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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 2nd Nov 2019, 9:33 am   #1
Martin G7MRV
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Default SARBE-5 and SARBE-6 schematics?

Hi, Does anyone know where I can source the circuit diagrams for the SARBE-5 and/or SARBE-6 units?

It is my intention, before power gets anywhere near them, to fully disable the Tx sides! Having the schematics would make this a much easier task.

Cheers
Martin
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Old 2nd Nov 2019, 10:30 am   #2
M0AFJ, Tim
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Default Re: SARBE-5 and SARBE-6 schematics?

I’ll ask some of my ex Burndept colleagues but I doubt that much will be available, might be worth contacting VMARS
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Old 2nd Nov 2019, 11:08 am   #3
David Simpson
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Default Re: SARBE-5 and SARBE-6 schematics?

I'll echo Tim's advice - try VMARS.
SARBE eh, my first RAF posting after Boy Entrant training was on S & R helicopters. They were initially equipped with SARAH & 10 channel 1985 series VHF. The following year the Whirlwinds were modified & upgraded to SARBE/Violet Picture & ARC52. The reason for these reminiscences is to ask if you've also got the Violet Picture/ARC52(or PTR175) set-up. That would be really something.
Right enough, transmitting on 121.5 or 243 MHz is a definite no no, but you're the first guy I've heard of who has shown an interest in this once tremendously important bit of military equipment.
I know of two establishments who may still have the SARBE/VP/ARC52 set-up :- The MORAVIA Aircraft Museum at Kinloss Barracks(formally RAF Kinloss), & and the '963' Shackleton MR Restoration Project at Coventry Airport. (An AEW Shack has been restored to an MR2), (I once worked on '963' when it was at Lossiemouth).

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Old 2nd Nov 2019, 11:54 am   #4
Martin G7MRV
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Default Re: SARBE-5 and SARBE-6 schematics?

Sadly, no, I dont have a Violet Picture kit! My main interest is actually in using, on air, the Clansman manpacks, but as im sure you will appreciate, there is a tendency to deviate so long as its radio and green...

I remember we had some BE477 (?) TACBE's (variant of the BE375 SARBE-5) in squadron signals stores, but they were never taken anywhere!

I will take a look on the VMARS site later, sadly I cant access it from here due to the network security settings, and the text is too small to read on my phone.

At the very least, I should be able to identify the Tx crystals and PA transistors, and remove them, and the Tx supply line. That should shut them up!
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Old 2nd Nov 2019, 4:41 pm   #5
M0AFJ, Tim
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Default Re: SARBE-5 and SARBE-6 schematics?

I’ve had a message from my old Burdept colleague, unfortunately he can’t help, it’s been many years since they were produced and of course the company no longer exists. They were also on the restricted list as far as I remember.
I’d go with removing the crystals and disabling the PTT. I don’t think you will hear very much, they were pretty deaf when manufactured!.
Brings back memories though of huge temperature and humidity cycling machines that we had, and a fish tank that was used to make sure they didn’t leak...
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Old 2nd Nov 2019, 5:55 pm   #6
Martin G7MRV
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Default Re: SARBE-5 and SARBE-6 schematics?

Thanks for asking Tim, theres no great rush, and as we say removing the crystal and the Tx supply and PTT lines should pretty much kill the Tx side,

Being a tad deaf shouldnt be a worry (lets face it who isnt!), if I do recrystal them they will go on frequencies where I will be pretty close to the action. Mind you, I bet that would cause a bit of a stir down at Donna Nook...

I dont have them yet, hopefully they will arrive this week. One -5 with antenna but no battery, and one -6 with battery (likely dead) but no antenna. I 'think' they both have the pins still with them! If im right, these have no squelch?
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Old 3rd Nov 2019, 8:40 am   #7
Martin G7MRV
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Default Re: SARBE-5 and SARBE-6 schematics?

I have received a BE375 service manual, so just looking for the same for the BE515 (SARBE-6) now
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Old 3rd Nov 2019, 10:13 am   #8
Martin G7MRV
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Default Re: SARBE-5 and SARBE-6 schematics?

Well, the SARBE-5, this is a very interesting machine!

Hermetically sealed, all external controls are electromagnetic - operating internal reed switches with external magnets!

In terms of 'repurposing', the Tx as expected is crystal controlled. So, remove the Tx supply lines and thats the Tx disabled. Essential of course if this is to be powered and used for anything other than getting a visit from the RAF MRT!

Now, the receiver(s), two separate receivers (emergency and aux channels), with shared audio stage. The receivers are self quenching super-regeneratives! No crystals, frequency set entirely by an LC circuit! So changing the receive frequencies is just a case of adjusting a trimmer cap and maybe the coil winding. There is a Pi LPF in the antenna line, that may need a little adjustment as well.

These also have a self test function, which in the case of the receivers, is a single transistor LC oscillator, one per channel, its output fed back to the receiver via the aerial line (now isolated from the antenna by the 'test' reed switch.

It looks like the Tx oscillator/multiplier chains and the PA are powered all the time when the unit is on, with just the Tx buffer amp supply switched. For safety to ensure the unit absolutely cannot transmit, it will probably be best to remove certain components in the oscillator chain and PA to cripple it.

I wonder if the SARBE-6 retains this architecture?

Martin
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Old 4th Nov 2019, 10:25 am   #9
Martin G7MRV
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Default Re: SARBE-5 and SARBE-6 schematics?

Quote:
Originally Posted by M0AFJ, Tim View Post
I donít think you will hear very much, they were pretty deaf when manufactured!.
This is an interesting aspect ive discovered! The actual spec for the mk5 is 20uV, which is probably ok enough for line of sight to a rescue aircraft, say 10-15nm, but poor for general reception.

Worryingly, the super-regenerative receiver used in the set is a single stage, with no isolating RF stage ahead of it. I wonder if it was deliberately designed 'down' in order to reduce radiation of the receivers oscillation from the antenna? Its fairly standard practice to use an isolating RF stage ahead of a regenerative detector, so its odd these dont.

Perhaps for the original purpose a bit of radiation on-frequency is largely irrelevant, since the whole point is to home in on the sets transmission. But for conversion for general monitoring (and especially if it is to remain on the distress frequencies!!!), a retrofit RF stage might well be prudent! Assuming of course, it can be made small enough to fit in the case!
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