LDMOS 432MHz 500W Latest Pics 19-07-2015...

New image of final amplifier including the letraset modified pallet view showing cleaner output coupling another view showing front panel and added shielding to the panel bargraphs.

front panel

update dpallet

pallet and front panel

LDMOS 432MHz linear amplifier project

Autumn 2013... The project starts here with lots of parts...



November 2013... At last my case arrived from RS components (out of stock for 3
months .. grrr) so i can now proceed with construction. Its still very much the
metalworking stages and you will see I have now added a chassis plate within the RS
enclosure and will now be working out the optimal location for other parts – keep
tuned for further updates – 73s Rich G6HKS


Just before Christmas... I got a little distracted from the amplifier and completed my HA8ET
masthead LNA for 432 – pic shows inside less final cabling and fuse otherwise its
completed – the hot end uses RG400 good for 800w at 432. I also got a chance to make
up a section of the conformable Huber and Suhner coax and flow solder onto the N
Type females good for about 2 kw at 432 but alas they wouldnt quite fit the
enclosure – the LNA will be fed from my 4 x 18eles which are ready to go and will
be powered / sequenced from the LDMOS amplifier of which 60% of the metalwork now
completed. Over the next few weeks i intend to complete the chassis bashing and
complete the RF stage – the scary bit being flow soldering the device onto the
copper spreader – more updates to follow ...


3rd January 2014... getting time for this project has been tough in between
fulfilling all your orders. However, i managed to sneak away during the festive break
and the following pics show completion of the rear and front panels – to be honest I
like to get this part out of the way and move onto the fun part that is the pcb
assemblies – the RS enclosure used incorporates very workable aluminium front and
rear panels with a stainless steel wraparound.

The paint is excellent with no chipping of any kind and i will certainly use this case for future units. The pics
show how i made the required shapes using basic tools which i hope are useful. The
meters are relatively expensive units from RS components (£23 each all in) but
really make the unit look the part - you can choose to mount them inside the unit
with just the screen in view but i prefer the external mount which also provides a
bit more room inside and removes the need to cleanly cut the window panel...

So now we move onto the fun part (and the scary part of flow soldering the device onto the
copper spreader) – keep checking for the next update .... 73s and good dxing Richard

11th January 2014... Finally decided built the courage and attempt to flow solder the
freescale device to Jim W6PQLs copper spreader. I used a standard (£10) electric hot
plate together with a half inch aluminium plate to act as a heat capcitor , added
some masking tape to act as the temperature measurement point and a cheap (£15 ebay
temperature gun with laser sight) – after about 5 minutes abd with the temp showing
215 degrees celcius I nervously added the spreader and device per Jims tutorial (see
W6PQL website) and after about 90 seconds – hey presto solder flows and device bonds
to the spreader. Testing suggests the device is intact so the construction continues
.... 73 Richard G6HKS

9th February 2014...

I've been busy this weekend constructing and have enclosed some new pics of the
almost completed RF pallet, filter assembly and a work in progress view of the

21st April 2014...

Got the HP supply converted – working well and it appears to be a soft starter which
is a bonus – good for 60 amps ive twin wired the outputs with 30 amp cables – these
are soldered directly to the supply outputs – take care you will need to supply a
lot of heat to get a good bond – care needed here to avoid damaging the output PCB.
I use 2 150 watt irons simultaneously to get good flow . Notes on converting this
supply can easily be found courtesy of Google . I have not modded the board so off
load voltage is 51.4 volts which should drop to 50 or less under load (plus of
course any power lead induced voltage drop). you can see the mains is connected via
tags – these are also soldered to the HP unit to ensure good connection (the unit
connectors are angled for rack mounting and otherwise are likely to work free unless
soldered) – i also added a dual pole switch for on/off capability 10A handling per
pole. I may add some mesh for safety at a later stage. The power lead to the
amplifier will include dual fuses and additional ferrite screening

Now to get stuck into the control boards - watch for further updates – 73s Richard

17th May 2014...

Well thats the logic boards all completed - pic shows the control board, FET
switches and LED bargraphs...

Just the wiring to go now (probably 3 weekends work) and then onto the

15th June 2014...

Some more pics of the 432 deck - getting close now, all being well might be
to testing phase next weekend!

20th July 2014...

Final assembly and testing begins!

September 2014...

Finished and working 432MHz LDMOS amplifier!


Nov 2014... I decided to build a new QRO LDMOS amplifier for the 2M band...

1994 - 2014 (20 Years)

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