Swinburne DR600 Airband Radio will not tune

[milairuk]

Hi again Heavy747 and Superhet Si.
I've got the RF, Mixer & Osc circuits now, along with the Xtal and part of the scanning circuits. See attached. There is as much again to do, but these should give you the basics. As far as I can see, if you leave out a Xtal, the Rx tunes to wherever you trim the preset pot, as the circuit is the same with the variable tuning pot. Putting in a xtal "locks" the frquency more accurately. The Xtal Osc and Variable Osc are still a bit confusing, and I cannot find any coupling to the MIxer - I think it is down to stray coupling only. Heavy747 - where did you get Ron's email from ? If you can send it to me I will make contact, hopefully he will remember me from all those years ago, and I'll see if I get any more luck with a proper circuit. If so, I'll probably put a lot more work into it and describe it on my website, along with more comprehensive pictures indicating the components. I'm sure there are still more out there.

Have fun

John

[HEAVY747]

Hi Milairuk

Email address has been sent to your private account.

What happeneded to the Ambit airband thumbwheel radios? Did they do well? I want to make one my self a easy design any suggestions please?

[HEAVY747]

Hi All

Please can anyone advise where I can get a free circuit diagram for a FDK ATC-720 airband radio which operates by binary decimal coded switches to change frequencies. The radio makes a humming noise when it recives signal and signal is not audible.

http://www.ragnoli.it/Mario/images/a...C-720%20SP.jpg


Please help - humming stays same if I turn radio volume up or down and batteries don't charge. Also when it receives voices distorted and all blue electroylics are new no difference in sound!!! Attached are pictures of internal workings and link shows what radio looks like. The radio company was Fukuyama Electronics Co., Ltd I believe but no history on the internet whatsoever.

Please help!!!

[jimmc101]

Interesting arrangement, looks like the VCO is injection locked by the crystal oscillator when running.
By the way the BF440 is a PNP device which at least makes the biasing more understandable.
see http://www.datasheetarchive.com/pdf-...ook519-735.pdf

Jim

[milairuk]

Originally Posted by HEAVY747

Hi Milairuk

Email address has been sent to your private account.

What happeneded to the Ambit airband thumbwheel radios? Did they do well? I want to make one my self a easy design any suggestions please?

Thanks' I'll check when I get home.
Was that the one on the front cover of R&EW taken inside Stansted Tower ? I vaguely remember it , especially all the red tape I had with the CAA to take pictures in there !! Never sold in thousands as far as I remember. I have the synthesiser part driving my homebrew airband radio along with a 256 memory addon unit. I made this after that design came out. Have the mag somewhere, so if you want more details I'll see what I can find. May mean a trip into the loft though ....

John

[milairuk]

Originally Posted by jimmc101

Interesting arrangement, looks like the VCO is injection locked by the crystal oscillator when running.
By the way the BF440 is a PNP device which at least makes the biasing more understandable.
see http://www.datasheetarchive.com/pdf-...ook519-735.pdf

Jim

Aha !! Thanks Jim, so the collector does feed the coil after all !! Did think it a bit odd, that's what you get for assuming all are NPN's !!
John

[milairuk]

Originally Posted by HEAVY747

Hi All

Please can anyone advise where I can get a free circuit diagram for a FDK ATC-720 airband radio which operates by binary decimal coded switches to change frequencies. The radio makes a humming noise when it recives signal and signal is not audible.

Please help!!!

Looks like this is an elusive one - did find one site selling the data for 10 dollars - not a lot really if it solves your problem ?? I had a similar fault on a DAB radio - never could work it out as the PSU was fine. Went in the bin eventually !!

Thanks for your email link, I have sent one to Ron - fingers crossed.
John

[Superhet Si]

Originally Posted by milairuk

Hi again Heavy747 and Superhet Si.
I've got the RF, Mixer & Osc circuits now, along with the Xtal and part of the scanning circuits. See attached. There is as much again to do, but these should give you the basics. As far as I can see, if you leave out a Xtal, the Rx tunes to wherever you trim the preset pot, as the circuit is the same with the variable tuning pot. Putting in a xtal "locks" the frquency more accurately. The Xtal Osc and Variable Osc are still a bit confusing, and I cannot find any coupling to the MIxer - I think it is down to stray coupling only. Heavy747 - where did you get Ron's email from ? If you can send it to me I will make contact, hopefully he will remember me from all those years ago, and I'll see if I get any more luck with a proper circuit. If so, I'll probably put a lot more work into it and describe it on my website, along with more comprehensive pictures indicating the components. I'm sure there are still more out there.

Have fun

John

John thank you very much for your time in drawing out he circuit and insight to it's operation.

