Hi Gents,
We updated the documentation for the GLCD display and the software for the PICAXE in combination with this display.
You can download the info here
http://www.vk4dd.com/forum/viewtopic.ph ... p=159#p159
The GLCD is now in stock and avalible on request.
(as long as stock lasts).
73 Ron
VK4DD
144 Mhz home brew 600W solid state PA
Re: 144 Mhz home brew 600W solid state PA
GLCD ARRIVED, CONSTRUCTED and WORKING 5.5 Hrs latter
Just to let you know, that Ron and Patrick has done a STIRLING job with the GLCD (and other products of theirs).
Parcel was sent overnight, arrived at 10:30am (at the work address). Guess what I did during the lunch break).
Powered up prior to leaving at 1530. (Afternoon smoko)
Final touches when I got home and absolutely wrapped with the final product. Now just need an AMP to go with it
Pictures speak for themselves.
Just to let you know, that Ron and Patrick has done a STIRLING job with the GLCD (and other products of theirs).
Parcel was sent overnight, arrived at 10:30am (at the work address). Guess what I did during the lunch break).
Powered up prior to leaving at 1530. (Afternoon smoko)
Final touches when I got home and absolutely wrapped with the final product. Now just need an AMP to go with it
Pictures speak for themselves.
- Screen Shot
- The Test Bed
- The Flip side
-
VK4DD
Insufficient grounding and related problems
Hi Gents.
Over time the contact between the bottom of the PCB and the copper heat spreader degrade because of oxides, metallic reaction between different metals etc.
An other problem could be that some heat paste are not electrically conductive or simply too much heat paste. Resulting in poorly grounded FETS.
Also ... I think we should not use heat paste between the heatsink and the copper heat spreader.
This has been tried once resulting in stability problems. Most likely because earthing is not good enough.
The result of all these poorly grounded FETS can be Oscillation. The amps takes off and is no longer stable.
This can not only damage the FET but also cause interference.
Recommend: use 8 to 10 screws to ground the PCB for a single BLF248 PCB.
For the double BLF248 MKII this 24 to 30 screws to hold down the PCB. (fets not included).
The higher the gain of the FET, the quicker you run into this problem.
Lessons learned:
Use many screws to bolt down the amplifier to the PCB. Do not try to save money or time on screws.
Use these toothed washers to improve grounding between screw and PCB material.
Have sufficient torque (but not too much that you kill the thread).
I would also recommend ground the top of the FET. Not the white part, but the flanges on the side.
This will help grounding the FET if you used non conductive heat past.
Using less heat past will help... also because the metal of the Fet is in closer contact with the heat spreader.
Do not use heat sink paste between copper heat spreader and heatsink !
Note that the amp may work now without these measures but over time it might develop a grounding problem because corrosion kicks in.
How do you notice the amp is not stable...?
If you see one of these symptoms in your low voltage transistor or Fet amplifier.... clean up the oxides and improve grounding. Add more screws, remove excess heat paste.
Ground the flanges of the FET with some copper.
That is easy, just monitor the current and you will see that the amp is drawing more current than the idle current you have setup.
Or ... it is almost impossible to setup the bias current. It is either to high or to low. At a certain point it just takes off.
Information is shared because ...at the end of the day we don't want to reinvent the wheel every time.... as such it is good if we pass this on.
73 Ron
VK4DD
Over time the contact between the bottom of the PCB and the copper heat spreader degrade because of oxides, metallic reaction between different metals etc.
An other problem could be that some heat paste are not electrically conductive or simply too much heat paste. Resulting in poorly grounded FETS.
Also ... I think we should not use heat paste between the heatsink and the copper heat spreader.
This has been tried once resulting in stability problems. Most likely because earthing is not good enough.
The result of all these poorly grounded FETS can be Oscillation. The amps takes off and is no longer stable.
This can not only damage the FET but also cause interference.
Recommend: use 8 to 10 screws to ground the PCB for a single BLF248 PCB.
For the double BLF248 MKII this 24 to 30 screws to hold down the PCB. (fets not included).
The higher the gain of the FET, the quicker you run into this problem.
Lessons learned:
Use many screws to bolt down the amplifier to the PCB. Do not try to save money or time on screws.
Use these toothed washers to improve grounding between screw and PCB material.
Have sufficient torque (but not too much that you kill the thread).
I would also recommend ground the top of the FET. Not the white part, but the flanges on the side.
This will help grounding the FET if you used non conductive heat past.
Using less heat past will help... also because the metal of the Fet is in closer contact with the heat spreader.
