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Old 3rd Nov 2017, 1:34 pm   #21
Philips210
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

Thanks Lawrence. I tried a search for 1A2 but it returned zero results.

Regards
Symon.
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Old 3rd Nov 2017, 1:38 pm   #22
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

No problem, some more equivalents here:

http://analogmetric.com/download/Vac...ce%20table.pdf

Lawrence.
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Old 3rd Nov 2017, 1:47 pm   #23
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

Hi Richard.

It looks to be quite a challenge, super regens aren't the easiest of things to get working at the best of times. From Lawrence's link to the Radio Museum website, the European equivalent is a DK91. I would have thought the later DK96 is a better proposition as it has a lower current heater. I've a number of DK91s and DK96s lurking around in the loft somewhere so at least the valve can be swapped for one known to be serviceable.

I am trying to complete the loop aerial project (Gary Tempest) thread but have had many day to day obstacles to overcome. My trouble is I take on far too many projects when the running of the home has to take precedence. I wish I had more time to spare. It's funny, as you get older the days somehow seem to get shorter.

As I say, I'll order the 1A2 kit and hope that I can get somewhere with it.

Regards
Symon

Last edited by Philips210; 3rd Nov 2017 at 1:49 pm. Reason: typo
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Old 3rd Nov 2017, 1:48 pm   #24
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

Good one Lawrence, thanks again.

Regards
Symon.
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Old 3rd Nov 2017, 4:59 pm   #25
Neil Purling
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

It makes me wonder if whoever designed the kit ever managed to get sound out of one.
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Old 3rd Nov 2017, 6:19 pm   #26
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

The Super Regen section of the 19 set apparently did work but unfortunately not very well. It's been mentioned a few times over the years and there was at least one aricle in PW [I think] during the sixties re one valve re slope detection at VHF. Tanuki started a thread this year in March WS 19 'B' set. I've always had the impression that the Regen Type circuits lasted longer [as a working concept] in the USA but I'm not sure where I've gone that from except maybe, reading ARRL Handbooks!

Dave W

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Old 3rd Nov 2017, 8:48 pm   #27
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

Hi.

I've just ordered one of those kits which is going to take quite a while to arrive but hope that I'll be able to get it built before Christmas.

I know it's slightly OT but the transistor super regen circuit I mentioned in posts #7 and #10 worked quite well as I seem to recall. When time permits, I'll revisit this after 12 years and see if it will work again. I think Raymond Haigh's circuits are well thought out and fully repeatable and certainly worth building. He seems to know his subject extremely well.

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Old 3rd Nov 2017, 11:17 pm   #28
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Arrow Re: Chinese 1A2 Super Regenerative FM radio kit

Quote:
Originally Posted by Neil Purling View Post
The description of the kit online says Super Regenerative, but perhaps they aren't.
So this receiver is a Chinese product and the original title (in Chinese) has, presumably, been translated into English. However, one must be cautious of such translations: the Chinese have a tendency to use certain adjectives to make their products sound exciting, typically by inserting the word 'super' (or the Chinese near-equivalent for that word) in their product description.

I think we can all see where this line of thought is taking us . . . . .

Al.
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Old 4th Nov 2017, 1:27 am   #29
Neil Purling
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

At these sort of frequencies the components have to be as close together as possible, don't they?
So there are no stray capacitances to impair function. I feel that there is far too much that is not mentioned in the instructions. Even if your command of the various types of Chinese was flawless the instructions seem pretty useless.
How much of an aerial does it need? That is not said.
It must have an effect on such a crude circuit
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Old 4th Nov 2017, 8:41 am   #30
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

I tried a 300Ω dipole and a few long wires, maybe between 6' and 25' but didn't get any reception.
I didn't put the components close together, except the two coils.
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Old 4th Nov 2017, 10:00 am   #31
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

Hi.

I know this might sound daft, but not totally unreasonable, could it be that the 1A2 valves are defective, a duff batch perhaps? Did anyone who built the kit try a known working DK91 or DK96?

