ELECTROMAGNETIC RADIATION occurs from an OPEN HIGH POWER AMP.
Some manufacturers like NEC, do not permit field service of amplifiers and they may only be powered up in workshop conditions.
If you choose to run one of these PAs OPEN you risk injury to your eyes, you may suffer RF burns.
They are not toys or 2M radios
they are 1/2 and 1 KW AMPS running at voltages which may cause electric shock and injury.
This has been done to death elsewhere but having seen the degree of difficulty and
COST of converting Video (NO I STAND CORRECTED VISION)
Solid state POWER amps to 6M and 2M band here are my thoughts and solutions for an easy 400w rated amp..
BROADBAND VISION or AURAL they can be swapped into either MODE.
46-108 MHZ
CH0-CH4.
SOURCES:
Old TV sites.
Contact local techncial manager or Prime, Southern Cross or WIN TV,
or local DMB Broadcast Australia.
DO NOT CALL BROADCAST AUSTRALIA SYDNEY the answer is NO.
What you need
An IPA ( Intermediate Power Amplifier) or half a main power amplifier.
from a LARCAN
or from an ITELCO
or from an NEC
or Harris but havent found any in VK and from US $500 + freight.
My choice
LARCAN IPA 2 VIsion DRIVER stage rated at 400 watts CCS.
ex Ch1 Ch2 CH0 or CH3 they are all the same driver stage.
If you use half a MAIN PA you will have to purchase two broadband ANAREN ISO couplers and remove the CH1 couplers.
Part number 1A0230-2 rated at 500-700 watts.
Col VK5DK has the details.
If you blow any fets VK5PJ says a set of four are $250 ex USA.
If you blow fets you have to use the fet mounting proceedure and a tension wrench to tension them down or they will blow again.
If you get any PAs from WAGGA many had blown fets, the TX was operating with several stages in distress.
Mt Burr PAs imo were all working 100%.
IPA 2. B/B VISiON DRIVER.
Get rid of the Coupler x 6 way not needed, so shown here is what you need to keep.
DC BIASING ONLY:
Do this before mounting without any rf drive applied.
Adjustments on LARCAN CLUSTER but basically lift each fuse use, dc mm to adjust idle pots after applying 50 VDC
and set to manufacturers idle current.
Less power bias them back less to cut off.
CW maybe 200 ma to 250ma.
Lots of reading material on FET idle currents, you choose.
MOUNTING CHOICES:
FIND A BIG AERATED BOX or an enclosed 18 inch rack.
Mount PA inside bottom lid of box.
Using two sets of side rails the one you got and the one you scrounged,
mount the pa upside down in a box after connecting RF and DC wiring QED..
Serves as RF screen.
Unbolt side rails, disconnect all silicon coax and wiring.
Discard 6x filter and 7KG heat sink good for some other project.
Mount rh brackets or two end pieces ex Larcan onto heat sink/IPA
and after connecting up DC, and setting IDLE CURRENT to 400-500 Ma for each chipset
mount it all and forget it.
Buy yourself a COMET Model CF-50MR 1KW low pass filter from local retailer or build a LPF
http://www.realhamradio.com/DC_54_mhz_l ... filter.htm
OH! while at TV site SCROUNGE Cooling Tray from NEC UHF TX ex SBS which has been switched off also.
Every site has one of these txers with two exciters and two fan trays.
Slide out exciter on this tx and remove two screws and power leads and you have your fans.
They will be stuffed so buy four new fans 12V 24V 50V whatever.
You have 12V and 50V power so choose the way you feed the fans,
cut the edges off the NEC 1RU or mount it in the rack.
and mount fans on top cover.
So far so good.
FILTER ESSENTIAL
You put that IPA on air without this and a KNOCK will be on your door..
The blue wire is SILICON by the way..
So cooling is done
Next relays your choice, I used Dowkey well rated at 400 watts.
And Sm P/S ex EBAY $50.00
Terminals are a bit of a problem and mine are a bit dodgey.
RF drive 3-5 watts 400w pep out easy.
APPLYING DRIVE.
NB MAKE SURE YOUR RADIO DOESNT HAVE AN ALC SPIKE.
These IPAs are 20-23 db in gain so a spike will punch the daylights out of your fets.
MAIN PA has protection IPA 2 does not.
If you want a smaller project get an IPA1 rated at 50 watts they are the SOUND and VIDEO First driver stages.
QED.
Take care dont get into trouble, if in doubt seek assistance from a more experienced ham.