Do not use heat sink paste between copper heat spreader and heatsink !
Note that the amp may work now without these measures but over time it might develop a grounding problem because corrosion kicks in.
How do you notice the amp is not stable...?
If you see one of these symptoms in your low voltage transistor or Fet amplifier.... clean up the oxides and improve grounding. Add more screws, remove excess heat paste.
Ground the flanges of the FET with some copper.
That is easy, just monitor the current and you will see that the amp is drawing more current than the idle current you have setup.
Or ... it is almost impossible to setup the bias current. It is either to high or to low. At a certain point it just takes off.
Information is shared because ...at the end of the day we don't want to reinvent the wheel every time.... as such it is good if we pass this on.
73 Ron
VK4DD
Last edited by VK4DD on Fri Nov 20, 2009 9:02 am, edited 2 times in total.
-
VK4DD
Re: 144 Mhz home brew 600W solid state PA
Hi Gents,
An important lesson was learned today with the Amp from VK4CRO. If something goes wrong with the 78L05 regulator circuit the BLF248 is dead.
The VK4CRO has been commissioned months ago and develloped a problem with the 78L05 regulator circuit.
Resulting in a too high gate voltage and taking out the BLF248 becuase of that.
What the cause was for the 78L05 to be blown up isn't known. It could be either a bad soldering, Oscillation or what ever.
Lesson learned ..there needs to be a Zener in the circuit to make sure the voltage never exceeds 5.1V !!!.
The 78L05 circuit did work fine but decided to stop working resulting in a too high gate voltage....
resulting in 28V to the bias circuit .... result -> dead FET
The 3k3 before the zener will limit the current enough so that the zener does not blow up as well.
So keep an eye out for the updated schematic.... and put a 5.1V zener in your amplifier
KISS works best (KEEP IT SIMPLE STUPID).
Not such a good idea to use the 7805 regulator in the typical schematic (NXP BLF248_3 data sheet.
73 Ron
VK4DD
An important lesson was learned today with the Amp from VK4CRO. If something goes wrong with the 78L05 regulator circuit the BLF248 is dead.
The VK4CRO has been commissioned months ago and develloped a problem with the 78L05 regulator circuit.
Resulting in a too high gate voltage and taking out the BLF248 becuase of that.
What the cause was for the 78L05 to be blown up isn't known. It could be either a bad soldering, Oscillation or what ever.
Lesson learned ..there needs to be a Zener in the circuit to make sure the voltage never exceeds 5.1V !!!.
The 78L05 circuit did work fine but decided to stop working resulting in a too high gate voltage....
resulting in 28V to the bias circuit .... result -> dead FET
The 3k3 before the zener will limit the current enough so that the zener does not blow up as well.
So keep an eye out for the updated schematic.... and put a 5.1V zener in your amplifier
KISS works best (KEEP IT SIMPLE STUPID).
Not such a good idea to use the 7805 regulator in the typical schematic (NXP BLF248_3 data sheet.
73 Ron
VK4DD
Last edited by VK4DD on Wed Nov 18, 2009 9:15 am, edited 1 time in total.
-
VK4DD
Re: 144 Mhz home brew 600W solid state PA
Hi All,
The parts list rev1 contains a mistake for the PICAXE Station monitor PCB (thanks Wayne VK5APN for pointing this out).
R5 = 560 K (not 100K) as such some of us may have received a 100K in their kit instead of the required 560K Ohm.
The Schematic is correct.
http://www.vk4dd.com/forum/download/fil ... &mode=view
I hope that this does not cause too much inconvenience.
73 Ron
VK4DD
The parts list rev1 contains a mistake for the PICAXE Station monitor PCB (thanks Wayne VK5APN for pointing this out).
R5 = 560 K (not 100K) as such some of us may have received a 100K in their kit instead of the required 560K Ohm.
The Schematic is correct.
http://www.vk4dd.com/forum/download/fil ... &mode=view
I hope that this does not cause too much inconvenience.
73 Ron
VK4DD
Re: 144 Mhz home brew 600W solid state PA
PICAXE GOING
All
Just like to say that the documentation that Ron has supplied re Picaxe programming, is very precise and straight forward. I have never played with these devices before and the hold your hand documentation is a great reassurance. It was very pain free to do. Worked first time. Even changing some of the program (very minor for testing purposes).
Wish the temperature will cool a little (forecast for today is 43C) so I can get out into the shack and continue the amp project.
Anyhow enjoy the picture.