[HEAVY747]

Originally Posted by milairuk

Thanks' I'll check when I get home.
Was that the one on the front cover of R&EW taken inside Stansted Tower ? I vaguely remember it , especially all the red tape I had with the CAA to take pictures in there !! Never sold in thousands as far as I remember. I have the synthesiser part driving my homebrew airband radio along with a 256 memory addon unit. I made this after that design came out. Have the mag somewhere, so if you want more details I'll see what I can find. May mean a trip into the loft though ....

John

Yeah yeah the radio was sat on top of the control tower handlers desk as he looked out. The radio had a long aerial sticking out. Absolutely classic picture!!!

What a small world I still have photo copies of that project!!

Can you suggest where I could purchase kit form airband radio?

[HEAVY747]

Originally Posted by milairuk

Looks like this is an elusive one - did find one site selling the data for 10 dollars - not a lot really if it solves your problem ?? I had a similar fault on a DAB radio - never could work it out as the PSU was fine. Went in the bin eventually !!

Thanks for your email link, I have sent one to Ron - fingers crossed.
John

Thanks for that anyway

[milairuk]

Originally Posted by HEAVY747

Yeah yeah the radio was sat on top of the control tower handlers desk as he looked out. The radio had a long aerial sticking out. Absolutely classic picture!!!

What a small world I still have photo copies of that project!!

Can you suggest where I could purchase kit form airband radio?

In the days when Stansted had not got too big for it's boots !! The aerial was a fiddle if I remember - not actually connected. Poetic licence indeed. No idea where you can get a kit these days, I suspect the parts for the Ambit are long ago obsolete, especially the synth chips. Technically listening to Aircraft is still illegal in the UK due to an archaic law passed after WW2. Getting a bit off topic now. Have sent Ron an email and hope to hear back, I then plan to feature the DR600 on my website if I get enough data.

John

[Superhet Si]

This is great, this set deserves not to be forgotten!

[HEAVY747]

Originally Posted by milairuk

In the days when Stansted had not got too big for it's boots !! The aerial was a fiddle if I remember - not actually connected. Poetic licence indeed. No idea where you can get a kit these days, I suspect the parts for the Ambit are long ago obsolete, especially the synth chips. Technically listening to Aircraft is still illegal in the UK due to an archaic law passed after WW2. Getting a bit off topic now. Have sent Ron an email and hope to hear back, I then plan to feature the DR600 on my website if I get enough data.

John

Absolutely brilliant idea!!! I look very much forward to your presentation

[milairuk]

Good news and maybe bad news - phoned Ron this morning who was very surprised to hear from me after 30+ years. He told me they made approx 1800 DR600's and was amazed that they were still in existence. Mine is one of the first, I think he said after the 1st 500 they had to change the cases as the supplier no longer made the blue case that mine has. Now the "maybe" bad news - he's not sure if he has any data / circuits around, but he has told me he will talk to his brother who may have.

Let's leave the thread be for now, as soon as I have anything to report I'll post to it again, or make a new one if this has been closed.

73 John G3VUO

[HEAVY747]

Originally Posted by milairuk

Good news and maybe bad news - phoned Ron this morning who was very surprised to hear from me after 30+ years. He told me they made approx 1800 DR600's and was amazed that they were still in existence. Mine is one of the first, I think he said after the 1st 500 they had to change the cases as the supplier no longer made the blue case that mine has. Now the "maybe" bad news - he's not sure if he has any data / circuits around, but he has told me he will talk to his brother who may have.

Let's leave the thread be for now, as soon as I have anything to report I'll post to it again, or make a new one if this has been closed.

73 John G3VUO

Good work Milairuk!! Blimey he turned over about £360,000 on these DR600 radios!!! That's a serious amount of money!! Well done to him!!

Question is where did they all disappear to?

[milairuk]

Originally Posted by Superhet Si

I have had one in the loft for a while after I blew the charging regulator up. It is now working and is at work. This is ideal as the Gatwick is next door.
Would love a circuit as the unit drifts on warm up when the presets are selected.
Any idea what crystals are used?

Sorry, forgot this one - the xtals are calculated by taking the desired Rx frequency + 10.7Mhz and then divide by 3. Example 127.70 + 10.7 / 3 = 46.1333Mhz. Not sure if these are fundamental xtals, I'm guessing they are 3rd overtone in which case this would be 15.3777Mhz. All I can say is that my counter reads 46.1333Mhz on the xtal. My xtals all have the final frequency marked on them - they came from a Bearcat hand held scanner.

John

[milairuk]

Hi everyone,

The first page is now on my website http://www.milair.co.uk/airband.html for the DR600. I'll add more assuming Ron sends me more after Xmas.

Happy New Year to all on the Forum

John

[HEAVY747]

Hi John

Spot On!!!!!!!!!! Very well doen can't wait to read this!!!

All The Best
HEAVY747