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Old 4th Nov 2017, 11:40 am   #32
Neil Purling
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

There are other FM kits around. One is on PCB and that has the components clustered fairly tightly around the valve-holder. It is not a kit that uses the 1A2. It had an 6J1/EF95 run from an included HT transformer
mole42UK: Maybe you can re-work your kit and see if keeping component wires as short as possible makes any difference.
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Old 4th Nov 2017, 2:19 pm   #33
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

To my my eyes,the circuit is not a superregenerative.
The 1A2/1R5/DK91 valves struggled over 10 MHz.

In 1949 Sylvania introduced the 1L6 "hotrod" version of the 1R5/DK91 for use by Zenith in the Transcontinental receiver that covered up to 30MHz (just,with an 1L6 testing 100%)

I think the Chinese 1A2 kit is doomed to fail,it may however be a good source for 50mA 1R5/DK91 replacements since these are starting to become scarcer.

Neil mentions a different kit based on EF95 or its eastern Bloc equivalents.
The EF95 is a really good valve into VHF well above broadcast bands as most already know.
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Old 4th Nov 2017, 8:13 pm   #34
Neil Purling
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

VT FUSE: So the kit could never work. Glad I wasn't tempted..............
I don't know what chances you would have of getting Classic FM playing from one of those EF95 based kits would be. Better odds with a printed circut board.
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Old 4th Nov 2017, 8:30 pm   #35
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

I don't see why it shouldn't work: I recall similar circuits using battery valves being used for 27MHz radio-controlled-models in the 1960s.

http://www.seekic.com/circuit_diagra...tron_Tube.html shows a similar circuit, as does http://theradioboard.com/rb/viewtopic.php?t=1464


OK, the more-usual superregen has a centre-tapped coil/capacitor, but when you study the detail this isn't absolutely necessary!

[Some interesting history of supoerregen R/C receivers here: http://www.norcim-rc.club/Radio17.htm ]
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Old 4th Nov 2017, 8:56 pm   #36
VT FUSE
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

Well,I don't see an obvious feedback path in the circuit therefore it is a straight TRF receiver to my eyes.

I still have some valve RC receivers as well and can still visualise circuits in the FC Judd "radio control for model aircraft and boats" book from 1950's.

I have seen many 27 MHz receivers utilising "hard" pentodes and "soft" thyratrons in articles inc those referred too as well.

The device under discussion uses the heptode valve strapped as a pentode,this is entirely feasible,however I have no conviction that it can operate at 88MHz let alone 108MHz.

Guess the only conclusive answer is for an electronics engineer to buy the kit and then subject it to real life signal strength levels that would be expected from the expected short aerial but employing a signal generator and seeing what comes out of the kit.
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Old 4th Nov 2017, 9:16 pm   #37
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

It's a variant of the "ultra-audion" oscillator, which is itself a sort-of-Colpitts oscillator. See http://messui.polygonal-moogle.com/valves/VR199902.pdf for some discussion
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Old 4th Nov 2017, 11:16 pm   #38
Philips210
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

Hi.

It does seem a mystery and begs the question, why would they go to the trouble of making a PCB for this circuit if it never worked in the first place?
I do agree that pushing a 1A2/DK91 to 88MHz and beyond does seem somewhat ambitious. It appears that the circuit will work in principle but not necessarily at Band 2 VHF frequencies.
From what I've read, I'm not overly confident (understatement of the year) about having any success with this little project. We shall see in due course.

Regards
Symon.
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Old 5th Nov 2017, 10:09 am   #39
Neil Purling
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

What are the coils U2 and U2 like? Two free standing enamelled copper coils, or are they on a former?
The spacing of the turns in each winding and the proximity of U2 and U3 to each other is also critical to proper operation. That is what I gain from that American PE FM one valve receiver.
A kit working at these frequencies really does need comprehensive instructions expressed in without technical jargon in the buyers native language.
It looks as if whoever is producing these kits has not had anyone attempt to assemble and use it.
If they had any technical knowledge they would have realised the 1A2 will not work at the intended frequencies.
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Old 5th Nov 2017, 10:22 am   #40
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Default Re: Chinese 1A2 Super Regenerative FM radio kit

There is no specification for the coils other than the guage of wire, the number of turns and, in the case of the larger one, that it is wound on an AA battery which is then removed.

There is no indication of the physical relationship between the coils.
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