Wayne VK5APN
All
Just like to say that the documentation that Ron has supplied re Picaxe programming, is very precise and straight forward. I have never played with these devices before and the hold your hand documentation is a great reassurance. It was very pain free to do. Worked first time. Even changing some of the program (very minor for testing purposes).
Wish the temperature will cool a little (forecast for today is 43C) so I can get out into the shack and continue the amp project.
Anyhow enjoy the picture.
Wayne VK5APN
- Attachments
-
- GLCD in all its glory !!
-
VK4DD
OOPS we had a problem with an N-Connector....
Hi Gents,
We finally found the problem with the Amp from VK4CRO
Lots of things have been improved like ... better earthing.
The 5.1V zener...
I replaced coax relays.
SWR sensor.
The whole lot except one coax lead from the coax relay to the antenna connector
Guess what ..... I although that lead measured ok with the Ohm meter when I tested it...
I decided that it had to go as well....
So I took that lead out and had the opportunity to look at the FEMALE N-CONNECTOR CENTER PIN.
(I must admit my eyes are not as good as they used to be... )
But when I looked at the CENTER PIN of the FEMALE N-CONNECTOR... I saw immediately why
we the amplifier tripped every time.
THE CENTER PIN WAS WORN OUT. IT WAS TOO WIDE AND WAS NOT FULLY MATING WITH THE MALE CONNECTOR, RESULTING IN INTERMITTENT CONTACT
N-Connectors are famous for this problem...
Quite a few VHF's use professional hard line cable because of the low loss...and also eliminating the need for a preamp at the mast if you have a hot front-end (not including EME).
Using a stiff cable or using a N-connector with the centre pin sticking out a little bit too far... Damages your N-Conector. It pushes out the female center pin.
We have a lot of lightning during summer so disconnecting your amp is a must, every time you do this... you can damage the N-connector....
I am now considering to use a 9/16 Din connector for disconnecting the antenna lead.
This is a much more robust connector which will not have this problem as quick as the N type connector.
I still think that the extra earthing screws were good, because it increased the stability of the amp.
The zener is a good thing too.
But it would have been nice if I saw this connector first
73 Ron
VK4DD
We finally found the problem with the Amp from VK4CRO
Lots of things have been improved like ... better earthing.
The 5.1V zener...
I replaced coax relays.
SWR sensor.
The whole lot except one coax lead from the coax relay to the antenna connector
Guess what ..... I although that lead measured ok with the Ohm meter when I tested it...
I decided that it had to go as well....
So I took that lead out and had the opportunity to look at the FEMALE N-CONNECTOR CENTER PIN.
(I must admit my eyes are not as good as they used to be... )
But when I looked at the CENTER PIN of the FEMALE N-CONNECTOR... I saw immediately why
we the amplifier tripped every time.
THE CENTER PIN WAS WORN OUT. IT WAS TOO WIDE AND WAS NOT FULLY MATING WITH THE MALE CONNECTOR, RESULTING IN INTERMITTENT CONTACT
N-Connectors are famous for this problem...
Quite a few VHF's use professional hard line cable because of the low loss...and also eliminating the need for a preamp at the mast if you have a hot front-end (not including EME).
Using a stiff cable or using a N-connector with the centre pin sticking out a little bit too far... Damages your N-Conector. It pushes out the female center pin.
We have a lot of lightning during summer so disconnecting your amp is a must, every time you do this... you can damage the N-connector....
I am now considering to use a 9/16 Din connector for disconnecting the antenna lead.
This is a much more robust connector which will not have this problem as quick as the N type connector.
I still think that the extra earthing screws were good, because it increased the stability of the amp.
The zener is a good thing too.
But it would have been nice if I saw this connector first
73 Ron
VK4DD
-
N2GZ
Re: 144 Mhz home brew 600W solid state PA
I am a big proponent of the 7/16 (DIN) connector. The max power recomended by Amphenol for their Type-N connector is 600 Watts. Sure it can often handle more without failure, but the small center pin will heat up. 7/16 connectors have that beefy 7mm center conductor. Many can be found surplus on jumpers and hardline cables here in the US, they are popular at the cellular sites.
UHF connectors have the large center pins and can handle lots of power, but because they are non-constant impedance this creates passive IMD issues even on 144 when elevated powers are used. I also recomend avoiding connectors made from ferromagnetic materials such as nickel or steel, as they can generate passive IMD especially at higher power levels. Brass/Bronze/Copper/Silver/Gold materials are preferred.
