RM Italy KL503 HF 21 30 MHz Linear Amplifier User Manual
- June 10, 2024
- RM ITALY
Table of Contents
KL503
HF 21—30 MHz Linear Amplifier
Ver 1.0 Apr. 2019
Specifications:
| Operation Frequency: | 21—30 MHz (15/12/10m Amateur HF Bands) |
|---|---|
| Modulation Types: | SSB,CW,AM, FM, (All narrowband modes) |
| Transistor: | 8x RM 3 1x RM 4 MOSFET |
| Max I/P Current: | 32A |
| Power Supply: | 13.8VDC+/- 1V 40A |
| Input Fuse (Internal): | 3x10A (Auto Fuse) |
| Input RF Power: | 1-6W max (All modes) |
| Output RF Power: | 300W max |
| Maximum bypass power (Amplifier off): | 50W max |
| Input VSWR: | 1.1—1.5:1 |
WARNING: Before using this product please read carefully all of the
information in this manual or at least the quick start guide!!! To avoid
damage or incorrect operation this is extremely important!!!
Quick Start Guide:
A more complete guide to the installation is featured later
- Connect the RTX input connector to transceiver with 50 Ohm patch cable
- Connect the ANT Output of the Amplifier to SWR Bridge / Wattmeter (If required), and then the Antenna (50 Ohm load Impedance)
- Connect the Amplifier DC power Cable to a suitable 13.8VDC (± 1V) 40A Power Supply or Auto Battery. Pay attention to the correct polarity
- Make sure that the amplifier is switched off
- Adjust the Transceivers RF output power to 5W (6W max) if it is capable of more than 5W output
- Switch on the Amplifier and start operating
- Check that the antenna VSWR is acceptable with the amplifier in use. Any large increase in VSWR indicates that the Antenna is not suitable for the power being used. Operation should be halted immediately to avoid damage to the Amplifier / Radio / ATU etc.
Front / Rear Panel Description
Front Panel
- AM / SSB Switch
- Receive Pre-Amplifier ON / OFF Switch
- Amplifier ON / OFF Switch
- TX indicator LED
- Pre Amplifier ON LED
- Amplifier ON LED
- Input Attenuator
Rear Panel
- RTX SO239 RF input connector
- DC Input power connector. (Polarity is marked on the supplied mating connector)
- ANT RF Output SO239 Socket to Antenna
Installation:
Unpack the amplifier from it’s shipping carton and inspect for any signs of
damage. The amplifier should be installed (either fixed or mobile
installation), in a place that allows good ventilation and provides a suitable
base to support it. Failure to allow for reasonable ventilation will cause the
amplifier to overheat and damage may occur. A short 50 Ohm patch lead should
be used to connect the amplifiers RTX SO239 input [ connector to the output,
(Antenna Socket) of the drive Radio. This length of this cable is not critical
but should be of good quality and be kept as short as practically possible.
The ANT output ] connector of the amplifier should then be connected to
antenna being used. (If an external SWR/Power meter is to be used the
amplifier should be connected to the input and then the antenna to the output,
This order of connection is very important. Check also that the Antenna is
suitably rated for the power output level. (Antenna SWR should not change much
from low to high power). The antenna should be tuned before connecting the
power amplifier or with the amplifier switched OFF! .
In SSB mode the front panel switch [ should be set to SSB. This adds a short
delay to the release time of the RTX relays so that pauses in speech do not
cause the RTX relay to drop out. In AM or FM mode the SSB delay switch should
be set to AM.
The amplifier must be connected via the input power connector \ to a suitable
power supply of the correct voltage output and sufficient current rating. The
output should be 13.6 / 13.8V DC but the amplifier may be connected to a
supply from 12V to 14V DC without damage. The current rating of the power
supply must be at least 40A continuous. Be aware that the current rating must
be greater still if the drive radio is also connected to the same power
supply, although this is not generally advised.
The voltage output and current rating are very important for low voltage (12V)
RF transistors as voltage sag, (poor load regulation) or insufficient current
capability can drastically reduce the output power or cause distortion. If
full output is not seen then the first thing to check is that the voltage
remains above 12.5V at full load. Anything less indicates the power supply is
not suitable for the amplifier at full output.
The cross sectional area of the cables used to connect the amplifier to the
PSU should not be less than 6mm² or 10 AWG. They should also be kept as short
as practicably possible to avoid voltage drop due to ohmic losses. This is
less of a problem in a fixed installation where the power supply may be placed
close to the amplifier.
For a mobile installation the leads should not exceed a length of 3m and they
should be connected directly to the auto battery. An additional fuse may also
be connected inline to provide protection in case of cable short circuit to
chassis ground from the amplifier to the battery.
The installation location must also provide a suitable ground system both for
RF and the AC power supply, (if used). This is very important safety
requirement for any radio transmission equipment but as power increases
becomes increasingly important. A good RF ground will also help to prevent any
returned RF from causing problems with the equipment. Usually erratic
operation of equipment when in transmission may be attributed to RF being
present or poor RF grounding. Installations where a good RF ground is not
possible like operation above the ground floor may require alternative
solutions such as artificial earths or the connection of 1/4 wave
counterpoises to the operating equipment. Correct RF earthing techniques are
however beyond the scope of this manual.
Mobile use should ensure that the ground connections are well bonded to the
vehicle chassis ground for best operation.
Operation:
Before using the amplifier the user must be familiar with all of the controls and be sure that it has been connected correctly. Refer to Page 3 of this instruction manual.
Important!!
