Broadcast Concepts P1000FM-188PLA User manual

Broadcast Concepts Inc
11700 NW 102nd Road Suite 4Medley FL 33178
Tel: [phone] FAX [phone]
Broadcast Concepts Inc
Revised 8/20/2014 1
Model P1000FM-188PLA FM Pallet Amplifier
Electrical Specifications
Characteristics min typ max unit
Operating Frequency range 87.5 108.1 MHz
peak saturated power (@ 50V) 1000 1050 1100 W
P1dB @ 50V 900 W
Power Input 5.0 6.75 W
Input VSWR 1.2 1.7 VSWR
Power Gain 22 24 25 dB
Amplifier efficiency @ 1000W 82 85 87 %
Absolute maximum current rating - - 26 A dc
Insertion Phase variation (unit to unit) - +/-3.5 - degrees
Power gain (unit to unit) - +/-1.0 - dB
F2 Second Harmonic -35 -40 - dB
F3 Third Harmonic -25 -30 - dB
Bias Current Factory set @50V. 90 100 110 MA dc
Drain voltage supply 28 48 52 V
Base plate operating temperature 0 n/a 70 Celsius
Load Mismatch (All phase angles,
Id=16A, 10 seconds) 65:1 VSWR
Shipping Weight 1.5 LBS
This amplifier module is ideal for final
output stages in FM Broadcast
Applications.
•87.5 – 108.1MHz (FM BAND)
•50 Volts
•Input/output 50 ohms
•Pout: 1000W minimum
•Up to 85% efficiency
•24dB Gain
•NXP BLF188XR Mosfet
•Planar RF Transformers
Dimension (L x W x H inch) [5.00” x 2.375” x 0.85”]

Broadcast Concepts Inc
11700 NW 102nd Road Suite 4Medley FL 33178
Tel: [phone] FAX [phone]
Broadcast Concepts Inc
Revised 8/20/2014 2
The mechanical drawing may be downloaded in DXF format: http://broadcastconcepts.com/177300/PCB10222.DXF
Heatsink Mounting/Hardware
Tips for Mechanical Mounting:
1 All mounting holes are 0.156 inch thru and they are designed for a #6 Screw. Stainless Steel mounting hardware
is recommended, grade 18-8 or better. A lock washer of same material should also be used.
2 Ensure mounting surface is flat to better than 0.0025”
3 Use a thin layer of thermal compound on the backside of the PA - no more than 0.001” - 0.002” thickness!
4 Torque all screws to 10-12 in-lbs
Use of cooling air on top of pallet to keep the PCB cool is recommended but not required. There is a thermal pad
under the output side of the PCB. Most of the heat is dissipated through the ¼ inch copper base plate.
Warning: Failure to use a proper heat sink and/or improper installation will cause the transistors to burn out. This
type of failure is not covered by warranty. This product can be ordered with a custom heat sink. Please contact
factory for more information.
Electrical Drawing: Figure 1

Broadcast Concepts Inc
11700 NW 102nd Road Suite 4Medley FL 33178
Tel: [phone] FAX [phone]
Broadcast Concepts Inc
Revised 8/20/2014 3
Electrical Notes:
There is 1 +50V pad for the main power supply. The Meanwell RSP1500 is the suggested power supply
for this amplifier. Do not attempt to connect ground to the pallet or modify the PCB for ground
attachment. Ground can be attached to the heat sink that the pallet is mounted on.
The pot VR1 marked “Bias” controls the bias current for BLF188XR. The factory setting is 100ma and
adjustment is not required.
The adjustment pot VR2 marked sets up the thermal compensation slope. Adjustment of this pot is not
required; however, if it is accidently tampered with simply re-adjust it until “7.2 volts” is present at TP1 as
this is the factory setting. “Bias disable” removes bias voltage from the transistor. A voltage above 2.0V is
required to activate the “bias disable” condition.
If coax cables are being soldered to the module use Teflon cables MIL-C-17 rated only. Do not use a coax
larger than RG402 on the output. Attempting to solder large coax cables like LMR400 directly to the PCB
may damage the pallet and render it beyond economical repair. The best cable for the output is 0.141 inch
conformable 50 ohm type.
If transistor replacement is necessary always verify that the bias circuits are functioning before installing
new parts. Transistor pocket must be cleaned with alcohol, all debris removed and new thermal compound
applied prior to installing new transistor. Bias voltage should be adjusted to 0.5V before new part is
installed. We assume no responsibility for self repairs. Please consider sending pallet back to factory for
service.
When bias adjustment is required always use a small lab supply that is current limited. This will prevent
accidental over bias and loss of a transistor.
Warning: Solid state amplifiers can be easily destroyed! Operating the amplifier outside of its
specifications will cause the mosfets to fail. These failures are not covered by warranty.
•Do not over drive the amplifier.
•Do not run the amplifier into an open circuit. Do not run the amplifier when the SWR is unknown.
System integrator must foresee adding VSWR protection if there is a risk that the amplifier will be
subjected to high VSWR conditions. Do not adjust the bias settings or attempt transistor
replacement without a current limited lab supply.
•Do not allow the amplifier to overheat. Do not let the base plate temp exceed 70C. This amplifier
is capable of dissipating over 350W in the maximum working condition. This product requires
prior experience working with high power RF amplifiers. This is not for beginners.
•This amplifier has been designed for analog FM broadcast. Performance in digital FM has not been
evaluated.
•Expensive test equipment like RF wattmeters, dummy loads, Ammeters and thermal meters are
required to verify proper installation. Operating this amplifier without this equipment is like