Always inspect your Type-N connectors before installation. Sadly many type N cables I find here that were constructed by hams do not meet spec. The tip should not extend past the inner shild ring, and should not be set back from the inner shield ring by a noticable amount. Different vendors of the type N connector may vary slightly, but all will be compatable, and thus similar. A small set of calipers with a depth gauge make a decent addition to your tool-bag. Also look out for 75 ohm Type-N connectors. They are less common and have a smaller center pin. As such a 75 ohm connector is not likely to damage a 50 ohm connector, but the 75 ohm connector could be damaged. likewise, because the 75 ohm connector is smaller, poor connection may be made when interfaced with a 50 ohm connector.
I bumped into rflabs.com.au while looking for semi rigid coax's. They have 35 ohm semi-rigid in both .141 and .250 sizes. Anyone used any of this? They are located in Victoria, much closer to you guys than me. I was thinking it would be nice to use .250 coax on the output of the amplifier to the hybrid, to cut down on the resistive losses. Winding it through a ferrite might be more of a challenge, byt maybe some sort of split core could be used to help.
Rflabs/au also have low PIM 7/16 DIN to N type adapters. Might be a decent accessory for the amplifier, if the price is within our reach Adapters are easier to replace from damage, rather than connectors installed on the chasis.
-Greg, N2GZ
UHF connectors have the large center pins and can handle lots of power, but because they are non-constant impedance this creates passive IMD issues even on 144 when elevated powers are used. I also recomend avoiding connectors made from ferromagnetic materials such as nickel or steel, as they can generate passive IMD especially at higher power levels. Brass/Bronze/Copper/Silver/Gold materials are preferred.
Always inspect your Type-N connectors before installation. Sadly many type N cables I find here that were constructed by hams do not meet spec. The tip should not extend past the inner shild ring, and should not be set back from the inner shield ring by a noticable amount. Different vendors of the type N connector may vary slightly, but all will be compatable, and thus similar. A small set of calipers with a depth gauge make a decent addition to your tool-bag. Also look out for 75 ohm Type-N connectors. They are less common and have a smaller center pin. As such a 75 ohm connector is not likely to damage a 50 ohm connector, but the 75 ohm connector could be damaged. likewise, because the 75 ohm connector is smaller, poor connection may be made when interfaced with a 50 ohm connector.
I bumped into rflabs.com.au while looking for semi rigid coax's. They have 35 ohm semi-rigid in both .141 and .250 sizes. Anyone used any of this? They are located in Victoria, much closer to you guys than me. I was thinking it would be nice to use .250 coax on the output of the amplifier to the hybrid, to cut down on the resistive losses. Winding it through a ferrite might be more of a challenge, byt maybe some sort of split core could be used to help.
Rflabs/au also have low PIM 7/16 DIN to N type adapters. Might be a decent accessory for the amplifier, if the price is within our reach Adapters are easier to replace from damage, rather than connectors installed on the chasis.
-Greg, N2GZ
-
VK4DD
Re: 144 Mhz home brew 600W solid state PA
Hi Greg,
Never knew we sold 35 Ohm coax in VK... but my quess is that these guys are very expensive.
Believe it or not but most RF components are cheap in the US or China other markets inport their components from these countries and that makes them more expensive.
The UT141-35 is more than enough to handle 300W and when used on material 61 than the heat is not concentrated in one spot but more evenly spread-out over the winding
compared to material 43. UT250-35 (1/4 inch 35 Ohm) is far to heavy to make these small turns. I would not recommend that.
Apart from that ... It would cost you a fortune. It would be intresting to know what UT250-35 would cost because you can make nice high power combiners from that coax.
I have always seen the 7/16 connector as a connector for high power but now I start to realize than you can have 1dB loss or more in a connector where the pin contact is not real flash.
If you run 100W than you might not notice this in your SWR but 300W needs good connections.
I have bought some 7/16 connectors over the years which I will start using on my equipment from now on.
I received a picture from Wayne VK5APN over the weekend showing his progress on the BLF248 amplifier.
Wayne VK5APN is making good progress with his amplifier. I received some pics from him, and I must say his soldering skills are very nice.
Wayne used plenty grounding screws so I don't expect we will have a problem there.
I will attach the picture because I think it will be usefull also to others who want to build this single BLF248 amplifier (Single board BLF248 MKII).
Although the circuit board is not blue, the layout is copied from the blue MKII design. So it should give high efficiency and high power.
Other than that... i have made the last bit of documentation for the GLCD Station monitor.
It is an example how I interface the SWR trip from Jim W6PQL PCB to the Picaxe.
