categorically avoided ferrite antenna in A731 and twin set A730 (without tuned RF stage).

In my view atleast for MW and MSW bands the radio should have been given a ferrite rod.


Restoration:
========
What should be done in restoration exercise for improvements in MW and MSW bands?

Should one fiddle with and introduce a ferrite antenna?
OR
Should one recap everything and go by original design?

Even after recapping and restoring, if the MW and MSW are still appearing noisy and weak, what are the steps that can be taken to improve? Any suggestions?

A radio listener may have sacrificed on MW and MSW then in 1959-60 but modern day listener may want those two bands to come up well?

Can larger MW and MSW coil packs be built and mounted?

Suggestions welcome!

[Station X]

I'd get the radio working as per its original spec and then consider whether it needs improving.

I have numerous sets with no ferrite rod aerial and they work well on MW and LW using a few feet of wire as an aerial. I wouldn't dream of fitting ferrite rods to them.

[crackle]

It was possibly assumed the set would be used primarily on one of the many SW bands where a ferrite antenna would not be sufficient.
What antenna are you using with the set, how long is it?
The Radio Museum gives the frequency bands for the Ekco A731 as;
SW1 Band............20.88 - 22.1 MHz
SW2 Band............17.43 - 18.4 MHz
SW3 Band............14.92 - 15.75 MHz
SW4 Band............11.51 - 12.125 MHz
SW5 Band............9.33 - 9.95 MHz
SW6 Band............6.98 - 7.4 MHz
MSW Band...........2.36 - 8.0 MHz
MW Band.............520 - 1650 kHz

Mike

[PsychMan]

Restore it as it is, then construct an active ferrite rod antenna you can connect externally without modifying the set. There are also numerous active short wave antennas you could try, possibly with a balun to match to the set.

Also, very nice to see members from India posting here

[jsbhavsar]

Originally Posted by crackle

It was possibly assumed the set would be used primarily on one of the many SW bands where a ferrite antenna would not be sufficient.
What antenna are you using with the set, how long is it?
The Radio Museum gives the frequency bands for the Ekco A731 as;
SW1 Band............20.88 - 22.1 MHz
SW2 Band............17.43 - 18.4 MHz
SW3 Band............14.92 - 15.75 MHz
SW4 Band............11.51 - 12.125 MHz
SW5 Band............9.33 - 9.95 MHz
SW6 Band............6.98 - 7.4 MHz
MSW Band...........2.36 - 8.0 MHz
MW Band.............520 - 1650 kHz

Mike

The radiomuseum pictures are of my home radio set.


Antenna:
======
Around 8 to 10 meters long insulated wire stretched on the RCC building rooftop. On rooftop a 4 meters long bare copper wire 18 gauge is suspended between two porcelain insulators. The wire going from radio set is attached to this suspended copper wire.
On twice occasion the thieves have stolen the shining copper wire leaving just the long wire end fed in open air on terrace.

Is a small bobbin type "coil pack" sufficient & efficient & productive enough for MW?

Any experiences anyone have had a coil pack set? Any pictures?

[jsbhavsar]

Originally Posted by Station X

I'd get the radio working as per its original spec and then consider whether it needs improving.

I have numerous sets with no ferrite rod aerial and they work well on MW and LW using a few feet of wire as an aerial. I wouldn't dream of fitting ferrite rods to them.

Thanks,
What setup does those radios have inside for MW section that they sound super without a ferrite setup?

Within the radio technology, TRFs were replaced with superhetrodynes. But one thing we must know, ferrite rod antennas maybe having their own negatives or flaws but they have survived all along these years and even modern portables continue to use that today.

So if the ferrite is used correctly with proper trimming, it can remove the flaw that the designers left out in 1959?

I agree, it is still a good idea to first restore everything to original and recapping and then take a call.

[PsychMan]

I wouldnt call it a flaw, As I understand it, Ferrite rod antennas were about getting the best antenna into a small space. At MW band frequencies, decent wire antennas can be very long indeed. In practice, electrically shorter antennas can often work quite well, depending on what you are trying to receive. Long wire antennas can work very well, but are more subject to picking up electrical noise from other devices that unfortunately are now everywhere.

Ferrite rod antennas respond to the magnetic component of electromagnetic radiation and therefore pickup less noise, and its possible to rotate them to null out sources interference because they are directional, same with various forms of loop antennae, so they can work better in modern environments.

Of course at shortwave frequencies long wires can be much shorter and easier to locate.

If you want decent MW reception, why not look at constructing an active loop antenna and a way to couple that into your antenna input on the receiver. You will get a decent low noise antenna in a compact space and keep your radio original. Lots of guides and videos online, but essentially you need lots of wire, some kind of coil former frame and a tuning capacitor with reduction drive..

Or as stated before, active ferrite rod antenna. There are a few threads here detailing that...