Broadcast Concepts Inc
11700 NW 102nd Road Suite 4Medley FL 33178
Tel: [phone] FAX [phone]
Broadcast Concepts Inc
Revised 8/20/2014 4
driving blind. You won’t be able to see what’s really going on and the end result could be
transistors that burn out.
Calculating Die Temperature:
How do you know if the amplifier is running to hot? There are symptoms to watch for. If there is a
significant drop in power of more than 5% over a short period of time the amplifier is likely overheating.
There is a scientific method that must be used to verify that the amplifier is installed and running within
thermal limits. We do not recommend the “dropping power with time test” described above.
Use the thermal resistance (Rth) of the device to calculate the junction temperature. The Rth from the
junction to the device flange for the BLF188XR is 0.11 °C /W. If the device is soldered down to the pallet
baseplate, this same value can be used to determine Tj. If the device is greased down to the pallet
baseplate, the Rth(j-h) value becomes 0.26K/W, as the thermal resistivity for the grease layer from the
flange to the baseplate is approximately 0.15 °C /W.
Note: We always use thermal grease under transistors because soldering them directly would render the
pallets unserviceable.
Example: Assuming that the device is running at 950W with the RF output power at 48V while
consuming 25.3 amps on a pallet baseplate (e.g. 70 °C). Tj can be determined based on this condition for
the given baseplate temperature:
• Dissipated power (Pd) = (48V x 25.3A) – (950W) = 264.4W
• Temperature rise (Tr) = Pd ´ Rth = 264.4W (0.26 °C/W) = 68.7 °C
• Junction temperature (Tj) = Th + Tr = 70°C + 68.7 °C = 138.7 °C
The best way to make this calculation is to measure the temperature of the transistor flange directly. In this
case temperature rise is calculated using 0.11°C/W.
The maximum junction temperature for most LDMOS devices is 200C. We suggest staying under 175C.
In the example above a base plate temperature of 70C was used. When the pallet is mounted to an efficient
heatsink like one of our bonded fin models base plate temperatures in the 50C range are easily maintained
at full output power.

Broadcast Concepts Inc
11700 NW 102nd Road Suite 4Medley FL 33178
Tel: [phone] FAX [phone]
Broadcast Concepts Inc
Revised 8/20/2014 5

Broadcast Concepts Inc
11700 NW 102nd Road Suite 4Medley FL 33178
Tel: [phone] FAX [phone]
Broadcast Concepts Inc
Revised 8/20/2014 6
Low Pass Filter
A low pass filter is required to reduce harmonics. Harmonics from FM transmitters are regulated by most
government regulatory authorities. Any of our low pass filters rated for at least 1000 watts can be used with this
pallet. It is critical to install a 6.0 (or longer) inch piece of RG400 between the pallet output and the filter input to
prevent a filter reaction. When a filter reaction occurs the pallet sees a high mismatch which can cause the transistor
to overheat and slowly burnout. The cause of filter reactions is not fully understood; however, reflected harmonic
energy at a certain phase and frequency is strongly suspected. Filter reactions do not occur when 2 or more
amplifiers are power combined since the combiners provide isolation from the low pass filter.
The BLF188XR can operate into open and short circuits without damage; however, operation into a mismatched
load for even a few minutes can cause the transistor to fail from thermal stress. The BLF188XR is not clown proof.
Thermal overload and RF overdrive will still destroy the transistor. It should be noted that load mismatches that
cause the transistor to draw high current are the ones that are most likely to cause a thermal failure.

Broadcast Concepts Inc
11700 NW 102nd Road Suite 4Medley FL 33178
Tel: [phone] FAX [phone]
Broadcast Concepts Inc
Revised 8/20/2014 7
The 1000W rating for this amplifier is a maximum rating on a 50V supply. In a broadcast system there
needs to be a low pass filter and directional coupler. These components introduce losses. We feel that this
pallet can easily meet the design requirements for a 900W system. That’s 900W after the low pass filter
and directional coupler. This is a suggested operating condition with also takes into account the
requirement that the amplifier is capable of driving loads that are less than perfect (up to 1.8:1 VSWR).