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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 18th Jul 2013, 10:55 am   #1
marc_uk
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Default Mutek Masthead preamp info needed

Hi.
I picked up a SLNA 433spg 70cms masthead preamp.
Unfortunately there was no power plug included by the seller.
Its a 3 pin 180 socket for the DC - no idea which pin does what,
or what voltage it takes or how much RF power they can pass.

There's no info on the web that I've found, other than Mutek is
no more. I emailed ((info@mutekrf.com)) which seems to be the
last known address. No replies yet, and I'm not expecting any sadly.

can anyone help please ?

Mark
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Old 18th Jul 2013, 7:01 pm   #2
Sean Williams
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Default Re: Mutek Masthead preamp info needed

Voltage will be 13.8v.

Open it up, and trace the circuit for the power connector - one will be ground, one most likeley PTT, and the other VCC.

Through switching is likely to be around 100W maximum.

it may also be able to do RF sense switching - this is not a good thing - too unreliable.

Cheers
Sean
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Old 18th Jul 2013, 10:02 pm   #3
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Default Re: Mutek Masthead preamp info needed

RF sense switching as said is best avoided. It switches the relay with power on it and shortens its life. It lets your power amp run up before it gets switched to a load, and they do not like it back up 'em Captain Mainwaring, they most certainly do not!

Use PTT initiated change-over if you possibly can. If the relay contacts are burned, you can guess the cause.

Chris Bartram can still be found on the web if all else fails... I last saw him playing the fiddle at the Microwave Roundtable meeting, playing in a trio with Ian (G3SEK) and Nadine on concertina and auto-harp respectively. RF gurus are versatile people....

David
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Old 31st Jul 2013, 8:36 am   #4
marc_uk
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Default Re: Mutek Masthead preamp info needed

Thanks Sean, Thanks David too.

I found the +ve and obviously GND so I can test the thing, seems to work too, albeit at the shack end for now. started on a fairly flat PP3 battery and resistor.

Yes I've never been fond of RF sensed switching of things, because in my experience, whatever can go wrong, will go wrong. Seem to have trouble opening the thing up too, so I'll leave it for now as I don't want to round the screw heads off, but will drop a tiny bit of WD40 on them possibly later to un-fix the darn things. I figured 100W would be max or there about as not much use as a masthead preamp if you're only limited to a few watts!

I'm guessing the 3rd connector in the power input is the PTT but haven't advanced any further in that particular direction because, rather amazingly, the Guy I bought it off got in contact with the amateur he bought it off years ago who still has the original paperwork! Now whether this paperwork gives anymore useful info remains to be seen, but good detective work.

I'm not sure if I tried G3SEK whilst looking for a 70cms preamp some months ago, callsign rings a bell, but I've slept since then, though not constantly you understand!

Thanks Chaps, this is how i shall proceed with some good advice and help, so I guess we'll see what Mutek's 1980's instructions were like soon. Can post back if anyone's interested or for future reference perhaps, for other vintage Mutek masthead purchasers.

Thanks, Mark.
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Old 2nd Aug 2013, 11:36 am   #5
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Default Re: Mutek Masthead preamp info needed

Chris Bartram's callsign is GW4DGU but he's not listed on QRZ.COM.

He was at the Finningley Radio Club during the recent Microwave Roundtable weekend. I might be able to contact him through another forum if you still need the manual?

Dave
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Old 24th Aug 2013, 4:45 pm   #6
Mwaki Mbaki
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Default Re: Mutek Masthead preamp info needed

The vile 3-pin non-latching (!) plug muTek used to use is, fortunately, still available from RS (and maybe others).

The RS part# is:
738-9041
Brand Hirose

This is the male version with sockets in the plug. Its mating panel socket with matching pins is also available
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Old 25th Aug 2013, 8:49 pm   #7
Mwaki Mbaki
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Thumbs up Re: Mutek Masthead preamp info needed

I found this short spec from muTek for the preamp among my Big Radio Stuff files:

"SLNA 433spg

This masthead amplifier for the 70cms band features a low noise device. It has a GaAsFET with 14dB gain and a noise figure of 0.7dB. The amplifiers will handle up to 150W when sequenced (100W prior to 01/01/93) and up to 10W on RF sensing. Insertion loss on transmit is less than 0.3 dB. It is enclosed in a waterproof diecast box sealed to IP65, and is supplied with mast mounting hardware."

Enjoy

Last edited by AC/HL; 25th Aug 2013 at 11:43 pm. Reason: Please do not use textspeak
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Old 8th Nov 2013, 12:18 pm   #8
7severn7
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Default Re: Mutek Masthead preamp info needed

Quote:
Originally Posted by marc_uk View Post
.................Can post back if anyone's interested or for future reference perhaps, for other vintage Mutek masthead purchasers.

Thanks, Mark.
Sorry for the vary late reply.
It might be even more helpful to scan and send the info to mods.dk for global sharing.

http://www.mods.dk/
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