VK Logger Ham Radio Forum Archive

Has anyone on the forum used one of these for 70cm ? -
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... K:MEWAX:IT

73 Mike VK6MB

Just not sure how much work is involved setting it up.
I don't think it is just plug and play

73 Mike

Hi There Mike,

VK6MB wrote:Has anyone on the forum used one of these for 70cm ? -
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... K:MEWAX:IT

73 Mike VK6MB

I have two of these PA boards here that I sourced via a UK suppier on ebay, he was happy to strip out just the PA's and send them as bare boards with no heatsinks to save on freight. Not had a chance to put volts on them yet but have heard good stories from around the traps about them.

Regards,

Hi Peter,
this seller will do the same thing.What I am concerned about, is the lack of test equipment etc that I have and may require to set this up to work with my Rigs.

73 Mike

Hi All
I have two of the amplifier Pcb's as well. Don't buy from the supplier on Ebay as there is a second source which is cheaper.
Contact me before any purchase. My supplier is keen to see some working here in Australia but loath to send out anymore until he knows that their use has been successful.
There are at least 4 Pcb's here in Vic but it may take a while to see any on air. The man who sold me mine has been able to get 220 watts out of his by just doing the mod to the bias network so as to make the unit work in class B. As it comes it is set for many amps of standing current and a very clean output due to it;s use as a digital TX/RX.

The draw backs to using one is the dc power of 28 volts at 30 amps required and that the Power module is part of a much larger Pcb. No one that I know of has cut out the TX rf section to make a smaller easier managed board yet LOL. The rest of the large Pcb serves no purpose so you should be able do with out it.
The next problem is the heat sink requirements which will need to be large and with fan assisted cooling. You can buy the original box and heat sink that was used by the manufacturer but postage costs from the UK then becomes prohibitive with air mail. It can be sent via Sea but it wont arrive for 3 months.

Any questions ??? if you have any post them here so every one can get a better Idea of what and how to use one.

NOW a question from me to Mike VK6MB did you get the circuit or manual from where you bought yours ? as my supplier doesn't have one and yours wont part with one unless you buy from them as I've asked LOL

Best regards Fred VK3AZG aich1942@bigpond.com

Are you sure of the DC power requirements, Fred? The figures you quote, 220W output for 30A @ 28V (i.e. 840W DC input) calculates to 26% efficiency. That seems far too low a figure for a modern FET device and would need a MIGHTY big heatsink to ditch the remaining 620W of heat. From the photo on ebay the device looks to be a BLF548. Its data sheet http://www.nxp.com/documents/data_sheet/BLF548.pdf quotes an efficiency >50% (typically 55%) at 500MHz/150W output.

Philips rates this device at 150W, so 220W would be pushing it pretty hard into saturation.

Hi
There are two BLF548's on the Pcb so your calculations are right for one BLF548 so double it and you end with 50% or so efficiency.

Regards Fred

VK3AZG wrote:Hi All
I have two of the amplifier Pcb's as well. Don't buy from the supplier on Ebay as there is a second source which is cheaper.
Contact me before any purchase. My supplier is keen to see some working here in Australia but loath to send out anymore until he knows that their use has been successful.

grrrr you posted that too late I have already ordered one from the UK guy
will be interesting to see what I can do with it

cheers
Dave

Hi

There are two BLF548's on the Pcb so your calculations are right for one BLF548 so double it and you end with 50% or so efficiency.

If there's 840W going in and 220W coming out then the efficiency is 26% regardless of the number of devices involved.

Iain

Hi
You are looking at the capacity of the P/supply not the current drawn by the Fets.

The 840 watts is to assure that the 28 volts doesn't sag to much when the Fets draw 400 to 600 watts from the Psu. Hope this clears up your comments, perhaps I should have been a little clearer with my description.

Regards Fred

Hi Fred,
how much cheaper?
I have emailed him and can get the complete unit sent to Manchester UK, where I will be visiting in May next year and then can bring it back with me.
This will save sourcing a suitable heatsink etc.
I would be very happy to share the cct info with all concerned, then again we might be able to get the info from Dave now
I am just a little afraid it might be more than I can handle as I have very little test equip.

73 Mike

email me if you would like the info

73 Mike

Hi Has anyone got there Nokia TTRX up and running, I am just about to power mine up. 73 Gary VK2KYP

VK2KYP wrote:Hi Has anyone got there Nokia TTRX up and running, I am just about to power mine up. 73 Gary VK2KYP

I have one but no where near ready yet. Let me know how you go.
Fred VK3AZG

and I have too many other projects on the go ... But I do glance at and admire the board from time to time

Current main project is the assembly of the DEM 3.4 GHz xverter kit, hopefully up and running within the next week or 2

cheers
Dave

Hi All
I've decided not to ahead with modifying my 1.5 qty pcb LOL
I'M TO OLD and at the moment to depressed to care.
Look on VKHam tomorrow 19/3/11 for my add after lunch.
Free postage for VK logger members.

Fred Vk3azg

I don't bring mine back from the UK til June

I just ran one up this week and found it essential to bypass the output directional coupler to stop it melting.

After that 30W of drive and 28V at 17A gave a steady 250W RF.

At that power it will be SSB and CW duty I'd say.

73 de Paul GW8IZR

Old post, but I know I won't do anything with mine now.
It is the complete unit with Heatsink - I have never opened or applied power.
I have two 28V@300W power supplies also.

If anyone is interested email me via mycallsign@wia.org.au

73 Mike VK6MB

I will probably just stick it up for sale

73 Mike VK6MB