LDMOS Homebrew Project
Latest Pics 19-07-2015...
New image of the LDMOS Homebrew Project including the letraset modified pallet view showing cleaner output coupling another view showing front panel and added shielding to the panel bargraphs. But read on down for the whole story...
My 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. 73 Richard 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 432MHz. 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... 73 and good dxing Richard G6HKS
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 Celsius 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 chassis.
21st April 2014... Got the HP supply converted, working well and it appears to be a soft starter which is a bonus. It's good for 60 amps so I've 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, 73 Richard G6HKS.
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 testing!
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!