Some circuit did not have the kathode of the LED connected to GND as such I needed to use an Opto coupler.
Perhaps there other solutions also... this is what I have used here and it seems to work fine.
http://www.vk4dd.com/forum/viewtopic.ph ... 6&start=10
It won't be long now... but who ever hits the 10.000 post here on this forum can email me...
I got a surprise for him or her.
73's Ron
VK4DD
Never knew we sold 35 Ohm coax in VK... but my quess is that these guys are very expensive.
Believe it or not but most RF components are cheap in the US or China other markets inport their components from these countries and that makes them more expensive.
The UT141-35 is more than enough to handle 300W and when used on material 61 than the heat is not concentrated in one spot but more evenly spread-out over the winding
compared to material 43. UT250-35 (1/4 inch 35 Ohm) is far to heavy to make these small turns. I would not recommend that.
Apart from that ... It would cost you a fortune. It would be intresting to know what UT250-35 would cost because you can make nice high power combiners from that coax.
I have always seen the 7/16 connector as a connector for high power but now I start to realize than you can have 1dB loss or more in a connector where the pin contact is not real flash.
If you run 100W than you might not notice this in your SWR but 300W needs good connections.
I have bought some 7/16 connectors over the years which I will start using on my equipment from now on.
I received a picture from Wayne VK5APN over the weekend showing his progress on the BLF248 amplifier.
Wayne VK5APN is making good progress with his amplifier. I received some pics from him, and I must say his soldering skills are very nice.
Wayne used plenty grounding screws so I don't expect we will have a problem there.
I will attach the picture because I think it will be usefull also to others who want to build this single BLF248 amplifier (Single board BLF248 MKII).
Although the circuit board is not blue, the layout is copied from the blue MKII design. So it should give high efficiency and high power.
Other than that... i have made the last bit of documentation for the GLCD Station monitor.
It is an example how I interface the SWR trip from Jim W6PQL PCB to the Picaxe.
Some circuit did not have the kathode of the LED connected to GND as such I needed to use an Opto coupler.
Perhaps there other solutions also... this is what I have used here and it seems to work fine.
http://www.vk4dd.com/forum/viewtopic.ph ... 6&start=10
It won't be long now... but who ever hits the 10.000 post here on this forum can email me...
I got a surprise for him or her.
73's Ron
VK4DD
- Attachments
-
- Wayne VK5APN single BLF248 MKII board
Last edited by VK4DD on Sat Nov 28, 2009 10:40 am, edited 1 time in total.
-
VK4DD
Re: 144 Mhz home brew 600W solid state PA
Hi Gents,
It has been an interesting week so far. I have been helping hams to sort out antenna/coax problems....
Lately all problems have been related to bad N-connectors... water in the coax, too many joints, bad antenna connections etc etc.
If you run a bit of power ... than you need to insure your antenna system is in good condition.
For example I had a ham who had his amplifier constantly tripping.
The problem was a bad piece of coax. I was surprised to hear he used 3 different pieces of coax from the antenna to the amplifier.
This means a heap of connections, losses and points were water can get into the coax.
An other source of bad contact is the copper to aluminum interface at the antenna.
M2 does it nice with a machined block and hermetically sealed with silicon. These usually last 5 to 7 years before you have to open them up and install a new copper wire.
I use some Vaseline and hammer a new piece of copper in place. Than I reseal the box with Silicon and you hopefully you can enjoy the antenna for an other 5 years.
How often you need to clean up your antenna depends on your location. Near the Sea? or air polution (near by industry) can reduce this period to a yearly exercise.
But above all make sure the antenna and all the connectors you are has a VSWR of 1:1 to 1:1.5
Up to 100W you can get away with some bad connections ... but hey 300W or more will show all the problems you have in your antenna system.
If you use LMR200 see if you can get the professional version which has silicon in the dielectric. This has less problems with water.
If birds like to chew on your coax
.... mount it under the boom. Use hose clamps instead of tie-wrap 
s (ouch).
A big plastic OWL in the tower might help as well.... As long as it has scary EYES... paint two sets of eyes on the front or on the back.
Please put some effort in the antenna system.
You will be rewarded with a good VSWR and more DX.
Keep your amp happy
73 Ron
VK4DD
It has been an interesting week so far. I have been helping hams to sort out antenna/coax problems....
Lately all problems have been related to bad N-connectors... water in the coax, too many joints, bad antenna connections etc etc.
If you run a bit of power ... than you need to insure your antenna system is in good condition.
For example I had a ham who had his amplifier constantly tripping.
