23cm PA Module urgently needed for GB3EY

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G3GJA
Posts: 179
Joined: Sun Nov 20, 2011 3:44 pm

23cm PA Module urgently needed for GB3EY

Post by G3GJA » Wed Nov 17, 2021 12:23 am

EY is currently off-air whilst intermittent sensitivity issues are traced. One of the causes appears to be a faulty Mitsubishi RF module, where its gain in the transmitter chain is fluctuating and the linearity appears to suffer in step.

This is causing crud to appear on the receive frequency. Although the module is used to produce only 400mW to drive the PA, it seems that sanding the flange flat may have caused the module to start failing. This is disappointing as the amplifier has not been touched since it was purchased as a completed unit.

If anyone can help locate a replacement module it would be much appreciated. The usual UK suppliers have no stock and a USA source won't send to the UK. There are some Chinese sources but I'm wary of buying a fake!

Clive G3GJA

radiogareth
Posts: 831
Joined: Wed Jan 06, 2016 9:46 am

Re: 23cm PA Module urgently needed for GB3EY

Post by radiogareth » Wed Nov 17, 2021 8:26 am

If you only want 400mW I think Jim G7NTG used a small 900MHz brick which, with minor mods worked well at 1250. Somewhere I bought a couple to try and somewhere I saved the webpage.......
Or perhaps a G4BAO pre-driver might do the job?
Gareth

G3GJA
Posts: 179
Joined: Sun Nov 20, 2011 3:44 pm

Re: 23cm PA Module urgently needed for GB3EY

Post by G3GJA » Wed Nov 17, 2021 9:50 am

It's not so much the output (although at 400mW the RA18H1213G has good linearity) it's the gain that's critical. GB3EY has a DTX1 modulator with an output that's less than 0.1mW so a gain of around 36dB is needed; that's achieved with an ERA6 MMIC pre-driver built into the same milled aluminium box.

It would be a major rebuild to replace that unit with something having similar screening, linearity and gain. Two G4BAO drivers in series might do it but their thermal design leaves a lot to be desired. I've repaired two where the PD8004 MOSFET has expired burning a hole in the PCB due to overheating. They can also be prone to instability if the ports are not seeing 50 ohms, such as would be the case with two in series. Not ideal for 24/7 repeater use!

Clive

g0mjw
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Joined: Sat Sep 20, 2014 9:15 am

Re: 23cm PA Module urgently needed for GB3EY

Post by g0mjw » Wed Nov 17, 2021 2:02 pm

There are quite a few on Ebay. RF Parts have stock but won't export. Enigma are out of stock https://www.enigma-shop.com/component/h ... ier-module

You need to be looking at alternatives for longer term so it might be worth looking at minicircuits devices like the PHA-202+ if you only need 1W.

Mike

G3GJA
Posts: 179
Joined: Sun Nov 20, 2011 3:44 pm

Re: 23cm PA Module urgently needed for GB3EY

Post by G3GJA » Wed Nov 17, 2021 2:46 pm

The PHA-202+ looks useful. I'd need two cascaded to get the gain. However the package needs flow soldering that I don't have access to.

There are some modules on UTSource. They work out at about £70 each if you buy two and include carriage and VAT. Anyone have experience of using UTSource?

I've looked at eBay and they're all sourced from China but the lead times are excessive and you don't really know what your getting. I know UTSource is Chinese but at least they can deliver by the 26th.

Clive

radiogareth
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Joined: Wed Jan 06, 2016 9:46 am

Re: 23cm PA Module urgently needed for GB3EY

Post by radiogareth » Wed Nov 17, 2021 2:53 pm

RFParts do ship to the UK now, by registered post, quoting 10 days. At least I HOPE SO, as I've paid them money for capacitors and ferrites.....
Gareth

G3GJA
Posts: 179
Joined: Sun Nov 20, 2011 3:44 pm

Re: 23cm PA Module urgently needed for GB3EY

Post by G3GJA » Wed Nov 17, 2021 3:09 pm

I've used them before but they state "No longer available for export" against all of the Mitsubishi modules.

Clive

radiogareth
Posts: 831
Joined: Wed Jan 06, 2016 9:46 am

Re: 23cm PA Module urgently needed for GB3EY

Post by radiogareth » Wed Nov 17, 2021 3:53 pm

OK, I wonder what on earth caused that distinction. anyway, the one I used recently in my 23cms 'Boxer' came from here: https://www.aliexpress.com/item/4001238 ... 4c4dDqIqD6 and so far, delivers the goods. It 'survived the sanding' so far.... I needed +20dB in front of it to drive from my Pluto. Somewhere I have a note of the drive level needed, certainly not full Pluto power.
Delivery is usually 10-14 days, never had anything 'wrong' from Aliexpress....
HTH

Gareth

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