[jsbhavsar]

Originally Posted by PsychMan

I wouldnt call it a flaw, As I understand it, Ferrite rod antennas were about getting the best antenna into a small space. At MW band frequencies, decent wire antennas can be very long indeed. In practice, electrically shorter antennas can often work quite well, depending on what you are trying to receive. Long wire antennas can work very well, but are more subject to picking up electrical noise from other devices that unfortunately are now everywhere.

Ferrite rod antennas respond to the magnetic component of electromagnetic radiation and therefore pickup less noise, and its possible to rotate them to null out sources interference because they are directional, same with various forms of loop antennae, so they can work better in modern environments.

Of course at shortwave frequencies long wires can be much shorter and easier to locate.

If you want decent MW reception, why not look at constructing an active loop antenna and a way to couple that into your antenna input on the receiver. You will get a decent low noise antenna in a compact space and keep your radio original. Lots of guides and videos online, but essentially you need lots of wire, some kind of coil former frame and a tuning capacitor with reduction drive..

Or as stated before, active ferrite rod antenna. There are a few threads here detailing that...

Thanks. Appreciate a lot.

Unfortunately, given the living space issues in India, I am not looking at adding anything outside the radio, a tuned loop or whatever it maybe. It is an overhead to me especially when knowing that something can be done inside the set itself to meet the MW and MSW requirement, why explore something outside?

I am exploring ideas to do something that was intentionally or unintentionally left out in 1958-59 for whatever reasons.

A suggestion here from you to add a ferrite loop replacing the MW / MSW aerial circuit coil packs is welcome. I only want to ensure that ferrite may not interfere with the other SW bands. Ferrites might interfere with the other SW coil pack performance?

I like restoration projects that will improve things and remove original flaws and make radio sets sound better on all bands and make improvements even like adding low pass filters or something like that.

Adding 4 feet or 2 feet frame aerials is not a solution in space cramped India.
My Mumbai entire condo is just the size of the living room of most western countries. Frame aerials are out of scope. Very long wires of 25 to 30 meters long racing on top of the high rise terraces also not possible.

I am exploring "what can be done inside the set" to improve MW, MSW and SW41 well respecting the designers and not disturbing other bands?
A tough ask!

[jsbhavsar]

Some pictures of my Ekco A731

[Ed_Dinning]

It looks a very compact coil pack with adjustable ferrite cored coils so should be quite good unless the adjustments have been twiddled.
Do not be tempted to do this unless you have the correct procedure and a suitable signal generator

Ed

[Silicon]

Radio sets of this era were often fitted with a frame aerial on the inside of the rear cover.
They provided good performance on medium wave.

Shortwave usually required an external wire aerial.

Your radio has an RF amplifier stage and so it should be more sensitive than the average receiver.
When you have replaced the waxed paper capacitors and any resistors that have drifted more than 20% from their original value, you need to test the radio to see if it needs a better aerial.

A small loop aerial could be fitted to the rear of your receiver.
For the higher SW frequencies it may only need a single turn of copper wire.

It would plug into the aerial and earth sockets on the back of your radio.

[Graham G3ZVT]

It appears to have a BC GLS bulb as a scale lamp.

[jsbhavsar]

Originally Posted by rambo1152

It appears to have a BC GLS bulb as a scale lamp.

The lamp is not the original design of the 1959 set. Those days, they fitted with a small filament lamp of 4.2V or 6.2V whatever the voltage the radio circuit operated upon. Those lamps became slowly obsolete then the radio technicians in cities in India did this workaround by bringing the regular 230V AC from the power transformer and connected that with the ON OFF switch. This workaround is quite cheap and easy to replace the bulb now. This bulb is running as-is since 2001 since I got the set from the "thieves market" in downtown Mumbai.

I remember my Dad had Philips India 15RB487 from 1968 onwards. With varying voltages, radio dial lamps would often blow up. As a school kid I remember sitting with Dad in replacing the small bulb few times and it was difficult and would consume long long time. Philips India sets used to be "tight" and were difficult to work upon.

[jsbhavsar]

Originally Posted by Ed_Dinning

It looks a very compact coil pack with adjustable ferrite cored coils so should be quite good unless the adjustments have been twiddled.
Do not be tempted to do this unless you have the correct procedure and a suitable signal generator

Ed

The last time in 2002 a qualified Philips India tube radio engineer tried his best to decouple this small single bobbin coil pack and introduce a ferrite rod assembly from a very old tube radio. We failed in that project. He had a signal generator and Oscilloscope both. He checked all 8 bands and told me that the IF alignment is perfect on all coils.

We finally removed the ferrite rod and since that day, MW is lost. Something got messed in the connections of the MW coil pack that day.

I myself I am not a qualified radio technician so I would not attempt to do this. I will be getting everything done from a proper restorer.