The problem was a bad piece of coax. I was surprised to hear he used 3 different pieces of coax from the antenna to the amplifier.
This means a heap of connections, losses and points were water can get into the coax.
An other source of bad contact is the copper to aluminum interface at the antenna.
M2 does it nice with a machined block and hermetically sealed with silicon. These usually last 5 to 7 years before you have to open them up and install a new copper wire.
I use some Vaseline and hammer a new piece of copper in place. Than I reseal the box with Silicon and you hopefully you can enjoy the antenna for an other 5 years.
How often you need to clean up your antenna depends on your location. Near the Sea? or air polution (near by industry) can reduce this period to a yearly exercise.
But above all make sure the antenna and all the connectors you are has a VSWR of 1:1 to 1:1.5
Up to 100W you can get away with some bad connections ... but hey 300W or more will show all the problems you have in your antenna system.
If you use LMR200 see if you can get the professional version which has silicon in the dielectric. This has less problems with water.
If birds like to chew on your coax
.... mount it under the boom. Use hose clamps instead of tie-wrap s (ouch).A big plastic OWL in the tower might help as well.... As long as it has scary EYES... paint two sets of eyes on the front or on the back.
Please put some effort in the antenna system.
You will be rewarded with a good VSWR and more DX.
Keep your amp happy
73 Ron
VK4DD
- Attachments
-
- Good coax is important
I found this picture on the net from some one who run a bit of power trough RG213 on 23cm :-)
-
VK4DD
10.000 HITS thank you 73... BLF248 thread it's time to move
Hi Gents,
I just noticed we are past the 10.000 hits on this thread.
Thank you for reading my posts and for your interest in our home brew projects.
My BLF248 amp has been in heavy use on a daily basis and is still doing the job as well as the very first day I started using it.
48V DC has become a "standard" voltage for high power Mosfet devices. Single Mosfets produce up to 1.2kW pulse (radar).
These same devices are capable of 500 to 600W used conservatively with a max VSWR of 10:1.
However they are not as forgiving as this design... The option to power it up from 12V batteries is possible but it becomes a bit unpractical to use 4 batteries.
That is why I still like these 28V fets.
A single BLF248 MKII is all I need for portable work.
For a portable amplifier I seem to favor my single BLF248 MKII board. This gives me 300W in the field with very high efficiency.
I worked ZL1BK with this amp over a 2300KM tropo path and he reported that he never heard such a strong signal from VK4.
That was a nice compliment... but the propagation was also giving me a hand. He was using a 6EL yagi at the other end and gave me 5/9+.
I used a single 5WL yagi from M2 (very light and convenient for portable work) from an elevated location near home at 250M ASL over looking Brisbane and the Ocean.
As an advocate of more power, I must admit that I see no need to run more power from a good portable location and when the band is wide open in summer. .
I also liked the battery powered station I used 2 x 12V 205AH batteries in series (ex telecoms) . which gave me 26.5V unloaded and 24.4V under load.
This is so nice to have no generator or other noise on the back ground while getting good power on VHF.
However during poor propagation it just gives you a few extra dB allowing you to make that contact.... this could make up for power line noise on the other end or a receiver with a high NF.
I hope that every one has enjoyed this project as much as I did.
Patrick and I will be moving on to other projects and we will be on our own forum
http://www.vk4dd.com/forum
Completing other projects such as a GPS grid square location display, a 10Ghz TRX etc etc.
Just something else than amplifiers
73 Ron
VK4DD
I just noticed we are past the 10.000 hits on this thread.
Thank you for reading my posts and for your interest in our home brew projects.
My BLF248 amp has been in heavy use on a daily basis and is still doing the job as well as the very first day I started using it.
48V DC has become a "standard" voltage for high power Mosfet devices. Single Mosfets produce up to 1.2kW pulse (radar).
These same devices are capable of 500 to 600W used conservatively with a max VSWR of 10:1.
However they are not as forgiving as this design... The option to power it up from 12V batteries is possible but it becomes a bit unpractical to use 4 batteries.
That is why I still like these 28V fets.
A single BLF248 MKII is all I need for portable work.
For a portable amplifier I seem to favor my single BLF248 MKII board. This gives me 300W in the field with very high efficiency.
I worked ZL1BK with this amp over a 2300KM tropo path and he reported that he never heard such a strong signal from VK4.
That was a nice compliment... but the propagation was also giving me a hand. He was using a 6EL yagi at the other end and gave me 5/9+.