Before the amplifier is switched on, (switch ]), the power output of the drive
radio should be adjusted correctly if it is capable of outputting a power
greater than 6W. This may be done with the amplifier connected but switched
off. 6W is the maximum permissible input power to the amplifier, but
approximately 4-5W input should be sufficient to realise full output, and an
input power of 1-5W is OK as it is not necessary to run the amplifier at full
output if not required.
When the amplifier is switched on LED ‘is illuminated.
The amplifier does not have protection against excessive input power and as
such the responsibility will be with the user not to overdrive it. Maximum
input should not exceed 6W. The best performance of the amplifier will be
obtained if the amplifier is operated at just less than full output which
should be achieved with about 4-5W input.
If the drive radio cannot be reduced below 6W then the input attenuator should
not be used to lower the input to the amplifier. The input attenuator can ,
and should only be
used, to reduce the output of the amplifier if required. There are 6 levels of
attenuation.
Damage will occur if the amplifier is operated above 10W input power.
When the amplifier is in transmission LED is illuminated. When it is OFF the
amplifier is in receive state.
Antenna Considerations:
The KL503 is designed to work into a 50 ohms resistive load and any antenna
outside of this requirement must use an antenna tuning unit between the output
of the amplifier and antenna.
It is recommended to check that the antenna to be used is sufficiently rated
for at least 500W power handling before connecting this product. It is also
recommended to check that the VSWR does not change considerably with increased
power as this would indicate that the antenna was not suitable for high power
use.
Cable losses particularly increase with increasing frequency. Always use a
good quality 50 Ohm feeder and keep the length as short as possible. Not only
will this allow more power to reach the antenna but will also increase the
signal strength at the receiver.
This amplifier should not be operated into mismatched loads, (high VSWR), An
acceptable level should be less than 1.5:1. Less than 2.0:1 is acceptable but
some reduction in power may be seen and the amplifier will work less
efficiently and generate more heat. There is no protection for excessive VSWR
so it is advised that the antenna is tuned correctly for the frequency it is
to used on to avoid damage to the amplifier.
Mode:
The KL503 may be used for all of the common narrow band transmission modes
such as SSB, CW,AM,FM, SSTV and data modes etc.
RX Preamplifier:
The KL503 is fitted with an RX preamplifier, that when activated can help to
increase the received signal level. This can be used when the signal level is
low to help improve intelligibility of the received signal. The RX preamp can
be used independently of the amplifier however when the amplifier and preamp
are both activated the preamp is automatically switched out of line when the
amplifier is in transmission. Switch is used to switch the preamp on and off.
LED is illuminated when the preamp is switched on.
Warning: Transmit Time.
Hi Duty cycle modes such as FM and Data modes etc. operate the amplifier at
full power all of the time unlike modes like SSB and CW that are either
intermittent or only reach peak output for very short times, these high duty
cycle modes will run the amplifier much harder and generate more heat in the
same amount of time. It should be noted that the amplifier although capable of
being used with these modes should not be operated continuously. A
transmission time of more than a few minutes should be avoided to avoid
excessive transistor junction temperature. The exact time for transmission in
these modes will depend on numerous factors such as, how good the ventilation
around the amplifier is if there is sufficient space for freely flowing air to
circulate, etc. If the ambient temperature is high this will reduce the total
time in transmission. Common sense should be exercised, if the heat sink is
becoming too hot then sufficient time should be allowed to let it cool down
before reuse.
Input drive and power output:
The amplifier should give full output with approximately 4-5W input. Excessive
input power should be avoided and the amplifier should always be operated in a
responsible manner.
The KL503 features an input attenuator a that may be used to reduce the output
of the amplifier if the drive radio does not have the facility to reduce its
output power.
The input attenuator should NOT however be used to reduce the input power
level of the drive radio if it is greater than 6W! Otherwise the attenuator
may be damaged from overheating. There are 6 levels of input attenuation and
position 6 is direct input, with no attenuation. So setting to position 1 will
provide the lowest output power from the amplifier, and position 6 the maximum
output.
Maximum output power considerations:
All amplifiers have a maximum output and this occurs shortly after gain
compression where by Pin no longer produces a proportionate increase in power
output . The amplifier should always be operated at a point below its
saturated output. Trying to extract every last watt by overdriving the
amplifier will not actually help your signal to be stronger, you will in fact
cause higher levels of distortion which will make your signal less
intelligible at the distant receiver station.
Running the amplifier a little under max output will also allow the amplifier
to run cooler and make it more reliable for many years of use.
As an example consider the following situation.
1 ‘S’ point on a receiver is usually approximately calibrated at 6dB so for
example the difference between S5 and S7 2 ‘S’ points is 12dB. The difference
between 5W and 250W is about 17dB a big increase to your signal strength,
almost 3 ‘S’ points, with the same antenna. Now lets say for example you run
the amplifier at a moderate 200W output by slightly reducing the input power,
the difference between 250W and 200W is less than 1dB which when you compare
this to 6 dB per S point is actually very little and as the amplifier is not
running at its absolute maximum will give a cleaner output with less
distortion that will actually make a difference at the distant receiver for
the better!!
Typical Harmonic Output
KL503 Schematic
Attention:
The use of Linear Amplifiers are controlled by specific laws within the country of use. These laws must be known to the user and are entirely the responsibility of the user. The manufacturer declines any responsibility from unlawful use.
Warranty:
This product is covered by a 24 month warranty commencing from the date of purchase. The original purchase receipt will be required for any claim. This warranty does not cover aesthetic damage or damage to the RF power transistors from incorrect use.
Read User Manual Online (PDF format)
Read User Manual Online (PDF format) >>