I used a single 5WL yagi from M2 (very light and convenient for portable work) from an elevated location near home at 250M ASL over looking Brisbane and the Ocean.
As an advocate of more power, I must admit that I see no need to run more power from a good portable location and when the band is wide open in summer.
.I also liked the battery powered station I used 2 x 12V 205AH batteries in series (ex telecoms) . which gave me 26.5V unloaded and 24.4V under load.
This is so nice to have no generator or other noise on the back ground while getting good power on VHF.
However during poor propagation it just gives you a few extra dB allowing you to make that contact.... this could make up for power line noise on the other end or a receiver with a high NF.
I hope that every one has enjoyed this project as much as I did.
Patrick and I will be moving on to other projects and we will be on our own forum
http://www.vk4dd.com/forum
Completing other projects such as a GPS grid square location display, a 10Ghz TRX etc etc.
Just something else than amplifiers
73 Ron
VK4DD
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VK4DD
Re: 144 Mhz home brew 600W solid state PA
Hi Gents,
It has been quiet for some time on the forum and that is usually for a reason.
Patrick and I have been thinking about the way we build and control amplifiers.
We had good results making our solid state amplifiers ... but boy we needed a Swag of PCBs to control and monitor this.
There had to be a way to do this easier and better.
History
The way I used to make my amplifiers I used various circuit boards for various tasks.
- a W6PQL amplifier board (used for protection and sequencer).
Jim has done a wonderful job on making these kits available to Hams all over the world.
- Fet Switch or Solid state relay (used to switch of the supply to the amplifier).
- A Station monitor PCB (used to collect data, output power, Volts amps, and display trip etc).
- A display to show all the information.
- Power supply modules to make 12V.
- A PCB to measure current.
I counted at least 5 different functions and at least 5 circuit boards in total (not including the Display) !!
Read more about this topic in the VK4DD forum.
Amateurs for Amateurs.
http://www.vk4dd.com/forum/viewtopic.php?f=15&t=107
73 Ron
VK4DD
It has been quiet for some time on the forum and that is usually for a reason
.Patrick and I have been thinking about the way we build and control amplifiers.
We had good results making our solid state amplifiers ... but boy we needed a Swag of PCBs to control and monitor this.
There had to be a way to do this easier and better.
History
The way I used to make my amplifiers I used various circuit boards for various tasks.
- a W6PQL amplifier board (used for protection and sequencer).
Jim has done a wonderful job on making these kits available to Hams all over the world.
- Fet Switch or Solid state relay (used to switch of the supply to the amplifier).
- A Station monitor PCB (used to collect data, output power, Volts amps, and display trip etc).
- A display to show all the information.
- Power supply modules to make 12V.
- A PCB to measure current.
I counted at least 5 different functions and at least 5 circuit boards in total (not including the Display) !!
Read more about this topic in the VK4DD forum.
Amateurs for Amateurs.
http://www.vk4dd.com/forum/viewtopic.php?f=15&t=107
73 Ron
VK4DD
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ZL2WHO
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- Joined: Mon Dec 28, 2009 6:10 am
- Location: Palmerston North En Zed
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Re: 144 Mhz home brew 600W solid state PA
Looking foward to seeing this PCB roll off the production line. I will be one that is in line for a board or two. Cheers mark.
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N2GZ
Re: 144 Mhz home brew 600W solid state PA
Amazing work Ron, thanks for sharing your designs with us.
I have been working on the same thing, an amplifier control for my various SSPAs. Looks like you have made more progress though.
It looks like discussion has moved over to your site, and I will follow along there, kinda off topic for this thread anyhow.
-GZ
I have been working on the same thing, an amplifier control for my various SSPAs. Looks like you have made more progress though.
It looks like discussion has moved over to your site, and I will follow along there, kinda off topic for this thread anyhow.
-GZ
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9A5BS
Re: 144 Mhz home brew 600W solid state PA
Hello to everybody,
you have great forum, and this thread is very interesting. I am very interested for building this 600W 2m amplifier, but unfortunately don't have PCB board. Does anybody know or somebody have PCB layout and schematic for MK1 version of amplifier? Thanks.
Felix
you have great forum, and this thread is very interesting. I am very interested for building this 600W 2m amplifier, but unfortunately don't have PCB board. Does anybody know or somebody have PCB layout and schematic for MK1 version of amplifier? Thanks.
Felix
Re: 144 Mhz home brew 600W solid state PA
Lou - VK3ALB
Being right doesn't excuse bad behaviour
Being right doesn't excuse bad behaviour
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ZL2WHO
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- Joined: Mon Dec 28, 2009 6:10 am
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Re: 144 Mhz home brew 600W solid state PA
Hi Felix. I have 2 of these, http://www.communication-concepts.com/ar313.htm The twin amp has 1 combiner for 6m and another for 2m. I get about 750 watts on 6m and 600 watts on 2m. Just need some propergation !! Keen to discuss if your interested. Regards, Mark ZL2WHO.
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9A5BS
Re: 144 Mhz home brew 600W solid state PA
Thanks for quick reply Lou and Mark. I think I will buy PCB from Ron. I recently bought from Ebay SR401 RF power VDMOS transistor, and read in this forum that this transistor have the same performance like BLF248, but it's cheaper, and little better efficiency... so I will try with this one. For the start I will try to build one module amp, and then after if it all be OK I will build the other one.
Felix
Felix
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ZL2WHO
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- Joined: Mon Dec 28, 2009 6:10 am
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Re: 144 Mhz home brew 600W solid state PA
Hi Felix.
You cant go wrong there, I did not Rons amps when I started building with mrf151g. Althow i have good results with mine Ron has put alot of effort into his PAs and he is good to chat with. 73 Mark
You cant go wrong there, I did not Rons amps when I started building with mrf151g. Althow i have good results with mine Ron has put alot of effort into his PAs and he is good to chat with. 73 Mark
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VK4DD
Re: 144 Mhz home brew 600W solid state PA
Hi Felix and others,
The information is not maintained by me in this forum.
I don't use this form a lot these days. As such follow the topic on my site
http://www.vk4dd.com/forum
I would recommend to read it because it shows as lot techniques used. Some are good others not so good.
It certainly shows how much work is involved and that not everything goes right.
Be also aware that the info might not always be up to date in this forum.
As far as the SR401 on Ebay. There have been some problem fets from Ebay from sellers who did not sell you the real fets.
It is possible that they are not aware of that because they bought them also via via.
The SR401 I saw on ebay looked different from the ones I used. But even if they look the same they could be different.
Don't expect to see more than 300W out of an original SR401 also.
So as far as FETS go only though the official dealers. Ask the manufacturer of the Fet where to buy.
That is a valid point for the NXP / Phillips fets but also for the SR401 fets.
It is not my intention to hijack this forum but I simply don't log in often enough to give you up
to date feedback.
Also be aware that you can blow a fet up quicker than you can wink with your eye.
That is the experience we have now
.
The SR401 is not a drop in replacement for the SR401 but it does work ok in the first generation PCB.
Currently I have the MKII PCB which give the BLF248 a higher efficiency.
The price of the BLF248 has sort of sky rocket and I would not use it for new projects.
It simply gets to expensive now... I was shocked to see a price of US$230 for a Fet of 300W.
That is not funny any more. New fets have entered the market with as much as 600W out of single fet.
Even higher powers are possible but than the duty cycle is limited.
Have fun home brewing / experimenting with my PCB's.
73 Ron
VK4DD
The information is not maintained by me in this forum.
I don't use this form a lot these days. As such follow the topic on my site
http://www.vk4dd.com/forum
I would recommend to read it because it shows as lot techniques used. Some are good others not so good.
It certainly shows how much work is involved and that not everything goes right.
Be also aware that the info might not always be up to date in this forum.
As far as the SR401 on Ebay. There have been some problem fets from Ebay from sellers who did not sell you the real fets.
It is possible that they are not aware of that because they bought them also via via.
The SR401 I saw on ebay looked different from the ones I used. But even if they look the same they could be different.
Don't expect to see more than 300W out of an original SR401 also.
So as far as FETS go only though the official dealers. Ask the manufacturer of the Fet where to buy.
That is a valid point for the NXP / Phillips fets but also for the SR401 fets.
It is not my intention to hijack this forum but I simply don't log in often enough to give you up
to date feedback.
Also be aware that you can blow a fet up quicker than you can wink with your eye.
That is the experience we have now
.The SR401 is not a drop in replacement for the SR401 but it does work ok in the first generation PCB.
Currently I have the MKII PCB which give the BLF248 a higher efficiency.
The price of the BLF248 has sort of sky rocket and I would not use it for new projects.
It simply gets to expensive now... I was shocked to see a price of US$230 for a Fet of 300W.
That is not funny any more. New fets have entered the market with as much as 600W out of single fet.
Even higher powers are possible but than the duty cycle is limited.
Have fun home brewing / experimenting with my PCB's.
73 Ron
VK4DD